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Location : India

PostSubject: F-111   Sun Jan 24, 2010 2:35 pm




Role : Fighter-bomber
National origin : United States
Manufacturer : General Dynamics
First flight : 21 December 1964
Introduced : 18 July 1967
Retired USAF : 1998
Status : Active with RAAF
Primary users : United States Air Force ; Royal Australian Air Force
Number built : 563
Unit cost : US$9.8 million (FB-111A)[2]
Variants : EF-111A Raven



General Characteristics :

Crew : 2 (pilot and weapons system operator)
Length : 73 ft 6 in (22.4 m)
Spread wingspan : 63 ft (19.2 m)
Swept wingspan : 32 ft (9.75 m)
Height : 17.13 ft (5.22 m)
Spread wingarea : 657.4 ft² (61.07 m²)
Swept wingarea : 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
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)
Combat radius : 1,330 mi (1,160 nmi, 2,140 km)
Ferry range : 4,200 mi (3,700 nmi, 6,760 km)
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)
Wing loading swept : 158 lb/ft² (771 kg/m²)
Thrust/weight : 0.61
Lift-to-drag ratio : 15.8

Armament :

Guns : 1× M61 Vulcan 20 mm (0.787 in) gatling cannon (seldom fitted)
Hardpoints : 9 in total (8× under-wing, 1× under-fuselage between engines)
Armament capacity : 31,500 lb (14,300 kg) ordnance mounted externally on hardpoints and internally in fuselage weapons bay.



The General Dynamics F-111 "Aardvark" is a medium-range interdictor and tactical strike aircraft that also fills the roles of strategic bomber, reconnaissance and electronic warfare in its various versions. Developed in the 1960s and first entering service in 1967, the United States Air Force (USAF) variants were officially retired by 1998. The Royal Australian Air Force (RAAF) is the sole remaining operator of the F-111.

The F-111 pioneered several technologies for production military aircraft, including variable-sweep wings, afterburning turbofan engines, and automated terrain following radar for low-level, high-speed flight. Its design was highly influential, particularly for Soviet engineers, and some of its advanced features have since become commonplace. During its inception, however, the F-111 suffered a variety of development problems, and several of its intended roles, such as naval interception, failed to materialize.

In USAF service the F-111 has been effectively replaced by the F-15E Strike Eagle for medium-range precision strike missions, while the supersonic bomber role has been assumed by the B-1B Lancer. In 2007, the RAAF decided to replace its 21 F-111s in 2010 with 24 F/A-18F Super Hornets.
The beginnings of the F-111 were in the TFX program, an ambitious early 1960s project to combine the United States Air Force requirement for a fighter-bomber to replace the F-105 Thunderchief with the United States Navy's need for a long-range carrier-based Fleet Air Defense fighter to replace the F-4 Phantom II. The fighter design philosophy of the day concentrated on very high speed, raw power, and air-to-air missiles.

Early Requirements ::

The U.S. Air Force's Tactical Air Command (TAC) was largely concerned with the fighter-bomber and deep strike/interdiction roles, which in the early 1960s still focused on the use of tactical nuclear weapons. The aircraft would be a follow-on to the F-105 Thunderchief, which was designed to deliver nuclear weapons low, fast and far. Air combat would be an afterthought until encountering MiGs over Vietnam in the mid-1960s. In June 1960 the USAF issued a specification for a long-range interdiction/strike aircraft able to penetrate Soviet air defenses at very low altitudes and very high speeds to deliver tactical nuclear weapons against crucial targets.

Meanwhile the U.S. Navy sought a long-range, high-endurance interceptor to defend its carrier battle groups against the new generation of Soviet jet bombers, which by then were being armed with large, long range anti-ship missiles. The Navy needed a Fleet Air Defense (FAD) aircraft with range and load-carrying ability greater than the F-4 Phantom II, and one equipped with a powerful radar and a battery of long-range missiles to intercept both enemy bombers and their missiles. The Navy had studied, but rejected, a subsonic, straight-winged missile carrier, the F6D Missileer. The Navy had tried variable geometry with the XF10F Jaguar but abandoned that in 1953. By late 1960, the Navy had been reconsidering variable geometry for the FAD requirement. Variable geometry offered a compromise between swept wing for high speeds and a modestly swept wing with better payload, range and landing characteristics. This would allow larger and faster aircraft to land on an aircraft carrier.

