The General Dynamics F-111 Aardvark is a supersonic, medium-range interdictor and tactical attack aircraft that also filled the roles of strategic bomber, aerial reconnaissance, and electronic-warfare aircraft that was developed by General Dynamics. Previously known as TFX (Tactical Fighter "X"), the aircraft was developed in response to a joint services requirement for a superior fighter from the US Air Force (USAF) and US Navy in 1960.
The Royal Australian Air Force (RAAF) also ordered the type and began operating F-111Cs in 1973.Production of the F-111 was ceased in 1976 after building 566 aircraft in different versions. The variants of the F-111 were in service with the USAF until 1998.
The F-111 pioneered several technologies for production aircraft, including variable-sweep wings, afterburning turbofan engines, and automated terrain-following radar for low-level, high-speed flight. Its design influenced later variable-sweep wing aircraft, and some of its advanced features have since become commonplace. The F-111 suffered a variety of problems during initial development. Several of its intended roles, such as an aircraft carrier-based naval interceptor with the F-111B, failed to materialize.
Development
The F-111 was developed as part of the Tactical Fighter Experimental (TFX) programme during early 1960s. The programme was to develop, consolidate and meet the needs of a supersonic strike aircraft/ tactical fighter-bomber for the USAF and a long range interceptor for the US Navy. The aircraft with large long-range designs were based on swing-wing platform. They were developed with two-seat and twin-engine features. Both the USAF and US Navy aircraft versions were similar in design and could carry large warloads at high speeds. The USAF and the US Navy could agree only on swing-wing, two-seat, twin-engine design features. The USAF wanted a tandem-seat aircraft for low-level penetration ground-attack, while the Navy wanted a shorter, high altitude interceptor with side-by-side seating to allow the pilot and radar operator to share the radar display. Also, the Air Force wanted the aircraft designed for 7.33 g with Mach 2.5 speed at altitude and Mach 1.2 speed at low level with an approximate length of 70 ft (21.3 m). The Navy had less strenuous requirements of 6 g with Mach 2 speed at altitude and high subsonic speed (approx. Mach 0.9) at low level with a length of 56 ft (17.1 m). The Navy also wanted the aircraft with a nose large enough for a 48 in (1.2 m) diameter radar dish.
In 1961 a request for proposals (RFP) was called to develop the aircraft based on the TFX specifically designed for USAF. The General Dynamics designs were selected against the competitors, including Lockheed Martin and Boeing followed, by the TFX contract in December 1962. The General Dynamics proposal had similar structural components for both the USAF and US Navy aircraft versions, while Boeing designs lacked this commonality.
Design
The F-111 was given the name Aardvark due to its long and slightly overturned nose. The F-111's design features variable geometry wings and is mostly built with aluminium, titanium steel. It has an internal weapons bay and a cockpit with side-by-side seating in escape crew capsule.
The aircraft is capable of attacking in all-weather conditions and delivering ordnance through low-level penetration of enemy defences. The wing span in full forward and full sweep varies from 16° to 72.5°. The fuselage is made of honeycomb sandwich and stiffened panels, making it a semi-monocoque structure. The F-111 is powered by two Pratt & Whitney TF30 afterburning turbofan engines. The F-111 variants include a terrain-following radar system. General Dynamics collaborated with Northrop Grumman for designing the fuselage, landing gear and assembly and test of the aircraft.
The F-111 used a three-point landing gear arrangement, with a two-wheel nose gear and two single-wheel main landing gear units. The landing gear door for the main gear, which was positioned in the center of the fuselage, also served as a speed brake in flight. Most F-111 variants included a terrain-following radar system connected to the autopilot.
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| F-111 external payload of Matra Durandal concrete penetration bombs |
The F-111 fighter is armed with air-to-surface ordnance for the long-range attack. The internal weapons bay under the fuselage could include various weapons. The tactical combat variants, excluding the EF-111A or FB-111A/F-111G, could carry a M61 Vulcan 20mm cannon with a 2,084 round ammunition tank. It was, however, never used in any combat and was removed from the aircraft by the early 1980s.
