Convair F-106B Delta Dart

The F-106 was the ultimate development of the USAF's 1954 interceptor program of the early 1950s. It was the sixth iteration of the famous 1950s-era “Century” series of jet fighters. The initial winner of the competition had been the F-102 Delta Dagger, but earlier versions of this aircraft had demonstrated extremely poor performance, being limited to flying at subsonic speeds and relatively low altitudes. During the testing phase, the F-102 underwent numerous changes to improve its performance, notably the application of the area rule to the fuselage shaping, an engine change, and the dropping of the advanced MX-1179 fire control system and its replacement with a slightly upgraded version of the MX-1 already in use on subsonic designs. The resulting aircraft became the F-102A, and despite being considered barely suitable for its mission, the Air Force sent out a production contract in March of 1954, under which the first deliveries were expected during the following year.

 

By December 1951, the Air Force had already turned its attention to a further improved version, which was initially referred to as the F-102B. The main planned change was the replacement of the F-102A's Pratt & Whitney J57 (which had itself replaced the original J40) with the more powerful Bristol Olympus, which was produced under license as the Wright J67. By the time this engine would be available, the MX-1179 was expected to be available, and thus, it was also selected. The result would be the "ultimate interceptor" that the USAF had wanted originally. However, while initial work on the Olympus appeared to be going well, by August of 1953, Wright was already a full year behind schedule in development. Continued development did not resolve problems with the engine, and in early 1955, the Air Force approved the switch over to the Pratt & Whitney J75.

 

The J75 was bigger than the J57 in the F-102A and had a greater mass flow. This demanded changes to the inlets to allow more airflow, and this led to the further refinement of using a variable-geometry inlet duct to allow the intakes to be tuned to the best performance across a wide range of supersonic speeds. This change also led to the vents being somewhat shorter. The fuselage grew slightly longer and was cleaned up and simplified in many ways. The wing was partially enlarged in area, and a redesigned vertical tail surface was used. The engine's two-position afterburner exhaust nozzle was also used for idle thrust control. The nozzle was held open, reducing idle thrust by 40%, giving slower taxiing speeds and less brake wear.

 

Throughout the early development of the F-102B, it had to compete for attention and resources with the F-102As; the aviation author Marcelle Knaack observed that there were less funds to develop the more capable systems of the F-102B, which would have been useful in more quickly overcoming some of the technical difficulties that would be encountered. The number of F-102As on order grew substantially beyond that which had been originally forecast, indicative of the growing importance attached to what had once been intended to be an interim or 'stop-gap' aircraft to fill in until the F-102Bs could be delivered. In December of 1955, a mock-up with the expected layout of the MX-1179, now known as the MA-1, was inspected and approved.

 

On April 18th, 1956, in a clear sign of growing confidence that the aircraft was improving, an extended production contract for 17 F-102Bs was issued to Convair; however, this order was for substantially fewer aircraft than had been anticipated initially at this stage. On June 17th of that year, the plane was officially re-designated as the F-106A. On August 18th, 1956, the USAF issued a systems development directive that called for both the development and the production of the F-106s to occur simultaneously; Knaack attributed this policy to being responsible for several later problems in the program. In April of 1957, the USAF formally rejected Convair's F-102C proposal (essentially a re-engined model of the F-102) to concentrate on the more advanced F-106 program, which it had anticipated to enter service during the following year.

 

On December 26th, 1956, the prototype F-106, an aerodynamic test bed, performed its maiden flight from Edwards Air Force Base in California. On February 26th, 1957, the second prototype, which was outfitted with a fuller set of equipment, made its first flight. Early flight testing around the end of 1956 and the beginning of 1957 demonstrated somewhat disappointing results, having achieved less of a performance gain over the F-102 than had been anticipated. Specifically, both the acceleration and maximum speed were below Convair's estimates. Furthermore, both the engines and avionics proved to be somewhat unreliable. These combined problems and the delays associated with them were nearly responsible for the termination of the program.

 

However, the service decided to persist with the F-106 program after the Air Defense Command had heavily advocated for it. Based upon the test data submitted, USAF officials had determined that modifications to the inlet duct cowling and charging ejectors were likely to increase both acceleration and speed; modifications would be made following the completion of Category II testing and were evaluated during Category III testing. At this stage, the service enacted several measures to hasten development towards production; in April of 1957, it authorized the conditional acceptance of several F-106s being used by Convair for flight testing; it also took several quick decisions to settle outstanding development questions. By mid-1957, funding for 120 F-106As had been allocated. The USAF ultimately opted to order 350 F-106s, which was substantially less than the planned 1,000 fleet of aircraft. Deliveries of the single-seat F-106A and the twin-seat F-106B combat-capable trainer variant commenced to 15 fighter interceptor squadrons in October of 1959.

