THE 456th FIGHTER INTERCEPTOR SQUADRON

T PROTECTORS OF  S. A. C.

The Convair B-58 "Hustler" Bomber

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The Convair B-58 was the first supersonic bomber built in the West. The supersonic B-58 Hustler derived from a new concept developed in the late 1940s and early 1950s.

 

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This page shows many of the details of the B-58

 

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The Convair B-58 was the first supersonic bomber built in the West.

The Boeing B-47 and its bigger brother, the B-52 Stratofortress, developed in the early years after World War II, represented the application of jet power to conventional bombing concepts of the day. Still traveling at subsonic speeds, the two big Boeings were intended to penetrate enemy air space at great altitudes, and were originally designed to carry conventional bombs. The supersonic B-58 Hustler, on the other hand, derived from a new concept developed in the late 1940s and early 1950s--one which took into account the greatly increased capability of ground defenses, including radar tracking and ground-to-air missiles.

On the one hand, it was realized that the bomber of the future must have the highest possible speed, and therefore be capable of supersonic flight. This called for a relatively small aircraft of unconventional shape and with unconventional characteristics, the delta wing, in particular, coming into early prominence. A droppable, externally-carried bomb pod was visualized from the beginning as a means of bomb release at supersonic speed. On the other hand, it was clear that the enormous consumption of jet fuel at supersonic speed would not permit the small attack aircraft to go all the way from its continental base to the target in the enemy heartland at such velocity. The bomber was, therefore, to be carried as a parasite under a large, slow transport aircraft. For the composite weapon, the journey was divided into three zones: the "logistics" zone at the start, during which the parasite would be attached to the parent transport; the "combat" zone near the enemy's border where the parasite would be released; and the "target" zone, into which the short-range bomber would penetrate at supersonic speed, to bomb and return to the parent aircraft. Low-altitude penetration under the enemy radar was considered, as well as high altitude flight.

	The supersonic B-58 Hustler derived from a new concept developed in the late 1940s and early 1950s. It took into account the greatly increased capability of ground defenses, including radar tracking and ground-to-air missiles.

The Convair firm of Fort Worth, Texas--to be merged in 1954 with the General Dynamics Corporation--had been involved in advanced bomber design studies since October, 1946, when it had undertaken under contract with the Air Force a theoretical study of the long range subsonic bomber of the future, known as GEBO (GEneralized BOmber) I. Approximately 10,000 configurations on paper were studied and compared, with respect to speed, range, and gross weight, and involving different combinations of wing area, aspect ratio, sweep-back, turboprop and pure jet propulsion. Ultimately this study led to an Air Force requirement for a medium bomber with a gross weight of 200,000 lb., a radius of 2000 miles, and a 10,000-lb. bomb load. Boeing received a Phase I contract in 1948 under this requirement for their XB-65 with four jet engines and four turboprops, but the program was cancelled early in 1949 with the realization that this subsonic design would not have penetration capability against modern ground-to-air defenses. On June 6, 1949, Convair received from the Air Force a contract to continue generalized bomber studies under the designation of GEBO II. Initially, they were called on to attempt to settle the turboprop vs. turbojet power plant controversy, and to apply the solution to a bomber with a radius of 1200 to 2500 nautical miles with a 10,000 Ib. bomb load, cruising speed of over 450 knots, and flight altitude above 35,000 feet. In April, 1950, the GEBO II requirement was changed for a system able to attack targets 3000 to 4500 nautical miles distant at speeds of Mach 0.9 to 1.5. Convair had already proposed in January, 1950, a small delta wing composite carrying 2 men, which would be transported into the target zone by a B-36. With one engine in the tail, two droppable jet engines under the wings, and one in the tail of the long, finned bomb pod (all without afterburners) the parasite would have a launch weight of 100,000 pounds, would cruise to the target at Mach 1.3 (increasing to Mach 1.6 over the target), and reach a maximum altitude of 48,500 feet before pod release. After the attack the "return component" would fly back to the B-36 with its single engine at Mach 0.9. A modification in the fall of 1950 involved two fixed jet engines buried in the wings, two droppable engines under the wings, and a fifth in the long, streamlined pod, plus an advanced bombing/navigational system and passive electronic countermeasures system but no active defense. Originally the pod was intended to carry conventional explosives, but early in the GEBO II program a thermonuclear warhead was incorporated. The long, finned and streamlined bomb with a jet engine in its tail could function as a free-fall bomb; with small wings as a powered glide bomb or an air launched missile, and as late as 1953 it was expected that the pod, with propellant system and fins, would have a range of 100 nautical miles.

Though Boeing's large jet and turboprop XB-55 had been cancelled, the Seattle firm was working on a four jet shoulder wing bomber, their Project MX-1022, with 47-degree sweep-back of the leading edge, a tail reminiscent of that of the B-47, and a three-man crew. (Later this was to be referred to as the XB-59). Radius was 2,280 nautical miles at Mach 0.9, or 1,737 nautical miles at Mach 0.9 plus 185 nautical miles at Mach 1.3. The Air Force budget for fiscal 1951 and 1952 supported both the Boeing design and the Convair GEBO II delta parasite, and in February, 1951, both firms received Phase I contracts. The Convair MX-1626 proposal was for a small delta wing bomber to be carried as a parasite under a turboprop powered B-60, the swept-back variation of the B-36. It would now have only three non-after-burning engines, two fixed ones in wing nacelles and one in the pod, a gross weight of 107,000 Ib., a two-man crew, and a minimum landing gear to carry the weight of the "return component" only.

During the Phase I studies of the MX-1626 proposal the parasite approach was dropped in favor of in-flight refueling using the early probe-and-drogue method just then coming into service. The expendable engine principle was also discarded, and the MX-1626 design which emerged in December, 1951 was for a small delta with two fixed engines in nacelles in the wings--for the first time with afterburners--and a long slender bomb pod, its nose extending forward beyond that of the aircraft and containing search radar gear, its tail garnished with three long swept-back fins, and its upper surface fayed flush to the lower portion of the fuselage. With a crew of three, this craft had a radius of 2300 nautical miles from advance bases, or 4000 nautical miles in intercontinental operations, with a single out-bound refueling at a distance no greater than 2500 nautical miles; the bomb pod, functioning as an air-to-ground missile, had a range of 50 nautical miles.

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The progress of the two supersonic designs encouraged Headquarters USAF Directorate of Requirements to publish on December 8, 1951, a General Operational Requirement (GOR) for a strategic bombardment system (SAB-51) with a minimal operational radius using the single refueling concept of 2000 nautical miles, a 2300 nautical mile radius at 50,000 feet, low altitude capability at high subsonic speed, and maximal supersonic dash capability. A strategic reconnaissance system (SAR-51) of February 1, 1952, sketched a similar aircraft for reconnaissance purposes. Both Boeing and Convair competed for a contract under the two GORs, the Convair contender, designated the MX1964, resembling the MX-1626, but having four jet engines with afterburners in paired pods in each wing, takeoff gross weight increased to 140,000 lb., the wing area increased to 1400 square feet, with leading-edge sweep-back of the delta wing decreased to 60 degrees. A tail turret with machine cannon was added. Boeing continued work on their design, now the MX-1965, reducing the weight from 200,000 to 180,000 lb., but when both detail Phase I designs were presented to Air Research and Development Command on October 9, 1952, the larger Boeing design was rejected as being less capable of achieving the specified supersonic performance. The Convair design was held to provide the most promising means of achieving supersonic capability with minimum size, thanks to the Convair engineering staff's insistence on producing a "high density" aircraft. In addition, Convair was 4 to 6 months ahead of Boeing in detail design. Convair thus received a full scale Phase I development contract under the Weapon System concept, using the MX-1964 design as a basis, with the further instruction that the aircraft would be known as the B-58. At this time the Convair design staff was using the name "Hustler" within the family to designate the MX1964; to the regret of some, the name stuck, and even became official.

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	The Convair design staff was using the name "Hustler" within the family to designate the MX1964; to the regret of some, the name stuck, and even became official.

The rest was refinement and detail. In March, 1953, the after fuselage was fined down under the transonic "area rule" and the four engines were distributed in four separate, staggered pods. The leading edge of the wing was cambered and twisted to minimize loss of efficiency at the tips. A small 10-degree trailing edge angle was added to the wing, increasing the area to 1542 square feet, and the takeoff weight increased to 150,000 Ib. In September, 1953, the four jet engines were again in twin pods hung on pylons under the wings, with added fuel for intercontinental flight in wing tip tanks. The search radar, which had extended out ahead in the nose of the bomb pod, was mounted in the nose of the aircraft, enabling the pod to be shortened. In August, 1954, the airframe was redesigned for the last time in the light of the supersonic "area rule." The jet engine nacelles were hung individually under the wings, the fuselage redesigned, with added room for fuel permitting the tip tanks to be eliminated. Wind tunnel tests confirmed that a significant increase in supersonic performance could be expected. This design was unchanged up to the date of the first flight on November 11, 1956, though for some time further the pod carried small canard lifting surfaces forward, and triangular wings amidships.

Among the many revolutionary advances embodied in the B-58 Hustler was the use of new procedures and materials in constructing the aircraft. Special demands were made on the airframe structure, not only in terms of aerodynamic loads, but also by virtue of its high speed, which through skin friction at Mach 2 could heat the exterior surfaces above 250 degrees F. With the inboard jet engines venting their exhausts beneath the wing, there was also concern over sonic fatigue at high sound levels affecting the wing structure. In tie-down tests Convair actually ran the inboard engines of a B-58 for ten hours with afterburners in maximum re-heat and sound levels up to 171 decibels to test the wing structure for sonic fatigue.

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	Among the many revolutionary advances embodied in the B-58 Hustler was the use of new procedures and materials in constructing the aircraft.

Internally, the B-58 is framed like a Navy destroyer, with transverse duralumin spars, corrugated for strength, spaced only 11 to 15 inches apart running from one wing margin through the fuselage to the opposite wing. There are no chordwise ribs, only chordwise members or bulkheads to serve as attachments for elevons, engine nacelles and landing gear. For covering the wing, Convair evolved a new material--at once stiff, strong, light, relatively easy to replace, and with good thermal-insulating qualities--the so-called bonded sandwich panel. The top and bottom of the sandwich are sheets of duralumin alloy about 1 mm. thick; the half-inch-thick filling consists of tiny honeycombs of either phenolic resin-fiberglass cloth, or less commonly, of very light gauge duralumin. The core is bonded to the duralumin outer layers with phenolic adhesives and cured at a pressure of 175 p.s.i. at 350 degrees F. for two hours. Absolute cleanliness is essential for solid bonding, and the department of the Convair plant where this was done was known as the "hospital section." The panel is then attached to the wing structure with titanium screws. Because it is absolutely impossible to bend or deform a cured sandwich panel, those with curved surfaces have to be set up in a jig before bonding. Fuselage structure panels are reinforced with beaded inner skins bonded to the outer skins. In a few areas exposed to high temperatures, such as the after portion of jet engine nacelles and the elevons which dip into the blast of the inboard jet units, panels of brazed stainless steel sandwich replace the duralumin and fiberglass ones.

In line with the high-density concept under which Convair engineers designed the B-58, the entire interior of the wing, and most of the interior of the fuselage, are filled with fuel. Actually the space enclosed by the wing and fuselage aft of the crew compartment is divided by bulkheads into four tanks. The largest is the after tank, filling the after portion of the wing and containing a maximum of 39,794 Ib. of JP-4 fuel. The forward tank in the forward part of the wing contains a maximum of 20,648 Ib., and the reservoir tank above the wing, 4,163 Ib. In the tail of the aircraft at the level of the elevons is the balance tank, containing a maximum of 8,195 Ib. of fuel. The pod or pods carried beneath the aircraft are also largely filled with fuel. The single 57-foot-long MB pod contains mostly fuel. The 54-foot-long lower element of the two-part TC pod, designed to be dropped before run-in to the target, is filled entirely with fuel, while the 35-foot-long upper pod contains at least 2,450 Ib. of fuel as well as a warhead. When fully serviced by air refueling, the Hustler can carry in its internal and pod tanks a maximum of 101,627 Ib. of JP-4--over 57% of its gross weight of 176,890 Ib. in this condition.

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	Internally, the B-58 is framed like a Navy destroyer, with transverse duralumin spars, corrugated for strength.

The balance tank in the rear serves a particular purpose. At supersonic speeds, the center of pressure moves well aft of its location at subsonic velocities, and the aircraft's center of gravity should follow it, to reduce drag for the most economical cruise condition. The location of the center of gravity is presented as a percentage of the mean aerodynamic chord (MAC) of the aircraft, and for certain flight conditions the pilot is advised to set the center of gravity at the corresponding correct MAC. (For example, with a gross weight over 100,000 Ib. and speeds above Mach 1.3 the center of gravity below 50,000 feet must be kept within limits of 30% forward and 33% aft of the MAC). An automatic computer-controlled programmer will arrange for fuel to be pumped aft from the forward tank to the balance tank, or forward into the forward tank, as necessary to bring the center of gravity within the required limits. The four engines of the B-58 Hustler--General Electric J 79-5As or 5Bs--are rated at 10,000 lbs with maximum afterburner. The engines are remarkable for having variable-position inlet guide vanes and variable-position stator vanes in the first six stages of the compressor. These are automatically set in relation to engine speed and compressor inlet temperature, to admit the correct amount of air to the compressor, and to direct it against the rotating compressor vanes at the proper angle of attack, thereby minimizing the possibility of compressor stall. Primary and secondary exhaust nozzle flaps in the engine outlet area provide for optimum thrust and specific fuel consumption under different engine operating conditions, and are opened or closed by the throttles. In addition, they prevent engine overheating. The throttles have six settings, OFF, IDLE, and MILITARY. To achieve "design speed" the Hustler has to be driven by the afterburners, and these increase their thrust as the throttles are advanced to MIN A/B, MAX A/B, and OVSP. In the latter setting the engines are allowed to over-speed to 103.5%; operations at 105 to 107% r.p.m. are permitted for five seconds or less, but operation above 107% r.p.m. for any length of time requires that the engines be returned to the factory for overhaul.

With a takeoff gross weight of 163,000 Ib., and a landing gross weight of 75,000 Ib. and a touchdown speed of 165 knots, the landing gear, wheels and brakes of the B-58 take terrific punishment. The steerable nose gear has two tires; the two main gears roll on four non-frangible steel wheels, each bearing two 22-in diameter tires inflated to 240 p.s.i. Should all the tires blow and disintegrate in a bad landing, the aircraft will roll on the non-frangible steel wheels. Enormous amounts of energy, up to ten million foot-pounds per brake, may be absorbed in a normal landing. Even higher energies may heat the brakes to such a degree that tires or hydraulic fluid may ignite, and firefighters must remember to approach the landing gear from front or rear only due to the danger of tire explosions.

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The pod or pods carried beneath the aircraft are also largely filled with fuel. The single 57-foot-long MB pod contains mostly fuel. The 54-foot-long lower element of the two-part TC pod, designed to be dropped before run-in to the target, is filled entirely with fuel, while the 35-foot-long upper pod contains at least 2,450 Ib. of fuel as well as a warhead.

Generators driven by # 1, 2 and 3 engines provide 115/200 volt alternating current, which powers most of the instruments, some of the radar equipment, the fuel pumps and some of the navigational equipment. Some of the alternating current is rectified to provide multiple direct current between 28 and 250 volts including caution and warning lamps, autopilot, navigational electronics equipment, and some of the radar apparatus. A 28 volt battery emergencies. The Defense Systems Operator's cockpit is practically lined with panels of individual fuses which may be checked by running the hand over them, a small pin protruding about an eighth of an inch from a blown fuse. Other fuse panels are in the navigator's cockpit.

There are two separate and independent hydraulic systems, the utility and the primary, each having two engine-driven pumps maintaining a pressure of 3000 p.s.i. Both systems share in the operation of the flight controls, the elevons and rudders; should one fail the other system assumes the full load; should both hydraulic systems fail, the pilot has no means of controlling the aircraft and the crew must eject. The hydraulic systems also operate the landing gear, nose wheel steering, wheel brakes, tail turret, aileron, elevator and rudder damper servos. A pneumatic system is provided for emergency extension of the landing gear and for emergency braking.

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	There is no physical communication between the three cockpits.

