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It was a YF-12A that made an emergency landing at Castle AFB, and royally teed off SAC by insisting on going into the ADC 456th FIS area for repairs instead of the base Transit Aircraft Center.

• 6934/ #1001
  • Lost on 14 August 1966 (some sources say 14 July 1966), at Edwards AFB, CA. Seriously damaged during a landing at Edwards. The rear half of the YF was fused with the front half of the SR-71 static model to make the SR-71C #64-17981.

   

• 6935/ #1002
  • On display in Annex of USAF Museum, Wright-Patterson, OH

   

• 6936/ #1003
  • Lost on 24 June 1971, Edwards AFB, CA. While in the traffic pattern at Edwards AFB, a fire broke due to fuel line rupture, while on final the entire aircraft became engulfed in fire and both crew members ejected safely, Lt. Col. Ronald Layton, and Major Bill Curtis.

By Joe Baugher

 

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The Lockheed YF-12A Mach 3 interceptor of the mid-1960s had its origin in the top-secret A-12 spy-plane which had been designed by Lockheed at Central Intelligence Agency request as a successor to the U-2 spy-plane.

The basic U-2 concept dated back to 1954, but as early as 1957 the CIA had concluded that the high-flying U-2 might soon be vulnerable to missiles and would have to be replaced with something more advanced if reconnaissance missions over Soviet territory were to continue unmolested. The CIA wanted an aircraft with a maximum cruising speed of over Mach 3 which could operate at altitudes exceeding 80,000 feet, which should render the aircraft immune from interception by any known threat. The Agency gave the project the code name Project Gusto.

After some preliminary studies, both Convair and Lockheed were given funds to carry out detailed design studies. Even before this study had gotten underway, the Lockheed Skunk Works team (headed by the famous engineer Clarence R. "Kelly" Johnson) had already been trying to interest the government in a U-2 replacement, and had been experimenting with advanced propulsion concepts involving a turbojet powered by a liquid hydrogen/liquid oxygen mixture, but these ideas were abandoned as being impractical at an early stage in the process.

On August 29, 1959, Lockheed was officially declared the winner of the contest and was awarded a limited development contract for design, wind-tunnel testing, and the construction of a mockup. The project came to be known under the deliberately deceptive codename OXCART. The designation A-12 became associated with the project, which is sort of odd, since such a designation was not consistent with either the official USAF or the internal Lockheed company designation scheme. In some documents, the various Skunk Works proposals that were at various times being given consideration during the initial design phase bore the in-house design numbers of A-1 through A-12, and the A-12 designation was supposedly chosen because the 12th design was the one that was eventually produced. However, Lockheed's designer Clarence L. ("Kelly") Johnson seems to have referred to the aircraft as A-11 rather than A-12. To make things even more confusing, the designation A-11 was used by President Lyndon Johnson when he officially revealed the existence of the project in February of 1964, but this may have have simply been a slip of the tongue on Lyndon's part. It is possible that the CIA came up with the A-12 designation itself. The OXCART document claims that the aircraft WAS originally designated A-11, but was later re-designated A-12 as a result of changes that had been introduced to make the aircraft capable of achieving a lower radar cross section, with the designation A-11 later becoming associated with the YF-12A interceptor version.

On September 3, 1959, the CIA authorized Lockheed to proceed with antiradar studies, aerodynamic structural tests, and engineering designs, and on 30 January 1960 the Agency gave the green light to produce 12 aircraft. Serial numbers were 60-6924/6935 . Later, three more single-seaters (60-6937/6939) and nine two-seaters (60-6940/60-6948) were ordered. The aircraft were to be tested at a secret test site in Nevada know as Groom Lake or "Area 51", which had originally been developed for the U-2.

The technical challenges faced were enormous. The aircraft was to operate at sustained speeds that were nearly three times greater than that of existing aircraft, and was to be able to cruise at altitudes above 80,000 feet.