Tactical Fighter Experimental (TFX) ::

The Air Force and Navy requirements appeared to be different. However, on 14 February 1961 the new U.S. Secretary of Defense, Robert McNamara, formally directed that the services study the development of a single aircraft that would satisfy both requirements. Early studies indicated the best option was to base the Tactical Fighter Experimental (TFX) on the Air Force requirement and a modified version for the Navy.[6] In June 1961, Secretary McNamara ordered the go ahead on TFX despite Air Force and the Navy efforts to keep their programs separate. The USAF and the Navy could only agree on swing-wing, two seat, twin engine design features. The USAF wanted a tandem seat aircraft for low level penetration, while the Navy wanted a shorter, high altitude interceptor with side by side seating. Also, the USAF wanted the aircraft designed for 7.33 g with Mach 2.5 speed at altitude and Mach 1.2 speed at low level with a length of 66-72 ft (20.1-21.9 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). So McNamara developed a basic set of requirements for TFX based largely on the Air Force's requirements. Then on 1 September 1961 he ordered the USAF to develop it.

A request for proposals (RFP) for the TFX was provided to industry in October 1961. In December of that year proposals were received from Boeing, General Dynamics, Lockheed, McDonnell, North American and Republic. The proposal evaluation group found all the proposals lacking, but the best should be improved with study contracts. Boeing and General Dynamics were selected to enhance their designs. Boeing's proposal was recommended by the selection board in January 1962. However, the Boeing's engine was not considered acceptable. Switching to a crew capsule and alterations to radar and missile storage were also needed. The companies provided updated proposals in April 1962. Air Force reviewers favored Boeing's offering, but the Navy found both submissions unacceptable for its operations. Two more rounds of updates to the proposals were conducted with Boeing being picked by the selection board. Instead Secretary McNamara selected General Dynamics' proposal in November 1962 due to its greater commonality between Air Force and Navy TFX versions. The Boeing aircraft versions shared less than half of the major structural components. General Dynamics signed the TFX contract in December 1962. A Congressional investigation followed, but could not change the selection.

Design Phase ::

The F-111A and B variants used the same airframe structural components and TF30-P-1 turbofan engines. They featured side by side crew seating in escape capsule as required by the Navy. The F-111B's nose was 8.5 feet (2.59 m) shorter due to its need to fit on existing carrier elevator decks, and had 3.5 feet (1.07 m) longer wingtips to to improve on-station endurance time. The Navy version would carry a AN/AWG-9 Pulse-Doppler radar and six AIM-54 Phoenix missiles. The Air Force version would carry the AN/APQ-113 attack radar and the AN/APQ-110 terrain-following radar and air-to-ground armament. Titanium was planned for most of the airframe. However, this proved to be too expensive and more conventional metals were used instead.

Lacking experience with carrier-based fighters, General Dynamics teamed with Grumman for assembly and test of the F-111B aircraft. In addition, Grumman would also build the F-111A's aft fuselage and the landing gear. The F-111A mock-up was inspected in September 1963. The first test F-111A was rolled out of the General Dynamics' Fort Worth, Texas plant on 15 October 1964. It was powered by YTF30-P-1 turbofans and used a set of ejector seats as the escape capsule was not yet available. The F-111A first flew on 21 December 1964 from Carswell AFB, Texas. The first F-111B was also equipped with ejector seats and first flew on 18 May 1965.

F-111 development continued. To address stall issues in certain parts of the flight regime, the engine inlet design was modified in 1965-66, ending with the "Triple Plow I" and "Triple Plow II" designs. The F-111A achieved a speed of Mach 1.3 in February 1965 with an interim intake design. Flight testing of the F-111A ran through 1973. The F-111B was canceled by the Navy in 1968 due to weight and performance issues. The F-111C model was developed for Australia. Subsequently, the improved F-111E, F-111D, F-111F models were developed for the US Air Force. The strategic bomber FB-111A and the EF-111 electronic warfare versions were later developed for the USAF. Production ended in 1976 with a total of 563 F-111 variants built.



The F-111 is an all-weather attack aircraft capable of low-level penetration of enemy defenses to deliver ordnance on the target. The F-111 features variable geometry wings, an internal weapons bay and a cockpit with side by side seating. The cockpit is part of an escape crew capsule. The wing sweep varies between 16 degrees and 72.5 degrees (full forward to full sweep). The airframe is made up mostly of aluminum alloys with steel, titanium and other materials used in places.The fuselage is a semi-monocoque structure with stiffened panels and honeycomb sandwich panels for skin. Most F-111 variants included a terrain-following radar system connected to the autopilot. The aircraft is powered by two Pratt & Whitney TF30 afterburning turbofan engines. The F-111's variable geometry wings, escape capsule, terrain following radar, and afterburning turbofans were new technologies for production aircraft.