There is no physical communication between the three cockpits arranged in tandem, and except for the intercom each crew member is on his own, in cramped quarters which do not permit standing, for missions lasting 7 to 8 hours. The pilot has vision ahead and to the sides through a six-window wrap-around windshield, plus two small windows in the canopy for overhead vision. The bombardier/navigator and defense systems operator have a minute window measuring not more than 4 x 6 inches on each side of their compartments. These might seem to serve solely as antidotes to claustrophobia, but often are covered by opaque cloth curtains the better to view radar scopes within the cockpits. Each cockpit has its own individual, jettisonable canopy, hinged at the rear and moved pneumatically.

Each cockpit also has an individual escape capsule--the first enclosed escape system in an aircraft in regular service use. Flight personnel are "sized" for the capsule at the start of the training course, and failure to fit the capsule is a cause for separation from the B-58 program.

The capsule can be closed and pressurized within 7 seconds in case of loss of cabin pressure at high altitude, enabling flight personnel to dispense with pressure suits. In this situation the pilot can see part of his instrument panel through a window in the capsule door, and with full control through the stick inside the capsule, he may fly the aircraft to an altitude below 40,000 feet and de-capsulate. Buttons on the stick enable him while encapsulated to disconnect the autopilot, shift the center of gravity, and retard the throttles. In an emergency, rockets eject the capsule from the aircraft, with the enclosed personnel being protected against wind blast, wind blast erosion and thermal injury. After deceleration of the capsule, a 41-foot diameter parachute lowers it. The capsule contains survival gear, including a radio, rations, water, desalting gear, clothing, and a rifle, and will float if it lands in the sea.

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	So much can go wrong, so fast in the B-58 Hustler.

Liquid oxygen is carried, and crew members use the diluter-demand regulator, with pressure breathing masks. The interior of the crew space is cooled by two separate air conditioning systems. This is as much for the benefit of the large amount of electronic equipment carried as for the crew, and in fact, if the amount of air from the cabin cooling system is insufficient to maintain safe temperatures in the electronic gear, the cooling plant goes into "reverse flow" and the electrical equipment is cooled before the cabin. A pressure regulator in the cabin exhaust vent maintains a pressure differential of up to 7.45 p.s.i.

As for the electronic equipment itself--I still remember the laughter when I first told members of the 43rd Bomb Wing that I had heard that the Hustler was so complicated and tricky to fly that its operation was completely automated, with control movements automatically programmed by a reel of tape brought out from Operations and stuck in a black box in the nose! The Hustler is still a pilot's airplane, yet the extent and sophistication of the computerized and miniaturized control and navigational equipment is incredible, and enormously extends the perceptions and performance of the three human operators.

To guide the Hustler, the pilot has a pair of conventional rudder pedals and a massive plastic control stick with which he makes the conventional control movements. Yet he is not moving the rudder and the elevons--the horizontal control surfaces at the rear of the delta wing--but merely activates valves which, through a power control linkage assembly, move the control surfaces by hydraulic force. (Characteristic of the hydraulic control system is the phenomenon known as "stick talk back," the pulsating kick of the control stick when the hydraulic pressure fluctuates at the stick's extreme limits of movement). There is of course no transmission of control surface loads back through the stick and pedals, so artificial feel systems provide a substitute. Other sophisticated features of the flight control system are automatic, responding not to the will of the pilot, but to impulses from the autopilot amplifier computer assembly, which derives information from the air data computer (Mach number, temperature and altitude), the gross weight computer, the tracking and flight controller unit (pitch and roll corrections), the primary navigational system (pitch, roll and heading signals), and the rate gyro and accelerometer package. These assemblies not only control the action of the autopilot (which can even vary engine power), but also the operation of other automatic features of the flight control system. For instance, damper servos move the control surfaces automatically to damp the rate of pitch, roll and yaw, un-damped movement of the Hustler at supersonic speed, in particular, being dangerous as the aerodynamic loads may exceed the structural limits. An automatic elevator trim system will position the elevons to maintain constant 1G flight with the control stick in neutral. The angle assumed by the elevator will vary with air speed, gross weight and location of center of gravity, and is indicated on the instrument panel on the elevator position indicator. Another dial indicates the amount of elevator movement available. This depends in turn on the air speed, and is determined by the elevator ratio changer. The latter, in response to Mach signals, varies the stick-to-control surface mechanical ratio, in order to protect the aircraft against excessive G loads. Thus, large control movements are desirable and necessary at low air speeds; at high subsonic speeds, control surfaces movement should be limited because of the high air pressures involved; at supersonic speeds, with the control surfaces blanketed by shock waves, larger surface movements are required to produce the same effect. The aileron controls likewise have automatic trim and ratio changers.

	Wind tunnel tests confirmed that a significant increase in supersonic performance could be expected.

So much can go wrong so fast in the Hustler that two separate warning systems --visual and auditory--insistently draw the pilot's attention to any malfunction. On the left side of the instrument panel is a red MASTER WARNING light, and a yellow one marked MASTER CAUTION. When lit, these draw the pilot's attention to warning and caution panels on the right side of the cockpit, where individual lamps indicate the specific trouble--"left (fuel) manifold low pressure," "oil low #1," "reservoir tank not full," "aft pump #8," "hydraulic utility pump #2," "cabin pressure left," etc. An irresistible attention-getter, a voice warning system, has been developed for the Hustler: into the masculine chatter in the pilot's earphones a soft feminine voice (pre-recorded, unfortunately) breaks in with one of twenty announcements--"weapon unlocked," "hydraulic system failure," "check for engine fire," "nose too high." What dreams, I thought, the Hustler pilots must dream of this disembodied angel who watches over their destinies ! I was speedily disillusioned. "I've seen her," shrugged one, nonchalantly. "She's just like all the rest of them."

Of all the magically-performing electronic gear aboard the B-58, the Sperry-built AN/ASQ-42 bombing/navigation system gives the most astonishing performance. When operating in the navigation mode, it is literally capable of directing the B-58 Hustler, by acting through the autopilot, along a great circle track at constant Mach number and altitude to any point on the globe. The navigator simply sets the latitude and longitude of his true present position on his navigational control board, and the latitude and longitude of his destination position on the sighting and test panel. The computer filling the front of his cockpit does the rest, though not without the aid of a variety of sophisticated sensors which feed it data.

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Towards the rear of the aircraft, in the fuselage between the forward and after fuel tanks, is the inertial navigational system, the so-called stable table,3 whose attitude is gyroscopically fixed while the aircraft moves around it in pitch, roll and yaw. It also provides a secondary measure of ground speed. The primary ground speed source is a Doppler radar transmitter and receiver enclosed within the tail of the aircraft, measuring the true ground speed by the decrease in frequency between the transmitted radar pulse and the echo returned from earth. Atop the stabilization unit, and protruding slightly above the skin of the fuselage, is the rounded cupola of the star tracker unit. By setting on his astro control panel the Greenwich Hour Angle, the sidereal hour angle, and the declination of the sun or star to be used for navigational purposes, the navigator can cause the astro tracker to lock onto the heavenly body, after which it will provide continuous heading information to the computer. Should the celestial bodies be obscured, heading data comes in from the remote compass transmitter inside the leading edge of the fin. Search radar in the nose, displaying a radar representation of the terrain below on the scope in the navigator's cockpit, provides a further check on position. Crosshairs in the scope itself indicate when certain fix points on the ground, pre-set into the computer, are coming into view. A radio altimeter provides accurate height above the terrain. The air data system also feeds true air speed, pressure altitude and air temperature into the computer.

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	Each cockpit also has an individual escape capsule--the first enclosed escape system in an aircraft in regular service use. Flight personnel are "sized" for the capsule at the start of the training course, and failure to fit the capsule is a cause for separation from the B-58 program.

In the bombing mode, the bomb/navigator system takes the aircraft on a thumb line course over the target, compensating for wind drift and Coriolis effect, while offset points and fix points set into the machine beforehand come up beneath the crosshairs in the radar scope. During the run-in the navigator, while watching the terrain below on radar, can make small corrections in heading with the tracking and flight control stick in his right hand, which acts through the autopilot. At a time calculated to provide a burst over the target, the bomb/navigator system, in the bombing mode, automatically releases the weapon. For practice runs over radar bomb sites, the bombardier/navigator turns on a radio tone signal which is cut off abruptly at the moment of simulated weapon release.

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Air Crews

The Defense Systems Operator, in the third cockpit, assists the pilot during flight by reading check lists, advising the pilot on fuel consumption, optimum altitude, and location of center of gravity. His primary duties are in connection with the passive and active defense systems. The former comprises track-breaking electronic equipment designed to mislead and confuse the operators of enemy radar, to enable the Hustler to accomplish its mission unaffected by ground-to-air defenses. The latter includes a 6-barrel Vulcan 20 mm. cannon located in the extreme tail, and the remote-control equipment needed to direct and fire it. Enemy aircraft are presented as blips on the defense systems operator's radar scope, and the fire control equipment automatically locks onto the target, computes the lead and windage, aims the gun and notifies the DSO when to fire it--with the attacking enemy aircraft being at no time visible to the Hustler crew.

After a bewildering afternoon watching flight crew trainees at work in the pilot's, bombardier/navigator's, and DSO's cockpit simulators, I confided to my friends of the 43rd Bomb Wing that it was surely easier to get through four years of medical school than to learn to fly the B-58 Hustler. "Too bad you can't take the six-month training course and find out," they replied. I wish I could try it

Specifications:
Convair B-58A Hustler
Dimensions:
Wing span:	56 ft. 10 in (17.32 m)
Length:	96 ft. 9 in (29.49 m)
Height:	31 ft. 5 in (9.58 m)
Wing Area:	1,542 sq ft (470 sq m)
Weights:
Empty:	55,560 lb (25,201 kg)
Max T/O:	163,000 lb (73,935 kg)
Performance:
Maximum Speed:	1,321 mph (2,125 km/h) @ 63,150 ft (19,248 m)
Combat Ceiling:	63,150 ft (19,248 m)
Record Ceiling:	85,360 ft (26,017 m)
Combat Radius:	1,750 miles (2,816 km) to, 5,577 miles (8,975 km) with inflight refueling
Powerplant:
Four General Electric J79-GE-1 turbojet engines rated at 10,500 st. or 16,000 st. 69.4 Kn with afterburners.
Armament:
Single General Electric T-171E3 Vulcan 20 mm rotary cannon in the rear, plus nuclear or conventional bombs in the under-wing pod.

Notes:
The above was  adapted from:
1. Robinson, Douglas H. The B-58 Hustler New York: Arco Publishing Company, Inc., 1967.
 

 

The General Dynamics B-58 Hustler

By Phil Rowe 

 

The rapid development of American Mach 2 combat aircraft in the 1950s inevitably led to the development of a Mach 2 strategic bomber, the "B-58 Hustler". As it turned out, a Mach 2 bomber was not a particularly practical idea; the B-58 was produced only in small numbers and did not remain in service for very long.

However, the B-58 was one of the sleekest and most impressive combat aircraft ever built, and even in the 21st century the Hustler still looks futuristic. This document describes the rise and fall of the B-58.

 

The Origins Of The B-58

 

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By September, 1953, the B-58 had evolved into a virtually new design with a separate pod, Siamese nacelles, wing-mounted drop tanks, and the relocation of the search radar from the pod nose to the fuselage nose. These changes helped realize a considerable weight saving with virtually no drag penalty.

The Convair company of Fort Worth, Texas, USA, began conceptual studies on a supersonic bomber in October 1946, with the investigation designated "Generalized Bomber (GEBO)". GEBO led to a second, more practical study designated "GEBO-II", begun in March 1949, when the Cold War was beginning in earnest.

This was two years after Boeing had test-flown the first modern jet bomber, the B-47 Stratojet, and three years before Boeing would test-fly the B-47's bigger and badder successor, the B-52 Stratofortress. At the time, there were no supersonic combat aircraft in operational service, and first-line bombers of the US Air Force (USAF), such as the Convair B-36, were primarily piston powered. However, aeronautical engineering was advancing by leaps and bounds at the time, and it paid to be forward-looking.

Convair engineers focused on the delta wing for the supersonic bomber. The concept of the delta wing had been invented by Dr. Alexander Lippisch of Germany in the 1930s. Although the Germans never got a powered delta-wing aircraft into the air during the war, in 1948 Convair tested the delta wing on the XF-92 experimental interceptor. The XF-92 would lead along another path to the Convair F-102 Delta Dagger and its follow-on, the superlative F-106 Delta Dart.

The delta wing has a number of disadvantages: as a tailless aircraft, it cannot use flaps, and so has a long takeoff run; its low wing loading makes for a rough ride at low altitude; and it loses speed quickly on turns, limiting maneuverability. However, it is a simple, robust configuration that offers high straight-line speed and plenty of volume for fuel tanks. Many first-generation Mach-2 combat jets were delta-winged.

Convair engineers initially focused on "parasite bomber" schemes, involving a relatively small supersonic bomber that would be carried by a B-36 to the target area. The USAF's Strategic Air Command (SAC), which owned the service's nuclear strike role, wasn't impressed by the parasite scheme. Fortunately, Convair was also working on a more conventional bomber, and after a test program involving wind tunnel models, rocket-boosted models, and radio-controlled air-dropped models, in October 1952 the USAF requested that Convair develop a full-scale supersonic bomber prototype.

The Convair supersonic bomber was to be powered by the General Electric (GE) X24A afterburning turbojet engine, then in development. The X24A would emerge as the GE J79, which would be the powerplant for many American supersonic aircraft, including the Lockheed F-104 Starfighter and the McDonnell Douglas F-4 Phantom II. Initial prototypes of the supersonic bomber would be powered by the Pratt & Whitney J57 until the J79 became available.

Convair assigned the supersonic bomber project the designation "MX-1964". Boeing was working on a competing swept-wing supersonic bomber project with the designation of "Model 484" or "MX-1965". In mid-1952, the Air Force gave the Convair bomber the service designation of "XB-58" and the Boeing bomber the service designation of "XB-59".

In October 1952, the Air Force selected the Convair XB-58 for further development. This led to award of a contract in February 1953, specifying delivery of two prototypes of the Convair aircraft, including one "XB-58" bomber prototype and one "XRB-58" reconnaissance aircraft prototype. They were also known by the USAF "weapon system" designations of "WS-102A" and "WS-102L" respectively, and jointly by the company designation of "Convair Model 4".

* While the XB-58 was clearly seen at the outset as a delta-winged aircraft with four J79 engines and stores in a pod carried under the belly, little else was certain, and a wide range of different configurations were considered, some with engines podded together, some with engines above and below the wing, and so on.

One important design feature was presently added in the form of "area ruling", a concept devised by engineer Richard Whitcomb of the US National Advisory Committee for Aviation (NACA), the primary predecessor organization of the modern US National Aeronautics & Space Administration (NASA). Whitcomb's area ruling was based on the concept that an aircraft would have better supersonic performance if there were as little change as possible in its cross-sectional area along its length. This meant that as the wing span increased, the fuselage diameter shrank, resulting in a "wasp-waist" or "Coke bottle" configuration that not only improved performance but generally improved an aircraft's appearance as well.

However, the XB-58 design did not really begin to converge to a solution until the spring of 1953, after Convair had been bought out by General Dynamics (GD). The final design had a delta wing with a leading-edge sweep of 60 degrees and a trailing-edge sweep of 10 degrees, with down turned wingtips. The four engines were fitted in individual nacelles slung under the wings, and a new GE T-171 Vulcan six-barreled 20-millimeter Gatling-type cannon was fitted in the tail for defense.

A single high-yield nuclear weapon was to be carried in a long belly pod. A reconnaissance pod could be fitted as an alternate payload. The pod also carried equipment and fuel. The pod was used because attempting to include the payload in the aircraft itself inflicted too much of a performance penalty.

Unfortunately, when GD told the USAF in June 1954 that the XB-58's first flight had to be pushed back from January 1956 to June 1956, the service balked. This didn't seem like much of a schedule slip, but the XB-58 program had already cost $300 million USD, and there were doubts among USAF brass that a Mach 2 bomber really made any sense.

Even the SAC commander, General Curtis LeMay, stated in a January 1955 memo that SAC neither wanted or needed the B-58, as the B-58's range was only half that of the B-52. There were more general issues as well: subsonic bombers could do the conventional bombing job much more cheaply, and the future of strategic nuclear strike clearly seemed to belong with the intercontinental ballistic missile (ICBM), then in development by both the USA and the USSR. LeMay's logic was hard to argue with and, in fact, would grow even harder to argue with in the future.

