The General Dynamics F-111 is one of the most controversial aircraft that ever flew. Perhaps no other aircraft before or since has been so bitterly criticized in the media. It suffered a protracted development cycle in which numerous serious problems had to be identified and repaired, and cost overruns came to be a serious concern. Of the several thousand that had originally been planned, only 562 flightworthy examples of seven different variants were completed. The F-111 was the subject of protracted and bitter debates within the Congress, with opponents denouncing the aircraft as a "flying Edsel" that was more dangerous to the US than it was to any potential enemy.
However, after a prolonged gestation period in which many, many problems had to be identified and fixed, the F-111 turned out to be one of the most effective all-weather interdiction aircraft in the world. Although vilified by some as being an unsafe and dangerous plane, the F-111 series of combat aircraft established the best safety record of any of the aircraft in the Century Series of fighters--only 77 aircraft being lost in a million flying hours. There was no other aircraft in service with the USAF which can carry out the F-111's mission of precise air strikes over such long ranges in all-weather conditions. Although the aircraft has left USAF service, it still serves with distinction with the Royal Australian Air Force and may very well continue until 2020.
The history of the F-111 begins back in the late 1950s. At that time, the Tactical Air Command (TAC) of the USAF expressed a future need for a replacement for the F-100, F-101, and F-105 fighter-bombers which were currently in service. With this goal in mind, on March 27, 1958, the Air Force issued General Operational Requirement (GOR) Number 169, calling for Weapon System 649C, which was a Mach 2+, 60,000 foot altitude, all-weather fighter capable of vertical and short takeoff and landing. The Air Force wanted this aircraft to be ready for operational deployment by 1964.
This GOR lasted only a year, being cancelled on March 29, 1959, because the Air Force recognized that a V/STOL fighter capable of such performance was simply not feasible with the current technology. On February 5, 1960, the Air Force rewrote its requirements and issued System Development Requirement (SDR) No. 17, incorporating most of the provisions of GOR-169 but eliminating the VTOL requirement. It allowed the subsequent development of specific requirements for a new weapon system--WS-324A.
The general requirements of SDR-17 were brought together into Specific Operational Requirement number 183 (SOR-183), issued on June 14, 1960. It called for an attack aircraft capable of achieving a Mach 2.5 performance at high altitude and a low-level dash capability of Mach 1.2. It was to have a short and rough airfield performance, and was to be capable of operating out of airfields as short as 3000 feet in length. The low-level radius was to be 800 miles, including 400 miles right down on the deck at Mach 1.2 speeds. In addition, it was to have an unrefuelled ferry range capable of crossing the Atlantic Ocean. It was to have a 1000-pound internal payload plus a lifting payload between 15,000 and 30,000 pounds. The Air Force considered that a variable sweep wing and a turbofan engine would be needed to satisfy these requirements.
At the same time, the Navy had a requirement for a two-seat carrier-based fleet air defense (FAD) fighter that would replace the McDonnell F-4 Phantom and the Vought F-8 Crusader. This aircraft was to have the ability to loiter on patrol for much longer times with substantially larger and more capable air-to-air missiles, and was to be able to meet and counter threats to the carrier group at much larger ranges.
Originally, the Navy had planned to meet this FAD requirement with the Douglas F6D-1 Missileer. The F6D-1 was a subsonic aircraft that looked a lot like a scaled-up F3D Skyknight. It was to be powered by two 10,000 lb.s.t. Pratt & Whitney TF30-P-2 turbofans, and was to carry a three-man crew (pilot, co-pilot, and weapons system operator). The Missileer was to be capable of remaining on patrol for up to six hours, tracking targets at long range using its powerful Hughes pulsed-Doppler track-while-scan radar and attacking threats with its six long-range Bendix XAAM-10 Eagle air-to-air missiles. The Eagle was a massive long-range air-to-air missile with a maximum speed of Mach 4. It was equipped with an advanced pulse-Doppler active radar homer. The warhead of the Eagle could be either conventional or nuclear.
The F6D aircraft was considered by the Navy to be too costly and too specialized, and was thought to be too slow to be capable of defending itself once its missiles had been launched. Consequently, the F6D and its Eagle missiles were both cancelled in December of 1960 in the last waning days of the Eisenhower administration. This still left the FAD requirement unfulfilled.