The Pratt and Whitney Division of United Aircraft Corporation was chosen to develop the propulsion system. The J58 engine was based on a 1956 project known as Suntan, which was designed to produce a Mach 2.7 hydrogen-fueled aircraft. This project was cancelled in 1959. It was also based on the Pratt & Whitney JT9 single-spool high-pressure ration turbojet rated at 26,000 lbs.t. in afterburning, which had been designed for a US Navy attack aircraft which had been cancelled. The design team came up with a unique idea of a variable-cycle engine (later known as a bleed-bypass engine) in which air was extracted from the fourth stage of the nine-stage single-spool axial-flow compressor and fed through a series of bypass ducts and reintroduced into the turbine exhaust near the front of the afterburner. This reduced the exhaust gas temperature and produced almost as much thrust per pound of air as the main flow that had passed through the main part of the engine.

To minimize stalling of the front stages of the rotor blades at low engine speeds, moveable inlet guide vanes were incorporated. They changed from axial to a cambered position in response to the main fuel control.

When operating at high cruising speeds, the turbine inlet temperatures reached over 2000 degrees Fahrenheit, which required the development of a new type of fuel, known as JP7. It had a much higher ignition temperature than JP4. It required the use of a new type of chemical ignition system based on a fluid known as tri-ethyl borane.

The A-12 was to be built almost entirely of heat-resistant titanium alloys, chosen because of their relatively light weight and great strength. However, titanium is relatively costly and is a very hard metal which is very difficult to mill and machine. Consequently, its use as an important aircraft component required the development of entirely new technologies. The Titanium Metals Corporation was chosen as the primary contractor for the metal. Quality control is especially difficult during titanium alloy manufacture--even the most minute of impurities can render the batch into a useless brittle metal which shatters under the weakest of stresses. Of the early deliveries from Titanium Metals Corporation, some 80 percent had to be rejected as being flawed, and it was not until 1961 that quality became consistently satisfactory.

Since the airframe would undergo aerodynamic heating during sustained supersonic cruise, significant thermal expansion was expected. In order to accommodate for this thermal expansion, a set of chord wise corrugations were added to the central portion of the wing, and expansion gaps were provided between some panels.

When operating at high cruising speeds, the turbine inlet temperatures reached over 2000 degrees Fahrenheit, which required the development of a new low-volatility type of fuel, known as JP7. It had a much higher ignition temperature than JP4. It required the use of a new type of chemical ignition system based on a fluid known as tri-ethyl borane. During protracted operations above Mach 3 it was estimated that the fuel tanks would heat up to about 350 degrees Celsius, and the tanks themselves had to be rendered inert with nitrogen gas to prevent fuel explosions in the tank because of the heat. Special lubricating oil had to be developed for operation at 600 degrees F., and contained  diluents in order to remain fluid at operation below 40 degrees.

The wing was of short-span modified delta planform, supplemented by long fuselage chines which extended forward all the way to the nose. These chines had the beneficial effect of contributing to yaw damping at high speeds and also provided additional space for fuel and equipment. The blending of the fuselage, chines, and wings also helped to reduce the A-12's radar signature over that of other aircraft.

The engines were housed in long nacelles that were mounted at approximately mid-span on each wing. The nacelles were provided with a complex inlet and ejector system, with the inlets contributing as much as 60 percent of the total engine thrust at Mach 3. During takeoff, suck-in doors mounted on the side of the engine nacelles open up to admit additional air to the engines. The engines contained large conical-shaped inlet spikes which could be pushed forward or backwards to adjust for aircraft speed. During takeoff and low-speed flight, the inlet spikes were fully forward, but as speed increased, the inlet spikes were pulled to the rear a maximum of 26 inches so that the shockwave could be maintained at the inlet throat.

A vertical tail was mounted above the rear of each engine nacelle. The vertical tails were all-moving, and were canted inwards. Fixed fins were mounted underneath each nacelle, and a fin was mounted underneath the rear fuselage which could be folded aside for takeoffs and landings. The landing gear was fairly conventional, with the three-wheeled main members retracting inwards into bays in the fuselage and the nose-wheel retracting forward into a bay in the forward fuselage.