Nonetheless, B-58 advocates won out in the short run, with the Air Force ordering 11 more "YB-58" trials machines in December 1955. The first XB-58 prototype took to the air on 11 November 1956. The aircraft was fitted with GE J79-GE-1 engines, with 39.58 kN (4,035 kgp / 8,900 lbf) maximum dry thrust and 64.5 kN (6,575 kgp / 14,500 lbf) afterburning thrust. As it turned out, the J79 was available in time and no B-58 was ever fitted with P&W J57s. The second prototype, which was completed simply as an "XB-58" and not as an "XRB-58", first flew in February 1957.

First service delivery of the "Hustler", as it was named, was in February 1959. In the interim, 17 more trials aircraft had been ordered, for a total of 30.

 

 

The B-58 In Detail

 

The B-58 was a spectacular aircraft in almost every regard, elegant with its long, slender, wasp-waisted fuselage and its clean delta wing, sporting four J79 engines, with the inner pair on long swept-forward pylons and the outer pair on short stub pylons. All but the first seven B-58s were fitted with J79-GE-5A or -5B turbojets, with 43.16 kN (4,400 kgp / 9,700 lbf) maximum dry thrust and 69.4 kN (7,075 kgp / 15,600 lbf) afterburning thrust. Most earlier B-58s were retrofitted with these engines.

The B-58 had long, spindly-looking, strong, tricycle landing gear to allow ground clearance for the engines and the weapons pod. Flight controls used redundant hydraulic systems.

   GENERAL DYNAMICS B-58 HUSTLER:
   _____________________   _________________   _______________________
 
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                17.3 meters         56 feet 10 inches
   wing area               143.25 sq_meters    1,542 sq_feet
   length                  29.5 meters         96 feet 9 inches
   height                  9.6 meters          31 feet 5 inches

   empty weight            25,200 kilograms    55,560 pounds
   max loaded weight       80,200 kilograms    176,890 pounds

   maximum speed           2,205 KPH           1,370 MPH / 1,190 KT
   cruise ceiling          19,500 meters       64,000 feet
   range (typical)         6,600 kilometers    4,100 MI / 3,565 NMI
   _____________________   _________________   _______________________

Click on Picture to enlarge

By August, 1954, the final B-58 configuration, four individually pylon-mounted engines and all fuel contained internally and in the podded lower component, had evolved and the design was frozen. Few major changes would transpire between the completion of the August, 1954, B-58 full-scale mock-up study and the roll-out of the actual prototype aircraft.

The B-58 gave an impression of being a very big fighter jet. This was emphasized by the seating arrangement, which was much more like that of a fighter than a bomber. There were three crew members, including pilot, bombardier-navigator, and defense systems operator (DSO), with each sitting in his own individual enclosure in tandem, accessed by separate clamshell doors on top of the fuselage.

There was no room to move around, except for a crawlway between the second and third seats. The crew was essentially strapped into their seats as they would be in a fighter. The pilot had a good view through a six-piece windscreen, with his seat offset so he didn't have to stare through the center post, but the two back-seaters had to make do with small windows on either side of their seats.

Early production featured conventional ejection seats, but in 1962, after the deaths of aircrew in high-speed ejections, a new "escape capsule" scheme was introduced that sealed each crewman into a clamshell capsule to improve his chances of survival in a supersonic ejection. The capsule would self-stabilize after ejection; had inflatable floatation devices for water landings; and featured a survival kit, including a radio, a survival rifle, and even a change of clothing. The escape capsule was retrofitted to older B-58s.

The B-58's construction was as innovative as its appearance. Much of the aircraft was made of sandwich panel composed of fiberglass sheet faced by thin aluminum on each side, a scheme that proved both strong and heat resistant, as required for Mach 2 flight. In areas where the fiberglass sandwich wasn't strong enough, a similar sandwich scheme with thin aluminum sheet filler was substituted. In areas exposed to unusual levels of heat, as was the case in areas under the wing near the engine exhausts, a sandwich material based on stainless steel was used. The panels were held in place by titanium screws.

The end result was an aircraft with a remarkably low empty weight. There was a literally a price to pay, however, since fabricating the honeycomb sheets to the desired tolerances was a difficult and expensive process, and fitting the panels in place on the aircraft during manufacture was equally troublesome. Expensive high-precision jigs were required. Worse, replacing a panel in the field meant placing the entire aircraft in such a high-precision jig. This made maintenance difficult, to say the least, particularly in comparison to other aircraft in the USAF inventory.

The aircraft's GE J79 engines were another marvel. They had an inlet spike that automatically adjusted for airflow and reduced the chances of high-speed engine stall. In afterburner, the engines could easily move the Hustler to its redline speed of Mach 2.2. They could provide even more thrust in an emergency, but the airframe itself simply wasn't strong enough to fly any faster.

The B-58 had a large fuel capacity, with a "wet" wing divided into fore and aft tanks. Total wing fuel capacity was 34,100 liters (9,000 US gallons). The skin panels were fitted with gaskets to allow them to serve as the tank walls. In addition, there were two tanks in the rear fuselage, providing a total fuselage fuel capacity of 19,000 liters (5,000 US gallons). The weapons pods could also accommodate fuel, and in fact the fuel capacity of the aircraft was so great that it could not get off the runway when fully loaded. It took off with an incomplete fuel load and then "topped off" from a tanker once airborne.

The rearmost fuselage tank was mostly intended as a ballast tank to maintain pitch trim as fuel was expended. Fuel trim proved to be a major problem during initial aircraft flight tests, and the aircraft's fuel system was correspondingly elaborate. The B-58 was fitted for boom-type inflight refueling, with a refueling socket in the nose forward of the cockpit.

A considerable amount of engineering effort was expended on the Hustler's landing gear, which perched the aircraft about 2.75 meters (9 feet) off the ground with the weapons pod removed. The steerable nose gear had twin wheels and a vertical travel of about 38 centimeters (15 inches). Each of the main gear had a total of eight wheels, with four mounted on two axles, with a vertical travel of about 43 centimeters (17 inches). All three gear assemblies retracted backward.

The main gear tires were relatively small, only 56 centimeters (22 inches) in diameter, to allow them to fit inside the thin wings, which still had to be fitted with shallow fairings to accommodate the gear. The tires were filled with nitrogen to a pressure of about 19 atmospheres / bars (280 pounds per square inch), about eight times the pressure of an automobile tire.

The aircraft's tires had to bear up under tremendous loads at high rolling speeds and often blew out. Extended taxiing was ruled out and sharp turns had to be avoided. After a hot landing, the tires were often cooled by a blower system pulled out on the runway by the ground crew. In fact, on touchdown the Hustler's tires tended to tear up bits of the runway, until the Air Force figured coated the runways down with a mixture of sand and epoxy to make the surface more durable. Delta-wing aircraft tend to land fast, and so the B-58 had a ribbon-style drag parachute to reduce the landing roll.

A state-of-the-art avionics suite was included. A Raytheon targeting radar was fitted in the nose, and the pilot was assisted by an autopilot that provided a "watchdog" capability, preventing the pilot from taking maneuvers that would be dangerous in supersonic flight. The bombardier-navigator, in the second seat, used a Sperry-Rand AN/ASQ-42V electronic navigation system that was highly capable and accurate, though as it was built with 1950s technology it weighed about 550 kilograms (1,200 pounds). Today a system with better capabilities could be picked up with one hand.

The DSO sat in the third seat. He controlled a powerful electronic countermeasures (ECM) system to blind enemy radars, including an AN/ALQ-16 active jammer and an AN/ALE-16 chaff dispenser. If an enemy fighter still managed to get on the Hustler's tail, an unlikely event since the aircraft moved very fast at altitudes above the ceilings of most contemporary fighters, the DSO could direct the Vulcan cannon in the tail "stinger" via a radarscope to engage the fighter.

The standard "MB-1C" weapons pod carried by the B-58 was a big spindle with tailfins. It was 17.4 meters (57 feet) long, 1.5 meters (5 feet) in diameter, and had a fully loaded weight of 16,325 kilograms (36,000 pounds). It carried both a W39Y1-1 multi-megatonne nuclear weapon and fuel, with the fuel stored in tanks at both ends to ensure trim. The pod was mounted slightly off center from the aircraft's centerline so that it would begin to spin for stabilization after being dropped. When the B-58 was parked on the runway without the pod, a counterweight had to be attached to the aircraft to keep it from tipping back on its tail.

The B-58A was originally to have carried an "MA-1C" liquid-fuel stand-off missile with a range of 260 kilometers (160 miles) rather than a weapons pod. However, the guidance systems available at the time were not accurate enough to make the MA-1C practical.

After the introduction of the B-58, the Air Force began to have doubts about the utility of a bomber that could only carry a single nuclear weapon, and so between 1961 and 1963 all B-58s were retrofitted with four stub pylons, arranged in tandem under the wing roots, to carry Mk 43 or Mk 61 nuclear weapons.

A photo-reconnaissance pod, designated the "LA-331", was fielded. It was a modification of the MB-1C pod, carrying a Fairchild KA-56 panoramic camera rather than a nuclear bomb. The camera was fitted in the pod's nose, along with a scanner system that directed the camera to provide un-blurred images at high speed and low level.

More specialized pods were considered but not fielded. An "MD-1" ECM pod was built but apparently not flown. A radar reconnaissance pod fitted with a huge Hughes AN/APQ-69 side looking airborne radar (SLAR) was test-flown in 1959, leading to tests of the more compact AN/APS-73 SLAR in the early 1960s. A Hustler carrying the AN/APS-73 SLAR was sent over Cuba during the Missile Crisis in October 1963. This was apparently the only time a Hustler ever over flew hostile airspace.

Problems with fuel leaks led to the development of a new "two component pod (TCP)" system that used twin stacked pods, with the upper pod carrying a BA53-Y1 nuclear weapon along with barometric sensors, and the lower pod amounting to a big drop tank that would be discarded during an operational mission once it was exhausted. Oddly, few pictures of the stacked pod system are available. Whether this was because it wasn't used very much, or because it was simply un-photogenic, is difficult to say.

 

 

The B-58 In Service

 

Click on Picture to enlarge

Loading of a single component bomb/fuel pod on one of the test force B-58, test force aircraft were marked by the red triangle on the tail.

After production of the first 30 trials aircraft, 86 production B-58s were built, for a total of 116 Hustlers in all. Production ended in the fall of 1962. Most of the trials aircraft were brought up to operational specification, though eight other trials aircraft were modified into "TB-58A" trainers. The primary B-58 users were the SAC 43rd Bomb Wing at Carswell, Texas, and later Little Rock, Arkansas, and the 305th Bomb Wing at Bunker Hill, Indiana, later renamed Grissom Air Force Base.

The Hustler's performance was astounding. It was capable of flying as fast or faster than any fighter it might encounter, and generally at higher altitudes than a fighter could reach. The B-58 had a blazing rate of climb, often described as "like a rocket", particularly when the aircraft was lightly loaded. The B-58 was also surprisingly maneuverable for an aircraft of its size, and although delta wings are supposed to give a bumpy flight at low altitude, the Hustler was perfectly adept at low-level penetration flights. 

The B-58 set a number of records, including a low-level flight covering 1,930 kilometers (1,044 nautical miles) at altitudes of under 150 meters (500 feet) with an average speed of 1,100 KPH (610 knots), and a dash climb to a maximum altitude of 26,025 meters (85,360 feet). One Hustler flew from Los Angeles to New York and back in four hours, 41 minutes.

In October 1963, another B-58 appropriately named GREASED LIGHTNING flew from Tokyo to London. Despite the fact that it had to slow down for five aerial refuelings, its average speed over the 14,850 kilometer (8,028 nautical mile) flight was 1,726 KPH (933 knots). Cruise speed for five hours of the journey was 2,276 KPH (1,230 knots) at an altitude of 16,160 meters (53,000 feet), and the aircraft would have had an even higher average speed if it had not lost an afterburner late in the mission.

The Hustler was a very demanding aircraft. Only very experienced flight crews were assigned to the type, and some aircrew were frightened of it. This was not because it was badly engineered, it was just because it was pushing the envelope of aircraft design and could be dangerously unforgiving. Ignoring the prescribed ranges of angle of attack in takeoff, landing, and cruise could be deadly. Loss of an engine at high speed could cause the aircraft to yaw drastically and rip itself to pieces. Loss of hydraulic control demanded an immediate bailout.

A total of 26 of the 116 B-58s built were lost in accidents, and the type had the unfortunate distinction of suffering fatal crashes twice at the Paris Air Show, once in 1961 and again in 1965. The TB-58A rebuilds were performed to help deal with the difficulties in flying the type.

By the late 1960s, the argument over the manned supersonic bomber that had gone back and forth since the Hustler's development tipped decisively against it. The B-58 was an amazing aircraft, but it was just too expensive to operate. To the extent that SAC still believed in the manned bomber, the subsonic Boeing B-52 could do the job. For the cost of operating two B-58 wings SAC could operate six B-52 wings. Some SAC brass also disliked the B-58 because of its high accident rate.

The B-58 never fired a shot in anger. Although the war in Southeast Asia was in full blaze by the mid-1960s, the Hustler was simply not cost-effective for conventional bombing, though in 1967 the Air Force did experiment with several B-58s for conventional strike in "Project Bullseye". The four stores pylons were modified for the carriage of conventional bombs and flown on low-level strike test missions out of Eglin AFB in Florida. Some rumors have it that B-58s were painted in jungle camouflage in place of the normal natural metal finish for these tests, but there is little evidence that this is true.

The last B-58 was removed from operational service in early 1970. The type's operational career only spanned a decade, a modest interval for a modern military aircraft. Seven survive on static display and one derelict is apparently being rebuilt, but it seems very unlikely the Hustler will ever fly again.

 

 

The B-58 Variants

 

A wide range of B-58 variants were considered, though in practice only one version of the B-58 was built, plus some minor variations and experimental fits.

Trials aircraft were designated "YB-58". Production aircraft were designated "B-58A", or usually just "B-58" as there never was a B-58B. Trainers were designated "TB-58" or "TB-58A", and were intended to give new B-58 pilots the necessary familiarization required to fly their demanding aircraft. This could not be done very well in a standard B-58 as there was no copilot seat, meaning a pilot new to the type was on his own on his very first flight. The second seat position was modified to accommodate a flight instructor, and distinctive additional rear windshield panel extensions were added to give the instructor a decent view. Most combat systems were removed.

Click on Picture to enlarge

Side view of then test double component bomb/fuel pod.

Hustlers fitted with the LA-331 reconnaissance pod were designated "RB-58" or "RB-58A". It seems that RB-58As also carried some specialized equipment to control the pod and support the reconnaissance mission.

B-58s were used in limited numbers as test aircraft. One particularly impressive test configuration involved the fit of the huge YJ93 engine for the North American XB-70 bomber to the third B-58 built, replacing the aircraft's weapons pod. This aircraft was designated the "NB-58A".

Another B-58 was used to test the AIM-47 missile weapons system for the Lockheed YF-12A, an interceptor version of the SR-71 Blackbird reconnaissance aircraft. This B-58 was fitted with an extended nose to accommodate the ASG-18 radar for the missile and was affectionately known as "Snoopy", after the long-nosed beagle in the popular contemporary PEANUTS comic strip. The missiles were fired from a modified weapons pod, with such tests conducted from May 1962 to February 1964.

GD proposed a "B-58B" in 1958, featuring uprated J79-9 engines; a fuselage stretch; canards; and a conventional weapons capability. A B-58A was slated for conversion to a B-58B prototype, but the program was cancelled. A "B-58C" was also proposed, involving a larger aircraft powered by two or four Pratt & Whitney J58 engines, used on the SR-71 Blackbird, with 144.6 kN (14,740 kgp / 32,500 lbf) thrust each. The B-58C would have had Mach 3 performance, but the Air Force wasn't buying.

Proposals were considered for using the B-58 as a strategic missile launcher, and Lockheed built a 9.15 meter (30 foot) long solid fuel "air launched ballistic missile (ALBM)" derived from the company's X-17 test booster. The ALBM was test-launched four times in 1958 and 1959, with two successful launches. In the fourth and last launch, on 22 September 1959, the ALBM was launched into space to take a picture of an American Explorer satellite under "Project Snap Shot". This was a proof-of-concept test with applications for satellite inspection and anti-satellite interception, but that particular launch failed. The B-58 ALBM program was then abandoned, though the B-52-based "Skybolt" ALBM program persisted for a few more years.

A screwball scheme was proposed in which the Hustler would launch a high-speed ramjet-powered expendable aircraft to penetrate enemy airspace at speeds of up to Mach 4. The expendable aircraft would be piloted, but most of the aircraft would be discarded before the piloted section returned to base. Nothing came of this idea directly, though the basic concept would be revived with the Lockheed D-21 unmanned ramjet reconnaissance drone of the 1970s.