The internal bay could carry two Mk 117 type (340kg) bombs,one nuclear bomb or practice bombs. The F-111 could carry various free-fall nuclear weapons such as B43, B57 and B61 bombs. The F-111C and F-111F were equipped to carry the AN/AVQ-26 Pave Tack targeting system on a rotating carriage that kept the pod protected within the weapons bay when not in use. Pave Tack featured a forward looking infrared (FLIR) sensor, optical camera and laser rangefinder/designator. The Pave Tack pod allowed the F-111 to designate targets and drop laser-guided bombs on them. Australian RF-111Cs carried a pallet of sensors and cameras for aerial reconnaissance use. The FB-111 could carry two AGM-69 SRAM air-to-surface nuclear missiles in its weapons bay. General Dynamics trialed an arrangement with two AIM-9 Sidewinder air-to-air missiles carried on rails in a trapeze arrangement from the bay, but this was not adopted. Early F-111 models had radars equipped to guide the AIM-7 Sparrow medium-range air-to-air missile, but it was never fitted.
The F-111 could not carry any external weapons due to its fuselage design,but two stations were available on the underside for electronic countermeasures (ECM) pods and/or datalink pods; one station was on the weapons bay, and the other on the rear fuselage between the engines. The F-111's maximum practical weapons load was limited, since the fixed pylons could not be used with the wings fully swept. The F-111C can launch AGM-142 Popeye stand-off missile, AGM-84 Harpoon anti-ship missile and AGM-88 HARM anti-radiation missile.
Tactical F-111s were fitted with shoulder rails on the four inner swiveling pylons to mount AIM-9 Sidewinder air-to-air missiles for self-defense.
Countermeasures / sensors
The variants F-111C and F-111F could carry the AN/AVQ-26 Pave Tack targeting system sensor pod equipped on a rotating carriage. The rangefinder/designator and forward looking infrared (FLIR) of the Pave Tack allowed the aircraft to drop laser-guided bombs on designated targets. The Australian RF-111C also carries a reconnaissance pallet with KA-93A4 high-altitude panoramic cameras, Honeywell AN/AAD-5 infrared linescan, a Fairchild KA-56E low-altitude, two CAI KS-87C split vertical cameras and video cameras.
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| Pratt & Whitney TF30 bypass turbojet |
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| FB-111A at the Barksdale Global Power Museum |
The F-111A was the initial production version of the F-111. Early A-models used the TF30-P-1 engine. Most A-models used the TF30-P-3 engine with 12,000 lbf (53 kN) dry and 18,500 lbf (82 kN) afterburning thrust and "Triple Plow I" variable intakes, providing a maximum speed of Mach 2.3 (1,450 mph, 2,300 km/h) at altitude. The variant had a maximum takeoff weight of 92,500 lb (42,000 kg) and an empty weight of 45,200 lb (20,500 kg).
The A-model's Mark I avionics suite included the General Electric AN/APQ-113 attack radar mated to a separate Texas Instruments AN/APQ-110 terrain-following radar lower in the nose and a Litton AJQ-20 inertial navigation and nav/attack system. The terrain-following radar (TFR) was integrated into the automatic flight control system, allowing for "hands-off" flight at high speeds and low levels (down to 200 ft).
The nose of F-111B was 2.59m shorter than the first variant and featured 1.07m longer wingtips. The design allowed the carrier to equip elevator decks, and also improve the on-station endurance time. The F-111B could carry six AIM-54 Phoenix missiles and an AN/AWG-9 Pulse-Doppler radar. The US Navy, however, did not accept the F-111B due to its performance and weight issues.
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| RAAF F-111C is equipped with a terrain-following radar (TFR). |
The variant F-111C was developed with improved wings and landing gear for export to Australia. RAAF ordered 24 aircraft in 1963. Though the first aircraft was delivered in 1968, there were development delays and structural problems.
F-111D
The F-111D was an upgraded F-111A equipped with newer Mark II avionics, more powerful engines, improved intake geometry, and an early glass cockpit. The variant was first ordered in 1967 and delivered from 1970-73. The F-111D reached initial operational capability in 1972. Deliveries were delayed due to avionics issues. 96 F-111Ds were built. The sole operator of this variant was the 27th TFW stationed at Cannon AFB, New Mexico.
F-111E
F-111E was an interim variant, developed as a result of delays in the F-111D building. It had the same Mark I avionics and the TF30-P-3 but with Triple Plow II intakes.
