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The F-106 was designed in response to the 1954 interceptor program. Envisioned as an imagined "Ultimate Interceptor", it was a development of the F-102 Delta Dagger, and commenced as the F-102B prior to being redesignated by the United States Air Force (USAF). The F-106 was designed without a gun or provision for carrying bombs, instead carrying its AIM-4 Falconair-to-air missiles within an internal weapons bay; its clean exterior was beneficial to supersonic flight. Major differences from the F-102 included the adoption of the more powerful Pratt & Whitney J75turbojet engine, heavily redesigned air inlets along with a variable-geometry inlet duct to suit a wide range of supersonic speeds, and a general increase in size. On 26 December 1956, the first prototype performed its maiden flight. After flight testing demonstrated lesser performance gains than anticipated, the USAF only ordered 350 of the planned 1,000 F-106s.
Becoming operational in June 1959, the F-106 was the primary all-weather interceptor aircraft of the USAF through much of the Cold War era; it ended up being the final specialist interceptor to be used by the service to date. It was never used in combat nor were any exported. During the 1960s, a competitive evaluation between the F-106 and the McDonnell Douglas F-4 Phantom II determined the latter to be marginally superior, yet the type continued to be operated for a further two decades due to extensive demand for the F-4 in other roles. Convair proposed various improved models of the F-106, typically focused on the radar, communications, and other avionics, but none of these schemes were pursued. In one incident over Montana on 2 February 1970, an unmanned F-106 recovered from a flat spin after its pilot had ejected, belly landing relatively intact in a snow-covered field; it was recovered and continued to be flown for numerous years afterwards.
The F-106 was gradually withdrawn from USAF service during the 1980s as the arrival of newer air superiority fighters, particularly the McDonnell Douglas F-15 Eagle, had made the role of dedicated interceptors obsolete. Numerous F-106s were operated for a time by the Air National Guard. Many withdrawn aircraft were converted into target drones and redesignated QF-106 under the Pacer Six program, which were used up in 1998.[1][2][3] A handful of F-106s were operated by NASA for experimental purposes, such as the Eclipse Project, until 1998.
The F-106 was the ultimate development of the USAF's 1954 interceptor program of the early 1950s.[4] The initial winner of this competition had been the F-102 Delta Dagger, but early versions of this aircraft had demonstrated extremely poor performance, being limited to flying at subsonic speeds and relatively low altitudes.[5] 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, under which the first deliveries were expected during the following year.[6][7]
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[8]) with the more powerful Wright J67 (a Bristol Olympusproduced under license).[9] By the time this engine would be available, the MX-1179 was expected to be available, and thus it was selected as well. The intended result would be the "ultimate interceptor" that the USAF had originally sought.[10] However, while initial work on the Olympus design appeared to go well, by August 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 to the Pratt & Whitney J75.[11][12]
The J75 turbojet engine was a bigger engine than the J57 in the F-102A and it needed greater airflow in the engine. This demanded changes to the air inlets of the engine to allow more airflow and led to the further refinement of using a somewhat shorter variable-geometry inlet duct to allow the intakes to be tuned to best performance across a wide range of supersonic speeds. 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 two-position afterburner exhaust nozzle was also used for idle thrust control, held open to decrease thrust by 40%, resulting in slower taxiing and less brake wear.[13]
Throughout its early development, the F-102B had to compete for attention and resources with the F-102A; the aviation author Marcelle Knaack observed that there were fewer 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 arose.[12] 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-102B could be delivered. During December 1955, a mock-up with the expected layout of the MX-1179, now known as the MA-1, was inspected and approved.[14]
On 18 April 1956, an extended production contract for 17 F-102Bs was issued to Convair, representing substantially fewer aircraft than had been originally anticipated at this stage.[14] On 17 June of that year, the aircraft was officially re-designated as the F-106A.[15][16][17] On 18 August 1956, the USAF issued a systems development directive that called for development and production of the F-106 to occur simultaneously;[clarify] Knaack attributed this policy as being responsible for several later problems in the program.[18] During April 1957, the USAF formally rejected Convair's F-102C proposal (essentially a reengined model of the F-102) to concentrate on the more advanced F-106 program, which it had then anticipated to enter service during the following year.[19]
On 26 December 1956, the first prototype F-106, an aerodynamic test bed, performed its maiden flight from Edwards Air Force Base. On 26 February 1957, the second prototype, which was outfitted with a fuller set of equipment, made its first flight.[20][18] Early flight testing around the end of 1956 and 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 beneath Convair's own estimates.[21] Furthermore, both the engine and avionics proved to be somewhat unreliable.[22] These combined problems, and the delays associated with them, were nearly responsible for the termination of the program.[20][23]
However, the service decided to persist with the F-106 program after the Air Defense Command had heavily advocated for it.[24] 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.[21] At this stage, the service enacted several measures to hasten development towards production; in April 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.[25] By mid-1957, funding for 120 F-106As had been allocated.[26] The USAF ultimately opted to order 350 F-106s, substantially fewer than the planned fleet of 1,000 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 1959.[27][26]
F-106A Delta Darts from 5 FIS at CFB Moose Jaw in 1982
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).[28][29][30] That year, Charles E. Myers flew the same model aircraft at 1,544 mph (2,484 km/h).[31]
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.[26] 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.[32][33]
Similarly to the F-102, 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 Falconair-to-air missiles (either AIM-4G infra-red guided missiles or semi-active radar homing (SARH)-guided (which detected reflected radar signals) AIM-4E/F missiles[34]), 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.[35] Like its predecessor, the F-102 Delta Dagger, it could carry a drop tank under each wing.[36] 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 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 which 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 speeds below 120 knots (140 miles per hour; 220 kilometres per hour) and 2,000 feet (610 metres). 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.[37][38] 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 viewed an ejection at low altitude and slow speed as the most likely possibility. The ejection sequence with the B-seat was quite complicated and there were some unsuccessful ejections that resulted in pilot fatalities. The third seat, that replaced the Convair B-seat, was the Weber Zero-Zero ROCAT (for Rocket Catapult) seat. Weber Aircraft Corporation designed a "zero-zero" seat to operate at up to 600 knots (690 miles per hour; 1,100 kilometres per hour). High-altitude supersonic ejections were rare and ejections at relatively low altitudes and low speeds were more likely. The Weber "zero-zero" seat was satisfactory and was retrofitted to the F-106 after 1965.[39]
Florida National Guard F-106A "City of Jacksonville" Livery for the U.S. Bicentennial
A Soviet Tu-95 is intercepted by a F-106A off Cape Cod in 1982
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.[40] During December 1959, all F-106s were temporarily grounded following the accidental jettisoning of the canopy mid-flight on one aircraft. Many, but not all, of these problems were resolved by the start of 1961; this can be partially attributed to two major modification and retrofit program conducted during this timeframe.[41] Following the resolution of initial teething problems – in particular an ejection seat that killed the first 12 pilots to eject from the aircraft[42] – its exceptional performance led to the aircraft becoming relatively popular amongst its pilots.
The F-106 served in the contiguous US, Alaska, and Iceland, as well as for brief periods in Germany and South Korea.[43] 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."[44] 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, such as the North American F-86 Sabre and the Northrop F-89 Scorpion.[45]
Although contemplated for use in the Vietnam War, the F-106 never saw combat, nor was it exported to foreign users. 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 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 carry as large a bomb load as the Republic F-105 Thunderchief fighter-bomber.[46] 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 Air Defense Command in the 1970s.
An F-106A of the 87th FIS above Charleston AFB, SC in 1982
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.[47][33]
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). The Phantom had better radar – operated by an additional crewman – 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 a disappointment for dogfighting over Vietnam.[48] The F-4 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.
