Profile-Convair F-102 & F-106

This ADO very quickly became a formal RFP (Request For Proposals) from American industry in June 1950. The aircraft would have the world’s first semi-automatic integrated interceptor fire-control system with a radar linked to its flight control system and would be armed not with guns but with either a battery of rockets or several guided AAMs (air-to-air missiles) all carried internally. Quite a proposal considering AAMs were at that time not even a reality! The airframe of the new weapons system was known as Project MX-1554. Development of the Project MX-1179 ECS (Electronic Control System) around which it would be built was contracted to the Hughes Aircraft Co in October 1950.

Out of nine proposals submitted by six manufacturers, the USAF invited Convair, Lockheed and Republic to proceed with development up to and including the mock-up inspection stage. The most promising proposal would receive a firm production contract. Lockheed’s submission was dropped shortly afterwards and Republic’s XF-103 eventually fell victim to budget reductions. By September 1951, Convair’s submission, based on its earlier Model 8, XF-92A delta research aircraft, was consequently the only real contender.

Back in 1945 it had become apparent that the Germans were well ahead of the Allies in designing new wing plan forms for high speed flight. One of these was the delta wing, a pure triangle named from the Greek letter D. Flying apex first, such a wing shape offered large area for light weight and a minimum of structural problems yet appeared capable of supersonic flight.

In September 1945, the US Army had contracted with Convair at San Diego for a delta prototype to fly at Mach 1. 2 and this had materialised as the XF-92, the first delta aircraft in the world, flown on 9 June 1948. Its wing had a thickness/chord ratio of just over 5%, at that time regarded as extremely thin, and the leading edge was swept at 60°. There was no horizontal tail, all control in pitch and roll being by powered elevons on the trailing edge. Convair believed that the XF-92 might reach Mach 1, but its Allison J33 did not have sufficient thrust. Even with an afterburner added the XF-92A only reached Mach 0. 95 but this was still much faster than any of the jet fighters then in service. As noted, Convair had proposed its Model 8, basically an XF-92 scaled up in the ratio 1. 22 (linear), and with lateral inlets to a Pratt & Whitney J57 afterburning turbojet to leave the nose free for radar. Guided missiles were to be carried in a fuselage weapon bay, the doors of which incorporated tubes for launching 24 rockets.

Unsheathing the Dagger

Spurred on by events in the Korean War, in November 1951 the USAF had elected to implement the “Cook-Craigie Plan” in an attempt to accelerate the project. This called for early tooling and a limited initial production batch of aircraft without waiting for completion of prototype testing. It was hoped that changes dictated by the flight test program would beminor. Unfortunately, this was not to be the case.

Nicknamed “Deuce”the first YF-102 prototype, 52-7994, took to the air on 24 October 1953, followed by the second, 52-7995, on 11 January 1954. These were the first of ten YF-102 (Model 8-80) prototypes but it was soon evident that the expected speed could not be attained. The first prototype displayed poor flying characteristics with severe buffet and yaw below Mach 93. On the seventh flight it suffered engine flameout while taking off and was severely damaged in the resulting wheels-up landing. Despite frantic revisions, the YF-102s stayed stubbornly subsonic.

A major crisis was looming because the F-102 production line was already well under construction. It was apparent that the time allocation for development was unrealistic and work schedules began to slip behind badly. The USAF responded by altering requirements into a two-stage interceptor development program with an initial interim limited production design, theF-102 A, which would be followed later by the F-102B “Ultimate Interceptor”.

Meanwhile, Richard T Whitcomb, at the US National Advisory Committee for Aeronautics (later NASA), discovered what was to become known as the Area Rule concept, which explained how an aircraft should be shaped to have minimum transonic drag. Application of the Area Rule formula required a major revision of the fuselage profile to reduce the cross-sectional area over the wing and the bulging of the aft fuselage (often called Marilyn Monroe fairings) to fill the channel section between the wing, fuselage and vertical tail in order to delay flow breakaway. This gave the fuselage a pinched-in “coke bottle” shape. Overall length of the fuselage was increased, the cockpit canopy redesigned and the nose drooped to give better visibility over the radome. Wing leading edges were partially cambered, the jet air intakes were revised and the more powerful Pratt & Whitney J57-P41 turbojet installed. A drastic revision of the structure took place, together with relocation of a number of systems to simplify maintenance and production.