Armament ::

F-111 cockpit prior to a night flight.Although conceived as a multi-role fighter, the F-111 became a long-range attack aircraft primarily armed with air-to-surface ordnance.

Weapons bay ::

The F-111 has an internal weapons bay under the fuselage for various weapons.

Cannon : All tactical combat versions (that is, not the EF-111A or FB-111A/F-111G) could carry a single M61 Vulcan 20 mm cannon with a very large (2,084 round) ammunition tank, covered by an eyelid shutter when not in use. Although carried by some USAF aircraft, the cannon was never actually used in combat, and was removed by the early 1980s; provision for the cannon has also been deleted from Australian F-111Cs.

Bombs : The bay can alternately hold two conventional bombs, usually the Mk 117 type of nominal 750 lb/340 kg weight, although weapons up to the Mk 118 (3,000 lb/1,400 kg) were cleared.

Nuclear weapons : All F-111 models except the EF-111A and the Australian F-111C were equipped to carry various free-fall nuclear weapons: tactical models generally carried the B43, B57, or B61. The FB-111A was a dedicated nuclear bomber for most of its life, and carried all of those weapons just mentioned, as well as the B83 and the AGM-69 Short Range Attack Missile. The FB-111A could carry one or two AGM-69 SRAM nuclear missiles in its weapons bay and up to four SRAMs on external wing pylons.

Sensor pod : 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 is a FLIR and laser rangefinder/designator that allows the F-111 to designate and drop laser-guided bombs.
Reconnaissance pallet: Australian RF-111Cs carry a package of reconnaissance sensors and cameras for tactical recce missions. It contains two video cameras, a Honeywell AN/AAD-5 infrared linescan (recorded on video or film), a Fairchild KA-56E low-altitude and KA-93A4 high-altitude panoramic cameras, and a pair of CAI KS-87C split vertical cameras. It can also record photographs of the attack radar's display.

Missiles : The F-111B was intended to be capable of carrying two AIM-54 Phoenix air-to-air missiles in the bay. General Dynamics proposed an arrangement that would allow two AIM-9 Sidewinders to be carried on a trapeze mounting in the bay (at the expense of the M61 cannon), along with a single (usually nuclear) bomb. This was not adopted, with the USAF and RAAF opting for the cannon instead. The AIM-7 Sparrow or AIM-4 Falcon, standard on the F-4 Phantom II, was never fitted, though later F-111 models had radars equipped to guide the Sparrow.

Other equipment : Auxiliary fuel tanks and baggage pods were sometimes carried.

External ordnance ::

The design of the F-111's fuselage prevents the carriage of external weapons under the fuselage (although there are two small stations, one on the weapon bay, the other on the rear fuselage between the engines, for ECM pods and/or datalink pods for guided weapons). All aircraft, except the FB-111A have provision for eight underwing pylons, four under each wing, with a capacity of 6,000 lb (2,700 kg) each. The inner pylons i.e. 3 , 4 , 5 and 6 pivot with the wing, but only one on each side can be loaded at maximum sweep. The outer pylons i.e. 1 , 2 , 7 and 8 are fixed, and can be loaded only if the wings are spread at less than 26°, causing drag at takeoff angle. The outermost pylons i.e. 1 and 8 have never been used operationally, and the second pair of fixed pylons i.e. 2 and 7 are fitted only rarely, for the carriage of fuel tanks. FB-111/F-111G models have provision to jettison their empty pylons in flight, reducing drag.

The limited number of fully swiveling pylons restricts the F-111's maximum practical weapons load, since the aircraft cannot use all pylons with the wings fully swept. By contrast, aircraft such as the F-14 and Tornado can carry their maximum bomb loads with fully swept wings.