F-111F
F-111F was a Tactical Air Command aircraft using Mark IIB avionics system. It used an improved wing carry through box and Triple Plow II intakes with TF30-P-100 turbofan engines having 112kN afterburning thrust. The engines were subsequently upgraded to TF30-P-109.
F-111K
The F-111K was to be supplemented later by the Anglo-French Variable Geometry Aircraft then under development. The F-111K was based on the F-111A with longer F-111B wings, FB-111 landing gear, Mark II navigation/fire control system, and British supplied mission systems. Other changes included weapons bay modifications, addition of a centerline pylon, a retractable refueling probe, provisions for a reconnaissance pallet, and a higher gross weight with the use of FB-111A landing gear.
FB-111A/F-111G
The FB-111A was a strategic bomber variant developed for the USAF Strategic Air Command. It had increased load-carrying capacity and range and used SAC Mark IIB avionics suite. It had Triple Plow II intakes and TF30-P-7 engine. The main armament of FB-111A was Boeing AGM-69 short-range attack missile. In 1972, 42 existing F-111As were converted to electronic warfare version, EF-111A Raven by Northrop Grumman. They were retired from USAF service in May 1998.
EF-111A Raven
To replace the aging Douglas EB-66, the USAF contracted with Grumman in 1972 to convert 42 existing F-111As into electronic warfare aircraft. The EF-111A can be distinguished from the F-111A by the equipment bulge atop their tails. In May 1998, the USAF withdrew the final EF-111As from service, placing them in storage at Aerospace Maintenance and Regeneration Center (AMARC).
Specifications (F-111F)
General characteristics
Crew: two (pilot and Weapon Systems Officer)
Length: 73 ft 6 in (22.4 m)
Wingspan:
Spread: 63 ft (19.2 m)
Swept: 32 ft (9.75 m)
Height: 17.13 ft (5.22 m)
Wing area:
Spread: 657.4 ft² (61.07 m²)
Swept: 525 ft² (48.77 m²)
Airfoil: NACA 64-210.68 root, NACA 64-209.80 tip
Empty weight: 47,200 lb (21,400 kg)
Loaded weight: 82,800 lb (37,600 kg)
Max. takeoff weight: 100,000 lb (45,300 kg)
Powerplant: 2 × Pratt & Whitney TF30-P-100 turbofans
Dry thrust: 17,900 lbf (79.6 kN) each
Thrust with afterburner: 25,100 lbf (112 kN) each
Zero-lift drag coefficient: 0.0186[172]
Drag area: 9.36 ft² (0.87 m²)
Aspect ratio: spread: 7.56, swept: 1.95
Performance
Maximum speed: Mach 2.5 (1,650 mph, 2,655 km/h) at altitude; Mach 1.2 (915 mph, 1,473 km/h) at sea level
Ferry range: 3,700 mi (3,210 nmi, 5,950 km) ; with external drop tanks
Service ceiling: 66,000 ft (20,100 m)
Rate of climb: 25,890 ft/min (131.5 m/s)
Wing loading:
Spread: 126.0 lb/ft² (615.2 kg/m²)
Swept: 158 lb/ft² (771 kg/m²)
Thrust/weight: 0.61
Lift-to-drag ratio: 15.8 (subsonic L/Dmax)
Armament
Guns: 1× 20 mm (0.787 in) M61A1 Vulcan 6-barreled Gatling cannon in weapons bay (seldom fitted)
Hardpoints: 9 in total (8× under-wing, 1× under-fuselage between engines) plus 2 attach points in weapons bay with a capacity of 31,500 lb (14,300 kg) and provisions to carry combinations of:
Missiles:
AGM-69 SRAM thermonuclear air-to-surface missile
AGM-130 stand-off bomb
Bombs:
Free-fall general-purpose bombs including Mk 82 (500 lb/227 kg), Mk 83 (1,000 lb/454 kg), Mk 84 (2,000 lb/907 kg), and Mk 117 (750 lb/340 kg)
Cluster bombs
BLU-109 (2,000 lb/907 kg) hardened penetration bomb
Paveway laser-guided bombs, including 2,000 lb (907 kg) GBU-10, 500 lb (227 kg) GBU-12 and GBU-28, specialized 4,800 lb (2,200 kg) penetration bomb
BLU-107 Durandal runway-cratering bomb
GBU-15 electro-optical bomb
B61 or B43 nuclear bombs