The Air Force and Navy requirements were at first sight completely different. However, on February 16, 1961 the new Secretary of Defense, Robert McNamara, directed that the Services study the development of a single aircraft that would satisfy both the requirements of the Air Force's SOR 183 mission and the requirements of the Navy's FAD mission. In addition, McNamara wanted the aircraft to be capable of being used by the Army and the Marine Corps as a close-support aircraft. It was hoped that this strategy would reduce procurement costs substantially. The project came to be known as the Tactical Fighter Experimental, or TFX for short.
It did not take long for the services to convince Secretary McNamara that the close air support mission requirement could not be satisfied by the TFX, and the Marine Corps and the Army were dropped from the program at an early stage. However, Secretary McNamara stuck doggedly to his idea of maximum commonality between USAF and Navy versions of the TFX, and in June 1961, he instructed the Air Force and the Navy to work closely together to combine their requirements before issuing a joint RFP. Although both the USAF and the Navy thought that this idea was completely unrealistic, Secretary McNamara was the boss and they reluctantly followed orders.
Both the USAF and the Navy agreed that the use of variable-geometry wings would be a good idea. However, on just almost everything else, they differed substantially. The Navy favored side-by-side seating for its FAD fighter, whereas the Air Force preferred tandem seating. The Navy wanted an aircraft equipped with a long-range search and intercept radar having a dish 48 inches in diameter, whereas the Air Force needed an aircraft equipped with a terrain-following radar optimized for low-altitude operations. The Navy wanted an aircraft that was optimized for long loiter times at medium to high altitudes at subsonic speeds, whereas the Air Force insisted on an aircraft capable of low-altitude operations and supersonic dash performance. Undaunted, Secretary McNamara pressed forward with the project and directed that the Air Force would be the lead service for the development of a common TFX aircraft.
By August of 1961, the Secretary of the Navy reported to Secretary McNamara that the compromise TFX design could not meet the Navy requirements. The Air Force wanted an aircraft weighing 75,000 pounds gross, while the Navy wanted the gross weight to be kept below 50,000 pounds. In addition, carrier operational requirements necessitated that the overall length be kept below 56 feet so that it could fit aboard existing carrier elevators. McNamara ordered the Navy to accept a design sized to accommodate a 36 inch radar rather than the 48 inch radar it really wanted and to accept a gross takeoff weight of 55,000 pounds.
On September 29, 1961, a new Request For Proposals was issued to Boeing, General Dynamics, Lockheed, Northrop, Grumman, McDonnell, Douglas, North American, and Republic. The Air Force's version of the TFX was to be designated F-111A, with the Navy's version being designated F-111B. In the spirit of commonality, the Air Force and Navy versions did not carry separate designation schemes.
Nine responses were received in early December of 1961. Only Northrop turned down the invitation to submit a proposal. In their first evaluation of the proposals on January 19, 1962, the Air Force Selection Board and a Navy representative endorsed the Boeing proposal, but the Air Force Council rejected the Boeing bid as requiring much more work. In late January of 1962, both the Air Force and Navy agreed that none of the proposals were really acceptable, but that two of them--the Boeing and General Dynamics proposals--warranted further study. A letter contract was issued to each company requesting more design data.
In the spring of 1962, Boeing and General Dynamics submitted second proposals. In May of 1962, both the Air Force and Navy Secretaries rejected the two contractor's second proposals for lack of sufficient data. A third submission took place in late June. At this time, the Air Force endorsed the Boeing proposal, but the Navy was unhappy with their version and refused to commit themselves. A frustrated Secretary McNamara ordered a final competition for later that year on the basis of a point system for categories based on performance, cost, and commonality.
Boeing and General Dynamics resubmitted their final proposals in September of 1962. The Air Force Council, the Air Force Logistics Command, and the Bureau of Naval Weapons (the Navy organization which had replaced the Bureau of Aeronautics in 1959) all indicated that they preferred the Boeing design, but on November 24, 1962 the Defense Department announced that the General Dynamics design had been selected. The reason given for the selection of the General Dynamics proposal was its promised greater degree of commonality and its supposedly more realistic approach to the cost problem.
A political storm broke out, with Senator Henry Jackson leading the fray in Congress in loudly denouncing the choice in no uncertain terms. The Boeing company was located in Jackson's home state of Washington and would lose a lot of business if the decision were allowed to stand. A series of congressional investigations was initiated, and the TFX stayed in the headlines for many months. Nevertheless, the decision of the Secretary stood, and the contract remained with General Dynamics.
