Convair F-106 Delta Dart

The Convair F-106 Delta Dart was the primary all-weather interceptor aircraft for the United States Air Force (USAF) from the 1960s through the 1980s. Designed as the so-called ultimate interceptor, it has proven to be the last dedicated interceptor in USAF service to date. It was gradually retired during the 1980s, although the QF-106 drone conversions of the aircraft were used until 1998. 

The F-106 emerged from the USAF 1954 interceptor program as an advanced derivative of the F-102 Delta Dagger known as the F-102B, for which the United States Air Force placed an order for in November 1955. The aircraft featured so many modifications and design changes it became a new design in its own right, redesignated F-106 on 17 June 1956. 

The F-106 served in the continental USA, Alaska, and Iceland, as well as brief periods in Germany and South Korea. Although contemplated for use in Vietnam, it never saw combat, nor was it exported to foreign users. The F-15A started replacing the F-106 in 1981, with Delta Darts typically passed on to Air National Guard units. The F-106 remained in service in various USAF and ANG units until 1988.

Convair F-106 Delta Dart
Class Aircraft
Type Fighter
Manufacturer Convair
Origin United States of America
Country Name Origin Year
United States of America 1956
ManufacturerName Production From Production To Quantity
Convair 340 View

The F-106 was the ultimate development of the USAF's 1954 interceptor program of the early 1950s. The initial winner of this competition had been the F-102 Delta Dagger, but early versions of this aircraft had demonstrated extremely poor performance, limited to subsonic speeds and relatively low altitudes. During the testing program the F-102 underwent numerous changes to improve its performance, notably the application of the area rule to the fuselage shaping and a change of engine, 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 in spite of being considered barely suitable for its mission, the Air Force sent out a production contract in March 1954, with the first deliveries expected the next year.

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

The J75 was somewhat larger than the J57 in the F-102A, and had 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 best performance across a wide range of supersonic speeds. This change also led to the ducts being somewhat shorter. The fuselage grew slightly longer, and was cleaned up and simplified in many ways. The wing was slightly enlarged in area, and a redesigned vertical tail surface was used. The engine's 2-position afterburner exhaust nozzle was also used for idle thrust control. The nozzle was held open reducing idle thrust by 40% giving slower taxiing and less brake wear.

A mock-up with the expected layout of the MX-1179, now known as the MA-1, was inspected and approved in December 1955. With growing confidence that the aircraft was now improving, an extended production contract for 17 F-102Bs was sent out on 18 April 1956. On 17 June, the aircraft was officially re-designated as the F-106A.

The first prototype F-106, an aerodynamic test bed, flew on 26 December 1956 from Edwards Air Force Base, with the second, fitted with a fuller set of equipment, following 26 February 1957. Initial flight tests at the end of 1956 and beginning of 1957 were disappointing, with performance less than anticipated, while the engine and avionics proved unreliable. These problems, and the delays associated with them nearly led to the abandoning of the program, but the Air Force decided to order 350 F-106s instead of the planned 1,000. After some minor redesign, the new aircraft, designated F-106A were delivered to 15 fighter interceptor squadrons along with the F-106B two-seat combat-capable trainer variant, starting in October 1959.

On 15 December 1959, Major Joseph W. Rogers set a world speed record of 1,525.96 mph (2,455.79 km/h) in a Delta Dart at 40,500 ft (12,300 m).

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 other roles such as daylight air superiority or fighter-bombing. To support its role, 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 proved extremely troublesome and was eventually upgraded more than 60 times in service. Similar to the F-102, it 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, along with a single GAR-11/AIM-26A Falcon nuclear-tipped semi-active radar homing (SARH) missile (which detected reflected radar signals), or a 1.5 kiloton-warhead AIR-2 (MB-2) Genie 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 fighters such as the McDonnell Douglas F-4 Phantom II and McDonnell Douglas F-15 Eagle carried missiles recessed in the fuselage or externally, but stealth aircraft would re-adopt the idea of carrying missiles or bombs internally for reduced radar signature.