 

On December 15th, 1959, an F-106 flown by Major Joseph W. Rogers made history when his plane set a new world speed record for fighter jets, reaching an incredible speed of 1,525.96 mph (2,455 kph) at 40,500 ft (12,300m). The F-106 was envisaged as a specialized all-weather missile-armed interceptor to shoot down bombers. It was complemented by other Century Series fighters for different roles, such as daylight air superiority or fighter-bombing. To support its part, the F-106 was equipped with the Hughes MA-1 integrated fire-control system, which could be linked to the Semi-Automatic Ground Environment (SAGE) network for Ground Control Interception (GCI) missions, allowing the aircraft to be steered by controllers. The MA-1 system proved to be highly troublesome and was eventually upgraded more than 60 times while in service.

 

Like the F-102s, the F-106 was designed without a gun or provision for carrying bombs, but it carried its missiles in an internal weapons bay for clean supersonic flight. It was armed with four Hughes AIM-4 Falcon air-to-air missiles (either AIM-4F/G infra-red guided missiles or semi-active radar homing (SARH)-guided (which detected reflected radar signals) AIM-4E missiles, along with a single 1.5 kiloton-warhead AIR-2 (MB-2) Genie unguided air-to-air rocket intended to be fired into enemy bomber formations. Like its predecessor, the F-102 Delta Dagger, it could carry a drop tank under each wing. Later, jet fighters such as the McDonnell Douglas F-4 Phantom II and the F-15 Eagle took missiles recessed externally in the fuselage. However, stealth aircraft would re-adopt the idea of carrying missiles or bombs internally for a reduced radar signature.

 

The first ejection seat fitted to early F-106s was a variation of the seat used by the F-102 and was called the Weber interim seat. It was a catapult seat that used an explosive charge to propel it clear of the aircraft. This seat was not a zero-zero seat and was inadequate for ejections at supersonic speeds as well as ground-level ejections and ejections at rates below 120 knots (140 mph; 220 kph) and 2,000 ft (610 m). The second seat that replaced the Weber interim seat was the Convair/ICESC (Industry Crew Escape System Committee) Supersonic Rotational B-seat, called the supersonic "bobsled," hence the B designation. It was designed with supersonic ejection as the primary criterion since the F-106 was capable of Mach 2 performance. Fighter pilots viewed high-speed ejections as the most important. Seat designers considered an ejection at low altitude and slow speed the most likely possibility. The ejection sequence with the B-seat was quite complicated, and some unsuccessful ejections resulted in pilot fatalities. The third seat, which replaced the Convair B-seat, was the Weber Zero-Zero ROCAT (Rocket Catapult) seat. Weber Aircraft Corporation designed a "zero-zero" seat to operate at up to 600 knots (690 mph; 1,100 kph). High-altitude supersonic ejections were rare, and ejections at relatively low altitudes and speeds were more likely. The Weber "zero-zero" seat was satisfactory and was retrofitted to the F-106 after 1965.

 

Early operations of the F-106 were troubled by numerous technical issues; these included generator defects, fuel-flow issues (particularly during cold weather), and combustor-starter malfunctions. In December of 1959, all F-106s were temporarily grounded following the accidental jettisoning of the canopy mid-flight on one aircraft. Many of, but not all, of these problems were resolved by the start of 1961; this can be partially attributed to two significant modification and retrofit programs conducted during this timeframe. Following the resolution of initial teething problems—in particular, an ejection seat that killed the first 12 pilots to eject from the aircraft—its exceptional performance led to the aircraft becoming relatively popular amongst its pilots.

 

The F-106 served in the contiguous U.S., Alaska, and Iceland, as well as for brief periods in both Germany and South Korea. The F-106 was the second-highest sequentially numbered P/F- aircraft to enter service under the old number sequence (the F-111 was highest) before the system was reset under the 1962 United States Tri-Service aircraft designation system. In service, the F-106's official name, "Delta Dart," was rarely used, and the aircraft was universally known simply as "The Six" as it was the sixth and last member in Convair’s Century series of jet fighters. The arrival of the F-106 in quantity quickly led to the withdrawal of various older aircraft that were being used in the interceptor role at that time, such as the North American F-86 Sabres and the Northrop F-89 Scorpions.

 

Although contemplated for use in the Vietnam War, the F-106 never saw combat, nor was it exported to any foreign users. However, after the cancellation of their own Avro Arrow, the Canadian government briefly considered purchasing the F-106C/D. To standardize aircraft types, the USAF was directed to conduct Operation Highspeed, a fly-off competition between the USAF F-106A and the U.S. Navy F4H-1 (F-4B) Phantom, which was not only as capable as the F-106 as a missile-armed interceptor but could carry as large a bomb load as the Republic F-105 Thunderchief fighter-bomber. The Phantom was the winner but would first be used to escort and later replace the F-105 fighter bomber in the late 1960s before replacing older interceptors in the Air Defense Command in the 1970s.

 

The F-106 was progressively updated in service, with improved avionics, a modified wing featuring a noticeable conical camber, an infrared search and track system, streamlined supersonic wing tanks that provided virtually no degradation to overall aircraft performance, better instrumentation, and features like an inflight refueling receptacle and an arrestor hook for landing emergencies.