There were even schemes for building a supersonic transport based on the Hustler. One military transport concept involved a Hustler fitted with a modified pod with accommodations for five passengers, to be used when getting important personnel to a location was critical and cost wasn't a problem. More practically, GD also considered a commercial Hustler transport derivative with the fuselage stretched by about 50% to provide seating for 52 passengers. This concept was designated the "Model 58-9". Nothing came of these ideas, either.

 

 

Comments

 

Click on Picture to enlarge

Loading of a single component bomb/fuel pod on one of the test force B-58, back view.

The B-58 was in general a much more advanced aircraft than the B-52, but at the beginning of the 21st century the the B-52 was still flying operational missions, while the B-58 had been grounded for three decades. The logic that argued against the supersonic manned bomber was simply too hard to dispute. Strategic strike could be performed by missiles, while conventional strike could be performed by attack aircraft and, increasingly, cruise missiles.

Two North American XB-70 supersonic heavy bombers would be built in the 1960s, but only as test aircraft. Supersonic B-1 bombers would be built in the 1980s, but only about 100 were manufactured, even less than the B-58. Only about 20 Northrop B-2s were built, and they weren't even supersonic. It is possible that the USAF may field another heavy bomber, but if so it will most likely be an economical, relatively low cost aircraft with extremely long range and heavy payload capability, dispensing cruise missiles and other stand-off weapons from outside defended airspace.

In hindsight, it is remarkable that the B-58 ever entered service at all. Whether it was a good use of taxpayer's money is arguable. However, it is almost impossible to not be pleased with the result. 

I wrote this document as something of a "knock-off" on what I thought would be a fairly straightforward write-up on an attractive aircraft. It was straightforward, but led to more detail and work than I had expected. It always does.

I have to mention that some Hustler fans have written data sheets on a Hustler variant with eight J79 engines, and even a twin-fuselage variant with ten engines. I suspect these sheets were released on 1 April of some year.

By Phil Rowe 

Sources include:

THE ILLUSTRATED ENCYCLOPEDIA OF 20TH CENTURY WEAPONS AND WARFARE, edited by Bernard Fitzsimons, 1978 edition.

"B-58: Diehard Of The Manned Bombers" by Anson McCulloch, AIRPOWER, November 2000, 8:35. This document began an an outline of this article.

"B-58 Hustler: Convair's Ultimate Delta" by Bill Yenne, INTERNATIONAL AIR POWER REVIEW, Volume 2 / Fall 2001, 116:149.

I also picked up some details on the more exotic variants from Joe Baugher's exhaustive website on US military aircraft.

 Greg Goebel / Public Domain

 

 

The B-58 Hustler

 

Click on Picture to enlarge

Future aircraft, "will move with speeds far beyond the velocity of sound,” said renowned Hungarian-born aerodynamicist Theodore von Karman in 1945. Highly regarded by Henry "Hap" Arnold, Commanding General of the Army Air Forces (AAF), and by Maj. Gen. Curtis L.eMay, the first Deputy Chief of Staff for Research and Development, von Karman, as the AAFs chief scientific advisor, most likely influenced L.eMay's vigorous and diverse research and development program. Part of the program prompted the impressive 14 October 1947 test flight of the Bell X-1 rocket airplane, a flight which shattered both the sound barrier and the speculation that aerodynamic forces became infinite at Mach 1.

Development in the late 1940s of the single-place, air-launched X-1 was a major achievement. Nevertheless, as time would show, production of a 3-seater aircraft, capable of sustained speeds approaching the muzzle velocity of a 30-caliber bullet and of functioning effectively as a strategic bomber, would be a challenge of monumental proportions. The controversial B-58 program that ensued was to illustrate the dangers of untried technology versus the necessity of pioneering state-of-the-art developments. Where to draw the line between the two would remain open to question long after the costly B-58 ceased to exist.

A 1946 study by Consolidated Vultee Aircraft Corporation (Convair), a contractor noted for interest in the delta-wing configuration, marked the beginning of the B-58. The project was so complex, however, that a new study was requested and a second contractor, Boeing, became involved. Proposed in 1951, the initial Convair design, as recommended by Dr. Alexander M. Lippisch, an eminent German scientist, foretold a delta configured, 100,000-pound bomber; the Boeing design, a conventional, 200,000-pounder. Suggestive of the future B-58's tumultuous history, the 2 contractors followed totally different development approaches, and drastically opposed concepts emerged within the newly independent Air Force. USAF engineers kept asking for realistic military requirements, but the Air Staff decided that instead of accepting technology as the determining factor against which a mission could be fitted, mission objectives would come first and technology would be developed to satisfy them.

In late 1952, believing it promised the best means of achieving supersonic speeds with a weapon system of minimum size,, the Convair design, already altered several times, was selected over that of Boeing. The choice was not unexpected. In a recent study, the Rand Corporation had clearly stated that by minimizing size, one reduced the radar reflectivity of a vehicle and, therefore, the probabilities of interception by surface-to-air missiles. Also, the Air Force's latest development directive had reemphasized the importance of minimum size, of high-speed and high-altitude performances and, finally, of the weapon system development technique, an objective with which Convair was familiar.

Click on Picture to enlarge

General LeMay, who by the fall of 1952 had been heading the Strategic Air Command (SAC) for 4 years, and who would remain in that position until promoted to Vice Chief of Staff in mid-1957, did not like the Air Staff's selection. Among other arguments, he pointed out that instead of fostering economy and reliability, combining unconventional design and operational techniques made "it entirely possible that the system might prove operationally unsuitable." General LeMay's objections did not prevail, which was unusual. Rejection of the more conventional, longer-range, supersonic bomber, proposed by Boeing and preferred by General LeMay, also was ironic, since it was LeMay who, back in early 1948, ensured that a new strategic jet bomber would be developed on the heels of the B-52.

Throughout the years, money had a great deal to do with the B-58's retention. By 1954, for example, after an investment of some $200 million, the B-58 project could show no tangible achievements. Cancellation at this stage, the Air Staff reasoned, would mean an unacceptable financial loss. Hence, despite production slippages, soaring costs, and General LeMay's continued opposition, the B-58 survived. Yet, the program that finally emerged was emaciated, in terms of numbers as well as military capabilities.

The Air Force bought 116 B-58s, less than half of the minimum initially planned. At long last operational in 1961, the B-58 still harbored deficiencies of varying importance. Its bombing and navigation system was unreliable, and the aircraft was unable to carry several kinds of new weapons. Although expensive, necessary modifications were accomplished between 1962 and 1964. However, significant problems remained. In the early 1960s, technological advances had radically altered the anti-air defenses that the B-58 was expected to challenge. Defensive nuclear-tipped air-to-air and surface-to-air missiles appeared to preclude penetration of enemy airspace at high altitude. Since the B-58 structure incurred significant fatigue damage when flying at low level, and since the new bomber had no terrain-following radar, extensive modifications would be needed to permit effective low-level penetration. Such modifications did not materialize because of their prohibitive cost, and all B-58s were phased out of the Air Force inventory by early 1970, less than 8 years after the last ones rolled off the assembly line.

While the $3 billion price tag of the B-58 program did not help the manned bomber's cause, the aircraft did represent an important technological achievement. In its day the B-58 broke 12 world speed records and won almost every major aviation award in existence. The aircraft marked the first major departure from the monocoque riveted metal construction techniques of the 1930s and prompted the investigation of non-metallic composite structural methods. It brought about major technical advances, entailing technical uncertainties which remained until such an aircraft was flown. The Air Force took the risk, and the results may not have been cost-effective. Nonetheless, similar developmental risks again would have to be taken to assure progress in aerospace technology.

 

 

The Design Of The B-58

 

Click on Picture to enlarge

The B-58 had a delta wing design that included many firsts for strategic bombers. It had four turbojet engines with afterburners, and was the first supersonic aircraft with engine pods mounted outboard on the wings. The wings had a span of 56 feet, 10 inches and were swept 60; the length was 96 feet, 9 inches; the height at the tail was 29 feet, 11 inches; and the maximum takeoff gross weight was 160,000 pounds. The crew consisted of a pilot, navigator, and defensive systems operator seated in tandem. While a retrofit provided each crew member an individual ejection capsule for supersonic bailout, the cramped crew cockpit made long missions like airborne alert very exhausting for the crew.

The configuration of the B-58 was characterized by a delta wing and the absence of a horizontal tail. The wing had 60° sweepback at the leading edge, an aspect ratio of 2.09, and airfoil sections that varied in thickness ratio from 3.46 percent at the root to 4.08 percent at the tip. Conical camber was employed in the leading edge to reduce drag at lifting conditions and thus increase cruising efficiency. (A conically cambered wing is one which has a leading-edge camber shape formed from part of the surface of a cone whose apex is located at the longitudinal plane of symmetry of the wing. The amount of camber accordingly increases progressively with span-wise distance from the fuselage.) Absence of a horizontal tail for trimming prevented the use of any trailing-edge high-lift devices. Elevons for pitch and roll control extended from the side of the fuselage to the outboard engine nacelles. All the controls were power operated.

The four General Electric J-79 turbojet engines were located in individual nacelles suspended below the wings on swept-forward pylons - an arrangement analogous to that employed on the B-47 and B-52. Area ruling was employed in the high-fineness-ratio fuselage with the single vertical fin and rudder mounted at the rear. Crew members consisting of pilot, bombardier-navigator, and defense-systems operator were housed in a tandem arrangement to aid in maintaining the desired long, narrow shape of the fuselage. Each crew station was an individual rocket-powered escape module capable of providing safe crew egress even at Mach 2.0. The entire crew compartment as well as the wheel wells and electronics bay were pressurized and air-conditioned. Cooling of the tires and electronic equipment was required because of the high temperatures generated by prolonged flight at Mach 2.0. Landing gear consisted of a tricycle design with each main gear having eight wheels arranged in two rows of four. The large number of wheels was used to maintain the landing-gear footprint pressure within acceptable limits while, at the same time, allowing the use of small diameter wheels capable of being stored in the thin wing with only small fairings bulging from the lower wing surfaces. The conventional nose gear had two wheels; a braking chute was provided to assist in stopping the aircraft on landing rollout.

A large streamlined pod under the fuselage of the aircraft served the dual purpose of housing a nuclear warhead (bomb) and several thousand gallons of fuel. Large amounts of fuel were also carried in the wings and fuselage. The pod was divided into two main parts: the portion containing empty fuel tanks was to be jettisoned on the outboard flight to the target, and the other component containing the warhead, as well as additional empty fuel tanks, was then to be dropped at the target. The B-58 might thus be considered as a sort of two-stage system. Armament on the aircraft consisted of a single six-barrel 20-mm rotary cannon controlled by the defense-systems operator.

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 The B-58 did not have a bomb bay but could carry one nuclear weapon externally with the centerline fuel pod fitting over it. Four weapons, whether nuclear or conventional, could be carried on external hard points if the fuel pod was eliminated, thus degrading the aircraft's range further. With fewer aircraft deployed, a larger payload was needed to deliver as many weapons as its predecessor, the B-47. But the amount of space available for modifications was less than that for the B-47. In an era of improving SAM technology, ECM modifications have been continually needed to meet the evolving threat, and space was not available for additional ECM.

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To give a light, strong, stiff structure for the thin high-fineness-ratio elements of the aircraft, the B-58 made extensive use of aluminum honeycomb panels. Most of the outer covering of the aircraft consisted of such panels having outer and inner aluminum skins bonded to a honeycomb of aluminum and fiber glass. In addition to its light weight, this type of structure had a smooth exterior surface. In service, however, problems were encountered in ascertaining and maintaining the integrity of the bonded joints.

With a gross weight of 163,000 pounds and a maximum speed of 1,321 miles per hour (Mach 2.0) at 63,150 feet altitude, the B-58 was an impressive aircraft by any standard. This performance was dramatically demonstrated in a number of record flights. Perhaps the most notable of these was the May 26, 1961, nonstop flight of 3 hours and 19 minutes from New York to Paris. Average speed for the 3,669 mile flight was 1,105 miles per hour; three in-flight refueling by KC-135 aircraft were required. Interestingly, almost 34 years earlier on May 20 and 21, 1927, Charles A Lindbergh required 33.5 hours to make the first nonstop flight from New York to Paris - a remarkable advancement in aeronautical technology during a time period of just a little more than three decades.

Specifications Of The B-58 Hustler
Manufacturer:	Convair Division of General Dynamics Corporation, Fort Worth, Tex
Designation:	B-58
Nickname:	Hustler
Type:	Bomber
Length/Span (ft)	96.8/56.8
Wing Area (sq. ft)	1,542.5
Weights (lbs):	Empty - 55,560 Combat - 82,595 Takeoff - 163,000
No. of Engines:	4
Powerplant:	J79-GE-5B (with afterburner)
Thrust (each):	15,000 lbs
Takeoff ground run (feet)	Sea level - 7,850 Over 50-ft obstacle - 13,700
Combat Speed:	503 mph
Max Speed:	1147 mph
Rate of climb	Sea level - 17,830 feet per minute
Service Ceiling:	63,500 ft
Combat radius	1400 nautical miles
Guns:	1 M-61 Gatling Gun

In spite of the spectacular records set by the B-58, the aircraft was woefully deficient in range performance. Without in-flight refueling, the radius of action, including a 450-mile supersonic dash, was only 1,500 miles. With no supersonic dash, the maximum radius increased to 2000 miles, thus indicating the relatively poor supersonic cruising efficiency of the aircraft. Ferry range at subsonic speeds was 4025 miles. With in-flight refueling, a target distance of 4,300 miles, including a supersonic dash of 500 miles, was possible. After weapons delivery, the aircraft had a range of 1,500 miles - hopefully enough to reach a friendly base but not enough to reach the point of departure. With in-flight refueling, ferry range was 6,995 miles.

The limited range capability of the B-58 can be directly traced to the compromises required in its aerodynamic design. The Mach 2.0 dash requirement dictated the use of a delta wing with leading-edge sweep angle of 60° and a low aspect ratio of about 2. As a consequence, the value of the maximum subsonic lift-drag ratio, without the fuel and weapons pod, was only 11.3 (compare this with the value of 21.5 for the B-52G); an even lower value would be expected with the pod attached. The value of (L/D)max at Mach 2.0 was slightly greater than 5. Thus, the aircraft was not capable of efficient cruising flight at either subsonic or supersonic speeds. Aircraft configuration design for highly efficient cruising flight at subsonic speeds is well understood, as demonstrated by the B-47 and B-52 as well as by the numerous highly efficient jet transports described in the following chapter. Unfortunately, the design of a highly efficient and practical supersonic cruising aircraft still remains somewhat elusive although much progress has been made since the design of the B-58. Still more elusive is a configuration concept that enjoys high cruising efficiency at both subsonic and supersonic speeds, such as required by a commercial supersonic transport. Variable sweep, however, offered a means for achieving good subsonic cruising efficiency in combination with a reasonably efficient supersonic dash capability.

References

• B-58 Stuff - Phil Rowe

• List of All B-58's - Phil Rowe

• List of All B-58's Compiled by Duane Mantick

• B-58 Hustler Encyclopedia of US Air Force Aircraft and Missile Systems Volume II by Marcelle Size Knaack

 

 

Development Of The B-58

 

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Development of a long-range supersonic bombardment aircraft was officially initiated by a generalized bomber study (GEBO, Identified as GEBO I in June 1949, after the Air Force issued a contract for a second GEBO), begun in October 1946 by Convair (The corporation subsequently became a division of the General Dynamics Corp). In requesting GEBO, the AAF called for determination of which design trends would be necessary to achieve unspecified, yet ambitious supersonic performances. Of necessity, the scope of the study was very broad, but "investigation of low aspect wings in general and Delta Wings in particular" was emphasized. Although already acquainted with the delta wing and, therefore, well suited for the work, Convair had to investigate countless configurations to determine the effects of wing area, aspect ratio, thickness and sweep, as well as the impacts of type (turbojet and turboprop), size, and number of engines on airplane speed, range, and gross weight. The GEBO findings were described in 3 reports, which were completed in June 1948. Yet, this was only a beginning. Indicative of the magnitude of the project, in late 1948 the Air Materiel Command (AMC) Engineering Division of the now independent Air Force asked for a continuation of the GEBO study. The USAF engineers presented many valid reasons for their request, but their most telling arguments were that the findings so far obtained be used to show the "feasibility of military characteristics;" and to assist in establishing "balanced characteristics and desirable design compromises." Meanwhile, pre-GEBO studies, conducted by Convair, had formed the basis of the winning interceptor design submitted by the company in 1946. Forerunner of the F-102, the ensuing rocket-propelled, XF-92 interceptor was extremely costly and highly impractical. Though the aircraft failed to earn a production contract, it proved to be an important step in the development of the delta wing, one of the future B-58's most striking features.