The F-111A and B aircraft shared the same primary structure, the same fuel system, the same pair of Pratt & Whitney TF30-P-1 turbofans, and the same two-seat cockpit in which the two crew members sat side-by-side. The side-by-side seating was a concession to Navy demands. The Navy also insisted that the cockpit be capable of doubling as an escape capsule for the crew which could blown free from the aircraft in the case of an emergency and would be able to parachute to the ground as a single unit. The F-111B's nose was 8 feet 6 inches shorter than the F-111A's because of the need of the aircraft to fit on existing carrier elevator decks, and had 3 feet 6 inch extended wingtips in order to increase the wing area so that the on-station endurance time would be improved. The Navy version would carry a Hughes AN/AWG-9 pulse-Doppler radar and an armament of six Hughes Phoenix missiles, which had both evolved from the F6D program. The Air Force version would carry the General Electric AN/APQ-113 attack radar and the Texas Instruments AN/APQ-110 terrain- following radar and would carry an armament of air-to-ground stores.
On December 21, 1962, the Air Force amended the Letter Contract that had initially covered General Dynamics' second competitive proposal and initiated procurement of 18 F-111As (serial numbers 63-9766/9782) and 5 F-111Bs (BuNos 151970/151924). These were to be exclusively research, development, test, and evaluation (RDT&A) aircraft.
Plans originally envisaged using titanium for almost all the airframe in order to save weight, but this proved to be too costly and more conventional materials had to be used.
Since General Dynamics lacked any experience with carrier-based fighters, it teamed with Grumman for the integration of the naval electronics package and Grumman was to assemble and test the entire F-111B aircraft. In addition, Grumman would build the aft fuselage and the landing gear of the F-111A aircraft.
The F-111A mockup was inspected in September of 1963.
By the spring of 1964, AiResearch, AVCO, Bendix, Collins Radio, Dalmo Victor, General Electric, Hamilton Standard, Litton Systems, McDonnell, Texas Instruments and seven other major subcontractors had become involved with the F-111 project. An associate prime contract for the F-111B's Phoenix missiles had been awarded to Hughes. These major subcontractors were doing business with no less than 6703 suppliers located in 44 states. The TFX project became a close approximation to the ideal weapons project--one with at least one contractor located in each Congressional district. :-)
The first test F-111A (serial number 63-9766) rolled out of the General Dynamics Fort Worth, Texas plant on October 15, 1964, 37 months after the OSD go-ahead decision, 22 months after the program's actual beginning, and two weeks ahead of schedule. It was powered by YTF30-P-1 turbofans. Pending the availability of the escape capsule, it was fitted with a pair of conventional ejector seats.
63-9766 took off on its maiden flight from Carswell AFB, Texas on December 21, 1964. Dick Johnson and Val Prahl were at the controls. Although the flight was shortened to 22 minutes because of a flap malfunction, the results were generally satisfactory. On its second flight, on January 6, 1965, the wings were swept from the minimum 16 degrees to the full aft 72.5-degree position. During early flight testing, the F-111A achieved a speed of Mach 1.3. A second F-111A took off on its maiden flight on February 25, 1965.
In 1965, a cost rise from an estimated 4.5 to 6.3 million dollars per aircraft caused the Defense Department to cut the F-111 program sharply. A contract for 431 production aircraft was placed on April 12, 1965. This was more than 50 percent less than the amount originally planned. Eleven production F-111As were added to the extensive test and engineering program.
The ninth aircraft (63-9775) crashed on approach to Edwards AFB on January 19, 1967. The aircraft landed short of the runway due to the wings being accidentally swept in the wrong direction.
The escape capsule was first fitted to F-111A number 11 (63-9777)
The Pratt & Whitney TF30-P-1 turbofan was first flown on an F-111A on July 20, 1965. The first 30 F-111As were equipped with this engine, but they experienced numerous engine compressor stalls, particularly at high speeds and at high angles of attack. These necessitated a change to the 18,500 lb.s.t. TF30-P-3 and to new "Triple Plow I" variable-geometry inlet ducts with larger areas. This engine was later retrofitted in several of the first 30 F-111As. These changes did not entirely cure the stall problems, but the did help somewhat. Many fixes and many years of hard work were necessary before the appropriate air intake geometry was finally found.
Movable underwing pylons were introduced from the fourth production aircraft onward, and from the eleventh production aircraft onward a 20mm M61A1 Vulcan cannon was installed in the internal weapons bay in place of two 750 lb. bombs. However, this cannon was rarely carried by actual operational aircraft, the space in the weapons bay being used for bombs, fuel, or electronics.