On 19 December 1954, only 115 days after completion of the design changes, YF-102A, No 53-1787, the first of four pre-production aircraft took to the air. This aircraft very soon provided proof that the various modifications had indeed achieved the desired effect when, two days later, it exceeded Mach 1 on its second flight. Eventually it attained Mach 1. 22 and a ceiling of 53,000 feet (16155m), both very close to the required performance levels. From this point on the Delta Dagger project began to make very real progress.

The “Deuce” was still tormented by bugs during its early operational career. Many of these related to the fire control system, and the initial service period was one of progressive updating. An example was the substitution of the MG-10 FCS in place of the original MG-3, whilst data-link facilities were also provided. A new wing was evaluated in prototype form from May, 1957, and installed on production aircraft with effect from October onwards. It was progressively retrofitted to earlier examples as they came up for overhaul. With this wing the F-102A was capable of reaching 55,000 feet (16765m) and had much greater stability particularly at low speeds.

Flight testing of modified aircraft occupied much of 1955, one remarkable highlight occurring in July when an YF-102A launched six Falcon air-to-air missiles and 24 unguided rockets in under 10 seconds. These trials also dictated a number of other modifications to the vertical tail surfaces, air brakes and air intake duct.

At Convair, meantime, development of the F-102B was being held back by problems with its projected Wright J67 powerplant and the MX-1179 fire-control system. Because of this the air force boosted F-102A production to over 700 machines since it needed aircraft quickly even if the type did not meet all expectations. On the other hand, F-102B orders were restricted to only 17 aircraft for test purposes. It looked as though the “Ultimate Interceptor” was being phased out of the USAF’s future planning. The peak ADC (Air Defense Command – later the Aerospace Defense Command) strength of 26 Delta Dagger squadrons was reached during 1958, but this total was maintained only briefly because the F-102A was still viewed largely as an interim type. It did continue in front line service with elements of the USAFE (United States Air Forces in Europe), AAC (Alaskan Air Command) and PACAF (Pacific Air Forces) for some time, as well as providing the backbone of ANG (Air National Guard) interceptor forces for most of the 1960s and early 1970s. The type remained

The first production F-102A Delta Dagger, 53-1791, was handed over to the Air Force Flight Test Centre at Edwards Air Force Base on 29 June 1955 and was fitted with the much improved J57-P23 turbojet. However another year was to pass before any Daggers were issued to squadrons, the first going to the 327th Fighter Interceptor Squadron (FIS) at George Air Force Base, California. The “Deuce” was still tormented by bugsduring its early operational career. Many of these related to the fire control system, and the initial service period was one of progressive updating. An example was the substitution of the MG-10 FCS in place of the original MG-3, whilst data-link facilities were also provided. A new wing was evaluated in prototype form from May, 1957, and installed on production aircraft with effect from October onwards. It was progressively retrofitted to earlier examples as they came up for overhaul. With this wing the F-102A was capable of reaching 55,000 feet (16765m) and had much greater stability, particularly at low speeds.

Flight testing of modified aircraft occupied much of 1955, one remarkable highlight occurring in July when an YF-102A launched six Falcon air-to-air missiles and 24 unguided rockets in under 10 seconds. These trials also dictated a number of other modifications to the vertical tail surfaces, air brakes and air intake duct.

At Convair, meantime, development of the F-102B was being held back by problems with its projected Wright J67 powerplant and the MX-1179 fire-control system. Because of this the air force boosted F-102A production to over 700 machines since it needed aircraft quickly even if the type did not meet all expectations. On the other hand, F-102B orders were restricted to only 17 aircraft for test purposes. It looked as though the “Ultimate Interceptor” was being phased out of the USAF’s future planning. The peak ADC (Air Defense Command – later the Aerospace Defense Command) strength of 26 Delta Dagger squadrons was reached during 1958, but this total was maintained only briefly because the F-102A was still viewed largely as an interim type. It did continue in front line service with elements of the USAFE (United States Air Forces in Europe), AAC (Alaskan Air Command) and PACAF (Pacific Air Forces) for some time, as well as providing the backbone of ANG (Air National Guard) interceptor forces for most of the 1960s and early 1970s. The type remained in front line operational use with the air arms of Greece and Turkey for several more years, these air forces having taken delivery of a number of surplus USAF single and two seat Delta Daggers during the early 1970s.

