The F-111's variable-sweep wing provides aerodynamic efficiency from the slowest to the fastest operating speeds. The F-111's variable-sweep wings allowed 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. With wings fully extended, the F-111 can take off and land in as little as 2,000 feet. With wings fully swept back, it can reach supersonic speeds at high or low altitudes. The F-111 could operate from tree-top level to altitudes above 60,000 feet (18,200 meters). 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. As the F-111's mission changed and it was required to operate at lower altitudes using terrain-following radar, the plane experienced several bird strikes. The Air Force's Arnold Engineering and Development Center [AEDC] provided testing of the aircraft's canopy for more than two decades as the system evolved.
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