In the spring of 1967, a series of tests known as *Combat Bullseye I* were carried out with test F-111As. They confirmed the superior bombing accuracy of the aircraft's radar.
A total of 141 production F-111As were delivered from July 17, 1967. The electronics package was known as the Mk I avionics system. It included a Litton AJQ-20 inertial navigation and attack system, a General Electric AN/APQ-112 attack radar, a Honeywell APN-167 pulsed-type radar, a Texas Instruments AN/APQ-110 terrain-following radar, and Collins ARC-109 UHF and ARC-112 HF radio transceivers.
The underside of the central fuselage of the F-111A was occupied by a giant airbrake which was forced open by a large hydraulic jack. Together with the main landing gear, the presence of this airbrake precluded carrying any bombs or fuel tanks underneath the fuselage. The massive main landing gear had two huge low-pressure tires which, together with the long-stroke legs that are pivoted near the aircraft centerline, enabled no-flare landings to be made at high weights. The large airbrake helped to cover the main gear retraction bay, and wasactually partially extended when the main gear was down. The nose landing gear had twin wheels and was hydraulically steerable.
The Triple Plow I air intakes for the TF30 turbofans were mounted underneath the leading edge of the fixed wing glove. A triangular-shaped wedge was fitted to the upper, inner corner of each intake, and a large planar wedge was mounted ahead of each intake parallel to the sides of the fuselage . The entire intake cowls could be moved forwards or backwards as needed to optimize the air flow into the engines for the given speed or angle of attack. A set of vortex generators is fitted inside the intake ducts to provide a homogeneous flow of air to the engine. The primary disadvantage of the low-mounted air intakes was that they tended to suck up a lot of runway debris, dictating that the F-111A use only prepared runway surfaces that are kept thoroughly swept at all times.
The fixed inner wing has a set of pivoted surfaces that normally lay flush to the surface but at high angles of attack or in high-lift situations they could be extended to improve air flow over the glove-wing junction. >[? The variable-geometry wing outer panels were pivoted to the fixed inner wing gloves and could be driven symmetrically to any sweep angle from 16 degrees to 72.5 degrees. The upper surface of the wing had a set of spoilers which were used for roll control, no ailerons being provided. The main wing had a set of double-slotted flaps which occupied the entire trailing edge of the wing. The flaps were automatically disconnected when the wing was at maximum sweep so that they coule not be operated in such a configuration. A set of slats occupied the entire width of the wing leading edge. These slats could be extended by a rack and pinion system when the aircraft was flying at low speeds or at high angles of attack to increase lift and to prevent the aircraft from stalling.
In an emergency, the cockpit doubled as an escape capsule which separated completely from the aircraft and was blown free from the aircraft by a rocket motor. The pilot and systems officer sat side-by side in a shirt-sleeve environment, eg, wearing no pressure suits or oxygen masks. If they decided to eject, the first step in the sequence was to fire a bunch of explosive guillotines that severed all the hydraulic lines and cables. Then, a quite hefty rocket charge separated the entire cockpit from the plane. When it separated, the ejection capsule took with it a small portion of the fuselage above and to the rear of the cockpit which acted as a stabilizing airfoil. After the chutes opened, anti-radar chaff was dispersed, and a cushion/flotation bag was inflated to cushion the impact when the capsule landed. All of this could be accomplished from zero/zero airspeed/altitude (eg; from an F-111A parked at rest on a runway). In the case of an over-water ejection, the capsule was supposed to be completely submersible and was capable of floating for a considerable amount of time. While the capsule is floating in the water, the joy stick could double as a bilge pump by moving a pin in its base.
The escape capsule was used with success on several occasions. However, there was a problem with excessively hard landings which were so jolting that they injured the crew members. However, I suppose it's better to be injured than to end up as a smoking hole in the ground :-).
The horizontal tailplane was of the all-flying variety with no separate elevator.
At the rear of the tailcone, between the two engine exhausts, was a fuel vent for the dumping of fuel. This device was sometimes used for a rather spectacular airshow demonstration, in which the pilot vents fuel while in afterburner, producing a spectacular torch behind the aircraft.