The F-106 served in the continental US, Alaska, and Iceland, as well as for brief periods in 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."

Although contemplated for use in the Vietnam War the F-106 never saw combat, nor was it exported to foreign users. 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 made it very popular with its pilots. After the cancellation of their own Avro Arrow, the Canadian government briefly considered purchasing the F-106C/D.

In an effort to standardize aircraft types, the USAF was directed to conduct Operation Highspeed, a flyoff 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 also carry as large a bomb load as the Republic F-105 Thunderchief fighter-bomber. The Phantom was the winner, but would first be tasked to escort and later replace the F-105 fighter-bomber in the late 1960s before replacing older interceptors in 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 which provided virtually no degradation to overall aircraft performance, better instrumentation, and features like an inflight refuelling receptacle and an arrestor hook for landing emergencies.

Air-to-air combat testing suggested "The Six" was a reasonable match for the McDonnell Douglas F-4 Phantom II in a dogfight, with superior high-altitude turn performance and overall maneuverability (aided by the aircraft's lower wing loading). However, the Phantom had better radar – operated by an additional crewman – and could carry a load of up to four radar-guided Sparrow and four infrared Sidewinder missiles, while the Falcon missiles proved a disappointment for dogfighting over Vietnam. The F-4 had a higher thrust/weight ratio, superior climb performance, and 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 that involved fitting the F-106 with a new bubble canopy, a canopy without the metal bracing along the top. This greatly improved pilot visibility. Also added was an optical gunsight, and provision for a single M61 Vulcan 20 mm cannon. The M61 Vulcan had 650 rounds of ammunition in the center weapons bay and it replaced the AIM-26 Super Falcon or Genie.

The F-15A started replacing the F-106 in 1981, with "The Sixes" typically passed on to Air National Guard units. The F-106 remained in service in various USAF and ANG units until 1988.

Role Interceptor
Manufacturer Convair
General Dynamics
First flight 26 December 1956
Introduction June 1959
Retired August 1988 (ANG); 1998 (NASA)
Primary users United States Air Force
Air National Guard
Number built 342 (2 prototypes, 277 F-106A, 63 F-106B)
Unit cost US$4.7 million (1973)
$25.1 million (2014)
Developed from Convair F-102 Delta Dagger


General characteristics

  • Crew: 1
  • Length: 70.7 ft (21.55 m)
  • Wingspan: 38.25 ft (11.67 m)
  • Height: 20.28 ft (6.18 m)
  • Wing area: 661.5 ft (61.52 m)
  • Airfoil: NACA 0004-65 mod root and tip
  • Empty weight: 24,420 lb (11,077 kg)
  • Loaded weight: 34,510 lb (15,670 kg)
  • Powerplant: 1 x Pratt & Whitney J75-17 afterburning turbojet, 24,500 lbf (109 kN)
  • Zero-lift drag coefficient: 0.0083
  • Drag area: 5.8 ft (0.54 m)
  • Aspect ratio: 2.10

Performance

  • Maximum speed: Mach 2.3 (1,525 mph, 2,455 km/h)
  • Range: 1,800 mi (1,600 nm, 2,900 km) combat
  • Ferry range: 2,700 mi (2,300 nm, 4,300 km)
  • Service ceiling 57,000 ft (17,000 m)
  • Rate of climb: 29,000 ft/min (150 m/s)
  • Wing loading: 52 lb/ft (255 kg/m)
  • Thrust/weight: 0.71
  • Lift-to-drag ratio: 12.1
  • Time to altitude: 6.9 min to 52,700 ft (16,065 m)

Armament

  • Guns: 1 x 20 mm (0.787 in) M61 Vulcan gatling gun
  • Missiles:
    • 2 x AIM-4F Falcon
    • 2 x AIM-4G Falcon
    • 1 x AIR-2A Genie nuclear rocket

End notes