A small Skunk Works engineering team worked with engineers from Pratt & Whitney and were able to construct the first prototype in only 22 months. In December 1961, the first A-12 (article number 121, USAF serial number 60-6924) was trucked from Palmdale, California to the secret base at Groom Lake, Nevada, so chosen that it would be well-distant from prying eyes. However, the J58 engine was still not ready, and it was decided that a pair of Pratt & Whitney J75 engines would be used for the initial test flights.

Finally, on 26 April 1962, aircraft 121 was ready. On that day, Lockheed test pilot Louis Schalk took it for an unofficial, unannounced, maiden flight lasting some 40 minutes. The first official flight took place on April 30, 1962, piloted again by Louis Schalk. The aircraft broke the sound barrier on its second official flight, 4 May 1962, reaching Mach 1.1.

Aircraft No. 122 arrived at Groom Lake on 26 June, and spent three months in radar testing before engine installations and final assembly. Aircraft No. 123 arrived in August and flew in October. Aircraft No. 124, a two-seated version intended for use in training OXCART project pilots, was delivered in November. It was to be powered by the J58 engines, but delivery delays and a desire to begin pilot training prompted a decision to install the smaller J75's. The trainer flew initially in January 1963. The fifth aircraft, No. 125, arrived at the area on 17 December.

On October 27, 1962 a U-2, flown by a Strategic Air Force pilot on a SAC-directed mission, was shot down by a surface-to-air missile while flying over Cuba in search of Soviet missile sites. This raised the dismaying possibility that continued manned, high-altitude surveillance of Cuba might become too dangerous, and the OXCART program suddenly assumed greater significance and its achievement of operational status became one of the highest national priorities.

By the end of 1962, speeds of Mach 2.16 and altitudes of 60,000 feet had been achieved, still with the lower-powered J75 turbojets, although some flights did take place with just one J58 installed. However, by the end of January 1963, ten J58 engines were available, and the first flight with two of them installed occurred on 15 January. Thenceforth all A-12 aircraft were fitted with their intended propulsion system.

In the meantime, an entirely new mission had appeared for the OXCART. In September of 1959, the USAF had cancelled its contracts for the North American F-108 Rapier, a Mach 3-capable aircraft that had been proposed as the USAF's next-generation interceptor to replace the F-106. The reason given for the cancellation was that the F-108 was simply too expensive for the USAF, now that the primary Soviet threat to the US mainland was its battery of intercontinental range ballistic missiles rather than its fleet of long-range bombers. Nevertheless, Lockheed thought that the Air Force might still be interested in a less-costly F-106 replacement should the Soviet bomber fleet ever again be perceived as a significant threat. Lockheed suggested to the Air Force that the A-12 design would make a good platform for a Mach 3+ interceptor, and might make a good replacement for the F-106 at a more reasonable cost than the abortive F-108 Rapier. Sufficient interest was expressed by the Air Force that in October of 1960 they gave Lockheed permission to modify three A-12 Airframes (the 7th, 8th, and 9th) to interceptor configuration. The designation AF-12 was initially assigned to this project. Serial numbers were 60-6934/6936. One of the unsaid reasons for the Defense Department approval of the interceptor project was perhaps that it might make a good cover for the real CIA-supported intelligence-gathering nature of the project. In September of 1962, these three aircraft were secretly assigned the designation YF-12A in the new Defense Department tri-service scheme..

The YF-12A was quite similar in overall configuration to the A-12 from which it was derived. It differed from the A-12 primarily in having a second crewman in a position immediately behind the pilot This second crewman was added to operate the extremely powerful and capable Hughes AN/ASG-18 pulse Doppler fire control radar, which had originally been developed for the F-108 Rapier. The AN/ASG-18 was installed in the extreme nose of the aircraft, with the forward chines being cut back to accommodate the 40-inch radome. The ASG-18 radar supposedly had a search range as great as 500 miles. Infrared sensors were installed in the forward edges of the cut-back chines.