The F-111A had six underwing pylons for carrying bombs, rockets, or fuel tanks. The outboard underwing pylon on each wing was fixed and could not pivot. Consequently, ordnance could be carried on them only when the wing was set at between 16 and 26 degrees of wing sweep. However the four inboard pylons did pivot and remained parallel to the aircraft centerline throughout the entire sweep range. There was a small internal weapons bay which could accommodate a pair of 750-pound bombs. Alternatively, the bombs in the internal weapons bay could be replaced by a 20-mm M61A1 rotary cannon with 2000 rounds of ammunition.
In an extreme situation, the F-111A could carry as many as 50 750-pound conventional bombs (two of them being carried internally, the rest on the six underwing hardpoints), or 26 1000-pound bombs. However, such loads could only be carried if the wing was swept no more than 26 degrees and would therefore be unlikely to be carried in actual combat. If the wing needed to be swept back at an angle of 54 degrees, the bomb load was limited to 26 750-pound bombs. In standard USAF form, the F-111A's useful payload varies from 8000 pounds to 20,000 pounds, according to range. For example, for a mission range of 1725 miles, the payload is of the order of 16,000 pounds.
The APQ-113 forward-looking attack radar was a large liquid-cooled set that operates in the J-band (16-16.4 GHz). It was used by the navigator sitting in the right hand seat for navigation, air/ground ranging and weapons delivery. It could also be used in the air-to-air mode in conjunction with the 20-mm M61A1 cannon or Sidewinder missiles, although the air-to-air role was not the primary mission of the F-111A.
The F-111A is equipped for midair refueling. A receptacle for a refuelling boom is fitted on the top of the fuselage behind the cockpit. The F-111A has no provision for refuelling by the probe/drogue method.
The first F-111A deliveries took place on July 18, 1967 to the 428th, 492nd and 430th Tactical Fighter Squadrons of the 474th Tactical Fighter Wing based at Cannon AFB in New Mexico. In early 1968, this outfit moved to Nellis AFB.
Based on the results of the Combat Bullseye I tests of the spring of 1967, the Air Force decided to rush a small detachment of F-111As to Southeast Asia under a program known as Combat Lancer. This program was preceded by the Harvest Reaper program of June 1967 which was intended to identify known F-111A shortcomings and to prepare the aircraft for combat. It was anticipated that the Harvest Reaper modifications would enter the F-111A production lines if they were successfully proven in combat.
Six 428th TFS F-111As were allocated to the Combat Lancer program, and departed Nellis AFB for Thailand on March 15, 1968. By the end of that month, 55 night missions had been flown against targets in North Vietnam, but two aircraft had been lost. 66-0022 had been lost on March 28, and 66-0017 on March 30. Replacement aircraft had left Nellis, but the loss of a third F-111A (66-0024) on April 22 halted F-111A combat operations. However, the aircraft remained poised for combat, but they saw little action before their return to the USA in November. It turned out that the three F-111A losses were not due to enemy action but were caused by wing and tail structural defects. One of the Combat Lancer crashes had been traced to a malfunction of the aircraft's tail servo actuator. The USAF later discovered (as a later returning prisoner of war would confirm) that a tailplane problem could cause a sudden and uncontrollable pitch-up and roll. This failure in the flying controls system caused the aircraft to break up in flight. The other two crashes in Vietnam were traced to poor mounting of the M61A1 cannon and to pilot error.
These losses caused a storm of controversy in the USA--Senator William Proxmire denouncing the F-111A as an unsafe and defective plane. The aircraft became known as "McNamara's Flying Edsel", and was accused of being a potential "technological gold mine for the Reds".
However, the Air Force and General Dynamics remained hard at work trying to fix the problems with the F-111A. The 428th TFS of the 474th TFW reached an initial operational capability in the spring of 1968. Harvest Reaper modifications validated by the Combat Lancer operations followed shortly thereafter. The Harvest Reaper modification took a lot longer than expected, and the Wing was not fully operational until July of 1971.
F-111 testing and training incidents (including two crashes in early 1968) had dictated a detailed and involved investigation. On August 27, 1969, a wing-carry-through-box failed during a ground fatigue test. This failure was traced to the manufacturers of the box, the Selb Manufacturing Corp, which had been paying off inspectors for approving unauthorized weldings. Extensive retrofits were required because most F-111As had already cleared the production lines.
The last of 158 F-111As was delivered on August 39, 1969. This total included 17 of the 18 RDT&E F-111As initially ordered in December 1962. The 18th test F-111A was used as a test prototype for the FB-111A bomber program.