A NASA QF-106 Delta Dart from the Eclipse program shows its area ruled fuselage
In 1972, some F-106As were upgraded in Project Six Shooter that involved fitting the F-106 with a new canopy without metal bracing which greatly improved pilot visibility.[49] Also added was an optical gunsight and provision for a M61 Vulcan 20 mm cannon. The M61 Vulcan had 650 rounds of ammunition in the center of the weapons bay, being used in place of the AIR-2 Genie. Many F-106 units opted to fly without the gun, retaining their nuclear payload instead. The F-15A Eagle 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.[1]
Between 1 June 1983 and 1 August 1988 the Delta Darts were incrementally retired and sent to the Military Storage and Disposition Center in Arizona.[50][51] 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.[52] The last was destroyed in January 1998.[2][3] The drones were still capable of being flown as manned aircraft, such as for ferrying to a test; during the test they were flown unmanned.[53] The QF-106 replaced the QF-100 Super Sabre drone; the last shoot down of a QF-106 (57-2524) took place at Holloman AFB on 20 February 1997 after which the QF-106 was superseded by the QF-4S and QF-4E Phantom II drone.
Six F-106s were retained by NASA for test purposes through 1998. An F-106B two-seat trainer was operated by NASA Langley Research Center between 1979 and 1991.[54] This Delta Dart was used in research programs ranging from testing supersonic engines to improving maneuverability of fighters. Between 1980 and 1986 the aircraft was modified for the purpose of lightning strike research and became known as the Lightning Strike Plane and was struck 714 times without damage.[55][56] On one hour-long flight at 38,000 feet (12,000 metres) in 1984, lightning struck the research aircraft 72 times.[57] One significant modification was the replacement of the composite nose radome by 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 miles per hour; 560 kilometres per hour) from 5,000 to 40,000 feet (1,500 to 12,200 metres).[58] 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 to 1998.[59][60] 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 transport aircraft. The test demonstrated the possibility of towing and launching a space launch vehicle from behind a tow plane.[61][62]
On 2 February 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. The resulting change of balance caused the aircraft to stabilize and later belly land in a snow-covered field, suffering only minor damage. The aircraft, promptly nicknamed "The Cornfield Bomber", was then sent back to base by rail, repaired and returned to service, and is now on display at the National Museum of the United States Air Force.[63]
F-106A: (Convair Model 8-24) Improved version of the F-102. Fitted with the MA-1 Integrated Fire Control System with SAGE datalink, J-75 afterburning turbojet, enlarged intake, variable-geometry inlet ramps and shortened intake ducts, refined fuselage shape, modified wings and redesigned tailfin; tailpipe fitted with a device to reduce the tendency of the jet exhaust to blow unsecured objects around while taxiing, yet allowing virtually maximum performance at high thrust settings including afterburner. Performance was deemed unsatisfactory and modifications were made. The aircraft was capable of low supersonic speeds without afterburner (but with a significant range penalty) and had a maximum altitude at least 57,000 ft (17,000 m). Many were fitted with a conically cambered wing for improved takeoff, supersonic and high-altitude flight. To improve the aircraft's range the aircraft was fitted with two streamlined external supersonic tanks that still kept the aircraft capable of sustained roll rates of 100 degrees per second. Since these tanks produced virtually no significant performance degradation they were rarely jettisoned and were routinely carried around. After 1972, many F-106s were refitted with a new canopy featuring improved visibility, improved optic sights and provision for a gunpack in the center weapons bay.
A two-seat F-106B trainer variant of the New Jersey ANGF-106B: (Convair Model 8-27) Two-seat, combat-capable training version. Pilot and instructor are seated in tandem. Due to the extra seat, the fuselage is actually better area ruled; combined with a likely reduction in weight.[64][N 1] Weapons configurations same as F-106A.
NF-106B: This designation was given to two F-106Bs used as test aircraft with NASA and associated research facilities from 1966 to 1991.[65]
F-106C: Unbuilt version. Aircraft was intended to have the AN/ASG-18 radar and fire control system fitted originally developed for the North American XF-108 Rapier. For its time, it was the largest radar to ever be fitted to a fighter, actually requiring hydraulic actuators to turn the antenna. To accommodate this larger radar system, the nose cone was longer and of greater diameter. The design featured an improved raised canopy design featuring better visibility, canards and lengthened rectangular inlet ducts. The aircraft was to be capable of carrying one GAR-9/AIM-47A in its center bay and one AIM-26A in each side bay. At one time, the US Air Force had considered acquiring 350 of these advanced interceptors, but the F-106C/D project was cancelled on 23 September 1958.[66][67][N 2]
F-106D: Unbuilt two-seat version of the F-106C.[68]
F-106X: Unbuilt version (early 1968). It would have been outfitted with canards and powered by a JT4B-22 turbojet. It was envisioned as an alternative to the Lockheed YF-12, and was to have had a fire control system with "look-down/shoot-down" capability fed by a 40-inch (102 cm) radar dish.[29][69]
F-106E: Unbuilt version. On 3 September 1968, Convair issued a proposal for an "improved" interceptor that was to be designated F-106E/F. It was to be compatible with the upcoming airborne warning and control systems as well as with the over-the-horizon radar defense network. The F-106E/F would have had a longer nose and a new and improved radar with a look-down/shoot-down tracking and missile launch capability. It would also have had a two-way UHF voice and datalink radio. It would have been capable of launching both nuclear and non-nuclear missiles, including the AIM-26 Nuclear Falcon and the AIM-47.[70]
F-106F: Unbuilt two-seat version of the F-106E.
QF-106A: Converted into drones, were still capable of being flown both as manned and unmanned aircraft.
F-106 RASCAL Project: Unbuilt version. It would have been a low cost satellite launcher.[71]
^It is uncertain if the F-106B was fitted with the modified "Project Sharpshooter" optic sights and gunpack provision.
^ After the cancellation of the Avro Canada CF-105 Arrow, the Canadian government briefly considered purchasing the F-106C/D. After the F-106C/D project was canceled, it acquired McDonnell CF-101 Voodoos, instead.
^ ab"The "Pacer Six" Program". The 456th Fighter Interceptor Squadron. 1998-2014 www.F106DeltaDart.com. Archived from the original on 26 July 2014. Retrieved 16 July 2014.
^"The Convair F-102A". 456FIS.ORG. THE 456th FIGHTER INTERCEPTOR SQUADRON. Archived from the original on 14 July 2014. Retrieved 17 June 2014.
^"CONVAIR F-106A DELTA DART". The Official Web Site of National Museum of the USAF. National Museum of the US Air Force. Archived from the original on 14 September 2011. Retrieved 17 June 2014.
^Baugher, Joe. "Convair F-106A Delta Dart."Archived 2010-11-24 at the Wayback MachineUSAAC/USAAF/USAF Fighter and Pursuit Aircraft: Convair F-106 Delta Dart, American Military Aircraft, 19 December 1999. Retrieved: 8 April 2011.
^Carey, Christopher T. "Ejectorseats History". ejectorseats.co.uk. AEOLUS AEROSPACE 5960 S. Land Park Drive, Suite 341 Sacramento, CA 95822-3313. Archived from the original on 29 May 2014. Retrieved 18 July 2014.
^"Lightning and the Space Program"(PDF). tstorm.com. John F. Kennedy Space Center Kennedy Space Center, Florida 32899 AC 321/867-2468 - FS-1998-08-16-KSC August 1998 Page 2. Archived(PDF) from the original on 4 March 2016. Retrieved 18 July 2014.
^Tucker, Tom. "The Eclipse Project"(PDF). NASA History Division, Office of Policy and Plans. U.S. Government Printing Office, Washington DC 20546. Archived(PDF) from the original on 12 January 2010. Retrieved 18 July 2014.
^"Factsheets: Convair F-106B". NationalMuseum.af.mil. National Museum of the United States Air Force. Archived from the original on 3 September 2014. Retrieved 18 July 2014.
^Baugher, Joe. "Convair F-106B Delta Dart."Archived 2010-11-24 at the Wayback MachineUSAAC/USAAF/USAF Fighter and Pursuit Aircraft: Convair F-106 Delta Dart, American Military Aircraft, 18 December 1999. Retrieved: 8 April 2011.