The YF-12A also differed from the A-12 in having armament. This armament consisted of four Hughes AIM-47A Falcon air-to-air missiles housed internally in chine bays that had previously been used to carry the reconnaissance equipment. The AIM-47A had originally been known as the GAR-9 and (like the ASG-18 radar) had originally been intended for the F-108 Rapier. When fired, the Falcon missiles were explosively ejected from their bays, and their rocket motors were fired. Powered by a storable-propellant liquid-fuelled rocket, the AIM-47A had a maximum speed of Mach 6 and an interception range of 115 miles. It had a launch weight of about 800 pounds. The missile relied on semi-active radar homing for midcourse guidance to the immediate vicinity of the target, homing in on reflections off the target resulting from transmissions from the huge ASG-18 radar. However, it used terminal infrared homing for the final run in to the target. The AIM-47 could carry a 250-kiloton nuclear warhead.

Early wind-tunnel testing indicated that there would be directional stability problems resulting from the revised nose and cockpit configuration, and a large folding fin was mounted under the aft fuselage and two shorter fixed fins were mounted underneath each nacelle.

The first YF-12A (60-6934) took off on its initial flight on August 7, 1963, piloted by James D. Eastham. It was equipped with a streamlined camera pod mounted underneath each engine nacelle for photographing AIM-47 missile launches. Three YF-12As were built. Serials were 60-6934/6936.

While on a routine INS test flight with A-12 number 123 on May 24, 1963, CIA detachment pilot Kenneth Collins entered some clouds. Water vapor froze in the pitot tube, giving an erroneous airspeed reading. With the airspeed indicator giving the wrong reading, the aircraft stalled. Collins ejected safely from the aircraft after it entered an inverted flat spin. The aircraft crashed 14 miles south of Wendover, Utah. The wreckage was recovered in two days, and people at the scene were identified and requested to sign secrecy agreements. A cover story for the press described the accident as occurring to a F-105, and is still listed in this way on official records.

Although this particular loss was ultimately traced to a problem that was easily corrected, it nevertheless precipitated a policy problem within the Agency. With the growing number of A-12s flying out in the western desert, the CIA felt that there was a danger that the OXCART project's cover could be blown at any moment. Although the program had gone through development, construction, and a year of flight testing without attracting any public attention, the Department of Defense was experiencing increasing difficulty in concealing its participation in the OXCART program because of the delays and cost overruns that had increased the rate of expenditures to such an extent that they might eventually get large enough to attract unwanted attention from congressional budget oversight committees. There was also a realization that the technological data would be extremely valuable in connection with feasibility studies for the SST. Finally, there was a growing awareness in the higher reaches of the aircraft industry that something new and remarkable was going on. Several commercial airline crews had reported sighting unidentified aircraft in flight. The magazine Aviation Week indicated to its readers that it was vaguely aware that there was some rather unusual project going on at the Skunk Works at Burbank.

Soon after President Lyndon Johnson took office following the assassination of President John Kennedy on November 22, 1963, he was briefed on the OXCART project and directed that some sort of cover announcement be prepared for the spring of 1964. On February 29, 1964, President Johnson announced that "The United States has successfully developed an advanced experimental jet aircraft, the A-11, which has been tested in sustained flight at more than 2,000 miles per hour and at altitudes in excess of 70,000 feet. The performance of the A-11 far exceeds that of any other aircraft in the world today. The development of this aircraft has been made possible by major advances in aircraft technology of great significance for both military and commercial applications. Several A-11 aircraft are now being flight tested at Edwards Air Force Base in California. The existence of this program is being disclosed today to permit the orderly exploitation of this advanced technology in our military and commercial program."

The "A-11" referred to by President Johnson had been the original design designation for the aircraft first proposed by Lockheed prior to the adoption of stealth technology for the design. Subsequently, it became the design designation for the YF-12A interceptor version. The parallel OXCART project remained black. Although there was at the time considerable speculation about a Central Intelligence Agency role in the A-11 development, this was never acknowledged by the government.