The Air Force lost its 15th F-111A on December 22, 1969, the cause being due to failure of the forged wing pivot fitting. All F-111As were grounded the next day. The grounding was lifted on July 31, 1970. This accident cast doubt on the structural integrity of the aircraft and compounded the aircraft's modernization. Each F-111A had to be carefully checked and fixed as necessary.
The F-111A returned to Southeast Asia in September of 1972. They entered combat not long after yet another crash and yet another grounding. Two F-111A squadrons (the 429th and 430th) left Nellis AFB for Thailand. They participated in the Linebacker II aerial offensive against North Vietnam. They flew bombing missions against targets in North Vietnam and Laos in the midst of the monsoon season. They flew without electronic countermeasures escort aircraft or KC-135 tankers. On November 8, 1972, they flew 20 strikes over North Vietnam in weather that grounded other aircraft. Four F-111As could deliver the bomb loads of 20 F-4s.
Shortly after returning to SEA, an F-111A experienced double engine rollback after encountering heavy rain. There were continual problems with the terrain-following radar and the attack radar. Malfunctions of the internal navigation and weapons release system also cropped up on a regular basis. Nevertheless, the 429th and 430th TFS flew some 4000 combat missions with excellent success rates in hitting targets even when visibility was near zero. Only six aircraft were lost in action.
In 1977, surviving F-111As were transferred to the 366th TFW based at Mountain Home, Idaho, where they equipped the 389th and 391st Squadrons.
42 F-111As were converted into EF-111A Raven electronic warfare aircraft.
In 1982, four F-111As were transferred to the Royal Australian Air Force to cover attrition in their F-111C fleet.
Two of the pre-production F-111As (serial numbers 63-9771 and 63-9777) were used for tests by NASA at the Dryden Flight Research Facility between the years 1967 and 1971. Another pre-production F-111A (63-9778) became the Transonic Aircraft Technology demonstrator for NASA. It was fitted with a supercritical wing with a shorter span and blunt wingtips and reduced aspect ratio. It flew for the first time at Edwards AFB on November 1, 1974. During mid-1980, it was flown with laminar flow glove-sections on the wing then rebuilt with a Boeing variable-camber "mission adaptive" wing for Advanced Fighter Technology Integration tests. The F-111/AFTI continued further flight testing until early 1989 when it was retired to the USAF Museum at Wright Patterson AFB in Ohio. However, I don't remember seeing it there when I visited the museum in 1992
In the early 1990s, surviving F-111As began to be transferred to AMARC at Davis Monthan AFB in Arizona for storage. The last F-111A which had not been converted into EF-111A electronic warfare format reached AMARC in 1997. Some of them are being stored there for possible eventual transfer to Australia to keep their F-111Cs operating for another 20 years. Others have been scrapped.
During its long service, the F-111A/F series never had an official Air Force popular name. However, because of its long, pointed nose, the F-111A came to be known unofficially as the "Aardvark", or just 'Vark for short. In October 1996, at the time of the official retirement of the F-111F from the USAF, the name Aardvark was officially assigned.
63-9766/9782 General Dynamics F-111A 9776 converted to RF-111A recon aircraft 65-5701/5710 General Dynamics F-111A 66-0011/0058 General Dynamics F-111A 66-9277 General Dynamics F-111A 67-0032/0114 General Dynamics F-111A
Engines: Two Pratt & Whitney TF30-P-3 turbofans, 12,000 lb.s.t. dry and 18,500 lb.s.t. with afterburning. Weights: 46,172 pounds empty, 63,051 pounds combat, 82,819 pounds gross, 98,850 pounds maximum takeoff. Performance: Maximum speed 1453 mph at 53,450 feet, 914 mph at sea level. Initial climb rate 25,550 feet per minute (clean). Service ceiling 58,000 feet, combat ceiling 56,650 feet, absolute ceiling 66,000 feet. Combat radius was 1330 miles, with ferry range being 3165 miles with maximum external fuel being carried. Internal fuel capacity was 5043 US gallons. With underwing fuel tanks, a maximum of 7443 US gallons of fuel could be carried. Dimensions: wingspan 63 feet 0 inches (maximum) and 31 feet 11 1/2 inches (minimum), length 73 feet 5 1/2 inches, height 17 feet 6 inches, wing area 525 square feet. Armament: Armed with one 20-mm M61A1 rotary cannon with 2000 rounds, which was only rarely actually fitted. Up to 30,000 pounds of bombs, missiles, or fuel tanks could be carried on six underwing hardpoints and in the internal weapons bay.