THE 456th FIGHTER INTERCEPTOR SQUADRON

THE PROTECTORS OF  S. A. C.

 

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The F-102A

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The Air Force designated Convair interim interceptor the F-102A. The production delayed, ultimate MX-1554, while retaining its original designation, would acquire a subsequent model letter series and become the F-102B. In 1956, after numerous engineering changes had further widened the two interceptors' dissimilarities, the Air Force re-designated the F-102B as the F-106.

A number of design changes were requested. The Air Force decided the F-102A should be capable of carrying external stores (fuel tanks, armament, and the like). Also, cockpit components of the MX-1179 ECS (simultaneously inspected with the F-102A) had to be rearranged.

The Air Force, Convair, and Hughes agreed to equip the F-102A with an interim fire control system, since it had become certain service test quantities of the MX-1179 ECS would not be available prior to October 1955. Huges E-9, a modified E-4, was selected. The MX-1179 ECS and the MX-1554 airframe had been specifically designed to complement each other, and the MX-1179's temporary deletion from the F-102A proved to be an important decision. In effect, it marked the defeat of the weapon system concept's first application, for the MX-1179 never reached the F-102A. The E-9 (renamed MG-3 after a number of technical changes had substantially increased its overall capability) was eventually replaced by the MG-10. This system (itself a former MGR incorporating the AN/ARR-44 data link, the MG-1 automatic flight control system, and the AN/ARC-34 miniaturized communication set) became a permanent feature of the F-102A. Meanwhile, by almost imperceptible steps, the interim F-102A took on greater importance, and the quantities discussed grew larger. More emphasis on the F-102A meant less on the ultimate interceptor, leading to an insidious program change. The realities of the development situation, however, dictated this undesirable trend.

The F-102A's development problems first centered on its weight, which was increasing continuously. The Westinghouse J-40 (the most powerful US turbojet engine qualifed for production in early 1961) lacked the thrust to give the F-102A the minimum requisite speed and altitude. Its replacement, the Pratt and Whitney J-57P-11, officially rated as being in the 10,000 lb class and due to enter production in February 1953, was heavier. The post mockup inspection requirements for additional armament also generated extra weight, as did the aircraft's new fire control system, heavier than the future MX-1179. Meanwhile, a much more serious problem loomed.

NACA wind tunnel tests in early 1953 showed that the maximum altitude of 57,000 feet and combat radius of 350 miles (304.3 nm) predicted for the F-102A were too optimistic. The designers of the original Convair proposal (MX-1554) had failed to make proper allowance for a delta wing aircraft's aero-dynamic drag. The area rule concept of aircraft design (that interference drag at transonic speed depends almost entirely on the distribution of the aircraft's total cross-sectional area along the direction of flight) was verified during December 1962 by Richard T. Whitcomb in NACA's new transonic wind tunnels.

Convair drag estimates of the F-102A in its bulky amid-ship configuration did not coincide with the data upon which they were based. The solution was to indent the fuselage to a "coke-bottle" or "wasp waist" configuration, but first the contractor had to be convinced that its original design was in error. However, it was not until mid-1953 that Convair accepted the implications of the "NACA ideal body theory" and joined in the recommendations that the F-102A's design conform to this theory's requirements.

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 The LCs, previously awarded to Convair, were superseded by a definitive contract. This contract, still based on the Cook Craigie production plan, did not affect the number of aircraft initially ordered. Out of the 42 aircraft under procurement, several were earmarked for testing and two (F-102A prototypes) were scheduled for flight in October and December 1953, respectively. Production dates were significantly changed, however. Limited production would not begin until April 1954--10 months later than programmed in December 1951. Accelerated production of a combat ready, fully tested weapon system was planned for December 1955--almost 2 years later than first anticipated.