The President also said that "the A-11 aircraft now at Edwards Air Force Base are undergoing extensive tests to determine their capabilities as long-range interceptors." This statement was untrue, since at the time the President spoke, there were no A-11's actually at Edwards and there never had been. Project officials were aware that some sort of public announcement was about to be made, but they had not been told exactly when. Caught by surprise, they hastily arranged to fly two of the Air Force YF-12A's to Edwards to support the President's statement. Thenceforth, while the OXCART continued its secret career out at the Groom Lake site, the A-11 performed in its YF-12A guise at Edwards Air Force Base under a considerable glare of publicity.

In 1964, Kelly Johnson was awarded the prestigious Collier trophy for his achievements in the YF-12A project, becoming the first person in history ever to be honored by this recognition twice.

On April 16, 1964, the first airborne AIM-47 missile separation test was conducted. Unfortunately, the missile's nose-down position was not correct, and had the missile's rocket motor actually fired, the aircraft would probably have shot itself down. On March 18, a YF-12A successfully engaged a Q-2C target drone at 40,000 feet while the interceptor was flying at Mach 2.2 at an altitude of 65,000 feet. The first powered launch was undertaken on March 18, 1956. Six out of seven AIM-47 tests resulted in hits, including One fired from an altitude of 75,000 feet and a speed of Mach 3.2 against a target approaching head-on at 1500 feet.

The three YF-12As served initially with the 4786th Test Squadron at Edwards AFB. The USAF was sufficiently impressed with the performance of the YF-12A that on May 14, 1965 they ordered a total of 93 definitive F-12B aircraft into production and Congress had voted $90 million toward the project. However, Secretary of Defense Robert McNamara saw no need for the F-12B and refused to free up the money, the reason being given that the expanding war in Southeast Asia was consuming all available funds in the USAF budget. McNamara chose instead to purse the cheaper "F-106X" interceptor. The YF-12As served primarily in various and sundry operational evaluation projects throughout the remainder of the 1960s.

Even though there was to be no production of the YF-12A, the three prototypes carried out an extensive program of flight research with the Air Force. On May 1, 1965, the following world records were set by YF-12A 60-6936:

• 15/25 km closed-circuit speed record: 2070.102 mph. Piloted by Col Robert L. Stephens and LtCol Daniel Andre. This counted as a new world absolute speed record and was the first record to exceed 2000 mph.
   
• Sustained altitude record of 80,257.86 feet. Piloted by Col. Robert L. Stephens and LtCol Daniel Andre.
   
• 500-km closed-circuit speed record: 1642.042 mph. Piloted by Majors Walter F. Daniel and Noel T. Warner.
   
• 1000-km closed circuit speed record: 1688.891 mph. Piloted by Major Walter F. Daniel and Capt James P. Cooney.

In December of 1969, YF-12A 60-6935 was handed over to NASA at the Dryden Flight Research Facility. 60-6936 was delivered to Dryden a year later.

While serving with NASA, YF-12A 60-6936 was lost on June 24, 1971 when USAF pilot Lt. Col Ronald J. Layton and WSO Maj. William A. Curtis were forced to eject after the plane caught fire due to a fuel line fatigue failure during approach to Edwards. Both crewmembers survived.

In November of 1979, its research program being completed, YF-12A 60-6935 was donated to the USAF Museum at Wright Patterson AFB in Dayton, Ohio. It is now permanently on display at the museum. This is the only YF-12A that survives.

The prototype YF-12A (60-6934) was briefly placed in storage following the end of its flight test program. In 1969, it was taken out of storage and cut up and used for parts in the construction of SR-71C 64-17981, a two seat trainer.