The primary external armament of USAF tactical F-111s included:

Free-fall GP bombs :
1. Mk 82 (500 lb/227 kg)
2. Mk 83 (1,000 lb/454 kg)
3. Mk 84 (2,000 lb/907 kg)
4. Mk 117 (750 lb/340 kg)

Cluster bombs

BLU-109 (2,000 lb/907 kg) hardened penetration bomb

Paveway laser-guided bombs, including :
1. GBU-10 (2,000 lb/907 kg)
2. GBU-12 (500 lb/227 kg)
3. GBU-28, a very specialized 4,800 lb (2,200 kg) penetration bomb

U-107 Durandal runway-cratering bomb

GBU-15 electro-optical bomb

AGM-130 stand-off bomb, with a range of 40 miles (64 km).

Although all F-111s can carry laser-guided munitions, only those with Pave Tack (i.e., F-111F and Australian F-111C) are capable of self-designation. Others can drop laser-guided weapons only with the aid of another ground or air designator.

From the early 1980s onward, tactical F-111s were fitted with shoulder rails on the sides of the outboard swiveling pylon (designated stations 3A and 6A) for two AIM-9 Sidewinder air-to-air missiles for self-defense. The standard Sidewinder fit was the AIM-9P, rather than the more modern AIM-9L or AIM-9M, whose larger fins were not compatible with the shoulder rail. The RAAF has considered replacing the Sidewinder with ASRAAM.

FB-111As could carry the same conventional ordnance as their tactical brothers, but their wing pylons were more commonly used for either fuel tanks or strategic nuclear gravity bombs. Until the weapon was withdrawn in 1990, they could carry up to four AGM-69 SRAM nuclear missiles on the wing pylons, although two was the more normal fit.

Australian F-111Cs have been equipped to launch the AGM-84 Harpoon anti-ship missile, AGM-88 HARM anti-radiation missile, and the AGM-142 Popeye stand-off missile.

Similar Swing Wing Aircraft ::

The F-111 was the first production variable-geometry aircraft. The earlier subsonic Navy XF10F Jaguar had been cancelled in 1953. It inspired a number of aircraft throughout the 1960s, and even fictional aircraft on the Thunderbirds, but swing wings are extinct in newer designs due to higher cost, and the extra weight imposed by the swing wing mechanism. Nevertheless, several other types have followed, including the Soviet Sukhoi Su-17 "Fitter" (1966), Mikoyan-Gurevich MiG-23 "Flogger" (1967), Tupolev Tu-22M "Backfire" (1969) and Tupolev Tu-160 "Blackjack" (1981), the U.S. F-14 Tomcat naval fighter (1970) and B-1 Lancer bomber (1974), and the European Panavia Tornado (1974). The Sukhoi Su-24 "Fencer" (1970), which resembles the F-111, also has side-by-side seating.



F-111A ::

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).

Total production of the F-111As was 158, including 17 pre-production aircraft that were later brought up to production standards. A total of 42 F-111As were converted to EF-111A Ravens for an electronic warfare tactical electronic jamming role. In 1982, four surviving F-111As were provided to Australia as attrition replacements and modified to F-111C standard. These were fitted with the longer-span wings and reinforced landing gear of the C-model.

Three pre-production F-111A were provided to NASA for various testing duties. The 13th F-111A was fitted with new wing designs for the Transonic Aircraft Technology and Advanced Fighter Technology Integration programs in the 1970s and 1980s. It was retired to the United States Air Force Museum at Wright-Patterson Air Force Base in 1989. The remaining unconverted F-111As were mothballed at AMARC, Davis-Monthan Air Force Base in June 1991.

F-111B ::

The F-111B was to be a fleet air defense (FAD) fighter for the U.S. Navy, fulfilling a long-standing naval requirement for a fighter capable of carrying heavy, long-range missiles to defend carriers and their battle groups from Soviet bombers and fighter-bombers equipped with anti-ship missiles. The Navy had just cancelled the F6D Missileer, a concept for a slow, straight-winged jet with the advanced Hughes AN/AWG-9 pulse-Doppler radar, which could detect low flying targets among ground clutter, and lift eight new AIM-54 Phoenix long range, air-to-air missiles, which could attack multiple aircraft simultaneously at ranges out to 100 miles (160 km). The concept was soon cancelled, but the F-111 offered a platform with the range, payload, and Mach 2 performance of a fighter to intercept targets quickly, but with swing wings and turbofan engines, it could also loiter on station for long periods. The F-111B would carry six Phoenix missiles, but have no gun or other short range armament. General Dynamics, having no experience with carrier-based aviation, partnered with Grumman for this version.

