The F-111 was a multipurpose tactical fighter bomber capable of supersonic speeds. The aircraft was one of the more controversial aircraft ever to fly, yet it achieved one of the safest operational records of any aircraft in USAF history and became a highly effective all-weather interdiction aircraft. As a result of a poorly thought-out development specification, both the Navy and Air Force had become committed, much against their will, to a civilian-inspired "Tactical Fighter Experimental" (TFX) program. This called for developing a single aircraft-the F-111-to fulfill a Navy fleet-defense interceptor requirement and an Air Force supersonic strike aircraft requirement. In retrospect, this was impossible to achieve, especially since planners placed priority upon the Air Force requirement, and then tried to tailor this heavy landplane to the constraints of carrier-based naval operations. The naval aircraft, the F-111B, was never placed in production. The Air Force aircraft, which was produced in a variety of models, including the F-111A, F-11D, F-11E, and F-11F, as well as an FB-111A strategic bomber version, had numerous problems, and only the F-111F actually fulfilled the original TFX design specification. This was less the fault of General Dynamics than of the civilian planners in the Pentagon whose "cost effective" inclinations ironically produced the major aeronautical fiasco of the 1960s-and a costly one at that.
The early F-111As had extremely bad engine problems, suffering from compressor surge and stalls. NASA pilots and engineers wrung out the airplane in an attempt to solve its problems, studying the engine inlet dynamics of the plane to determine the nature of inlet pressure fluctuations that led to compressor surge and stall. Eventually, as a result of NASA, Air Force, and General Dynamics studies, the engine problems were solved by a major inlet redesign.
The F-111 could operate from tree-top level to altitudes above 60,000 feet (18,200 meters). The F-111 had variable-sweep wings that allow the pilot to fly from slow approach speeds to supersonic velocity at sea level and more than twice the speed of sound at higher altitudes. Wings angle from 16 degrees (full forward) to 72.5 degrees (full aft). Full-forward wings gave the most surface area and maximum lift for short takeoff and landing. The F-111 needed no drag chute or reserve thrust to slow down after landing.
The two crew members sat side-by-side in an air-conditioned, pressurized cockpit module that served as an emergency escape vehicle and as a survival shelter on land or water. In emergencies, both crew members remained in the cockpit and an explosive cutting cord separated the cockpit module from the aircraft. The module descended by parachute. The ejected module included a small portion of the wing fairing to stabilize it during aircraft separation. Airbags cushioned impact and help keep the module afloat in water. The module could be released at any speed or altitude, even under water. For underwater escape, the airbags raised the module to the surface after it has been severed from the plane.
The aircraft's wings and much of the fuselage behind the crew module contained fuel tanks. Using internal fuel only, the plane had a range of more than 2,500 nautical miles (4,000 kilometers). External fuel tanks could be carried on the pylons under the wings and jettisoned if necessary.
The F-111 could carry conventional as well as nuclear weapons. It could carry up to two bombs or additional fuel in the internal weapons bay. External ordnance included combinations of bombs, missiles and fuel tanks. The loads nearest the fuselage on each side pivoted as the wings swept back, keeping ordnance parallel to the fuselage. Outer pylons did not move but could be jettisoned for high-speed flight.
The avionics systems included communications, navigation, terrain following, target acquisition and attack, and suppression of enemy air defense systems. A radar bombing system was used for precise delivery of weapons on targets during night or bad weather.
The F-111's automatic terrain-following radar system flew the craft at a constant altitude following the Earth's contours. It allowed the aircraft to fly in valleys and over mountains, day or night, regardless of weather conditions. Should any of the system's circuits fail, the aircraft automatically initiated a climb.