^Baugher, Joe. "Convair F-106C/D Delta Dart."Archived 2010-11-24 at the Wayback MachineUSAAC/USAAF/USAF Fighter and Pursuit Aircraft: Convair F-106 Delta Dart, American Military Aircraft, 18 December 1999. Retrieved: 8 April 2011.
^"RASCAL Project". F-106 Delta Dart. Archived from the original on 2014-01-16. Retrieved 2014-03-04.
^Baugher, Joe. "F-106 Squadron Assignments."Archived 2012-06-05 at the Wayback MachineUSAAC/USAAF/USAF Fighter and Pursuit Aircraft: Convair F-106 Delta Dart, American Military Aircraft, 18 December 1999. Retrieved: 12 January 2012.
Donald, David (2003). "Convair F-106 Delta Dart: The Ultimate Interceptor". Century Jets: USAF Frontline Fighters of the Cold War. Norwalk, Connecticut: AIRtime Publishing. ISBN1-880588-68-4. OCLC56456861.
Drendel, Lou; Carson, Don A. (1974). F-106 Delta Dart in Action. Warren, Mich.: Squadron/Signal Publications. OCLC1010385.
Jenkins, Dennis R.; Landis, Tony R. (2008). Experimental & Prototype U.S. Air Force Jet Fighters. North Branch, Minnesota: Specialty Press. ISBN978-1-58007-111-6. OCLC184982545.
Pace, Steve (1991). X-Fighters: USAF Experimental and Prototype Fighters, XP-59 to YF-23. St. Paul, Minnesota: Motorbooks International. ISBN0-87938-540-5.
Peacock, Lindsay (October 1986). "Delta Dart ... Last of the Century Fighters". Air International. 31 (4). Stamford, UK: Fine Scroll: 198–206, 217.
The Convair F-106 Delta Dart was a supersonic all-weather interceptor aircraft developed for the United States Air Force (USAF) as the primary defender against potential Soviet bomber incursions during the Cold War era.[1][2] Evolving from the earlier F-102 Delta Dagger, it was initially designated the F-102B but redesignated F-106 on June 17, 1956, due to extensive redesigns including a more powerful engine and structural enhancements to meet advanced interception requirements.[1][2]The aircraft's development began in the early 1950s at Convair's San Diego facility, with the first F-106A prototype (serial 56-0451) achieving its maiden flight on December 26, 1956, powered by a Pratt & Whitney J75-P-17 turbojet engine producing 24,500 pounds of thrust with afterburner.[1][2] Deliveries to the USAF commenced in July 1959, starting with the 539th Fighter Interceptor Squadron of Air Defense Command, and it achieved full operational capability by October 1959 with the 498th Fighter Interceptor Squadron.[1][2] A total of 277 single-seat F-106A variants and 63 two-seat F-106B trainers were produced, with manufacturing concluding in late 1960.[1][2]Key specifications included a wingspan of 38 feet 4 inches, length of 70 feet 9 inches, maximum takeoff weight of 41,831 pounds, top speed of 1,525 mph (Mach 2.3 at 40,000 feet), service ceiling of 57,000 feet, and a combat radius of approximately 500 nautical miles (580 miles) with internal fuel.[1][2] It was equipped with the advanced Hughes MA-1 fire-control system, enabling semi-autonomous operation for detection, pursuit, missile launch, and return to base, though the pilot retained control for landing.[1] Armament consisted of one AIR-2A Genie unguided nuclear-tipped rocket and up to four AIM-4 Falcon infrared or semi-active radar-homing air-to-air missiles, launched from an internal weapons bay; some later aircraft were modified to carry an M61 Vulcan 20mm cannon.[1][2]In service, the F-106 formed the backbone of USAF continental air defense through the 1960s and 1970s, with squadrons deployed across the United States and Alaska, though it saw no combat deployments.[1][2] Notable achievements included setting a world absolute speed record of 1,526 mph (Mach 2.3) on December 15, 1959, piloted by Maj. Joseph W. Rogers.[3] The aircraft demonstrated remarkable resilience in an incident on February 2, 1970, when an F-106A (58-0787) from the 71st Fighter Interceptor Squadron at Malmstrom Air Force Base entered an unrecoverable flat spin during a training mission; the pilot, Capt. Gary Foust, ejected safely, but the aircraft's MA-1 system autonomously executed a wheels-up belly landing in a snowy field near Big Sandy, Montana, with minimal damage, allowing it to return to service until retirement after on-site repairs.[1][4]The F-106 was gradually phased out in the 1980s as the F-15 Eagle entered service, with active-duty retirement completed by 1983 and Air National Guard units operating until June 1, 1988.[1][2] Post-retirement, 194 examples were converted into QF-106 target drones for missile testing, serving until 1998, while others contributed to NASA research programs such as the ECLIPSE project for propulsion studies in 1997–1998.[3] Today, surviving airframes are preserved in museums, including the National Museum of the United States Air Force.[1]
Development
Origins and Requirements
The escalating tensions of the Cold War, particularly the perceived threat from Soviet long-range bombers capable of delivering nuclear payloads, prompted the United States Air Force (USAF) to initiate advanced interceptor programs in the late 1940s. In early 1949, the Air Defense Command (ADC) issued a Request for Proposals (RFP) under the Weapon System 201 (WS-201) designation, informally known as the 1954 Interceptor, to develop a dedicated all-weather aircraft for countering high-altitude Soviet bomber formations expected to enter service by the mid-1950s.[5][6] This program evolved from earlier efforts like MX-1554, emphasizing supersonic performance and integration with emerging ground-based radar networks to address vulnerabilities in continental air defense.[6]By 1954, the WS-201 requirements had advanced significantly, calling for an interceptor capable of sustained Mach 2 speeds, radar detection ranges supporting engagements up to 100 miles, and armament limited to nuclear-tipped air-to-air missiles for standoff intercepts, reflecting a doctrinal shift away from gun-armed fighters toward missile-centric all-weather operations.[6] Key specifications included seamless integration with the Semi-Automatic Ground Environment (SAGE) system for automated vectoring and fire control, ensuring rapid response to bomber incursions without reliance on visual acquisition. The design prioritized no onboard guns, focusing instead on internal bays for missiles like the nuclear-armed AIR-2 Genie and AIM-4 Falcon, to maximize speed and stealth in high-threat environments.[1]The F-106 directly evolved from the Convair F-102 Delta Dagger, an earlier WS-201A product that fell short of performance goals due to engine limitations and aerodynamic inefficiencies. In response to the 1954 Advanced Interceptor needs (later associated with WS-306A refinements), Convair proposed an improved variant initially designated F-102B, incorporating major redesigns such as an area-ruled fuselage for transonic drag reduction and a more powerful Pratt & Whitney J75 engine to achieve the required Mach 2 capability. These changes were so extensive that the USAF redesignated it the F-106 in June 1956, marking it as a distinct aircraft rather than a mere upgrade.[6][1]In November 1955, the USAF awarded Convair a contract for 17 pre-production F-102B (later F-106A) aircraft, including two prototypes. This order laid the foundation for production, emphasizing the interceptor's role as the backbone of SAGE-linked air defense forces. Subsequent contracts expanded production, resulting in a total of 340 aircraft built.[6]
Design Competition and Production
The F-106 originated as a proposed upgrade to the F-102 under the WS-306A program, with Convair selected to proceed based on their existing F-102 development and delta-wing expertise from the XF-92A. Production arrangements were established under cost-plus-fixed-fee contracts with Convair. Manufacturing was split between Convair's facilities in San Diego, California, which handled the majority of assembly, and Fort Worth, Texas, for component production and some final integration. Challenges arose with engine supply from Pratt & Whitney, as early development delays in alternative powerplants necessitated a shift to the more reliable J75 series, impacting initial timelines.[1][3]Key engineering decisions during the production phase included the adoption of the Pratt & Whitney J75-P-17 turbojetengine, which provided 24,500 pounds of thrust with afterburner and outperformed earlier alternatives like the Wright J67 in reliability and performance for sustained Mach 2 operations. The aircraft was designed around the Hughes MA-1 integrated fire-control and guidance system, enabling automated interception in all weather conditions when linked to the Semi-Automatic Ground Environment (SAGE) network. Armament was limited to missiles only, forgoing guns or bombs to prioritize internal carriage of one AIR-2A Genie nuclear rocket and up to four AIM-4 Falcon air-to-air missiles within a ventral weapons bay.[1][3][7]Prototype construction began at Convair's San Diego plant in 1955, with the first YF-106A (serial 56-0451) rolling out in late 1956 and achieving its maiden flight on December 26, 1956. The first production F-106A flew on 23 December 1958, marking the transition to full-rate manufacturing ahead of operational deliveries starting in 1959.[1][3]