 

Air-to-air combat testing suggested "The Six" was a reasonable match for the F-4 Phantom II in a dogfight, with superior high-altitude turn performance and overall maneuverability (aided by the aircraft's lower wing loading). Indeed, the Phantom had better radar—it was operated by an additional crew member—and could carry a load of up to four radar-guided AIM-7 Sparrow and four infrared AIM-9 Sidewinder missiles, while the AIM-4 Falcon missiles carried by the F-106 proved to be a disappointment for dogfighting over Vietnam. The F-4s had a higher thrust/weight ratio with superior climb, better high-speed/low-altitude maneuverability, and could be used as a fighter-bomber. Air combat experience over Vietnam showed the need for increased pilot visibility and the utility of a built-in gun, which had been added to the "E" variant of USAF Phantoms.

 

In 1972, some F-106As were upgraded in Project Six Shooter, which involved fitting the F-106 with a new canopy without metal bracing, significantly improving pilot visibility. Also added was an optical gunsight and provision for a M61 Vulcan 20mm cannon. The M61 Vulcan had 650 rounds of ammunition in the center weapons bay, replacing the AIM-26 Super Falcon or Genie. The F-15A Eagle started replacing the F-106 in 1981, with "The Sixes" being passed on to Air National Guard units. The F-106 remained in service in various USAF and ANG units until they were fully retired from service in August of 1988.

 

Between June 1st, 1983, and August 1st, 1988, the Delta Darts were incrementally retired and sent to the Military Storage and Disposition Center in Arizona. When the need for a high-performance Full-Scaled Aerial Target Drone was required, the USAF began withdrawing Delta Darts from storage. Starting in 1986, 194 of the surviving surplus aircraft were converted into target drones, and these were designated QF-106As and used for target practice vehicles under the Pacer Six Program by the Aerial Targets Squadron. The last one was destroyed in January of 1998. The drones were still capable of being flown as manned aircraft, such as for ferrying to a test; during the trial, they were flown unmanned. The QF-106 replaced the QF-100 Super Sabre drone; the last shootdown of a QF-106 (BuNo 57-2524) took place at Holloman AFB on February 20th, 1997, after which the QF-106 was superseded by the QF-4S and QF-4E Phantom II drone.

 

Six aircraft were retained by NASA for testing purposes through 1998. An F-106B two-seat trainer was operated by NASA Langley Research Center between 1979-1991. This Delta Dart was used in research programs ranging from testing supersonic engines to improving the maneuverability of fighters. Between 1980 and 1986, the aircraft was modified for lightning strike research and became known as the “Lightning Strike Plane” and was struck 714 times without significant damage. While on an hour-long flight at 38,000 ft (12,000 m) in 1984, lightning struck the research aircraft up to 72 times. One effective modification was the replacement of the composite nose radome with a metallic radome. Although the maximum speed of the F-106 was Mach 2.3, during the lightning experiments, it was flown at subsonic speeds into clouds at 300 knots (350 mph; 560 kph) from 5,000 to 40,000 ft (1,500 to 12,200 m). The aircraft was equipped with optical sensors, which consisted of a video camera and a light detector. Data acquisition was performed with 1980s state-of-the-art digital waveform recorders.

 

NASA used six drones in its Eclipse Project, which ran from 1997–1998. The Dryden Flight Research Center supported project Eclipse, which sought to demonstrate the feasibility of a reusable Aerotow-launch vehicle. The objective was to tow, inflight, a modified QF-106 aircraft with a C-141A as a transport aircraft. This test demonstrated the possibility of towing and launching a space launch vehicle from behind a tow plane.

 

On February 2nd, 1970, an F-106 of the 71st Fighter-Interceptor Squadron, piloted by Captain Gary Foust, entered a flat spin over Montana. Foust followed procedures and ejected from the aircraft safely. The resulting change of balance caused the plane to stabilize and later land "wheels up" in a snow-covered field, suffering only minor damage. The aircraft, appropriately nicknamed "The Cornfield Bomber," was then sent back to base via rail, repaired, and returned to service, and is now on display at the National Museum of the United States Air Force in Dayton.

 

This F-106B, BuNo 57-2513, was only the 33rd F-106 ever produced, and spent almost all of its career as a testbed, flying with the Air Force Flight Test Center at Edwards AFB, California after delivery in 1958, then assigned directly to USAF Logistics Command from then until 1982, usually flying from Kelly AFB, Texas. It was assigned to the 325th Fighter Weapons Wing at Tyndall AFB, Florida until 1986, when it returned to California; it was assigned to the B-1B development program at Palmdale to act as a chase plane. (Yanks' sources also claim that 57-2513 briefly served with the 120th Fighter-Interceptor Group (Montana ANG) at Great Falls, but the F-106.net page doesn’t confirm this.)

 

57-2513 flew with the B-1 chase program until 1990, when it returned to Tyndall and was assigned to 475th Weapons Evaluation Group, and was finally retired in 1993–one of the last (if not the last) non-drone F-106s to leave service. It would be acquired by the Yanks Air Museum in 2004 and restored to its markings with the B-1 program.

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