In the Vietnam War, Delta Daggers were deployed in the south for air defence until late in 1969 when the role was taken over by F-4 Phantoms. The enemy never did stage an air strike but on 1 July 1965, there was a Viet Cong mortar attack on DaNang which destroyed several aircraft including two F-102s while three others were damaged. The type was also use for Arc Light close escort missions for B-52s but the anticipated reaction by MiG-17s and MiG-21s never eventuated. Other duties performed included flying MIG CAP (Combat Air Patrol) for fighter bombers and also air-to-ground rocketry but F-102s were never credited with a MiG kill.

A total of 1,000 Delta Daggers were produced, consisting of 10 YF-1028; 4 YF-102As; 875 F-102As; and 111 TF-102As, the latter being a training version with the redesigned forward fuselage, side-by-side seating and duel controls, but still retaining full combat capability.

Almost 400 F-102s went into retirement between 1969 and 1975. Half of them were destined for the scrap yard torch but 200 were reserved for a more spectacular fate when, in 1973, the Sperry Corporation was awarded an Air Force contract to con- vert surplus F-102s into remotely controlled target drones. The first POM-102 unmanned flight taking place at Holloman Air Force Base in New Mexico on 13 August 1974.

Approximately 50 Delta Daggers are preserved either in museums or as monuments or gate guards. Except for three TF-102As reserved for the Air Force Museum, about 40 more were used as sources of spare parts until they were totally gutted and left derelict at the vast Davis-Monthan storage centre, Arizona.

Convair PQM-102A Delta Dagger 57-0909 was the last F-102 built and she was destroyed by an AIM-7E missile fired from an Air National Guard F-4 Phantom over the Gulf of Mexico on 3 March 1982.

Enter the Delta Dart As previously mentioned, Convair’s discussions with the USAF on the proposed F-102B had begun back in December 1954. The Air Force saw a new, more capable interceptor as the perfect link with the coast-to-coast Semi-Automatic Ground Environment (SAGE) direction centres then under construction as part of a new air-defence network.

To meet the USAF Weapon System number WS-201B require- ment, the company launched its Model 8-24. Although this began as an improved F-102A, it soon became obvious that not much was going to be left unchanged. The fuselage was completely new, with greater length, a slightly slimmer profile and shorter inlet ducts positioned back behind the cockpit. In order to achieve maximum supersonic performance, the inlets were given powered ramps for variable area and profile and they were made larger to cater for the greatly increased airflow. The vertical tail was given more sweep, a broad top and less height. In front, the nose gear was given two wheels and made steerable. The wing was changed least but again there were numerous modifications. It had to be re-stressed for the aircraft’s increased weight, have revised integral storage, the structural break between inner and outer elevons was shifted out further and the bay for the new main landing gear moved forward and redesigned. Changes were also made to the weapon bay for housing the latest missiles.

The redesign transformed a capable interceptor into one which was outstanding. The most significant item of equipment was its new fire-control system. This was the Hughes MA-1 incorporating Digitaire, the first airborne digital computer to go into production. One of its functions was to guide the aircraft automatically to the best point of interception according to continuous data incoming from SAGE centres without the need for human voice directions. A feasibility study was actually made to consider the advantages and disadvantages of leaving out the pilot altogether. This would have made the Model 8-24 the very first pilotless fighter but it was decided that having a human on board had its advantages.

Redesignated F-106A in acknowledgment of the major redesign which distinguished it from the F-102A, the new machine was named the Delta Dart. The USAF placed a contract for 17 Delta Darts for development and service tests in April 1956 and this was followed in June with another contract for 18 more.

Although new and complex, little more than a year after work began, the first F-106A, 56-451, had its maiden flight on 26 December 1956, with Dick Johnson as pilot at Edwards AFB. It was powered by a single Pratt & Whitney J75, the originally specified Wright J67 having been dropped. The extensive MA-1 system, 56-451 was not carried, instead large ballast weights were installed in the nose to preserve the centre of gravity.

Testing and Development

In general the flight development program was very successful. Almost all predicted speeds and heights were attained and manoeuvrability exceeded that of the F-102A despite its greater weight. This weight was mostly due to the internal fuel capacity being increased from 1,070 US gal (4050 litres) to 1,440 US gal (5456 litres).

There were some modifications: The four small wing fences were removed and replaced by a leading edge axial sawcut which caused hardly any drag: introduction of a new frameless canopy, and much development went into the cockpit during 1956-8 with improved radar displays, optical sight, projected map navigation display. vertical tape instruments and a modified twin-grip control column. The F-106 retained the Dagger’s acutely sloping windshield, with a thin black metal sheet dividing the interior into left and right halves to prevent internal reflections at night.