Flight Testing and Records
The prototype Convair F-106A Delta Dart, serial number 56-0451, conducted its maiden flight on December 26, 1956, at Edwards Air Force Base, California, piloted by Convair chief test pilot Richard L. Johnson. The 20-minute flight reached an altitude of 30,000 feet (9,144 meters) and a speed of Mach 0.8 before being aborted due to fluctuations in the air turbine motor frequency and failure of the speed brakes to retract fully.[8]The ensuing flight testing program, divided into multiple phases led by Convair and the U.S. Air Force, addressed initial challenges with aerodynamic stability, engine performance, and supersonic handling. Early evaluations in 1957 revealed disappointing acceleration and a top speed limited to Mach 1.9 at 57,000 feet (17,373 meters), attributed to inadequate enginethrust from the Pratt & Whitney J75-P-9 and inlet inefficiencies causing compressor stalls or "buzz" at high Mach numbers. Modifications, including an enlarged inlet capture area, thinner duct lips, leading-edge wing slots to replace boundary layer fences, and an upgrade to the more powerful J75-P-17 engine (producing 24,500 pounds of thrust with afterburner), resolved these issues over extensive test flights. Supersonic evaluations progressed to sustained speeds exceeding Mach 2.2, with additional work on canopy jettison systems following an accidental mid-flight release in December 1959 that temporarily grounded the fleet for safety inspections.[3][9][1]A highlight of the testing phase came on December 15, 1959, when Major Joseph W. Rogers, flying F-106A serial number 56-0467, established a Fédération Aéronautique Internationale (FAI)-certified world absolute speed record of 1,525.92 mph (2,455.74 km/h, equivalent to Mach 2.31) at 40,000 feet (12,192 meters) over Edwards AFB. This achievement, part of Project Firewall to surpass the prior Soviet record, followed an aborted attempt in another aircraft due to compressor stalls and demonstrated the refined aircraft's high-speed capabilities after overcoming early propulsion integration hurdles.[9][3]Production testing transitioned to acceptance trials starting in 1958, focusing on operational readiness and systems integration for Air Defense Command units. These efforts culminated in the first deliveries to the U.S. Air Force in mid-1959, enabling the 498th Fighter Interceptor Squadron at Geiger Field, Washington, to declare initial operational capability in June 1959, marking the aircraft's shift from prototype validation to frontline service.[10][11]
Design
Airframe and Aerodynamics
The Convair F-106 Delta Dart employed a delta-wing configuration optimized for supersonic performance, featuring a 60-degree leading-edge sweep that provided high lift at low speeds while minimizing drag at Mach numbers above 1.0. The airframe incorporated an area-ruled fuselage, often described as having a "coke bottle" shape, to reduce transonic wave drag in accordance with Richard Whitcomb's area rule principles developed at NASA's Langley Research Center. Overall dimensions included a length of 70 ft 9 in, a wingspan of 38 ft 4 in, and an empty weight of 24,420 lb, contributing to a low wing loading of approximately 35 lb/sq ft that enhanced maneuverability.[7][3][1]The airframe was constructed using a semi-monocoque structure primarily of aluminum alloy for the fuselage and wings, which provided strength and lightness while allowing for the integration of internal fuel tanks and a ventral weapons bay. Titanium was selectively employed in high-heat areas, such as around the engine inlets and exhaust, to withstand thermal stresses during sustained afterburner operation. Control surfaces included all-moving tail surfaces for pitch and yaw stability, augmented by split-speed brakes on the fuselage sides and trailing-edge elevons on the wings to manage deceleration and roll without compromising the clean aerodynamic profile.[7]Aerodynamic innovations in the F-106 design included the deletion of canard foreplanes from earlier conceptual studies, such as the proposed F-106X, in favor of a pure tailless delta configuration that simplified production and improved supersonic stability. To compensate for pitch authority, an enlarged vertical stabilizer with a clipped triangular shape was adopted, enhancing directional control at high altitudes and speeds. The side-mounted inlets featured variable geometry ramps to efficiently manage supersonic airflow into the engine, briefly integrating with the propulsion system for optimal compression without boundary layer divergence.[7][3]The ejection system evolved for enhanced pilot safety, with early prototypes equipped with downward-ejecting seats that posed risks during low-altitude operations. These were upgraded starting in 1958 to the upward-firing Weber Zero-Zero seat, capable of safe ejection at zero speed and zero altitude using a rocket-assisted catapult, significantly improving survivability in ground-hugging intercepts.[12][13]
Propulsion System
The Convair F-106 Delta Dart was powered by a single Pratt & Whitney J75-P-17 afterburning turbojet engine, a two-spool axial-flow design that provided the high thrust necessary for supersonic interception missions.[14] This engine delivered 17,200 lbf (76.5 kN) of dry thrust and 24,500 lbf (109 kN) with afterburner, enabling the aircraft to achieve Mach 2+ speeds.[15] Measuring approximately 12 feet (144 inches / 3.66 m) in length and 3 feet 7 inches (43 inches / 1.09 m) in diameter, the J75-P-17 had a dry weight of around 5,100 pounds (2,313 kg), making it a substantial but efficient powerplant scaled up from the earlier J57 series used in predecessor aircraft.[16]Early prototypes of the F-106 initially incorporated the less powerful J75-P-9 variant, which suffered from thrust deficiencies that limited performance during initial flight testing.[3] These issues were resolved through an upgrade to the J75-P-17, which offered enhanced compressor efficiency and afterburner capability, significantly boosting overall aircraft acceleration and top speed.[7] This transition addressed power shortfalls inherited from the design's evolution from the F-102 Delta Dagger, ensuring the F-106 met Air Defense Command requirements for rapid climb and intercept profiles.[17]The fuel system supported extended operations with an internal capacity of 1,514 US gallons (5,731 liters) of JP-4 fuel, distributed across integral wing tanks and a fuselage tank, plus provisions for two external drop tanks on wingtip pylons to achieve a ferry range of approximately 1,500 miles (2,400 km).[18] High afterburner fuel consumption—up to several thousand pounds per hour during sustained supersonic flight—necessitated careful mission planning, but the system's pressurized tanks and in-flight refueling probe, added later, mitigated range limitations for alert duties.[19]Air intake was managed by variable-geometry rectangular inlets with a multi-section ramp system to optimize airflow at supersonic speeds, incorporating boundary layer bleed slots to prevent separation and maintain engine efficiency across a wide Mach range.[20] The exhaust featured a variable-area nozzle with two positions for afterburner operation and idle thrust modulation, reducing ground idle thrust by up to 50% when opened, though it did not incorporate thrust vectoring in production models.[21]
Avionics and Armament
The Convair F-106 Delta Dart featured the Hughes MA-1 integrated fire-control system, which combined the AN/APQ-50 radar, a digital computer, and an autopilot to facilitate fully automatic intercepts from takeoff through missile launch and return to base vicinity.[1] The system's radar offered long-range detection capabilities of approximately 40–50 nautical miles against large targets like bombers, enabling precise guidance under ground control.[17][22] This setup allowed the pilot to monitor the intercept while the MA-1 handled navigation and targeting, with the pilot resuming manual control only for landing.[23]The F-106's armament emphasized standoff nuclear and guided missile strikes suited to its interceptor role, carried internally in a ventral tray to maintain aerodynamics. It typically loaded four AIM-4 Falcon air-to-air missiles—comprising semi-active radar-homing (SARH) and infrared-guided variants—for engaging multiple targets, alongside a single AIR-2 Genie unguided rocket armed with a 1.5-kiloton W25 nuclear warhead for area denial against bomber formations.[1][24] The absence of a cannon reflected the aircraft's focus on high-speed, beyond-visual-range engagements rather than dogfighting.[7]Supporting the MA-1 were additional avionics including the SAGE data link for real-time ground-directed intercepts, UHF and VHF radios for communication, and basic inertial navigation aids integrated with analog cockpit instruments for situational awareness.[1] The cockpit layout prioritized the pilot's oversight of automated systems, with displays for radar modes, weapon status, and flight parameters.[17]Despite its sophistication, the F-106 faced challenges with the AIM-4 Falcon missiles, which exhibited reliability issues including high failure rates in early tests—such as only one hit in 20 launches for initial variants—prompting ongoing upgrades to improve hit probabilities.[23] These limitations, including seeker interference and motor performance shortfalls, reduced overall effectiveness in simulated intercepts until later modifications.[7]