The F-111B was a compromise that attempted to reconcile the Navy's very different needs with an aircraft whose basic configuration was largely set by the USAF need for a supersonic strike aircraft. These compromises would harm both USAF and USN versions. The side-by-side seating was preferred by the Navy from the Missileer. The F-111B was shorter than the F-111A, in order to enable it to fit on aircraft carrier deck edge elevators between the flight deck and the hangar deck. The F-111B also had a longer wingspan than its USAF counterpart (70 ft/21.3 m compared to 63 ft/19.2 m) for increased range and cruising endurance. Although the Navy had wanted a 48-inch (122 cm) radar dish for long range, they were forced to accept a 36-inch (91.4 cm) dish for compatibility. The Navy had requested a maximum takeoff weight of 50,000 lb (22,686 kg), but then-Secretary of Defense Robert S. McNamara forced the Navy to compromise at 55,000 lb (24,955 kg). This weight goal proved to be overly optimistic.

Excessive weight plagued the F-111B throughout its development. The prototypes were far over the 55,000 lb (24,955 kg) limit. Design efforts reduced airframe weight but were offset by the addition of the escape capsule. The excessive weight made the aircraft underpowered.

Requirements for the F-111B had been formulated before air combat over Vietnam in 1965 showed the Navy still had a need for an aircraft which could engage MiG fighters at close range. The Navy desired a fighter with more performance than the F-4 Phantom II, yet in trials, the maneuverability and performance of the F-111B, especially in the crucial medium-altitude regimen, was decidedly inferior to the Phantom. During the congressional hearings for the aircraft, Vice Admiral Thomas F. Connolly, then Deputy Chief of Naval Operations for Air Warfare, famously responded to a question from Senator John C. Stennis as to whether a more powerful engine would cure the aircraft's woes with "There isn't enough power in all Christendom to make that airplane what we want !"

By October 1967, the Navy was finally convinced that the F-111B program was a lost cause and recommended its cancellation, which occurred in 1968 after seven had been delivered, two of which had crashed. The swing-wing configuration, TF-30 engines, Phoenix missiles and radar developed for this aircraft (and the earlier, canceled F6D Missileer) were used on its replacement, the F-14 Tomcat, also designed by Grumman. The Tomcat would be large enough to carry the AWG-9 and Phoenix weapons system while exceeding the agility and speed of the F-4 Phantom.

F-111C ::

The F-111C was an export version for Australia, combining F-111A/E avionics with the long-span wings and heavier landing gear originally designed for the F-111B. Twenty-four were originally ordered in 1963, although development delays and structural problems kept them from entering service until 1973.

Four aircraft were modified to RF-111C reconnaissance configuration, retaining their strike capability. The RF-111C carries a reconnaissance pack with four cameras and an infrared linescan unit.

F-111C aircraft have been equipped to carry Pave Tack FLIR/laser pods, and later underwent an extensive Avionics Upgrade Program, with AN/APQ-169 attack radar replacing the elderly AN/APQ-113, Texas Instruments AN/APQ-171 terrain-following radar, twin Honeywell H423 ring-laser gyro INS, GPS receiver, modern digital databus, mission computer, and stores-management system, and cockpit multi-function displays (MFDs). Their engines were updated to TF30-P-108/109RA standard, with 21,000 lbf (93 kN) thrust. Four ex-USAF F-111As were refitted to F-111C standard and delivered to Australia as attrition replacements.

In late 2001, wing fatigue problems were discovered with one of the F-111C fleet. As a result a decision was made in May 2002 to replace the wings with spares taken from ex-USAF F-111Fs stored at the Aerospace Maintenance and Regeneration Center. The short span wings underwent a refurbishment in Australia which included extending the span in effect making the wings the same as the F-111C and F-111G models.

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. First ordered in 1967, extensive development problems delayed service entry until 1974, and only 96 were built.

The F-111D used the new Triple Plow 2 intakes, which were located four inches (100 mm) further away from the airframe to prevent engine ingestion of the sluggish boundary layer air that was known to cause stalls in the TF30 turbofans. It had more powerful TF30-P-3 engines with 12,000 lbf (53 kN) dry and 18,500 lbf (82 kN) afterburning thrust.