The first YF-102A, flown from Edwards AFB in October 1953, crashed on 2 November, but not before the aircraft's anticipated poor performance was fully demonstrated. The flight tests, resumed several months later with the second YF-102A (first flown on 11 January 1954), could only confirm that the F-102A in its present configuration was drag limited to Mach .98 with a 48,000 ft ceiling considerably below the required. The F-86D, that the F-102A was supposed to supplant, had a service ceiling of 49,600 feet and a maximum speed of 601.7 kn (Mach .9). It was fully operational in mid 1968, the initial production date originally set for the F-102A.

While the MX-1179 deletion from the F-102A defeated the weapon system concept's first application, the aircraft's unavoidable redesign made havoc of the Cook Craigie plan for early tooling. Of the 30,000 tools already purchased by Convair in October 1953 (when testing established unequivocally that important changes had to be made in the plane's design), 20,000 had to be discarded and new ones bought, a sizeable increase in production costs. Meanwhile, the April 1954 wind tunnel and scale model tests of a remodeled F-102A (that included cambered leading edges, reflex wing tips, rearward relocation of wing, relocation of vertical fin, 7 ft fuselage extension, and redesign of fuselage to incorporate the principles of the area rule "coke-bottle" configuration) reflected continuing deficiency in performance. Moreover; airframe and component changes had added 3,500 pounds to the aircraft's weight.

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In May 1954 the Air Force approved further redesign of the first "coke bottle" configuration. The new drag reducing changes extended the fuselage another four feet and added: a new canopy (lighter and providing better visibility), new engine intake ducts, an aft fuselage fairing, and wing camber modifications. The J-57P-23 engine (generating 16,000 pounds of thrust, or approximately 1,200 pounds more thrust than the 11) was to replace the 11 and the interim -41 (an 11 engine modified for new air bleed probes to eliminate cabin fumes). A major weight reduction, likewise, was initiated.

Redesign of the F-102A, once agreed upon, was accompanied by new production decisions. The Air Force in March 1954 gave Convair a second production contract calling for delivery of 37 additional F-102As between February and July 1955. A third and larger order, placed in June 1954, scheduled the delivery of another 108 aircraft between August and December 1956.

Convair's new production contracts were soon followed by definite qualifications. In November 1964 the Air Force issued a set of general operational requirements that called for altitude performances up to 54,000 feet, a combat radius of 326 nautical miles, and speeds up to Mach 1.23 at 35,000 feet. The Air Force also placed an informal (but nevertheless meaningful) hold order on the FY 1956 funds for the 108 F-102As, recently ordered. This hold order would prevail until forthcoming flight tests of the new F-102A proved to be satisfactory.

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A "synthetically modified" production F-102A made its initial flight and demonstrated substantial performance improvement over the original configuration, reaching Mach 1.22 and an altitude of 53,000 feet. This demonstration "coke bottle" prototype (nick named the Hot Rod to distinguish it from the two earlier YF-102As and the few initial straight fuselage productions allocated to the testing program) was fitted with fillets designed to the latest, light weight configuration that had been approved by the Air Force in May 1954. It was powered by an advanced production of the improved J-57-P-23 turbojet, due for delivery in June 1955.

Evaluation of the Hot Rod prototype's preliminary flight tests led the Air Force to rescind in early 1955 its administrative hold order of the previous year. Ensuing flight tests by Air Force pilots, while demonstrating that the aircraft's stability needed improving, were also satisfactory. They ended in June 1955, after the aircraft's initial high speed had been equaled and its original altitude performance actually exceeded. Ten months of structural integrity testing were initiated in July, when the Air Force concluded (after numerous airborne firing tests) that the F-102A would be able to launch the Falcon missile, as well as 2.75 and 2 inch rockets. A high point in the series of armament tests was reached on 8 July, when the YF-102A fired 6 Falcons and 24 rockets in less than 10 seconds.

The first "Production Aircraft" flew on 24 June 1955. This was the first production F-102A built to the Hot Rod, lightweight, "coke bottle" configuration. The aircraft was accepted by the Air Force on 29 June, 5 days after its first flight.