The delta wing itself, like many other aerodynamic innovations, had its inception in the German wind tunnels of World War II (While the word "delta" is inextricably linked to the work of Alexander Lippisch, a brilliant aeronautics scientist, his work followed a path first taken by John Dunne, who developed such aircraft in Great Britain prior to the First World War. Actually, Dr. Lippisch's efforts paralleled those of G. T R. Hill and the Westland company in Great Britain and that of John K. Northrop in the United States). Although the National Advisory Committee on Aeronautics, independent of the German research, by 1945 had explained many of the delta configuration's theoretical advantages, the delta wing concept remained credited to Dr. Alexander M. Lippisch, leader of the German program (His primary interest lay in proving his assumption that aircraft could have the appearance of a flying wing and still be practical-a delta-wing aircraft from which came the modern delta supersonic design). In postwar years, U.S. governmental agencies and many of the American aircraft corporations studied extensively Dr. Lippisch's captured reports, with data on his never-flown, rocket-powered DM-1 glider and his spectacular, if not very successful, Messerchmitt-built Me-163B (the first operational liquid rocket propelled interceptor), introduced by the Germans in August 1944. Yet, while Dr. Lippisch was not the inspiration that caused Convair to continue working on the 60-degree delta, his comments reinforced and encouraged Convair engineers to believe that the delta wing could solve most of the problems of supersonic flights. Nature, Dr. Lippisch wrote, had designed the flying wing thousands of years before man even thought of flight. The flying wing was the Zanonia seed, a seed from a large vine of the cucumber family. It grew in the dense, moist jungles of Indonesia and adapted its reproductive processes to a region in which there was no wind to distribute the seeds. The vine climbed 150-foot trees, and from the top, the seed-a kidney-shaped platform-began its glide, rising on thermals from the jungle heat, and finally landing at considerable distance from its point of departure. The aerodynamic qualities of the seed attracted attention. Two Austrian engineers, Etrich and Weis, analyzed its stability. Etrich eventually combined the Zanonia wing with a conventional monoplane configuration, known as the Etrich "Dove”. The Dove became famous is the days before World War I, as the first German military aircraft. Its demise followed the onset of war, when it was abandoned in favor of the more maneuverable Fokker-designed aircraft.

The initial requirements for a new bomber were emphasized in 1947 by Maj. Gen. Curtis E. LeMay, Deputy Chief of Air Staff for Research and Development. In spite of the declining post-war budget, General LeMay directed improvements in research and development. He also asked for more money. Appearing often before congressional committees, he pointed out on one occasion that the entire annual budget of the propeller division at Wright Field, "wouldn't buy one set of B-29 propellers." In May, General LeMay wrote directly to Lt. Gen. Nathan R Twining, AMC Commander, to urge that studies be undertaken of a new jet bomber that could become operational in the late 1950s. This airplane, General LeMay stated, should have a combat radius of 2,500 miles, a cruising speed of at least 500 miles per hour, and a gross weight of about 170,000 pounds. No amount of modification to the B-50 or B-36 would bring these airplanes within the desired characteristics, General LeMay added. A completely new medium bomber was needed, and development and procurement of such an airplane could well follow the B-52's development. That the B-58, generated by the post-World War II enthusiasm for the unconventional delta-wing configuration, evolved from requirements advocated by General LeMay was to prove ironic. Meanwhile, General L,eMay's insistence prompted the Air Staff to solicit ideas about a new bomber from the Boeing Airplane Company of Seattle, Washington. Yet, several years would pass and many changes would occur before any specific projects started taking shape.

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 As suggested by AMC, Headquarters USAF asked Convair to begin a second generalized bomber study for the development of future long-range supersonic bombers. This study, GEBO II, was formalized on 6 June 1949 by contract AF33(038)-2664 and, like GEBO I, ended covering a myriad of configurations. There were many justifications, besides AMC insistence, for the Air Staff's continued interest in the Convair research. To begin with, the shortage of funds forced the Air Force to make difficult decisions. Boeing's XB-55, a design initiated as an immediate result of General LeMay's 1947 request, had been cancelled in January 1949 for lack of money, as well as the following reasons (requirements for a new medium bomber, submitted to industry in October 1947, proved Boeing the undisputed winner of the ensuing competition). First, there no longer seemed to be an immediate need to originate a design to meet the medium bomber requirements, in view of the currently projected B-47 growth. Also, since the XB-55's development promised to take longer than anticipated, the Air Force thought its design should have been predicated on greater aerodynamic achievements and an improved propulsion system. Finally, and most importantly, continued testing of the delta wing XF-92, first flown in June 1948, was starting to attract wide attention. Even though the Board of Senior Officers in early 1949 had rejected an unconventional strategic bomber proposed by the Fairchild Aircraft Corporation, it was obvious by mid-year that the Senior Officers, with Secretary of the Air Force Symington's full support, were searching for new and imaginative solutions to the strategic bombing problem.

While looking for novel ideas, the Air Force remained cautious and did not lose sight of Boeing's extensive experience in bomber design. The experimental B-47 earned a first development contract in December 1943; the XB-32, in July 1948. As already noted, the contractor had been encouraged to investigate the development of higher-performance aircraft, long before its XB-55 was cancelled. Boeing, therefore, had worked on a series of new turbojet designs in order to compare them with its original turboprop studies and with the XB-55 in particular. Aware of these facts, the Air Force issued termination orders for the XB-55 in such a way as to allow maximum benefit from the studies which Boeing had in progress. Mockup and detailed engineering on the XB-55 were stopped, but the study reports and tunnel tests then underway were to be completed. Moreover, the Air Force soon increased the scope of the Boeing tunnel tests and asked for firm study results.

On 26 January 1951, following completion of GEBO II, Convair offered to develop and manufacture a long-range supersonic reconnaissance bomber. Reconnaissance had not been mentioned before. Most likely, the Heavy Bomber Committee's year-old decision that the heavy bomber program be expanded to include reconnaissance, accounted for the Convair suggestion. As far as Boeing was concerned, reconnaissance, as an adjunct to bombing, was almost routine, the RB-47B being already on the drawing board in March 1951. The proposal, named Project MX-1626 by AMC, was accepted promptly by the Air Force. However, this did not spell the end of Boeing's related work. In fact, the Air Force endorsed in February the Phase I development of 2 reconnaissance bombers through wind tunnel testing, engineering design, and mockup. The Boeing project was designated MX-1712 and was initiated on 26 February by Letter Contract AF33(038)-21388. A similar document, Letter Contract AF33(038)-21250, had been signed by Convair on the 17th. It called for a 107,000-pound reconnaissance bomber, with a delta configuration and 2-stage system (release and retrieval) based on the parasite principle, using the B-36 as the carrier. The MX-1626's basic difference from the other Convair configurations studied in GEBO II lay in the use of 3 engines, 2 in wing nacelles and the third in a droppable bomb pod. In contrast, the Boeing MX-1712 project proposed a conventional, 200,000-pound medium-range reconnaissance bomber, capable of supersonic flight over a limited portion of its mission. The Boeing design objective involved a 2,000-nautical mile radius, 200 miles of which would be flown at Mach 1.3 or more, and the balance at Mach 0.9. For shorter missions, the supersonic radius would increase, while range extension devices such as refueling or extended wing tips would lengthen the range for longer missions. Power was to come from 4 J67-type engines with afterburners, and the aircraft as projected was to be capable of delivering atomic or conventional bombs from altitudes of 45,000 to 50,000 feet. Sea-level missions were another possibility being considered.

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 The parasite-carrier combination, proposed by Convair in early 1951, did not last long. As conceived, Project MX-1626's primary appeal stemmed largely from the stringent fiscal restrictions of the post-World War II period. Like the Glenn L. Martin Company, Convair at one point was also working on a Navy proposal for a money-saving carrier-based medium-range bomber. Since money was lacking, the parasite-carrier concept appeared to be the most economical method for tackling the unconventional approach to the long-range, strategic bombing problem. During 1951, however, the Air Force started to view MX-1626 from a different angle. Both the B-36 carrier and parasite aircraft (officially designated B-58 in December 1952) would require complete navigation equipment; the 2 might not locate one another on the return course of the mission; and once rejoined, the composite aircraft would be more vulnerable to attack. Finally, the 2-aircraft attack system would be far more expensive to build and maintain than would a single bomber. Hence, in December 1951, the MX-1626 configuration was altered drastically. The parasite mode of range extension was dropped in favor of air refueling; the third and expendable engine in the bomb pod of the original configuration was eliminated, while afterburners were added to the aircraft's remaining 2 engines. Moreover, a landing gear was provided to allow take-off at a gross weight of about 126,000 pounds, and the number of crewmen was increased from 2 to 3 (1 pilot, 1 navigator-bombardier, and 1 defense-systems operator).

 

 

Initial B-58 Requirements

 

 

Primary Construction Of The B-58

 

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In September final evaluation of the competing designs by the Wright Air Development Center left little doubt about the forthcoming decision. The center thought that the Boeing MX-1965 design would produce either an aircraft of small size with mediocre supersonic speeds or one so large as to almost preclude any supersonic capability. The Boeing supersonic bomber design was conventional. It featured wings swept at 35 degrees, an internal bomb bay, a fore and aft bicycle landing gear which, like that of the B-52, retracted into the fuselage. It called for 4 engines, similar to those proposed for the Convair bomber, but integral with the wing, 2 on each side, tucked inboard against the fuselage. It projected a supersonic speed of Mach 1.8 at 55,000, but promised plenty of room for its 3-man crew. Maximum take-off weight was about 156,000 pounds. On the other hand, the MX-1964 design, already nicknamed the "Hustler" by Convair, provided the more promising means of achieving supersonic speeds with a weapon system of minimum size. In addition, the center felt that the Convair approach best satisfied the "spirit" of the Development Planning Objective for Strategic Air Operations during the period 1956-1960. This objective, issues by the Air Force on 29 May 1952, favored a small bomber and underlined that future strategic aerial warfare could be most economically and effectively accomplished by a "combination system that incorporates a tanker cargo airplane for refueling in flight the combat zone airplane." The small bomber concept, embodied by the Development Planning Objective of May 1952, reflected the opinion of Col. Bernard A. Schriever, the USAF Assistant for Development Planning in the Office of the Deputy Chief of Staff for Development, and had been endorsed by the Air Force Council and Gen. Hoyt S. Vandenberg, Chief of Staff of the Air Force. But this Development Planning Objective of May 1952 also ran counter to many established principles. SAC officials and particularly General LeMay, who by 1952 had been heading the command for several years, generally favored large bombers, capable of greater ranges. "Even though the best intercontinental bomber available requires some refueling;" SAC insisted, "it does not follow necessarily that the optimum system requires a bomber which has no intercontinental capability without refueling." The command argued that "high performance alone" could "never insure mission success" against targets defended by modern interceptors and surface-to-air missiles, and pointed out that the small supersonic bomber's lack of range would prevent it from operating without refueling from most forward operating bases. Also, crew members would be very confined in such a small bomber. Finally, instead of fostering economy and reliability, combining unconventional design and operational techniques made "it entirely possible that the system might prove operationally unsuitable." SAC's arguments notwithstanding, a decision was near. In an unusual step, the decision makers would totally disregard SAC's concern. In late October, following ARDC's thorough review of the Wright Air Development Center's conclusions, Lt. Gen. Earle E. Partridge, the ARDC Commander, recommended to Headquarters USAF that the competition between Boeing and Convair be stopped immediately. General Partridge noted that the MX-1964 supersonic drag and gross weight figures appeared optimistic, and if true, this would further limit the aircraft's range. Also, costs had not been considered properly, and the forecast operational date would inevitably slip, perhaps to 1959. Nevertheless, the ARDC Commander endorsed prompt selection of the Convair project and asked that accelerated development of General Electric's J53 engine (from which the J79 derived) be authorized without delay. This was approved by the Weapons Board, the Air Force Council, and by General Vandenberg on 18 November 1952. Soon informed that the design competition was ended, Boeing reportedly took the bad news well.

The Air Force selection of Convair over Boeing was not a blanket endorsement of the MX-1964 design. It took several months and many consultations between Convair, National Advisory Committee on Aeronautics, AMC, ARDC, and Wright Air Development Center personnel to settle on a definite configuration which, as it turned out, was subjected to many later revisions. These initial delays were not unfounded. Development problems with the Convair F-102 interceptor were confirming the Air Force's suspicion that the contractor had failed to make proper allowance for the aerodynamic drag of a delta-wing aircraft, be it a fighter or a bomber. Moreover, the area-rule concept of aircraft design," discovered by National Advisory Committee on Aeronautics researcher Richard T. Whitcomb, had been verified during December 1952 in the agency's new transonic wind tunnels. This concept held that interference drag at transonic speed depended almost entirely on the distribution of the aircraft's total cross sectional area along the direction of flight. The solution was to indent the fuselage over the wing to equalize the cross section areas (and thus the volume) at all stations, thereby producing the so-called "coke bottle" or "wasp waist" configuration. Yet, as in the F-102's case, Convair did not accept the Whitcomb findings until its own engineers had confirmed their validity. Another delaying factor was the absence of military characteristics, which were deferred until the fall of 1953.

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Although the MX-1964 design was yet to be finalized, the Air Force proceeded with specific plans. In December 1952, the Deputy Chief of Staff for Development endorsed a production schedule developed by the Wright Center. This schedule was based on the 4-year procurement of 244 B/RB-58s (more than twice the final total). Thirty of these aircraft, with the first one due for delivery in January 1956, would be used for testing, while preparations would be made for full scale production of a version incorporating all test-dictated changes. The 30 initial planes would then be reworked on the production line into the approved configuration. This plan, drawn from the "Cook-Craigie production policy;" was expected to eliminate the faults in a basic design before many aircraft had been built and to speed the acquisition of operationally effective weapon systems (The Cook-Craigie production plan was actually a mere concept, developed in the late forties by USAF Major Generals Laurence C. Ctaigie, Deputy Chief of Staff for Development, and Orval R. Cook, Deputy Chief of Staff for Materiel. They both knew this concept could be expensive and thought "it was only applicable where you had a high degree of confidence that you were going to go into production." The F-102, a by-product of the "1954 Interceptor;' bared some of the pitfalls of the Cook-Craigie plan for early tooling. In October 1953, when testing established unequivocally that important changes had to be made to the F-102's design, 20,000 of the 30,000 tools already purchased by Convair had to be discarded.). Recent experiences seemed to justify such an approach. Building aircraft prototypes before selecting one of them, as occasionally done, had proved costly and time consuming. Moreover, the selected prototype, once produced, has often still been found to have design flaws that needed correction. In any case, the Cook-Craigie philosophy, if not an integral part of the weapon system concept, fitted it perfectly. The weapon system concept itself promoted significant changes and therefore more planning. In early 1953, General Putt, ARDC's new Vice. Commander, announced the Air Force's revised management tasks. The B-58 weapon system would require a minimum of government-furnished equipment since the prime contractor would be responsible for system design and engineering and would deal directly with subcontractors to acquire major components. The Wright Air Development Center, now headed by Maj. Gen. Albert Boyd, would contract for major components "only when limitations of industry, operations, or logistic considerations force the USAF to control source and/or methodology." Even then, such components would have to be designed, built, and tested to Convair's specifications. In short, the Air Force's role was to monitor the prime contractor's plans and progress; to approve specifications as well as subcontractors, and to supply the money. It also retained the right to veto any developments that could cause operational or logistical problems. The Air Force management of the B-58 weapon system would be exercised at the Wright Air Development Center by a 20-man joint project office, made up of ARDC and AMC representatives.