There was actually a FOURTH YF-12, sometimes referred to as a YF-12C. Its serial number is 60-6937. However, Aerofax claims that this aircraft is really SR-71A serial number 64-17951 that had been retained by Lockheed until 1969. In that year, Lockheed turned the aircraft over to the USAF. For some reason, the Air Force then changed its designation to YF-12C and assigned it a new serial number (60-6937) prior its delivery to NASA in July of 1971. NASA returned the plane to the Air Force in December of 1978. It was later put on outdoor display at Edwards AFB. The latest information I have is that the plane is now with the Pima Air Museum of Tucson, Arizona. Anyone have more current information on its whereabouts?

The A-12s continued on to become operational spy planes and carried out numerous reconnaissance missions, the details of which are still highly classified even today. The OXCART document (assuming it to be genuine) gives a few of the details. The OXCART fleet was taken out of service and placed in storage in the late 1960s.

In February 1963, Lockheed undertook redesign of the basic A-12 with additional fuel tanks, broader forward nose chines, and the provision for in-flight refueling and a seat for a second crewman. This eventually emerged as the SR-71.

Specification of Lockheed YF-12A:DIAGRAMS

Engines: Two Pratt and Whitney J-58 (JT11D-20B) turbojets, each rated at 32,500 lb.s.t. with afterburning. Performance (estimated): Maximum cruise speed: 2110 mph at altitude (Mach 3.2) Maximum operational ceiling: 85,000 feet Maximum un-refueled range: 2500 miles Dimensions: Length: 101 feet 7 inches, Wingspan: 55 feet 7 inches. Height: 18 feet 6 inches. Wing Area: 1795 square feet Weights: 60,730 pounds empty, 127,000 pounds maximum takeoff. Armament: Four Hughes AIM-47A air to air missiles which are explosively ejected downwards from paired tandem missile bays.

Sources:

1. Lockheed Aircraft Since 1913, Rene J. Francillon, Naval Institute Press, 1987.
    
2. The American Fighter, Enzo Angelucci and Peter Bowers, Orion Books, 1987.
    
3. The Illustrated Encyclopedia of Aircraft Armament, Bill Gunston, Orion Books, 1988.
    
4. Lockheed Blackbirds, Anthony M. Thorborough and Peter E. Davies, Motorbooks International, 1988.
    
5. The OXCART Story, Thomas P. McIninch, available from Skunk Works Digest.
    
6. Lockheed A-12/YF-12/SR-71, Paul F. Crickmore, Wings of Fame Vol 8, 1997.

By Joe Baugher

 
 

Lockheed YF-12A (60-6936)

 

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Lockheed built three YF-12A aircraft as prototypes of a long range, high-speed interceptor version of the A-12 spyplane. They were armed with AIM-47 air-to-air missiles, and incorporated the Hughes AN/ASG-18 fire control system. The airplanes were initially flown at the Area 51 test site at Groom Lake, Nevada, in 1963. They were transferred to Edwards AFB, California, in June 1964.

The number three YF-12A (60-6936/Article 1003) made its first flight at Area 51 on 13 March 1964, piloted by Robert Gilliland. On 3 April, Jim Eastham and John Wallace took 936 up for the very first sustained heat soak of a "Blackbird." The test card called for the airplane to cruise at Mach 3.16 for 10 minutes. After recovery at Area 51, an inspection revealed that due to an error in the pitot-static system, the pilot had exceeded Mach 3.2. The considerably higher stagnation temperatures incinerated practically all of the electrical wiring.

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Having been rewired, 936 was airborne again on 28 April. Once again piloted by Eastham and Wallace, the aircraft was flown to cruising speeds in excess of Mach 3 for 30 minutes. On this occasion, all systems functioned properly. The airplane was eventually delivered to Edwards AFB.

YF-12A 936 set nine world absolute speed and altitude records on 1 May 1965. Following an engine malfunction in 934, Col. Robert "Fox" Stephens and Maj. Daniel Andre used 936 to for a straight-course flight at 2,070.101 mph and 80,257.65 feet. Lt. Col Walter Daniel and Maj. James Cooney set a closed course record in 936 at 1,688.891 mph. Daniel and Maj. Noel Warner set another record at a speed of 1,643.041 mph over a closed course.