Operational History
Introduction to Service
The Convair F-106 Delta Dart entered operational service with the United States Air Force's Air Defense Command (ADC) in June 1959, when the 498th Fighter Interceptor Squadron (FIS) at Geiger Field (now Spokane International Airport), Washington, received its initial aircraft, marking the type's transition from testing to frontline duty. The squadron, previously equipped with F-102 Delta Daggers, completed full conversion to the F-106 by early 1960, replacing aging F-86D and F-86L Sabre interceptors as part of ADC's push to modernize its all-weather interceptor force against potential Soviet bomber threats.[11] This initial deployment established the F-106 as the USAF's premier supersonic interceptor, with the first aircraft declared fully operational capability on October 31, 1959.[3]To facilitate pilot conversion and maintain operational readiness, the two-seat F-106B trainer variant was introduced in late 1959, with early deliveries to Edwards Air Force Base for test and evaluation before wider distribution to operational units.[25] These combat-capable trainers enabled efficient transition training for pilots moving from earlier interceptors, supporting the rapid buildup of F-106 expertise across ADC. Concurrently, the Air Defense Weapons Center (ADWC) was activated at Tyndall Air Force Base, Florida, in 1959 under the 4756th Test Squadron, serving as the primary hub for F-106 weapons systems evaluation, pilot proficiency training, and tactical development.[26]Early service revealed significant challenges, including poor initial reliability of the Pratt & Whitney J75-P-17 turbojet engine, which suffered from frequent failures due to its high-performance design, alongside the aircraft's overall maintenance intensity stemming from its sophisticated MA-1 fire-control system and advanced avionics that demanded specialized ground support.[17] These issues led to temporary groundings, such as in December 1959 following a canopy jettison incident, and required extensive modifications under programs like "Wild Goose" starting in 1960 to improve serviceability.[10][3]The F-106 fleet expanded rapidly to meet ADC requirements, with 14 squadrons fully equipped by the end of 1960 and further growth to approximately 17 active-duty squadrons by 1962, distributed across bases in the continental United States, Alaska (such as Galena and King Salmon), and Iceland (Keflavík Air Base) to provide comprehensive coverage of North American airspace.[3][27] This basing strategy enhanced strategic air defense postures, with over 250 single-seat F-106As in service by 1962.[3]
Peacetime Air Defense Roles
The Convair F-106 Delta Dart fulfilled its peacetime air defense roles primarily as the backbone of the U.S. Air Force Air Defense Command (ADC), tasked with intercepting simulated Soviet bomber threats during routine operations. Integrated with the Semi-Automatic Ground Environment (SAGE) system, the aircraft received automated guidance and fire control data from ground-based radars and computers, enabling pilots to execute intercepts with minimal manual intervention beyond takeoff and landing.[3] Alert duties formed the core of these missions, with F-106 units maintaining Quick Reaction Alert (QRA) status, ready for 15-minute scrambles to counter potential incursions over North American airspace.[17]F-106 squadrons participated in major exercises to hone air defense tactics, including Operation Sky Shield in the early 1960s, which simulated large-scale bomber attacks on the continental U.S. to evaluate interceptor effectiveness against jamming and decoys, and ongoing NORAD drills that tested coordinated responses across commands.[28] Deployments enhanced polar region coverage, with units such as the 87th Fighter-Interceptor Squadron rotating to Keflavik Naval Air Station in Iceland in April 1978 to bolster North Atlantic defenses, while others, including the 318th and 498th Fighter-Interceptor Squadrons, deployed ten aircraft to Galena Airport in Alaska in July 1963 to strengthen defenses against transpolar threats.[3]Beginning in 1972, the F-106 transitioned to Air National Guard (ANG) units to extend its service life amid active-duty drawdowns, with six squadrons—the 102d, 119th, 125th, 171st, 186th, and 194th Fighter-Interceptor Squadrons—receiving the aircraft. Throughout its career, the F-106 saw no combat deployments, remaining dedicated to defensive operations, bolstered by 1970s upgrades that enhanced its AIM-4 Falcon missiles with improved guidance variants and incorporated electronic countermeasures (ECM) for better survivability against simulated threats.[29]
Deactivation and Transition
The retirement of the F-106 Delta Dart from active-duty U.S. Air Force units under Air Defense Command (ADC) began in 1981 as the aircraft were progressively replaced by the more versatile McDonnell Douglas F-15A Eagle interceptor.[3] This phase-out accelerated following the inactivation of ADC in 1979 and its absorption into Tactical Air Command, with the last active-duty F-106 flights occurring by late 1983, including the final sortie from McChord Air Force Base on November 4, 1983. The transition allowed the Air Force to redirect resources toward newer platforms capable of broader mission profiles beyond high-altitude interception.Air National Guard (ANG) units continued operating the F-106 for air defense missions into the mid-1980s, with retirements spanning 1985 to 1988 as they too transitioned to F-15A/C and F-16A aircraft.[3] These units, such as those in California, Montana, and New Jersey, maintained alert postures until newer fighters could be integrated, ensuring continuity in continental defense.[30] The process reflected evolving threats and budget priorities, prioritizing multirole fighters over dedicated interceptors.The final operational ANG sortie occurred on August 1, 1988, flown by the 119th Fighter Interceptor Squadron of the New Jersey Air National Guard, marking the end of the F-106's frontline service.[30]
Later Uses
Drone Conversion Program
The Pacer Six program, launched in 1986, converted 194 retired F-106A aircraft into unmanned full-scale aerial targets for U.S. Air Force training exercises. Modifications, carried out by Flight Systems Inc. at Mojave Airport, California, entailed removing the cockpit instrumentation and installing remote control systems along with telemetry equipment to enable ground-based operation.[31][32]Designated QF-106A, these drones served as high-performance targets simulating enemy bombers during missile tests, with the first conversion achieving flight in July 1987. They remained in active USAF service until 1998, supporting air defense evaluations by providing realistic supersonic maneuvering capabilities.[32][33]The QF-106As conducted over 1,000 sorties primarily at Tyndall Air Force Base, Florida, and Holloman Air Force Base, New Mexico, where they were controlled by the 82nd Aerial Targets Squadron and the 556th Test Squadron, respectively. In live-fire scenarios, the drones were engaged by fighter aircraft using AIM-7 Sparrow and AIM-120 AMRAAM missiles to validate weapon accuracy and tactics.[34][32]The program concluded with the final QF-106A flight in October 1998, by which time more than 30 drones had been destroyed in exercises, while the surviving airframes were either scrapped or transferred for preservation.[32][7]
NASA Research Applications