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 Contracting proved to be a difficult endeavor, far more complex than usual. Limited experience with the weapon system concept prolonged negotiations, as the Air Force and Convair worked out specific provisions to define each party's prerogatives and responsibilities. These clauses became part of Convair's letter contract on 12 February 1953, when a supplemental agreement was signed. This was the fifth and so far most significant amendment to Letter Contract AF33(038)-21250. The contract itself was not finalized until the end of 1955, even though the letter contract dated back to February 1951. This was an important turning point, indicating the B/RB-58 program was getting under way, with the B-58 mockup scheduled for the end of the summer, while that of the reconnaissance version would follow in the fall of 1953. The amendment also gave Convair $22 million to cover pre-production planning costs and the acquisition of long-lead time tools and equipment. Yet, it failed to resolve immediately a few basic problems. As single manager, Convair believed that compensation for its additional managerial efforts should be incorporated in the program's direct cost. The Air Materiel Command disagreed, contending that such payments should be added to the overhead administrative costs of present and future contracts, on a yearly pro-rated basis. AMC also postponed total approval of the funds requested by Convair to expand its Fort Worth facilities, causing the contractor to spend $500,000 of its own to secure extra office space.

The Air Force selected a firm configuration for the B/RB-58 and authorized Convair to begin work on each full-scale mockup version. The approved design incorporated the changes dictated by the National Advisory Committee for Aeronautics' transonic area rule. Specifically,; the airplane cross-sectional area was redistributed longitudinally to minimize the compressibility drag rise encountered at transonic speeds. This had been accomplished by fuselage redesign, housing the engines in 4 staggered nacelles, and adding a 10-degree trailing edge angle to the wing, which also increased the wing area to 1,542 square feet. In addition, the wing's leading edge had been cambered and twisted to reduce drag at lift.

 

 

B-58 Development Problems

 

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Approval of Convair's new design did not ease the Air Force's concern about the engine of the future aircraft. As summed up by General Partridge, every effort had to be made to safeguard the successful development of the J79 upon which the "vitally important B-58 and other projects will be so heavily dependent.” The J79 turbojet became the world's first production Mach 2 engine. In addition to the B-58, it eventually powered the Lockheed F-104, the McDonnell F-4, and the North American Aviation A-5. Equally concerned, General Putt informed the General Electric Company that the J79 project controlled "to a very major degree, this country's ability to defend itself during the 1958-1965 period." "This responsibility;" General Putt wrote, "should not be treated lightly." The fact remained that the development histories of American and British turbojets showed that 4 to 5 years were needed from the beginning of design to completion of the 150-hour engine test. This was confirmed by the General Electric engineers, who insisted that delivery of the J79 engine could not be scheduled until July 1957. Based on experience, the Air Force thought this schedule might still be unrealistic. The solution therefore was to equip early B-58s with a version of the already tested Pratt and Whitney J57, but this temporary expedient also would pose problems.

This first development engineering inspection replaced the formal mockup inspection which, obviously, had been scheduled to occur too soon for major subsystems to be available (A second development engineering inspection took place on 29 September 1953. It covered portions of the RB-58 that differed from the B-58. Also held in Fort Worth, the inspection did not cover major subsystems, most of them still remaining a long way off). Nevertheless, except for the missing components (for which space was provided), the B-58 mockup was complete. Air Force inspectors, including representatives from SAC, were able to get a good idea of the new weapon system, by then known as Configuration II. The inspection group, and General LeMay in particular, asked for many changes, but none appeared vital. Just the same, as the inspection neared its end, General Boyd most likely expressed everyone's opinion in stating: "It is a radical design, and we must be careful in following through with these technical developments." He added, however, that Convair seemed to have done a very good job.

Military characteristics (No. 345) for the B-58 high-altitude bombardment system, at long last issued in September 1953, did not bring any great surprises. The requirements fairly matched the specifications proposed by Convair in August 1952, and the lesser USAF demands embodied in the September GOR of the same year: Yet the new characteristics required the carrying of payloads in addition to the warheads originally specified. While this requirement had been anticipated, it implied that greater performance standards would have to be achieved in order to preserve the aircraft's range, which was unchanged. The B-58 would carry 20,000 pounds of munitions, a 13,000-pound increase. This could be expected to entail a reduction of the aircraft's fuel load and, therefore, a significant loss of range. There were a few other changes, most of which stemmed from SAC's criticism. For instance, the side-by-side seating that General LeMay preferred to the tandem seating arrangement of most Air Force planes was not provided, but the B-58 would at least contain a jump seat (subsequently omitted, for lack of space) for one of the crew members to sit alongside of the pilot during take-off and landing. The new characteristics also included some concessions. Maximum dash speeds at altitudes of 55,000 feet were reduced slightly, and the B-58's operational date was postponed from 1957 to 1958 or later.

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Much to the disappointment of ARDC, and despite application of the area rule, on-going wind tunnel tests of Configuration II continued to produce high-speed drag figures. Stability test results also caused concern. The elevons and rudder were not inherently balanced and depended on the rigidity of their actuating systems to prevent flutter. The engine positions and the anticipated Mach 2.1 speed similarly produced some qualms. In addition, as first identified by the development engineering inspection of August 1953, it had become obvious that the compartmented pod, housing the bomb and fuel, needed to be entirely redesigned. This was confirmed in October 1953, when the Air Force authorized Convair to shorten the B-58 pod and to sling it on a pylon under the fuselage. Finally, other changes had to be made to satisfy the anticipated new requirements of the September military characteristics. Meanwhile, other problems loomed ahead. Subsystem development, never considered to be easy, promised to be especially difficult in the B-58's case. As early as 1951, the Air Material Command strewed that it took much more time to design, develop, and produce new equipment such as guns, engines, and fire-control systems than it did to produce new airframes.

The future aircraft had already been acknowledged as a most complex, highly integrated, and mutually interdependent weapon system. The Air Force, consequently, kept a close watch on every component's progress. In December 1953, it asked for studies to determine if the Arma Company's A-3A Fire Control System could serve as a back-up for the Emerson Company's Active Defense System earmarked for the B-58. The Air Force also wanted to know if a modified M-2 Bombing System, built by the International Business Machine Corporation, could possibly substitute for the sophisticated Navigation-Bombing and Missile Guidance System, being developed by the Sperry Gyroscope Company. Aware of the state-of-the-art's current and foreseeable limits, the Air Force attached great importance to the B-58's forthcoming bombing and navigation system. How a B-58 would find and hit its targets, given its speed and altitude design characteristics, was a difficult question to answer. Worrisome comparisons came to mind. For example, in order to obtain a 3-minute bomb run for a B-17 operating at 25,000 feet, the bombardier would have to get on his target about V miles away; in the same vein, with a B-58 operating at 40,000 feet at an airspeed of 450 knots, the bombardier would have to spot and track his target from at least 25 miles away. But to have a 3-minute bomb run at the B-58's designed speed of Mach 2 and at an altitude higher than 50,000 feet, the bombardier would have to be on target some 66 to 70 miles away. The problem was serious enough to justify organizing a special committee to monitor the development of B-58 bombing and navigation procedures. This committee consisted of representatives from the Air Staff, ARDC, SAC, Air Training Command, and the contractors. In early 1954, the B-58 Joint Project Office considered the adoption of the monitoring committee idea for other component systems as well.

Configuration III, as devised by Convair, did not fare as well as expected. The reconfigured B/RB-58 featured a new bomb and fuel pod that had been shortened from 89 feet to 30 feet, and was now detached from the fuselage and suspended on a pylon. Tb compensate for the smaller amount of fuel carried by the pod, external fuel tanks had been added to the wing tips. The search radar had also been removed from the pod and placed into the fuselage nose. There were other alterations and deletions. The droppable nose gear was eliminated, and the positions of the bombardier-navigator and the defensive systems operator were reversed. For lack of space, Configuration III omitted a jump seat, a new requirement of the military characteristics. In any case, the Air Force did not share Convair's confidence that the reconfigured B/RB-58 would achieve better performance. Early 1954 tests in the tunnels of the Wright Air Development Center and National Advisory Committee on Aeronautics soon confirmed that the contractor's estimates once again were wrong. In addition, a problem thought to be solved had reappeared. In 1953, the contractor and the Air Force had decided to abandon the previously endorsed split nacelle engine arrangement in favor of 2 strut-mounted Siamese nacelles. The change would save weight, ease engine maintenance, and facilitate retrofit of J57-powered aircraft with new J79s. Unknown to all at the time, this last advantage would have been of no value since the B-58 schedule slipped and production of the J79 engine caught up with the Convair program. Recent tests, however, indicated that Siamese nacelles induced extra drag on the composite (pod- or missile carrying) B-58, although the airframe itself was affected almost equally by either type of nacelles. In practical terms, this meant a return to split nacelles, more testing, more delays, and postponement of the Configuration III's mockup inspection from the initially scheduled May date to September 1954.

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 Based on a preliminary review of the B/RB-58's third configuration, the Wright Air Development Center finally agreed on 4 December 1953 that Convair could begin the construction of airframe components. Yet, subsequent testing of Configuration III qualified this hopeful decision. In March, the B-58 program underwent a drastic change; research and development came to the fore at the expense of production, and the number of B-58s originally contemplated was reduced from 244 to 30, with the latter quota emphatically referred to as "test vehicles." Moreover, long lead time items such as ground training devices and maintenance and test equipment were cancelled. Secretary of the Air Force Harold E. Talbott approved the redirected program on 30 April 1954, and authorized release of the procurement funds necessary to support it (Secretary Talbott succeeded Thomas K. Finletter as Secretary of the Air Force on 4 February 1953. Mr. Finletter had replaced Mr. Symington, the first Secretary of the Air Force, on 24 April 1950). Yet, as illustrated by the June procurement directive that followed, the Air Force again qualified its authorization. The directive freed about $190 million of fiscal year 1955 money for 13 test aircraft, but no procurement of any kind could be initiated prior to determining a firm configuration. As it happened, these 13 aircraft were the only B-58s covered by the first definitive contract, at long last signed in December 1955. The remaining 17 test vehicles were carried on another procurement contract, finally initiated by a mid-1956 letter contract. Indicative of the uncertainties that surrounded the costly B-58 program, it took 5 definitive contracts to get less than half of the number of B-58s first ordered. Furthermore, most letter contracts ended with an unusually large number of supplements and amendments. The whole procedure eventually resulted in substantial amounts of termination costs.

Crucial events preceded Convair's achievement of its fourth B/RB-58 configuration. A development engineering inspection of Configuration III, held in mid-May, was a near fiasco. Not only did it endorse the poor results of past and concurrent wind tunnel tests, but SAC representatives insisted that the width of the configuration be altered to allow side-by-side seating of the pilot and the navigator-bombardier, a change considered totally impossible. But as the future of the B-58 appeared at its gloomiest, important research progressed. National Advisory Committee on Aeronautics aerodynamicist R. T. Jones at first had been mystified by the problems of airframes designed to the transonic area rule and tested at supersonic speeds. However, by the summer of 1954, he had ascertained that the position and the extent of the fuselage indentation was indicated by the aircraft's designed speed. This time, the Convair engineers did not question Jones' discovery. In August, Configuration III's fuselage was aligned to the modified transonic area rule for supersonic speeds (For a transonic body, the area rule is applied by subtracting from or adding to its cross-sectional area distribution normal to the air stream at various stations so as to make its cross-sectional area distribution approach that of an ideal body of minimum drag; for a supersonic body, the sectional areas are frontal projections of areas intercepted by planes inclined at the Mach angle).

Officially referred to as the B/RB-58A configuration, the new design featured other innovations. External wing fuel tanks were eliminated, the tail area was extended to 160 square feet, and the 4 engines were suspended by separate pylons, 2 under each wing. Convair was sure that the new B/RB-58A configuration would satisfy the performance requirements of the military characteristics of September 1953, but conceded that minor refinements might still be needed. The contractor also asserted that its new configuration was "the best design supportable by the current state of-the-art." However, delivery of the first test aircraft, already delayed by the program reorientation, would slip further if production was not authorized soon. Still in a quandary, the Air Force doubted that the new configuration would meet Convair's expectations, and refused to approve the model specifications. Even so, the Air Force in November asked ARDC to develop 2 important back-up systems, one for the Sperry bombing and navigation system, the other for the Emerson tail defense armament. That same month, after learning that Convair was about to reduce its labor force, the Air Force finally authorized limited fabrication of the new airframe.

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 After seeming to improve, the B/RB-58A's future once again appeared on the brink of disaster. A chief factor in the new crisis was SAC's dislike of the proposed aircraft. True to character, General LeMay had not changed his mind. At the urging of General LeMay, the Air Force in July 1934 instructed ARDC to initiate the research and development of an intercontinental bomber to succeed the B-52. This eventually promoted North American's ill-fated B-70, a bomber which had its origin in May 1933. Boeing was the recipient of the May 1933 study contract for a nuclear- or chemical-powered weapon system of intercontinental range. In 1933, the Air Force Council agreed that development of a nuclear-powered aircraft would not negate the requirement for a bomber using conventional fuel, and weapon systems 123 (nuclear-powered aircraft) and 1lOA (B-70) assumed their individual identities. Reminiscent of the B-38's case, North American in 1937 won the B-70 design competition over Boeing. In fact, based on the command's arguments of November 1952, a mid-1954 staff study, prepared by Maj. Gen. John P McConnell, SAC's Director of Plans, had excluded the B-58 from the 51-wing bomber force proposed for the period 1958-1965. At first unimpressed by the SAC omission, the Air Staff in late 1954 was having second thoughts. In early 1955, after General LeMay had directly confirmed to Gen. Nathan R Twining (Air Force Chief of Staff since 30 June 1953), that SAC wanted no B-58 aircraft for its operational inventory, the Air Force endorsed a thorough review of the program. A B-58 review board was appointed in February and chaired by Maj. Gen. Clarence S. Irvine, AMC Deputy for Production. The board faced the difficult task of recommending whether the B-58 program should be continued, modified, or canceled. General Boyd, one of the board's members, admitted that Convair's latest configuration might again not meet all requirements of the military characteristics, but still believed, that the B-58 should be built, even if the Air Force could not use it as originally intended. The B-58, the Wright Air Development Center Commander argued, represented major technical advances and, therefore, entailed technical uncertainties and the risk of high costs. These uncertainties would remain until "we have flown such an aircraft;" and "we must accept such a risk sooner or later."

The board studied anew other valued opinions that had been discussed in previous months. As already stated by Lt. Gen. Thomas S. Power, in charge of ARDC since April 1954, the B-58 was the first attempt to build a supersonic bomber (making in retrospect the production of supersonic fighters look relatively simple), and this task demanded extensive knowledge of aircraft materials and aerodynamic heating. The board's chairman agreed that from this standpoint the program was probably worth the money it had already consumed. Nevertheless, after an investment of 2 years and almost $200 million, no tangible achievements could be claimed. If the B-58 should now be canceled, the money would actually be lost, whereas another $300 million might suffice to build the 13 test-aircraft included in the reoriented program of April 1954. There were other pro-B-58 arguments. In his testimony before the review board, Convair's chief engineer maintained that, if allowed, the B-58 effort would produce the earliest and most inexpensive integrated weapon system, as well as a very outstanding bomber. At worst, he added, the B-58 would be superior to the existing B-47 medium bomber, a contention fully supported by General Power, who also noted that the aircraft might fulfill Tactical Air Command's requirements for a short-range attack bomber.

On 10 March 1955, the review board submitted its recommendations to the Air Force Council and to the Secretary of the Air Force. Aware that whatever suggestion was adopted could have far-reaching effects for years to come, the board took no chances. First, it emphatically recommended that the reoriented program be continued on a modified basis. Only 13 test vehicles would be ordered; they would be equipped from the start with J79 engines; and all back-up subsystems would be eliminated in order to reduce costs. The board observed that Convair could be asked to submit several new design proposals, one for a B-58 tactical bomber, one for special reconnaissance aircraft, and one for a long range B-58 interceptor. Finally, to complete developments vital to the design and operation of future strategic bomber weapon systems, the board did not exclude another possibility. Instead of limiting the program to 13 test-vehicles, it might be wise to buy also a number of B-58s for the operational inventory.

