General Dynamics/Grumman EF-111A Raven - Design and Development

Design and Development

In the late 1960s, the U.S. Air Force sought a replacement for aging EB-66 and EB-57 electronic warfare aircraft. The Air Force studied the use of Navy EA-6B Prowlers during 1967–68. However, the Air Force desired a penetrating electronic jamming aircraft with supersonic speed, and, in 1972, decided to modify F-111As into electronic warfare aircraft as a cost effective option.

In January 1974 the Air Force awarded electronic warfare study contracts to Grumman and General Dynamics. Grumman was selected as the EF-111 prime contractor in December 1974, then was awarded a contract to modify two F-111As into EF-111 prototypes in January 1975. The first fully equipped model, known then as the "Electric Fox", flew on 10 March 1977, and deliveries to combat units began in 1981. A total of 42 airframes were converted at a total cost of US$1.5 billion, the last delivered in 1985.

The Raven retained the F-111A's navigation systems, with a revised AN/APQ-160 radar primarily for ground mapping. The primary feature of the Raven, however, was the AN/ALQ-99E jamming system, developed from the Navy's ALQ-99 on the Prowler. The aircraft also utilized the ALR-62 Countermeasures Receiving System (CRS) as a Radar Homing and Warning (RHAW) System, the same system carried by all F-111 fighter/bomber models in the United States and Australia. The ALQ-99E primary electronics were installed in the weapons bay, with transmitters fitted in a 16 feet (4.9 m) long ventral "canoe" radome; the complete installation weighed some 6,000 pounds (2,700 kg). Receivers were installed in a fin-tip pod, or "football", similar to that of the EA-6B. The aircraft's electrical and cooling systems had to be extensively upgraded to support this equipment. The cockpit was also rearranged, with all flight and navigation displays relocated to the pilot's side, and flight controls except throttles being removed from the other seat, where the electronic warfare officer's instrumentation and controls were installed.

The EF-111 was unarmed. Its speed and acceleration were its main means of self-defense. It was not capable of firing anti-radiation missiles in the lethal SEAD role, which was a tactical limitation. The Raven's engines were upgraded to the more powerful TF30-P-9 of the D-model, with 12,000 pounds-force (53 kN) dry and 19,600 lbf (87 kN) afterburning thrust in 1986. From 1987 to 1994 the "Spark 'Vark" underwent an Avionics Modernization Program (AMP), similar to the Pacer Strike program for the F-model. This added a dual AN/ASN-41 ring laser gyroscope INS, AN/APN-218 Doppler radar, and an updated AN/APQ-146 terrain-following radar. Cockpit displays were upgraded with multi-function displays.

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