The airplane participated in AIM-47 missile firing tests at Eglin AFB, Florida in 1966. On 22 March, the crew of 936 successfully fired a missile from 74,500 feet while cruising at Mach 3.15. The target was a Ryan Q-2C flying at 1,500 feet. Another Q-2C, which was cruising at 20,000 feet, was downed on 13 May. On 21 September, the crew of 936 fired a missile from 74,000 feet and Mach 3.2 at a remotely piloted Boeing QB-47 flying near sea level. Shortly after these tests, the YF-12As were placed in storage for three years.

In 1969, YF-12A airplanes 935 and 936 were taken out of storage for use in a joint NASA/USAF research program. After 935 had made several flights, Col. Hugh "Slip" Slater and Maj. Gary Heidelbaugh took 936 up for a functional check flight on 3 March 1970. This airplane was designated as the primary aircraft for USAF tests during the joint program. It was mainly used for radar intercepts, performance tests, and handling qualities evaluations. NASA pilots Fitz Fulton and Don Mallick, and NASA Flight Test Engineer Vic Horton, were also checked out in 936.

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On 17 May 1970, F-12/SR-71 Test Force Director Col. Joe Rogers and Maj. Heidelbaugh piloted 936 for a performance at the Edwards AFB Armed Forces day air show. Following a test flight on 16 June, the airplane was grounded for instrumentation changes.

Maj. William Campbell and Maj. Heidelbaugh took 936 aloft for a functional check flight and inlet instrumentation shakedown on 29 August 1970. In September, Lt. Col. Ronald "Jack" Layton was checked out in 936. The airplane continued to serve as a test-bed for inlet data, handling qualities evaluations, and radar intercept tests.
 

 

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Aerial View Of The YF-12's Crash Site, Which Is Well Inside The Edwards AFB Boundary North Of Rogers Dry Lake.

The 62nd flight of 936 in the joint NASA/USAF research program was scheduled for 24 June 1971. Lt. Col. Ronald "Jack" Layton and Maj. Billy Curtis, of the 4786th Test Squadron, attended preflight briefings then proceeded to the Physiological Support Division to don their pressure suits. The crew then entered the cockpits and began preflight checks. The airplane's radar system was found to be inoperative, but it wouldn't interfere with the mission.

Takeoff, climb, and acceleration were normal. The YF-12A, mission call sign DUTCH 72, continued on to a local intercept training area. An intercept of a B-57 was cancelled due to the radar malfunction, but otherwise the mission was accomplished as briefed. Following completion of intercept training with F-4 and F-106 fighters, Dutch 72 rendezvoused with a KC-135Q tanker for refueling.

Layton then guided the YF-12A back to Edwards and entered the traffic pattern for a landing on Runway 22. He extended the landing gear on the downwind leg and leveled the wings. At this point he pulled the SURFACE LIMITER handle and heard a muffled explosion. He noted that the ball of the TURN AND SLIP indicator was deflected well to the left of center. Less than 10 seconds later the right engine FIRE warning light illuminated and Layton stop-cocked the throttle, as per the established procedure for that malfunction.

To maintain speed above single-engine minimum controllable airspeed and to obtain a more optimum altitude, Layton selected afterburner on the left engine and retracted the landing gear, resulting in asymmetrical thrust and yaw. He extended his downwind leg slightly before attempting a left base leg for landing. The crew declared an emergency and requested a visual check by personnel in the control tower. The tower informed DUTCH 72 that no fire was visible at that time.

The asymmetrical thrust of the left engine precluded a successful left turn to final approach, so Layton terminated afterburner and initiated a wide right turn to realign with the runway. At this time, witnesses on the ground reported seeing flames on the airplane's right engine nacelle. Layton was soon able to observe the flames himself through the cockpit periscope.

The fire seemed to be burning out of control. Layton decided that the runway was now too distant to reach and the difficulties in attempting an unassisted ground egress following a lakebed landing were unacceptably hazardous. He decided to abandon the aircraft. "We're going to jump out," he informed the tower.