The F-102A first entered service with the Air Defense Command's 327th FIS at George AFB. It became the Air Force's first delta-wing aircraft almost 3 years past the June 1963 production date in the LC of December 1951, some 7 months beyond the revised delivery schedule of 1954, and nearly 10 years after the experimental, delta wing F-92's first flight.

One month before the F-102A entered operational service, the Air Force and Convair decided to give the F-102A a larger fin. This new design change, endorsed after a period of extensive testing, would alleviate the aircraft's instability, a remaining problem particularly acute at high speeds. The change became effective with the 26th F-102A, after Convair production schedule had been adjusted for this purpose. Enlarged fins were retrofitted on the 25 aircraft already off the production lines.

As once planned and in order to simplify logistical support of the F-102A, the Air Force decided in mid 1956 that (beginning with all post-December productions) only the 2.75 inch Folding Fin Aerial Rocket would be used as backup to the Falcon (GAR-1 and infrared -1B) guided missiles the aircraft's primary armament. Operational F-102As and those released from production before the decision could be implemented, would exchange their T-214 2-inch FFARs for the standard 2.75 inch rockets. Necessary modifications were subsequently made in the field by teams from the Air Force San Antonio Air Materiel Area, Tex. Some 170 F-102s were modified. In the meantime, after the first air-firing of an MB-1 rocket was accomplished from a YF-102 in May 1956, the Air Force again considered equipping the F-102A with Genie rockets, even though this would entail another production delay. This project, however, was given up in early 1957.

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The Air Force gave Convair a fifth and final contract for 140 F-102As in September 1956, 10 months after the fourth and largest (562 aircraft) F-102A production contract had been placed.

One year after becoming operational, the F-102A still harbored a number of deficiencies, but most defects were being corrected. By November, all F-102As had been retrofitted with serviceable struts and the incorporation of a new oleo strut metering pin and revision of the side brace boss bearing of the landing gear in all future F-102A productions gave assurance that the long standing problem of landing gear failure (susceptible of affecting also the more advanced F-106 interceptor) was finally solved. Convair in addition had devised a fix for speed brake failures in flight, another critical problem which had dictated the re-inspection of speed brake in each F-102A.

While the F-102A's operational problems were being corrected, efforts to further improve the aircraft's performance did not slacken. After a successful prototype flight in May 1957, F-102As acquired a new wing. Referred to as the Case XX wing and phased into production after October 1967 (beginning approximately with the 550th F-102A), this final major structural change raised combat ceiling to 55,000 feet (a 5,000 ft increase), boosted maximum speed at 50,000 feet to Mach 1 (a Mach 0.06 gain), and, substantially improved maneuverability. The F-102A's stability at low speeds, still marginal despite the previous in-production incorporation of a larger fin, also improved vastly.

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 Modernization of the F-102A, undertaken almost concurrently with the aircraft's final production change, lasted several years from 1957-1963. The F-102A was still being modernized long after some of the aircraft had already begun to leave the regular forces. This took care of the air defense needs, increasingly provided by the Air National Guard, and of important oversea requirements.

First involved were the addition of data links (Data links furnished the pilot information electronically rather than by voice.) and replacement of the MG-3 fire control system by the improved MG-10. There followed the substitution of more sophisticated and less trouble some GAR missiles (as they became available) and the addition of the nuclear Falcon Model Y52A. This atomic missile, first known as the GAR-11 and subsequently re-designated the AIM-26A, had been designed by Hughes specifically for the F-102A. In 1963, after more than 450 aircraft had been modified and provided the necessary kits (one kit per aircraft, at an initial cost of $10,000 per kit), half of the F-102 interceptors (trainers included) could carry the AIM-26A. Ensuing modifications eventually provided interchangeable utilization of AIM-26 and AIM-4 (GAR 1 through 4 series of Falcons in post 1962 nomenclature) missiles in the center missile bay of a number of F-102As. Under project Big Eight (and still as part of the F-102A modernization), incorporation of an Infrared Search and Track System into the F-102 fleet also began in 1963.

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Last Updated

02/10/2014

 

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