NASA acquired several F-106B two-seat variants starting in 1966 for aeronautical research at centers including Lewis (now Glenn) Research Center and Langley Research Center. These aircraft, designated NF-106B, were selected for their delta-wing design and supersonic capabilities, serving as testbeds for propulsion, aerodynamics, and flight control experiments until the 1990s. The NF-106Bs accumulated significant flight time in crewed missions.[35]Key projects included propulsion integration and inlet dynamics at high speeds at Lewis Research Center, building on supersonic transport studies. Vortex flow studies at Langley utilized the F-106's leading-edge configuration to explore vortex generation and stability at high angles of attack, employing in-flight flow visualization to capture three-dimensional flow patterns and validate design tools for improved maneuverability. Notably, an NF-106B (57-2516, NASA 816) conducted lightning research from 1980 to 1986, enduring 714 direct strikes over 195 flights to assess threats to aircraft systems and structures.[36][37]In the late 1990s, NASA Dryden (now Armstrong) Flight Research Center supported the ECLIPSE project (1997-1998), using six QF-106 drones to demonstrate aerotow launch concepts for reusable space vehicles. The drones were towed aloft by a C-141A Starlifter to altitudes up to 25,000 feet across six flights, validating the aerotow method. The F-106's research service extended until 1998, logging over 2,000 hours across NASA's programs. These efforts contributed data to advanced flight control and aerodynamic studies, influencing later vehicles like the F/A-18 High Alpha Research Vehicle.[38]
Notable Incidents
One of the most famous incidents involving the Convair F-106 Delta Dart occurred on February 2, 1970, during a training mission from Malmstrom Air Force Base, Montana. An F-106A (serial number 58-0787) assigned to the 71st Fighter-Interceptor Squadron entered an uncontrollable flat spin at approximately 15,000 feet, prompting the pilot, 1st Lt. Gary Foust, to eject safely using the aircraft's Weber zero-zero ejection seat.[1][39] The unpiloted aircraft, trimmed for level flight prior to ejection, recovered from the spin due to the shift in center of gravity and aerodynamic changes, gliding to a gentle landing in a snow-covered field near Big Sandy, Montana, where it slid approximately 400 feet before coming to a stop.[1][39] Foust landed uninjured and was rescued by local snowmobilers, while ground crews later secured the intact airframe, which suffered only minor damage to its landing gear and canopy.[39] This event, dubbed the "Cornfield Bomber," highlighted the F-106's robust design and stability systems, becoming a symbol of the aircraft's exceptional durability in aviation lore.[39]Early testing of the F-106 was marred by significant accidents, including a fatal prototype crash on January 5, 1959. During a missile launch test against a drone target near Holloman Air Force Base, New Mexico, F-106B prototype 57-2511, piloted by Convair chief test pilot Francis "Fran" Everett Parker, suffered a catastrophic failure, possibly due to control issues or an onboard explosion, crashing 13 miles south of Alamagordo and killing both Parker and a backseater.[40] Another early loss occurred on April 8, 1959, when F-106A 57-229 crashed near Indian Springs, Nevada, resulting in the death of its pilot during a test flight.[41] These incidents underscored the challenges of integrating the advanced Pratt & Whitney J75 engine and supersonic aerodynamics into the delta-wing platform.The initial J75-P-9 engines fitted to early F-106s were plagued by reliability issues, including in-flight compressor stalls and fires, contributing to multiple losses between 1958 and 1960. For instance, on October 27, 1958, F-106A 57-242 was destroyed in a crash near Edwards Air Force Base, California, shortly after its first flight, attributed to engine-related turbine malfunctions.[42] Similar engine problems led to groundings and redesigns, with the more reliable J75-P-17 variant eventually retrofitted to address acceleration deficiencies and fire risks that had caused at least six hull losses in this period, including two fatalities.[3][41]Over its 29-year service life, the F-106 fleet of 340 aircraft (277 F-106As and 63 F-106Bs) suffered 112 losses to accidents or ground fires, representing approximately 33% of production.[3][41] Ejection performance was notably safe, with the Weber zero-zero seat—introduced in 1965 and retrofitted fleet-wide—enabling successful escapes in high-altitude and low-speed scenarios; records indicate a 100% survival rate in the 13 documented ejections, a testament to the seat's design for the F-106's operational envelope.[13][3]
Variants and Derivatives
Primary Interceptor Models
The F-106A served as the primary single-seat interceptor variant of the Convair F-106 Delta Dart, designed for all-weather air defense against Soviet bomber threats during the Cold War. A total of 277 F-106A aircraft were produced by Convair in San Diego, California, with deliveries to the [United States Air Force](/page/United_States_Air Force) commencing in 1959 and completing in late 1960.[3][1] These aircraft formed the backbone of the Air Defense Command's interceptor force, achieving initial equipping with the 498th Fighter-Interceptor Squadron at Geiger Field, Washington, in late May 1959, and full operational capability by October 1959.[3]Central to the F-106A's capabilities was the Hughes MA-1 integrated fire control and electronic guidance system, which interfaced with the Semi-Automatic Ground Environment (SAGE) data link for ground-directed intercepts, enabling fully autonomous flight, target acquisition, missile launch, and return to base without pilot intervention in certain scenarios.[1] For armament, the standard loadout included four AIM-4 Falcon semi-active radar-homing and infrared-guided air-to-air missiles, supplemented by a single AIR-2A Genie unguided rocket armed with a 1.5-kiloton nuclear warhead for area denial against bomber formations.[1] This configuration emphasized high-speed, long-range interception at altitudes up to 50,000 feet and speeds exceeding Mach 2.[3]Compared to the two YF-106A prototypes, production F-106As incorporated refinements based on flight testing, including a redesigned fuselage with a "coke bottle" shape for improved area ruling to reduce transonic drag, variable-geometry air inlets optimized for the Pratt & Whitney J75-P-17 turbojet engine, and adjusted inlet angles for enhanced supersonic airflow efficiency.[3] Early production blocks (1 through 20) featured initial configurations such as Case 14 wingtips and J75-P-9 engines, while later blocks (25 and above) included upgraded Case 29 wingtips with revised leading-edge camber for better low-speed handling and engine improvements for greater thrust.[3] Although specific electronic countermeasures (ECM) integrations occurred primarily through post-production modifications, the core MA-1 system in later aircraft benefited from incremental radar enhancements for improved target discrimination.[1]In total, 340 F-106 interceptors were built, including the 277 F-106As and 63 two-seat F-106Bs, supporting up to 14 Air Defense Command squadrons by 1960 and expanding to over 20 active units including Air National Guard elements at peak deployment in the mid-1960s.[3]
Training and Prototype Variants
The development of the Convair F-106 Delta Dart involved two prototype aircraft designated YF-106A, serial numbers 56-0451 and 56-0452, built by Convair in San Diego, California, with construction spanning 1955 to 1956. The first prototype (56-0451) conducted its initial flight on December 26, 1956, at Edwards Air Force Base, California, piloted by Convair's chief test pilot Richard L. "Dick" Johnson, who achieved Mach 1.9 during the test.[43] The second prototype (56-0452) followed with its first flight on February 26, 1957. Both prototypes were equipped with the Pratt & Whitney YJ75-P-1 afterburning turbojet engine and served to validate the aircraft's overall design, including the integration of the area rule for minimizing transonic drag, marking the F-106 as the first production fighter to incorporate this aerodynamic principle from inception.[7]One of the early F-106 variants experienced a fatal crash on January 5, 1959, when F-106B serial number 57-2511, assigned to Convair's flight test division, collided with terrain near Newhall, California, during a test flight, resulting in the loss of the aircraft and test pilot Francis Everett Parker.[40]The F-106B, designated as a two-seat combat-capable trainer (Convair Model 8-27), addressed the need for dual-control instruction in the interceptor fleet, with 63 units produced between late 1958 and 1960. It featured a redesigned fuselage with an enlarged, tandem cockpit covered by a single-piece clamshell canopy for improved visibility, while retaining the J75-P-17 engine and most avionics of the single-seat F-106A; however, internal fuel capacity was reduced to approximately 1,200 U.S. gallons to accommodate the second seat and controls, limiting its range compared to the standard model.[27][7] Although combat-ready, the F-106B's armament configuration was non-standard due to space constraints in the forward fuselage.[3]In operational training, the F-106B enabled efficient instructor-pilot oversight and supported pilot transition programs, including those for Air National Guard units integrating the Delta Dart into their squadrons. By 1962, these trainers formed about 30% of the active F-106 inventory dedicated to instructional duties, enhancing the USAF's all-weather interceptor proficiency without diverting single-seat aircraft from alert roles.[3]Several F-106B airframes were repurposed for research under the NF-106B designation after lease to NASA starting in 1966, with at least two (57-2507 and 57-2516) modified for advanced testing at facilities like Lewis and Langley Research Centers. These variants supported diverse programs, including supersonic transport aerodynamics, propulsion integration, and atmospheric research, remaining in service until the early 1990s.[35][44]