Layton ordered Curtis to eject, which he did without hesitation. Layton followed a few seconds later. The crew landed in their parachutes near the town of Boron and were assisted by local civilians. The YF-12A continued to fly in a slight climb, then rolled slowly into a right-hand descending turn. It pointed its nose toward the earth and slammed into the ground near the north end of Rogers Dry Lake.

Following a lengthy investigation, the cause was determined to be a fuel-line fatigue failure. The airplane had logged a total of 439.8 flight hours.
 

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These Five Frames Of Long Range Video Footage Show The YF-12A With Its Right Engine On Fire Slamming Into The Desert, Its Crew Safely Ejected Only Seconds Before.

 

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The YF-12 Crew Transcript

 

When Pete Merlin and Tony Moore, The X-Hunters, began researching the YF-12A crash, they found surprisingly little information. Press coverage at the time of the accident was sparse and the few articles available did not include photos of the crash site. The Air Force Flight Test Center History Office had no useful information, nor did NASA Dryden Flight Research Center. Pete ordered aerial photos of the crash site vicinity from the U.S. Geological Survey (USGS) and made a Freedom of Information Act (FOIA) request to the Air Force for the accident report.

One unlikely source of information was a book called A History of UFO Crashes by Kevin D. Randle. It listed an incident that occurred in the summer of 1971 "near Edwards Air Force Base." The narrative sounded like a garbled description of the YF-12A accident. A witness described hearing "a loud roaring sound and then a loud crash," and seeing a cloud of dust rising "several blocks away." She claimed to have walked to the crash site and joined a group of civilians who were "studying the craft" and "taking pictures." Air Force personnel then arrived, smashed the camera, and ordered the civilians to depart "or be arrested."

The witness said the vehicle "had no markings but seemed to be scratched. There were no windows or seams, and it appeared to be molded in one piece. It was a dark grayish color with greenish highlights. The texture was smooth." This could easily be a description of a damaged YF-12A engine nacelle. The witness said that military personnel "covered the craft with a large canvas and lifted it with cables" before hauling it away. The witness claimed that "there was no mention of the incident in the newspapers." This is consistent with the lack of media coverage noted by Pete and Tony. Kevin Randle classified the incident as neither genuine nor a hoax. He simply labeled it: "Insufficient Data."

The UFO crash story didn't add any really useful information to the search effort. The USGS photos finally arrived but were not immediately helpful. There was no obvious impact scar or evidence of excavation. Due to an administrative error, the accident report failed to arrive for two years and was not available as a reference during the search.

In the meantime the X-Hunters pooled what little information they had and began to search the desert on foot. Eventually, on 27 July 1996, Tony spotted a piece of titanium in the sand. A search yielded only a few other small pieces. They knew they were close, but had not yet found what they were seeking.

On 1 August, Pete returned to the spot where they had found the titanium fragments. Using an aerial photo to chart his progress, he followed a trail of debris for half a mile until he reached the main impact point.

The impact crater had apparently been filled in. The site was, in fact, visible in the aerial photo, but it was not very obvious. From the ground, however, the debris field was quite apparent.

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Pete and Tony later documented the site. They found numerous pieces of titanium skin and structure with part numbers and inspection stamps. There were components from the inlet spike assemblies and the engines. The largest piece they found was the right outboard elevon.

Two other planes, the A-12 and the YF-12, could easily be mistaken for the SR-71. The A-12 was the first plane developed out of the three. It is actually a host plane for the smaller, faster, and higher-flying D-21 drone, code-named Tagboard, which sat piggyback on the A-12 and used a ramjet engine once released for flight. The project was soon cancelled, however, due to a fatal accident, and the D-21 went on to use the B-52 as a transport host. The YF-12 was an SR-71 with an internal bay carrying three Hughes GAR-9/ AIM-47A air to air radar guided missiles, designed to shoot enemy airplanes flying at lower altitudes. Only three YF-12s were ever built.
 

 

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