 

 

The Re-endorsement Of The B-58

 

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Development of 13 B-58 test aircraft, and nothing more, was approved by Secretary Talbott on 2 June 1955. The Secretary's approval carried stern, if not unexpected conditions. The Air Force wanted the program's costs to be reduced, and it wanted the aircraft to begin flying before November 1956. Furthermore, ARDC was to plan the aircraft's utilization in light of the Air Force's new objectives. In short, there no longer was any question of producing a high-altitude, manned strategic bomber and reconnaissance weapon system out of the B-58 test-aircraft. The program's only purpose was to promote research and development. SAC was pleased with the decision, but thought a 13-aircraft research and development program was larger than necessary. The Air Force needed to learn more about the aerodynamic problems of sustained supersonic flights at high altitudes, and it needed to test subsystems and components for future weapon systems. There were no delays in satisfying most of Secretary Talbott's demands. AMC had been studying the aircraft's cost problem for several months. An April estimate showed that $554 million would cover 13 B-58s, 31 pods, all engines, other government-furnished equipment and support, as well as Convair's fee. With the aircraft now strictly earmarked for research and development, various items could be deleted. This would save about $50 million and bring total costs close to the Air Force's tentative maximum. Convair seemed unabashed by the cut of its program, believing time would work in its favor. Hence, it went all out to match AMC's cost reductions, while projecting costs for the production of up to 500 aircraft. In mid-June, AMC authorized Convair to resume work on development engineering, tool fabrication, airframe parts, and the like. At month's end, the contractor felt confident it could fly a B-58 by November 1956, which it did. Meanwhile, personnel of the B-58 project office coordinated with representatives of various offices to identify non-essential B-58 subsystems and components, while preserving the development of any B-58 hardware that could benefit other projects. Included in such projects were the B-70, the nuclear-powered aircraft, and a tactical bomber logged as Weapon System 302A.

Scheduled for production in December 1952, an object of indecision in April 1954, practically cancelled 10 months later, and relegated to research and development in June 1955, the B-58 project was yet to undergo another major change. Abruptly, on 22 August 1955, the B-58 weapon system once again emerged as a production candidate. The decision, approved personally by General Wining, climaxed weeks of debates.37 General Putt, now Deputy Chief of Staff for Development, had helped to initiate the program and still professed the B-58 could be "a useful SAC tool." General Irvine, the new Deputy Chief of Staff for Materiel, and others on the Air Force Council shared General Putt's opinion. However, attempts to sway General LeMay failed. This failure most probably accounted for the production directive's unusual wording. The directive of 22 August 1955, calling for a wing of B-58s by mid-1960, was most specific in stressing the need for economy but made no mention of the wing's recipient or of SAC in particular.

Convair's Letter Contract AF33(038)-21250 of February 1951 was superseded in December 1955 by a definitive contract of the cost-plus-incentive-fee type. This gave Convair an additional $340 million for 13 aircraft, 31 pods, and all contractor-furnished equipment, bringing the contract's total value to about $540 million. The incentive fees depended on technical performance, weight control, and contractor adherence to cost and to delivery schedule. A second letter contract, AF33(600)-32841, issued on 25 May 1956, provided another $13.6 million to buy long-lead items and to maintain B-58 production at a minimum sustaining rate through October 1956. The Air Force planned to decide in the fall of 1956, if it should buy 17 more upper components (B-58 airframes), 17 powered bomb pods, 12 free fall bomb pods, 3 photo pods, and 3 electromagnetic data (ferret) pods. If it did, an extra $14.9 million of pre-production funds would be needed. This planning was in line with the August 1955 decision to buy a wing of B-58s. As all along understood, this could only be done if there was sufficient evidence that the project was viable.

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 The initial B/RB-58 made its first flight on 11 November 1956, taking off from the Convair Fort Worth facilities at Carswell AFB, Texas. A second flight on 14 November lasted one hour and was also described as successful. On both occasions, the maximum altitude reached was 30,000 feet, while the maximum speed did not exceed Mach 0.9. Supersonic speeds of Mach 1.6 and Mach 1.35, at altitudes of 35,000 feet, were first reached in a third flight on 4 December. The 3 flights were made by the same plane which, like several subsequent ones, was temporarily identified as a prototype (YB-58). In another departure from the usual, a characteristic that typified the B-58 program from the start, the YB-58 flights of late 1956 and early 1957 proved extremely important. Although testing had just begun, they undoubtedly influenced the Air Force's ensuing decisions.

By virtue of the weapon system concept adopted for the highly complex B/RB-58, the core of the testing program was altered. Also, the Air Force's insistence in 1952 that technological developments fit requirements inevitably affected testing. The Air Force decision of 1952 was one of the many difficulties and momentary contradictions that plagued the B-58. A few years before, when the GEBO study was initiated, USAF engineers asked for more realistic military characteristics and advocated state-of-the-art design compromises. As a result of such innovations, the flight testing program, an always thorough undertaking, acquired a new, time-consuming, and occasionally frustrating dimension. By chance, this coincided with the end of the 8-phase concept of testing, under which a new aircraft was designed, built, and tested first by the contractor, then at various ARDC centers, and finally transferred to a major Air Force command for operational utilization. The new testing program, although counting only 3 categories, did not degrade in any way the former program's scope. The Category I tests, begun by the contractor in November 1956, accounted for almost 3,000 hours of flight tests by March 1962, and the destruction of 1 aircraft (the fifth YB-58, Serial No. 55-664) in November 1959. Furthermore, pod drops, aerial refueling, and a few other special tests, properly part of Category I, were completed under the Category II program, which did not officially start before March 1959.

While the production decision of 22 August 1955 failed to indicate which command would use the new aircraft, it soon again became obvious that the B-58 lay in SAC's future. General LeMay's lack of enthusiasm for the B-58 put the aircraft within the reach of the Tactical Air Command. It was a fact, however, that the Convair project had been geared from the start to meet SAC's performance criteria, that the recently flown YB-58 basically remained a SAC-configured aircraft, one that would require the time-consuming incorporation of many costly changes if it were to fulfill the Tactical Air Command mission. In early 1957, Gen. Otto P Weyland, who headed the command, wanted a minimum of 2 B-58 wings, but the Air Staff disagreed. As technological difficulties increasingly impaired the B-70 development, the command became more involved with the B-58. Willing to believe in the B-58's potential for improvement, SAC in late 1956 was actually preparing to participate in the aircraft's forthcoming test program. In the spring of 1957, imminent budget decisions affecting SAC aircraft nearly shattered the command's fragile cooperation. By that time, the B-58 had established itself as the world's fastest jet bomber. The Mach 2 speed success of the B-58, cited as one of the reasons for decreasing the B-52 production rate, did not satisfy General LeMay. He quickly reasserted his early 1955 position that no B-58s were needed. New studies, General LeMay explained, showed that the B-52G with its programmed penetration aids would be superior to the production-improved B-58 and to any "better" B-58, such as the new B-58B configuration proposed by Convair. This was particularly true from the standpoints of cost effectiveness and availability. As for the B-70, General LeMay added, there was no doubt that it would provide substantial improvements over the B-52G. Therefore, "the B-58 should be limited to a test program. Funding for procurement or model improvement testing should not be provided." The Air Staff bluntly disagreed with General LeMay, stating that it was "most desirable" that SAC get a supersonic bomber at an early date and that the decision had been made to buy a limited quantity of B-58s for the SAC inventory. In a mollifying gesture, the Air Staff underlined that the United States had to protect its technological lead over the Soviets as well as the money already invested in the B-38 program. Also, the B-38 would improve through normal growth, and the program's funding requirements would not affect the B-70's prospects. Indeed, the proposed B-70 fell under a different time period. Nevertheless, by focusing attention on cost, the enormously expensive B-58 program did not help the cause of future high-performance manned bombers.

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Flight testing of the first 3 YB-38s, while accounting for some spectacular achievements,43 brought to light several problems. By the end of 1957, the YB-58s had attained a maximum speed of Mach 2.11 at altitudes over 30,000 feet; made 2 successful pod drops from 42,000 feet at Mach 2 speeds; maintained a speed of more than Mach 1.13 during 91 minutes, and zoomed without pod from a speed of Mach 2 at 50,000 feet to a speed of Mach 1.13 at 68,000 feet. The J79-GE-1 prototype engines, installed on the YB-38s pending certification of the J79-GE-3s, had a number of flaws ( Even though General Electric's progress had negated the temporary use of Pratt & Whitney J57s, the J79-5's 150-hour preliminary flight rating test was not expected before year's end). Malfunctions in the fuel system sloshed the fuel around when the YB-58 accelerated or slowed down, impairing the aircraft's stability. Afterburner problems caused intermittent yawing at supersonic speeds. Of greater concern were already noted acoustical and sonic fatigue problems as well as excess vibration in the YJ79-GE-1 engines. The acoustical and sonic fatigue difficulties affected the aft area of the fuselage and would cause testing restrictions unless promptly solved. Fatigue created cracks along the rivet lines in the forward section of the fuselage. Since the cracks appeared after less than 30 hours of flight, replacing the YJ79-1 engine by the J79-3 would worsen the problem because the more powerful J79-3 would increase the sound level 10 decibels above the level induced by the YJ79-1. The engine vibrations also might affect components of the electronic equipment, installed in the fuselage's aft section and in the aft portion of the various droppable pods that were programmed for the aircraft. There were other difficulties of varying importance. The brake system was not satisfactory. Because of inadequate heat dissipation after braking, tire failures were frequent following landing at high gross weights and high-speed taxi runs. The upward-type of ejection seat put in the aircraft was unsafe at high speed, due to insufficient thrust. Convair tests of a more powerful, rocket-type catapult seat identified problems of another kind. Other sorts of ejection seats were being considered, with misgivings. The Air Force and the B-58 contractor greatly favored a capsule-type escape system, under development by both the Martin Company and the Goodyear Tire and Rubber Company, but time was of the essence. Finally, slippage in the bombing-navigation subsystem development program portended a serious delay in the delivery of the initial equipment. This would retard the B-58 flight-test program, as would shortages of spares for both the YJ79-1 and -5 engines.

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In 1958, the B-58 program came under renewed scrutiny. The YB-58 could fly fast and high, but its range remained poor. With 1 refueling, the aircraft had a radius of 3,800 nautical miles; without refueling, the distance dropped by almost 40 percent. In addition, limited testing had already uncovered far too many problems. Configuration changes worked out between Convair and an 85-man team from ARDC, AMC, and SAC, would probably help a lot. Yet, changes were always costly. In August 1958, General Power, who had been heading SAC for over a year,45 told the Air Staff that the B-58's deficiencies were exaggerated, a common occurrence, he remarked, when a program was expensive and it became difficult to obtain financial support. Believing that a mixed force of B-52s and B-58s was the best way to replace the B-47s, General Power pointed out that the B-58's bombing and navigation system, already late, might become available sooner than expected since performance of the system's Doppler radar was getting better (General LeMay, although acknowledging in November 1957 that the mixed force concept was apparently in the offing, continued to question the wisdom of the proposed combination. The cost, from the standpoint of refueling operations alone, did not favor the B-58. It would take 1 tanker to refuel 1 of the new bombers, while 2 tankers could take care of 3 B-52s. Among the members of the Air Force Council, General LeMay stood alone in his opinion.). Agreeing with General Power that the B-58's early difficulties had been taken out of perspective, General White nevertheless cautioned that, should the program survive, the quantity of aircraft to be purchased in fiscal year 1959 would have to be reduced. The money thereby saved would pay for the most important changes and inevitable cost increases. By the end of December, photo reconnaissance, one of the B-58 program's initial requirements, was deleted. ME-1 pods and ground photo processing equipment, under contracts but yet to be delivered, were canceled, as were 45 ALD-4 ferret pods. On the positive side, the MB-1 free fall bomb pod was exchanged for a 2-component bomb and fuel pod. The new 2-component bomb and fuel pod had special merits. After the fuel had been used, the bomb and integral tankage would be dropped on a target, making the aircraft lighter for its return flight. Other approved changes included improved communications equipment (single side band/high frequency and emergency ultra-high frequency radios), encapsulated crew ejection seats (another new development), tactical air navigation (TACAN) electronics, and various minor improvements. However, as indicated by General White, one-third of the fiscal year 1959 B-58 procurement was cancelled. Letter Contract AF33(600)-36700, issued on 1 November 1957, called for 47 B-58s, bringing forecast procurement to a total of 77-30 so-called prototypes and 47 aircraft for the operational inventory. But the letter contract of November 1957 remained to be finalized, and its 47 aircraft were reduced to 33 on 26 September 1958.

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 Officially initiated in March 1959, but actually started on 15 February 1958, the Category II tests first assumed some of the flight testing normally conducted under Category I. This variance was primarily due to the November 1957 decision to consolidate the B-58 flight test program under the direction of the weapon system office. While the ARDC testing role was not changed significantly, the proposed using command (SAC, as already confirmed) was to participate in all testing, which was unusual. In another departure from past procedures, testing would be carried out as close as possible to the contractor facilities, which made Carswell AFB the obvious location. The Air Force believed that, among other advantages, this arrangement should reduce costs for logistical training and for support of the Convair technicians. As to the consolidated testing program, it should help to discover and solve development problems quicker. SAC's 3958th Operational Employment 'Ii'sting and Evaluation Squadron was activated on 1 March 1958, too late to monitor the beginning of the Category I tests. Nevertheless, the 3958th, its ARDC counterpart (the 6592d Test Squadron), and representatives from AMC and Convair soon were in place, constituting the test force that took care effectively of the Air Force Category II and III tests. The Category II tests were completed on 30 June 1960, after accumulating 1,216 flight hours that were reached in 256 sorties. Except for a few authorized deviations and some unexpected delays, the Category II testing progressed as planned. Tivo YB-58As, undergoing stability and control evaluation, were flight tested from Edwards AFB, California, and from Convair's Fort Worth airfield. Another test-aircraft, earmarked for climatic hangar evaluation, went directly from Fort Worth to Eglin AFB, Florida. Finally, the accelerated service test of the J79-GE-5 engine, after 330 flight hours under Category II, was completed under Category III, when SAC crews accumulated 170 additional hours of flight. From the practical standpoint, the Category II tests proved invaluable. Yet, they probably accounted in part for the program's last near-cancellation and final reduction. Seven test-aircraft were lost between December 1958 and June 1960, including 1 which disintegrated in flight on 7 November 1959.

 

 

Final Construction Of The B-58

 

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While testing was going on, the B-58's fate once again appeared uncertain. A Rand Corporation study, requested by the Air Staff, proved disappointing. Rand thought that the B-52 was superior to the B-58 because the Boeing aircraft could carry heavier payloads and had a longer range than the B-58. Of course, the corporation agreed that air refueling was a means to extend range, but pointed out that such recourse could be unreliable and expensive. Instead, the cheapest way to solve the dilemma would be to equip the B-47s with improved engines. Penetration was another factor to be considered in assessing the bombers. However, in Rand's opinion, the aircraft's penetrative ability was unimportant since enemy defenses of the near future would be so sophisticated that bomber losses would be high, regardless of speed. While these observations appeared valid, the Air Force did not want to alleviate its financial difficulties through retention of an improved but still obsolescing B-47 fleet. The Air Staff, therefore, asked Rand to review its original conclusions. This second round of deliberations served no purpose. Rand returned its study unaltered and without any further solution.

Meanwhile, dissatisfaction with the B-58 program grew. The correction of obvious combat deficiencies was slow, and it seemed almost certain that early inventory aircraft would be short of components and would have no high frequency radio or identification equipment. Some SAC officials were beginning to think that 2 wings of B-58s would be plenty since the aircraft would require greater tanker support than the B-52s. Also, the B-58s would not be able to fly at low level without extensive and costly modifications. Others at SAC wanted more B-58s, having faith in the follow-on B-58B that could be expected to materialize after production of the first 105 B-58As (test-aircraft included).

In May 1959, after re-endorsing continued production of the B-52s, as well as support of the B-70 and of the nuclear aircraft program, Genera! White refused to discuss the B-58's future. Just the same, the Air Force on 11 June 1959 began to plan the production and delivery schedules of 185 B-58Bs which, counting the B-58As, would increase the total to 290 aircraft, or enough to equip 5 wings. While at SAC, General LeMay had not liked the B-58A, and as Vice Chief of Staff, he did not change his opinion. The new model would be too expensive, its automatic equipment for low-level flight too complex. The B-58B was also due to provide increased range, speed, altitude, and external stores such as multiple free fall bomb pods, fuel tanks, and air-to-surface missiles.

On 7 July, the Air Staff eliminated the B-58B from the program and the B-58A itself again appeared to be in serious jeopardy. The 60 B-58As, under Letter Contract AF33(600)-38975 and due to be funded in fiscal year 1960, were first reduced to 32, then to 20. General Power tried to justify retaining the 290-aircraft program, but the Air Staff retorted that budgetary considerations were sometimes overriding and Secretary of the Air Force James H. Douglas confirmed that the B-58B was a dead issue. The B-58A came very close to following the B-58B's path. A saving factor again proved to be the money already invested in its development. Also, as noted by Secretary of Defense Thomas S. Gates, a redeeming virtue of the B-58A was its availability in the near term. Yet, even the latter justification was weakening. Time had been catching up with the B-58 weapon system, originally designed to perform against enemy targets of the 1958-1965 period. It was now obvious that the B-58A would not be available in quantity before 1962. Once at the top of the Air Force's priority list, the B-58A program had lost its urgency. In July 1960 (FY 61), Letter Contract AF33(600)-41891 was initiated, but the 30 aircraft and % BLU-2/B pods covered by the document were subject to cancellation. The Air Force reached a final decision in December 1960. The fiscal year 1961 purchase was retained, but the fiscal year 1962 procurement was deleted. SAC would receive 2 wings of B-58As and no more.