More significant and problematic were the Mark II avionics. These were digitally integrated microprocessor systems, some of the first used by the USAF, offering tremendous capability, but substantial problems during introduction. The main radar was the General Electric AN/APQ-114, with Doppler beam-sharpening, moving target indicator (MTI), and continuous wave mode for guiding semi-active radar homing missiles (which the standard AN/APQ-113 set lacked). This was matched with an Autonetics inertial navigation/attack radar system, Marconi Doppler radar for navigation, a horizontal situation display, an IBM processor, and a Norden integrated systems display, with modern multi-function displays (MFDs). These last proved to be a major source of trouble, serving to multiply the development problems experienced with the individual systems. Considerable acrimony between the contractors resulted, and it took years before the problems were solved. F-111 crews considered the -D the most capable (and user-friendly) version of the aircraft when everything functioned, but that was rare before the 1980s.

Incidentally, the F-111D was never equipped to carry what proved to be the "Aardvark's" most useful sensor system, the AN/AVQ-26 Pave Tack pod.

The F-111D was withdrawn from service in 1992 for mothballing at AMARC.

F-111E ::

The F-111E was a simplified, interim model ordered after the prolonged teething troubles of the F-111D. It used the -D's Triple Plow 2 intakes and more powerful TF30-P-3 engines, but retained the -A's Mark I avionics.

Although conceived after the -D, the F-111E was actually delivered before it. The first flight of an -E was 20 August 1969. A total of 94 were built.

Some F-111Es were based with the 20th Fighter Wing at RAF Upper Heyford in Oxfordshire (United Kingdom) until 1993, and the type saw service in Operation Desert Storm. All F-111Es were withdrawn to storage in 1993 and 1994.

F-111F ::

The F-111F was the final F-111 variant produced for Tactical Air Command, with more modern and advanced Mark IIB avionics that were more capable than the F-111E and much more reliable than the F-111D. A total of 106 were produced between 1971 and 1976. The aircraft were initially assigned to the 366 TFW at Mountain Home AFB, Idaho. In 1977, the F-111Fs were reassigned to the 48 TFW based at RAF Lakenheath in the United Kingdom, with some assigned to the 57th Fighter Weapons Wing at Nellis AFB.

The F-111F's Mark IIB avionics suite used a simplified version of the FB-111A's radar, the AN/APQ-144, lacking some of the strategic bomber's operating modes but adding a new 2.5 mi (4.0 km) display ring. Although it was tested with digital moving-target indicator (MTI) capacity, it was not used in production sets. It used Texas Instruments AN/APQ-146 terrain-following radar, Litton inertial navigation, and the F-111E's Weapon Control Panel. The internal weapons bay was normally occupied by an AVQ-26 Pave Tack FLIR and laser designator system for the delivery of precision laser-guided munitions. The radar was subsequently upgraded to AN/APQ-161, with the AN/APQ-171 terrain-following set. The later Pacer Strike avionics update program added new digital electronics and databus.

The -F also used the Triple Plow 2 intakes, along with the substantially more powerful TF30-100 turbofan with 25,100 lbf (112 kN) afterburning thrust. This substantially improves the -F's performance, allowing a top speed of Mach 2.5 at altitude and enabling an unloaded F-111F to supercruise (fly at supersonic speeds without afterburner). In 1985-86, engines were upgraded to the TF30-P-111 turbofan.

The F-111F made its combat debut in Operation El Dorado Canyon against Libya in 1986, and was used in Operation Desert Storm against Iraq in an anti-armor ("tank-plinking") role.

Various plans to upgrade the F-111F, including the adoption of the General Electric F110 engine (used in the F-14D Tomcat), were proposed, but not implemented because they might have interfered with the USAF's political efforts to build the F-22 Raptor. As a result, the last USAF F-111s were withdrawn from service on 27 July 1996, replaced by the F-15E Strike Eagle.

F-111K ::

The British government cancelled the BAC TSR-2 in 1965, citing the lower costs of the TFX and ordered 50 F-111K aircraft in 1967. The F-111K was based on the F-111A, modified for British equipment and weapons. This included weapons bay changes, compatibility with the Martel anti-shipping missile, the addition of a retractable refuelling probe and the use of FB-111A landing gear for a higher gross take off weight. Prototypes of both the strike and TF-111K trainer aircraft were started and were in the final stages of build when the order was cancelled just over a year later. Updated estimates of performance indicated that range and speed at altitude would be worse than expected and fall short of the specification. Cost increase together with devaluation of the pound meant that the cost would be around £3 million each and this was the reason cited for cancellation.[40] As a substitute, Blackburn Buccaneers and F-4 Phantom IIs were purchased instead for the RAF. These would eventually be replaced by the Panavia Tornado, another variable-geometry design.