Drone and Proposed Models
The QF-106A was a drone variant developed by converting surplus F-106 airframes into full-scale aerial targets (FSAT) under the U.S. Air Force's Pacer Six program. A total of 194 aircraft, primarily F-106A single-seaters with some F-106B two-seaters, were modified between 1986 and 1990 at the 309th Aerospace Maintenance and Regeneration Center at Davis-Monthan Air Force Base, Arizona.[45][32] These conversions represented nearly two-thirds of the 340 F-106 airframes originally produced, transforming the interceptors into remotely piloted vehicles capable of simulating manned flights for missile testing while allowing optional manned control by safety pilots.[3]The QF-106A retained much of the F-106's aerodynamic structure but incorporated modifications for unmanned operation, including removal of the ejection seat and weapons systems, installation of wingtip recovery parachutes for safe landings, and onboard telemetry for real-time data transmission. Control was achieved through ground-based systems using RISC 6000 computers, joysticks, and video monitors, with television and infrared (TV/IR) seekers enabling remote guidance; infrared emitters on underwing pylons simulated heat signatures for heat-seeking missile training.[32] Unlike manned F-106s equipped with ACES II ejection seats, the drones lacked crew escape provisions, relying instead on self-destruct charges for missions where recovery was impossible. The first converted QF-106A flew in July 1987, and the fleet supported weapons testing at ranges like Holloman and Tyndall Air Force Bases until the program's end in 1998, with the final shootdown occurring in February 1997.[32][45]Several unbuilt advanced variants were proposed to extend the F-106's service life, though none progressed beyond conceptual or mockup stages due to budget constraints and shifting priorities. In the late 1950s, the F-106C and F-106D "Super Dart" upgrades were studied to enhance interception capabilities against advanced Soviet bombers, featuring a lengthened nose for the AN/ASG-18 radar, canards for improved maneuverability at high angles of attack, and the more powerful Pratt & Whitney J75-PW-50 (JT4B-22) engine enabling sustained Mach 3 speeds. The upgrades aimed to counter advanced threats but were deemed unnecessary due to evolving missile technology and budget constraints. A mockup with the extended nose was tested on F-106A serial 57-0239 for 10 flights in 1959, but the project was canceled on September 23, 1958, amid production cutbacks.[46][27]By the late 1960s, following the cancellation of the Lockheed F-12, Convair proposed the F-106E single-seat and F-106F two-seat variants as interim interceptors, incorporating a look-down/shoot-downradar, UHF datalink for integration with AWACS, and compatibility with advanced missiles like the AIM-26 and AIM-47. These designs aimed to bridge the gap until the F-15 Eagle entered service but were not pursued due to the F-106's impending retirement. In the 1980s, conceptual F-106X upgrades explored stealth enhancements, including radar-absorbent materials and revised air intakes to reduce infrared signatures, but these remained paper studies as focus shifted to newer platforms like the F-22.[46][47]An early concept from 1957, the F-106 RASCAL project, envisioned a nuclear-powered variant to provide unlimited endurance for long-range interception, adapting the Aircraft Nuclear Propulsion (ANP) program technologies developed by Convair. However, the initiative was abandoned alongside the broader ANP effort in 1961, primarily due to significant safety concerns over radiation shielding, crash risks, and ground contamination, as well as prohibitive development costs.[48][49]
Operators and Deployment
USAF and ANG Units
The Convair F-106 Delta Dart entered service with the United States Air Force's Air Defense Command (ADC) in 1959, equipping numerous fighter-interceptor squadrons across the continental United States, Alaska, and overseas detachments to provide all-weather interception capabilities against potential bomber threats. By the early 1960s, the F-106 fleet had reached its operational peak with approximately 340 aircraft distributed among about two dozen ADC squadrons, based at 12 primary installations in the continental U.S., forward operating locations in Alaska such as Galena and King Salmon Airports, and a detachment in Iceland at KeflavíkNaval Air Station.[1][3]Representative ADC squadrons included the 49th Fighter-Interceptor Squadron (FIS), which operated F-106s at Griffiss Air Force Base, New York, from 1960 to 1982, focusing on Northeast Air Defense Sector missions. The 5th FIS at Minot Air Force Base, North Dakota, flew the aircraft from 1960 to 1985, earning recognition as one of ADC's top units for its alert readiness and interception exercises. Overseas, the 57th FIS maintained a detachment at Keflavík from 1960 to 1969, conducting patrols over the North Atlantic to monitor Soviet reconnaissance flights. Other key units encompassed the 27th FIS at Loring Air Force Base, Maine (1959–1982); the 48th FIS at Langley Air Force Base, Virginia (1960–1982); and the 318th FIS at McChord Air Force Base, Washington (1960–1983), with rotational deployments to Alaska enhancing northern flank defenses.[50]As ADC phased out the F-106 in the early 1970s amid shifting priorities toward tactical fighters, the aircraft transitioned to Air National Guard (ANG) units starting in 1972, extending its service life through cost-effective maintenance programs. Six ANG squadrons adopted the interceptor for homeland defense, operating from existing air guard bases. The 101st FIS of the Massachusetts ANG at Otis Air National Guard Base flew F-106s from 1972 to 1988, participating in continental air defense alerts and exercises like William Tell. Similarly, the 119th FIS of the 177th Fighter Interceptor Group at Atlantic City Airport, New Jersey, under the New Jersey ANG maintained operations from 1972 to 1988, marking one of the last retirements.[51][52][53]The basing structure evolved from concentrated ADC hubs in the 1960s to dispersed ANG operations by the 1980s, with the type fully retired from active defense roles by 1988 as units converted to F-15 Eagles and other platforms. The ANG's adoption preserved the F-106's role in rapid reaction alerts until the end of the Cold War era.[7][54]
Research and Test Organizations
The National Aeronautics and Space Administration (NASA) retained six F-106 aircraft for research purposes through 1998, with its Dryden Flight Research Center (later renamed Armstrong Flight Research Center) operating two NF-106B research variants beginning in 1966. These aircraft, based at Edwards Air Force Base, California, were employed for advanced flight control system evaluations, including digital fly-by-wire technology to assess handling qualities, aileron-to-rudder interconnect systems, and high-angle-of-attack recovery maneuvers.[55] The program contributed to the development of reliable electronic flight controls for future aircraft, with testing continuing until 1991 when the Dryden fleet was retired.[44]Additionally, Dryden supported the ECLIPSE project, a collaborative effort with the U.S. Air Force and Kelly Space & Technology to demonstrate aerotow launch feasibility for space vehicles using modified QF-106 drones towed by a C-141A transport; Dryden provided engineering, instrumentation, and pilot support for flight safety during tethered and free-flight phases in 1997–1998.[56] This work built on the aircraft's delta-wing stability for suborbital launch concept validation without expending full launch vehicles.[57]Within the U.S. Air Force, specialized test organizations utilized F-106s for operational evaluations. The 4750th Test Wing at Tyndall Air Force Base, Florida, conducted weapons system trials in the 1960s, including AIM-4 Falcon missile firings and radar integration under the Air Proving Ground Center to refine interceptor tactics and armament performance.[58] At Edwards Air Force Base, the Air Force Flight Test Center's avionics divisions, including elements later formalized as the 6510th Test Wing, performed trials on radar, navigation, and electronic countermeasures systems throughout the 1960s and 1970s to enhance the F-106's all-weather interception capabilities.[59]Air National Guard units had limited involvement in F-106 test roles, primarily supporting early evaluations of conversion concepts.In total, NASA's six dedicated research aircraft complemented scattered USAF and ANG testbeds, enabling a diverse array of experimental flights that advanced interceptor technology and influenced subsequent aerospace designs.[60]