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Category II test results and several accidents postponed Category III testing to August 1960, a 6-month slippage. SAC did not want to start the Category III tests before correction of certain B-58 deficiencies. Electrical malfunctions, tire failures, difficulties with the flight control system, and possible structural weaknesses appeared responsible for a rash of recent crashes. Accident findings did not indicate any consistency in the causes, but the B-58 remained under flight restrictions and SAC would not accept the aircraft pending further investigation. Supersonic speed restrictions were raised to Mach 1.5 in March 1960, but only for the aircraft equipped with modified flight controls. Also, modifications required by SAC had to be made to improve safety. By mid-1960, some structural improvements were completed. The aircraft tail had been strengthened, critical side panels had been reinforced, and an ARDC ad hoc committee report was given to SAC. The report emphasized that there were no design deficiencies in either the aircraft or the flight control system, and that when all functioned, the systems met the specifications. The report also noted that SAC pilots had verified the B-58's good handling characteristics, but pilot training and high proficiency were necessary. In addition, maintenance and control personnel should be highly skilled since those areas could greatly affect B-58 operations.

Obviously satisfied with the committee's report, SAC on 1 August 1960 assumed executive management of the B-58, a function previously vested in ARDC. This marked the beginning of Category III testing, which was accompanied by a number of changes. For example, ARDC's 6592d Test Squadron was inactivated, and the squadron's aircraft and personnel were transferred to the 65th Bombardment Squadron (Medium) of SAC's 43d Bomb Wing. The B-58 Test Force was formally dissolved, although a small nucleus of ARDC people stayed at Carswell AFB to assist the 43d Wing through completion of the Category III tests.

SAC's 3958th Operational Employment 'li=sting and Evaluation Squadron had been a most important member of the now extinct test force. The 3958th was responsible for the proper development of a combat crew training program. It had to select and educate B-58 maintenance personnel and to create a cadre of flight crews that would serve as instructors in forthcoming combat crew training classes. In addition, the 3958th put together standard operating procedures for the future B-58 wings. When it took over, SAC's 65th Bombardment Squadron (Medium) found no fault in the 3958th's performance. Formal 3-month classes for combat air crews, started in mid-1960, encountered no personnel difficulties. Selected students, former B-47 pilots and regular officers for the most part, were highly qualified, with a minimum 1,000 hours of jet flying experience. Student navigators, with 500 hours of flying time on multi-jet aircraft, and defense system operators, with a minimum of 200 hours, were also excellent candidates. The 65th Combat Crew Training Squadron used Convair 2-place TF-102As to start training B-58 pilots and welcomed the August 1960 delivery of the first TB-58A trainer. As a rule, 3 TB-58 flights were made before a pilot could solo in a B-58A.

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 Even though nearly 1,879 combat crew training hours were flown as part of the Category III tests, the program had little to do with the 43d Bomb Wing's combat crew training. The Category III task was to evaluate the overall operational performance of the B-58A. Since the aircraft was a highly integrated, complex weapon system, the scope of the Category III tests was unusually broad. The tests covered all aircraft systems, passive defense, electronics, communications and the like, but also aerospace ground equipment and supply, for all these factors played a part. Still, because of its critical importance, a great portion of the Category III tests was devoted to the ASQ-42V Bombing-Navigation Electronic System. Ended on 31 July 1961, after the loss of 1 more B-58, Category III testing was credited with some 5,265 hours of flying time, of which about 945 hours were used strictly for testing. The rest was accumulated in various ways. A subtotal of 1,878 hours was flown to meet various Category III combat crew training objectives. The remaining hours, approximately 2,439 of them, encompassed maintenance test flights, the acceptance and delivery flights of new and retrofitted B-58As, airshows and record-breaking flights, and the hours flown for ferry missions.

B-58As, a first lot of 12, began reaching the 43d Bomb Wing at Carswell AFB in August 1960, but the 43d did not gain an initial operational capability until 1961, and waited until May of that year to get its full complement of 36 B-58s. In later years, this number was increased to 45, a total which included 4 of SAC's 8 TB-58As. The other 4 trainers went to SAC's second wing of B-58s. An unreliable bombing and navigation system, maintenance difficulties, shortages of ground equipment, and continuous involvement in the Category III tests combined to delay the 43d Bomb Wing's combat readiness. A second SAC wing, the 305th at Bunker Hill AFB, Indiana's received its first new bombers in May 1961 to start converting from subsonic B-47s to supersonic B-58s. SAC had earmarked the 305th as the first B-58 recipient. Initially, this was changed as a result of the new testing arrangement. Later, the 43d Bomb Wing's proximity to Fort Worth remained an important factor in view of the B-58's early operational problems. SAC expected that the 305th would have its full allocation of B-58s by May 1962. 'Iiventy KC-135 tankers were already in place at Bunker Hill. Aerial tests, completed in October 1959, showed that Boeing KC-135 tankers could refuel the B-58s. However, air refueling training and operations were limited at first because the B-58 search radar was not compatible with the refueling rendezvous equipment installed in the KC-135.

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 The first 47 B-58As did not have tactical air navigation (TACAN) electronics. The system, developed by the Hoffman Laboratories, was provided as government-furnished equipment and due to be retrofitted in most of these early planes. Also, the B-58As could not fly at low levels. Design changes to give the aircraft this added performance were being worked out. Prompt results could not be expected since the changes had only been authorized in mid-1959, when Convair's subsequent model series, the improved, low-level flying B-58B, was canceled. There were many other deficiencies of varying importance. The aircraft's ejection seats were still unsatisfactory. Development of a capsule-type of escape system for a single crewman, now handled by the Stanley Aviation Corporation, was progressing well. However, the capsule's stability remained marginal after ejection, thereby preventing Convair from incorporating the capsule during production. This meant that all B-58s would have to be retrofitted, a task started in late 1962. The B-58 was the first aircraft with individual escape capsules for emergency use at any speeds. This escape system could rocket the crew to safety from anywhere between ground level at 120 knots and 70,000 feet at Mach 2.2. The capsule, fitted with clam-shell doors, was pressurized. Once sealed and ejected, it stabilized itself and descended by parachute. It was equipped with a flotation system that deployed automatically in the event of a landing on water. The capsule was not large, restricting the size of the crew. Even so, the capsule consumed space and made the B-58'5 small crew compartments more cramped. Meanwhile, another retrofit project was taking place. B-58As were re-equipped with sturdier wheels and new tires, marking the end of at least one long-standing problem. The loss of a B-58A on 16 September 1959 (totally destroyed by fire after an aborted take-off from Carswell) was directly attributed to tire failure, followed by disintegration of the wheel. But this was just a beginning. In mid-1961, following completion of a 6-month study, the Air Staff decided that much more would have to be done to enhance the B-58A's performance. It also approved modification of existing B-585 (about 70 of them) to allow the aircraft to carry a greater variety of weapons, 4 of which would be transported externally. Subsequent B-58As would be so equipped on the production line.

Significant modifications were initiated in November 1962, under the code name of Hustle Up, a 2-phase project accomplished in Fort Worth by the prime contractor, and in San Antonio, Texas, by technicians of one of the Air Force Logistics Command's air materiel areas. The first phase of Hustle Up covered 59 B-58As; the second phase, only 36. However, Phase II also modified 76 pods of various configurations. Modification kits, including aircraft kits, pod kits, training kits and kit spares, were acquired through special contract at a cost of $6.1 million and used by both the Convair people and personnel of the San Antonio Air Materiel Area. Retrofitting the escape capsules and installing multiple weapons proved to be the most extensive modifications covered by Hustle Up, which was completed in May 1964. Meanwhile, contrary to SAC's hope that the development program would yield a trouble-free aircraft, the B-58A weapon system was again encountering more than its share of difficulties. TWo fatal accidents and 30 in-flight "incidents" between March and September 1962 imposed new flight restrictions and generated another major modification program. This program, centering essentially on the aircraft's flight control system, was also conducted in several phases. Phase I put a gang bar on yaw damper switches, but provided minimal improvements. Phase II (re-designated Phase I, following the May 1963 completion of the program's initial phase) modified the mach altitude repeater and improved the unreliable amplifier computer assembly circuitry, thereby allowing the B-58As to fly again at speeds up to Mach 1.65. Started in April 1964, the new Phase I closed before year's end, as scheduled, with 13 B-58s of the 305th Bomb Wing being so improved while undergoing the last part of the Hustle Up modification program. The next phase (Phase III, now known as Phase II) did not fare as well. It was due to further improve the flight control system, which in turn would allow the B-58A to use its desired Mach 2 speed. Many costly changes were involved, totaling $30 million. Furthermore, this phase was not intended to take place before the fall of 1966.

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 Besides its obvious shortcomings, the B-58A was plagued from the start by a very serious problem. Its bombing and navigation system (the AN/ASQ-42) was far less reliable than that of the B-52 and the B-47. The problem, confirmed during Category III testing, did not lend itself to easy solutions. The AN/ASQ-42 was extremely complex. Its electronic signal loops were generated and circulated within several interconnected electronic "black boxes." Thus, malfunctions were hard to track down, since it was difficult to identify which black box was primarily responsible for the failure. By 1965, the AN/ASQ-42 had become an old problem, with no remedy in sight. Occasionally, malfunction causes were identified, but more often, they were merely suspected or totally undetermined. That the AN/ASQ-42 system had to be made to work well was obvious. Tb begin with, it was SAC's most sophisticated bombing system. Also, once fully operational, the AN/ASQ-42 would allow the B-58A to find and bomb any target, be it at high-altitude/supersonic or low-altitude/subsonic speeds. Yet, improvement proposals, submitted by various contractors in September 1965, were found unacceptable. They did not meet requirements, carried no guarantees, and fluctuated around $70 million, twice the anticipated cost. In any case, circumstances beyond SAC's control raised doubts about the AN/ASQ-42's potential performance.

In December 1965, Secretary of Defense Robert S. McNamara directed phaseout of the entire B-58 force by the end of June 1970. The decision followed completion of a study of the comparative costs and performance of a proposed bomber (the FB-111A) and existing B-52 and B-58 strategic aircraft. Secretary McNamara also publicly announced that the FB-11 IA would be built. The FB-111A medium-range strategic bomber, like the B-58, was built in Fort Worth by the Convair Aerospace Division of the General Dynamics Corporation. The FB-111A, a modified version of the F-111A tactical fighter, was part of an interrelated and highly controversial program. The new bombers, along with improvement of the Minuteman and Polaris missiles and modernization of the B-52, would enhance strategic deterrence and make longer retention of the B-58s superfluous. In addition, Defense officials deemed necessary budget cuts another valid factor. Appalled by the decision, SAC pointed out that the B-58A, after coming off production with many weaknesses, was well on its way to becoming a sound, effective weapon system. Stressing the declining number of manned bombers, SAC in the ensuing 2 years kept pressing for retention of the B-58s, at least until June 1974. But the decision of 1965 was to prove unshakable. On 21 February 1968, General McConnell, Air Force Chief of Staff since I February 1965, reaffirmed before the Senate Armed Services Committee that the entire B-58 fleet would be phased out before June 1970. And while it did not spell the end of the modifications programmed at the time, the overall B-58 improvement program was immediately affected.

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Modifying the B-58A for low-level flying would be a meager improvement if the aircraft were not properly equipped. SAC insisted from the start that the B-58A, to be truly effective at low levels, needed a terrain-following radar to penetrate increasingly fierce enemy defenses. Prototype development of the radar, approved with misgiving in view of the entire venture's cost and technical hazards, was the first casualty of the B-58's early phase-out. It was canceled in late 1965, when SAC settled for a reliable radio altimeter and a forward-looking visual sensor (day/night television) system. This much less expensive project, installation and modification included, was completed in early 1969. Another modernization project had an even more disappointing fate. The B-58A's electronics countermeasures systems, never updated since the aircraft's production, were nearly obsolete. Should the high-altitude B-58A be committed to combat, it would be extremely vulnerable to surface-to-air missiles, such as the SA-2s. Several contemplated modifications had been held in abeyance pending the development of better techniques. One of them, modification 1180, had been approved in mid-1966 and would give the B-58A a new version of the ALQ-16 track breaker. However, when flight tested in 1968, this component did not work. As to other penetration aid improvements, they had not even reached the testing stage. Ongoing talks that the B-58s might, after all, be retained through 1974 kept the electronic countermeasures improvement projects alive until the end of 1969. When the B-58's longer retention did not materialize, all penetration aid modifications were canceled.

Retirement of the B-58 by mid-1970 meant that modifications, even if approved, would be deleted if not funded by mid-1968. Aware that several B-58 problems would take a long time to solve, SAC asked for a waiver of the so-called 2-year utilization rule, but the request was denied. Nevertheless, many of the modifications, pursued all along by SAC, came to fruition. After numerous setbacks, a solution was found for the B-58A's erratic flight control by adding a redundant yaw damper to the system. Retrofit kits were purchased in 1967, and the installation undertaken in May 1968 progressed smoothly. During the same period, an improved version of the AN/ASQ-42, flight tested in mid-1967, proved successful. Production of the improved system, approved on 27 September 1967 and funded within prescribed time limits, foretold no problem. Technical data and the delivery of spare parts had been included in the necessary contract. Moreover, installation of the system, as started in May 1968, was not expected to disrupt significantly SAC's operational plans. Another modification had also been sought by SAC, almost since the aircraft had become operational. The command wanted the B-58A crew to be capable of starting their engines without having to depend on pneumatic ground starting carts. Equipping the aircraft with a cartridge self-starter would allow it in an emergency to take off from dispersal, post-strike, and other remote bases. Yet the project had been handicapped from the start. It was approved, canceled, re-approved, modified, and constantly hampered by technical difficulties. SAC, nonetheless, won its case and the B-58 was equipped with a cartridge self-starter. The installation began on 7 May 1968, approximately 6 months after all B-58s had exchanged their J79-5B engines for improved J79-5Cs.

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In mid-1965, the San Antonio Air Materiel Area recommended a program of inspect and repair as necessary (IRAN) for a scheduled, comprehensive depot-level inspection of the B-58. So far, San Antonio and SAC had taken care of the aircraft's difficulties as they arose. However, increasingly serious problems were being uncovered. The plumbing and wiring of the B-58As and TB-58As were deteriorating, and the aircraft were also showing signs of structural fatigue and corrosion. SAC had no objections to the IRAN program proposed for the B-58, a routine procedure for most aircraft. Nor did it object to the 36-month cycle favored by the materiel area. However, the command qualified its approval. Since fuel leaks indicated that corrosion was further along than estimated, corrective action could not await the January 1966 implementation of the IRAN program. Also, B-58s of the 43d Bomb Wing should be treated first, which they were. Initially conducted from Convair's Fort Worth facilities, the IRAN program was moved in mid-1967 to James Connally AFB, near Waco, Texas. There were no other changes. The B-58 modification/IRAN program was thorough. Major tasks included removal of all releasable panels; inspection and repair of the aircraft's primary and secondary structures; and inspection and repair of all wire bundles and cables, hydraulic lines and fittings, and air conditioning and pressurization duct components. The program also included bench testing and calibration of all electronic units, removal and overhaul of landing gear assemblies, and repair and treatment of corroded areas. This work consumed 16,000 man-hours. In 1967, the cost per aircraft totaled $181,000; $201,000in 1968.

Production ended in the fall of 1962, with the last 3 B-58s being delivered on 26 October, 1 month ahead of schedule. All B-58s were built at the contractor's Fort Worth plant. The Air Force accepted 3 B-58s in FY 57; 8 in FY 58; 16 in FY 59; 11 in FY 60; 30 in FY 61; 33 in FY 62; 15 in FY 63 (the last 3 in October 1962). Research, development, evaluation, and testing cost, $1.4 billion. Cost per aircraft was: $12.44 million: Airframe, $6,447,702; engines (installed), $1,117,120; electronics, $1,294,791; ordnance, $26,674; armament (and others), $3,555,573.63

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