FB-111A/F-111G ::

The FB-111A was a strategic bomber version of the F-111 developed as an interim aircraft for the Strategic Air Command to replace the elegant but troublesome supersonic B-58 Hustler and early models of the B-52 Stratofortress. The planned replacement program, the Advanced Manned Strategic Aircraft, was proceeding slowly, and the Air Force was concerned that fatigue failures in the B-52 fleet would leave the strategic bomber fleet dangerously under strength. Although 263 airframes were planned originally, the total was finally cut to 76. The first production aircraft flew in 1968. The FB-111A never had an official popular name, but it was commonly called the "Switchblade".

When the United Kingdom canceled its order for the F-111K in 1968, 48 K-model airframes in early production were converted to FB-111As. The FB-111A featured longer F-111B wings for greater range and load-carrying ability. The bomber variant was 2 ft 1 in (63 cm) longer than the F-111A. Its fuel capacity was increased by 585 gallons (2,214 L) and had stronger landing gear to compensate for the higher maximum takeoff weight of 119,250 lb (54,105 kg). All but the first aircraft had the Triple Plow 2 intakes and the TF30-P-7 with 12,500 lbf (56 kN) dry and 20,350 lbf (90 kN) afterburning thrust.

The FB-111A had new electronics, known as the SAC Mk IIB suite. The Mk IIB retained the F-111A's Texas Instruments AN/ANPQ-134 terrain-following radar and Honeywell AN/APN-167 radar altimeter. Radar was the General Electric AN/APQ-114, with a new north-oriented display, a beacon tracking mode, and a photo recording mode. To those components, the FB-111A added a Rockwell AN/AJN-16 inertial navigation system, Singer-Kearfott AN/APN-185 Doppler radar, and the Litton AN/ASQ-119 Astrotracker astrocompass, which allowed navigation by stellar positioning (a similar system had been used on the SR-71 Blackbird). A Horizontal Situation Display was added along with the AN/AYK-6 cockpit display.

Armament for the strategic bombing role was the Boeing AGM-69 SRAM (short-range attack missile) which had Mach 3 speed and 110-mile (180 km) range. Two could be carried in the internal weapons bay and four more on the inner underwing pylons. Nuclear gravity bombs were also typical FB armament. Fuel tanks were often carried on the third non-swivelling pylon of each wing. Promotional photos showed a conventional bombload to a theoretical total of 50, 750 lb (340 kg) M117 weapons on eight pylons and bomb bay, but it was never used in a conventional role. The SRAM was withdrawn from service in 1990.

Multiple advanced FB-111 strategic bomber designs were proposed by General Dynamics in the 1970s. The first design, referred to as "FB-111G" by the company, was a larger aircraft with more powerful engines with more payload and range. The next was a lengthened "FB-111H". It featured more powerful General Electric F101 turbofan engines, a 12 ft 8.5 in longer fuselage and redesigned, fixed intakes. The rear landing gear were moved outward so armament could be carried on the fuselage there. The FB-111H was offered as an alternative to the B-1A in 1975. The similar FB-111B/C was offered in 1979 without success.

The FB-111A became surplus to SAC's needs after the introduction of the B-1B Lancer. With the disestablishment of SAC in 1992 and movement of all former SAC bomber aircraft to the newly established Air Combat Command (ACC), the remaining FB-111s were retired from Plattsburgh AFB, NY and Pease AFB, NH and subsequently converted to a tactical configuration and renamed F-111G. They were used primarily for training.

The F-111G did undergo an avionics upgrade program that added a digital computer, dual AN/ASN-41 ring-laser gyro INS, AN/APN-218 Doppler navigation, and an updated terrain-following radar. The astrocompass system was deleted. The G model did not remain in USAF service for long, being mothballed in 1993, but 15 were bought by Australia to supplement its F-111Cs.

EF-111A Raven ::

To replace the elderly and obsolescent Douglas EB-66, in 1972 the USAF contracted Grumman to convert 42 existing F-111As into electronic warfare/ECM aircraft. They can be distinguished from other A-models by the equipment bulge atop their tails, a feature leading to the nickname "Fat Tail". In May 1998, the USAF withdrew the final EF-111As from service, placing them in storage at AMARC. In the short term, EA-6B Prowlers are fulfilling this function for both the U.S. Navy and USAF.



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