Preservation
Surviving Airframes
A total of 340 Convair F-106 Delta Dart airframes were produced, comprising 277 single-seat F-106A interceptors and 63 two-seat F-106B trainers.[3] Of these, 112 were lost to accidents and ground fires during their service life, including early testing mishaps that accounted for several prototypes and initial production models.[3] Following retirement from active USAF and Air National Guard service in 1988, the majority of the remaining aircraft entered long-term storage at the Aerospace Maintenance and Regeneration Center (AMARC) at Davis-Monthan Air Force Base in Arizona, where approximately 50 airframes were placed in Type 2000 preservation to protect against environmental degradation and enable potential future restoration.[3]From the stored inventory, 194 surplus F-106s were selected and converted into unmanned QF-106A target drones under the Pacer Six program, beginning in 1986 and continuing through the early 1990s.[3] These drones served in training exercises until the program's end in 1998, during which most were expended through live-fire shootdowns between 1987 and 1998, resulting in significant attrition and leaving only a fraction intact.[3] By the late 1990s, around 24 non-flyable QF-106 airframes remained at Tyndall Air Force Base in Florida, while roughly 35 others persisted at AMARC primarily as parts donors for preservation efforts.[3] As of 2025, AMARC's current inventory lists just one QF-106A, reflecting ongoing scrapping and reclamation of components from the stored examples.[61]Private ownership accounts for a small number of surviving airframes, with seven non-flying F-106s sold to GrecoAir in El Paso, Texas, in the 1990s for potential civilian use, though none have been restored to airworthy condition.[3] No civilian-operated F-106s are currently flyable, and the intact survivors—estimated at approximately 26 overall—are retained value for their structural integrity and historical components, offering opportunities for future recovery from storage.[62]
Museum Displays and Restorations
The National Museum of the United States Air Force at Wright-Patterson Air Force Base in Dayton, Ohio, displays the famous "Cornfield Bomber," an F-106A with serial number 58-0787. This aircraft, assigned to the 71st Fighter-Interceptor Squadron at Malmstrom Air Force Base, Montana, entered an uncontrollable flat spin during a training mission on February 2, 1970, prompting pilot 1st Lt. Gary Foust to eject at 15,000 feet; remarkably, the autopilot system recovered control, and the jet executed a gentle belly landing in a snow-covered field near Big Sandy, Montana, with minimal damage. Following recovery by an Air Force team, the aircraft underwent repairs and avionics upgrades before returning to service with the 49th Fighter-Interceptor Squadron at Griffiss Air Force Base, New York, and was retired to the museum in August 1986.[1][39]The Hill Aerospace Museum at Hill Air Force Base, Utah, features an F-106A with serial number 58-0774, which served in various fighter wings before conversion to a QF-106 target drone and participation in the final Pacer Six program flights in 1998. Acquired by the museum in 2002 on loan from the U.S. Air Force Heritage Program, the aircraft was restored to static display condition, highlighting its role as the USAF's primary all-weather interceptor during the Cold War.[63]Several other U.S. museums preserve F-106 airframes for public exhibit, including the Castle Air Museum at the former Castle Air Force Base, California, which displays F-106A 58-0793; this example served with various fighter-interceptor squadrons. The Museum of Aviation at Robins Air Force Base, Georgia, houses F-106A 59-0123, delivered in September 1960 and retired in 1982 after service with the 318th and 48th Fighter-Interceptor Squadrons, arriving for display in 1992. At the Air Mobility Command Museum near Dover Air Force Base, Delaware, F-106A 59-0023 is exhibited; it operated with units including the 95th Fighter-Interceptor Squadron at Dover from 1972 to 1973 before conversion to a QF-106 drone in 1992 and placement on display in February 1998. The Pacific Coast Air Museum in Santa Rosa, California, also maintains F-106A 59-0086, underscoring the aircraft's legacy as a supersonic interceptor built in 277 single-seat variants from 1959 to 1961.[64][65][52][2]Restoration efforts for surviving F-106s have focused on static preservation rather than return to flight, as no operational examples remain airworthy. Beyond the Cornfield Bomber's post-incident repairs in 1970, which allowed it to fly again until 1986, notable projects include the 2002 restoration of 58-0774 at Hill Aerospace Museum, involving disassembly from drone configuration and repainting to represent its interceptor heritage. The McChord Air Museum in Washington state completed a multi-year restoration of F-106A 56-0459 starting in 1983, transforming it from storage at the Aerospace Maintenance and Regeneration Center into a display piece honoring the 318th Fighter-Interceptor Squadron by 2004, with volunteers addressing corrosion and avionics removal. Proposed initiatives, such as potential flying restorations of retired QF-106 drones, have not advanced due to structural fatigue and the absence of operational engines. Internationally, no F-106s are preserved in operational roles abroad.[39][63]
Specifications
General Characteristics
The Convair F-106A Delta Dart was designed as a single-seat all-weather interceptor, accommodating one pilot in a pressurized cockpit with an upward-ejecting seat for high-altitude operations.[1]The aircraft measured 70 ft 9 in (21.56 m) in length, with a wingspan of 38 ft 4 in (11.68 m), height of 20 ft 4 in (6.20 m), and wing area of 631 sq ft (58.65 m²), reflecting its delta-wing configuration optimized for supersonic flight.[9][52]Key weights included an empty weight of 23,760 lb (10,780 kg), gross weight of 35,226 lb (15,977 kg), and maximum takeoff weight of 41,831 lb (18,973 kg), providing a balance between structural integrity and payload capacity for interception missions.[52]Internal fuel capacity consisted of 1,514 US gal (5,731 L) of JP-4, stored in integral wing and fuselage tanks, supporting extended patrols without compromising the aircraft's clean aerodynamic profile. The design incorporated dedicated avionics bays in the nose section to house the Hughes MA-1 fire-control system, including radar and computer components essential for automated interception. The powerplant was a single Pratt & Whitney J75-P-17 turbojet engine providing 24,500 lbf (109 kN) thrust with afterburner.[66]The F-106B variant modified this configuration by adding a second tandem seat for training purposes, which necessitated rearranging avionics and reducing internal fuel capacity to 1,200 US gal (4,500 L) to accommodate the additional cockpit space and instrumentation.[7]
The Convair F-106A Delta Dart exhibited exceptional high-speed performance as an all-weather interceptor, attaining a maximum speed of 1,525 mph (Mach 2.3) at 40,000 feet and a cruise speed of 650 mph (Mach 0.98).[1][47] Its rapid initial climb rate of 29,000 feet per minute enabled quick ascents to operational altitudes, optimizing its role in bomber interception.[47]The aircraft's operational envelope featured a service ceiling of 57,000 feet and structural g-limits of +7/-3, providing a wide margin for high-altitude maneuvers while maintaining stability in supersonic flight.[47][15] Ferry range extended to 1,500 mi (2,400 km; 1,300 nmi) with external fuel tanks, supporting extended deployments without compromising intercept readiness.[15][1]Armament integration emphasized automated precision, with the internal weapons bay housing four AIM-4 Falcon missiles—typically two semi-active radar-homing and two infrared-guided variants—alongside one AIR-2 Genie unguided nuclear rocket.[1] The Hughes MA-1 fire control system governed launch parameters, enabling fully autonomous target acquisition, tracking, and weapon release during intercepts.[1]Typical endurance for intercept missions was approximately 2.5 hours, constrained by the afterburner's high fuel consumption rate of around 3,000 pounds per hour, which prioritized short, high-thrust bursts over prolonged loiter.[67] This limitation was offset by the Pratt & Whitney J75 engine's afterburner thrust contributions, ensuring sustained supersonic dashes.[1]