Deliveries to ADC began in May 1959 and the first unit declared operational with the Delta Dart was the 539th Fighter Interceptor Squadron in June 1959. The F-106A eventually equipped 13 units forming half the manned interceptors of the ADC by the time the 277th and last was delivered on 20 July 1961.

Each squadron also received three or four F-106Bs which were delivered in parallel with the single-seaters. The F-1068 had the company number Model 8-27 and was a duel trainer with full combat capability. It carried the complete MA-1 system and weapons, the only penalty of the second seat being the loss of one of the forward fuel cells. Tandem seating resulted in drag similar to that of the single-seater so performance figures, except for reheat, were almost matching though takeoff and landing speeds were slightly higher. The first F-1068, 57-2507, flew on 8 April 1958, and a total of 63 were built.

In service the “Six”, as the Dart was called, fulfilled every wish of the USAF and its pilots, proving solidly reliable and a delight to fly. On 15 December 1959, over Edwards AFB, California, Major Joseph W Rogers pushed his F-106A to a new absolute speed record of 1,525. 93mph (2455. 74km/h).

There were major differences between the various batches of aircraft produced as modifications and improvements were built in. The USAF detailled no fewer than 130 changes that had to be made to bring early machines up to late production standards. Improvements to those in service commenced in September 1960 with Project “Wild Goose”. Next, Project “Broad Jump”, a longer program completed in 1963, was the installation of an IR search/track sight immediately ahead of the windscreen. Running concurrently was Project “Dart Board” featuring the introduction of a new supersonic ejector seat, a thermal flash hood for the pilot and fuel transfer modifications to rectify a series of engine flameouts.

As well as these retrospective programs, there was progressive updating. In 1965, supersonic fuel tanks and an inflight-refuelling receptacle were installed along with a new TUCAN (Tactical Air Navigation) system. An ambitious SLIM (Simplified Logistics and Improved Maintenance) program in 1967 eventually, over several years, introduced improvements to the radar, automatic flight controls and a DC electrical system. Project “Sixshooter” included the replacement of the original heavily-framed main canopy by a clearer “Blown” type, better ECCM (Electronic Counter Countermeasures) and a new RHAW (Radar Homing And Warning) receiver. However, the main feature of “Sixshooter” was a sharp return to the old fashioned belief that a fighter may actually need to close with its enemy in aerial combat, something not even contemplated when the Dagger and the Dart were designed merely as stand-off missile platforms. A 20mm Vulcan M61A 1 six-barrel cannon was successfully tested and housed in the rear of the internal weapon bay. Not all F-106s were re-equipped in this way but those which were could be identified by a tell-tale in the underside of the fuselage which allowed for clearance as the cannon’s barrels rotated. Introduction of the gun was also an acknowledgment of the Dart’s excellent dog-fighting ability.

In terms of equipment, the F-106’s most important item remained the Hughes MA-1. This was fundamental to the aircraft’s interception missions but it had a chequered career needing constant corrections in the early days to make it fully effective. By the 198 0s the MA-1 was becoming obsolete and this ultimately became a major reason for the eventual retirement of the F-106.

In terms of numbers, by the late 1960s the Delta Dart was beginning to decline with only 11squadrons operational. In 1972 the ANG received its first secondhand F-106 and the type would serve in a maximum of six squadrons by the middle of 1974. F-106s of both models continued on until the final disbandment of ADC on 1 October 1979. After that it was a gradual process of attrition and replacement by more modern types such as the McDonnell Douglas F-15 Eagle and General Dynamics F-16 Fighting Falcon. These eventually saw the end of the Delta Dart’s longevity when the last was retired in 1988. Though a few flew on carrying out research duties with NASA at Edwards AFB, California.

The process of converting older aircraft into pilotless drones also continued with the Delta Dart. Having ironically flown many missions itself intercepting and destroying drones over the years, the F-106 has now assumed the role of target. Contracts for QF-106A drones have expanded to cover the conversion of 188 machines.

On 6 July 19 9 0, F-106A Delta Dart No 5 9- 0 061, one of the last of its kind, made what was probably its last manned flight when it was ferried from Palmdale, California, into retirement at Davis Monthan. One of five used as chase planes in the Rockwell B-1B Lancer project, it too is expected to end up as an expendable drone target, a sad fate for a type which, to the time of writing, still holds the world’s single-engine speed record, established as long ago as December 195 9 by Major Rogers.