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 Suppression of Enemy Air Defenses (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 dry and 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. Operational history The EF-111A achieved initial operational capability in 1983. The EF-111A received the official popular name Raven, although in service it acquired the nickname "Spark 'Vark". EF-111s first saw combat use with the 20th Tactical Fighter Wing at RAF Upper Heyford during Operation El Dorado Canyon against Libya in 1986, and Operation Just Cause in Panama during late 1989. The Raven served in the Gulf War during Operation Desert Storm in 1991. On 17 January 1991, a USAF EF-111 crew of Captain James Denton and Captain Brent Brandon achieved an unofficial kill against an Iraqi Dassault Mirage F1, which they managed to maneuver into the ground, making it the only member of the F-111/FB-111/EF-111 family to achieve an aerial victory over another aircraft. On 13 February 1991, EF-111A, AF Ser. No. 66-0023, call sign Ratchet 75, crashed into terrain while maneuvering to evade a perceived threat. killing the pilot, Capt Douglas L. Bradt, and the EWO, Capt Paul R. Eichenlaub. It was the only EF-111A lost during combat, the only loss killing its crew, and one of just three EF-111s lost during the aircraft's service. However, it is disputed whether there was an enemy present at the time, as two F-15Es watched Ratchet 75 make violent evasive maneuvers and crash into the ground, with no hostile aircraft in the area. Later action EF-111s were deployed to Aviano Air Base, Italy in support of Operation Deliberate Force during the mid-1990s. The Raven also flew missions in Operation Provide Comfort, Operation Northern Watch and Operation Southern Watch. The last deployment of the Raven was a detachment of EF-111s stationed at Al Kharj/Prince Sultan Air Base in Saudi Arabia until April 1998. Shortly afterward, the USAF began withdrawing the