Grumman/General Dynamics EF-111 Raven

The Grumman EF-111A Raven is a highly specialised electronic warfare conversion of over 40 General Dynamics F-111A strike bombers.

Grumman has considerable experience in designing, integrating and building electronic warfare aircraft, specifically the EA-6A and EA-6B Prowler variants of its Intruder for the US Navy. Thus Grumman was the logical choice as lead contractor to develop surplus F-111 As as electronic warfare aircraft for the US Air Force. Development work of an EW aircraft, or Tactical Jamming System, based on the F-111 airframe began in 1972, and the US Department of Defense awarded Grumman an initial contract to build two prototypes in 1975. An aerodynamic prototype flew in late 1975, while the first production standard prototype flew in May 1977. Extensive testing ensued, and the first production conversion flew on June 26 1981. In all, the USAF took delivery of 42 EF-111 conversions.

The Raven conversion is based on the basic F-111A airframe, featuring a Tactical Jamming System based on the ALQ-99 system in the EA-6B Prowler, but with a higher degree of automation, requiring one Electronic Warfare Operator (rather than three in the Prowler).

The jamming system’s antennae are housed in the System Integrated Receiver pod, the bulbous fairing on top of the fin, plus further receivers on the fin, and the two blade antennae protruding from the lower fuselage. The jamming transmitters are housed in a canoe fairing (with 10 transmitters, five exciters and six receivers) on the aircraft’s underside, occupying the internal weapons bay space. A central computer processes and analyses all data received, either presenting its findings to the EWO, or carrying out automatic jamming.

The primary feature of the Raven was the AN/ALQ-99E tactical jamming System. The receivers were housed in a distinctive pod carried on the top of the vertical stabiliser of the aircraft. The electronic components were installed in the weapons bay and the transmitters in a canoe-shaped fairing on the underside of the aircraft.

The AN/ALQ-99E worked in conjunction with the AN/ALQ-137 threat warning system and the AN/ALR-62 digital radar warning system. The EF-111A had a crew of two, the pilot and the electronic warfare officer

(EWO) known unofficially as a `Crow’.

The EF-111 also differed from the regular F-111 in that it had 90 kilovolt amperes (kVA) generators as opposed to the 60kVA ones of the standard F-111 because the Raven needed so much more power.

The cockpit was arranged so that the EW systems instrumentation and controls were on the EWO’s position on the right, with the flight and navigation instrumentation and controls on the pilot’s side.

The EF-111A retained the F-111’s navigation, Radar Homing and Warning (RHAW) and Terrain Following Radar (TFR) systems, but carried no offensive armament. It relied on its speed and countermeasures systems to keep it out of trouble.

Capt Robert (Z-Bob) Zaehringer came to the EF-111A after flying the Fairchild Republic A-10A Thunderbolt II with the 81st TFW based at RAF Bentwaters, Suffolk. He recalled: “I went from simple, slow and manoeuvrable to fast high-tech. I thought the EF-111 was a great aeroplane. It went straight and fast really well. It was a really heavy aeroplane; 88,000lb fully loaded, 34,000lb of which was fuel. It took a long take-off roll; but when flying low level in Europe it was like driving a Cadillac or a Rolls-Royce. It was a luxury ride. There’s no doubt about it.”

The EWO’s part in the planning process included navigation to the target area and, most importantly, the programming of the AN/ALQ-99E.

Maj Howard recalled: “The AN/ALQ- 99E had ten transmitters of between 1,000 and 3,000 watts. The ALQ-99E jammer was programmed by the EWO, either by an extremely long and time-consuming key entry system using the cockpit keypad [located where the right control stick was on other F-111s], or by a flight-planning device, which could save the programme to a data tape.

“The EWO could programme the system to look for speci­fic threats based on received radar characteristics and position from the Raven, or it could be set to pre-emptively jam targets, received or not. There was a programme for each transmitter. One aspect of the EF-111A/ALQ-99E system that isn’t well known was that the Raven had steerable horn antennas for all frequencies above the VHF band. This feature is why we could ‑ fly parallel to the FEBA and still deliver high power jamming to threat radars. The ALQ-99E would steer the antennas automatically based on how the EWO programmed the system, or the EWO could manually steer them. Most of our antennas have beam widths around 30 to 45°.”

The Raven’s principle mission types were to provide a standoff jamming barrage to disguise incoming air raids, direct escort of strike aircraft, and battlefield jamming support. The EF-111’s success in these roles in the Gulf War staved off premature retirement, although their role was handed over to US Navy EA-6Bs in 1999.

IN COMBAT

It was in two different theatres, rather than Central Europe, that the 42nd ECS was involved in combat. American tensions with Libya boiled over after a terrorist attack on the La Belle nightclub in West Berlin on April 5, 1986. Two US servicemen and a Turkish woman were killed in the bombing, which America linked to Muammar Gaddafi’s regime. Operation El Dorado Canyon involved USAF aircraft ­ flying from the UK to bomb targets in and around the Libyan capital Tripoli. The US Navy’s Sixth Fleet in the Mediterranean supported the operation in addition to carrying out their own raids on targets around the city of Benghazi.

The USAF’s attacking force consisted of F-111Fs from the 48th TFW at RAF Lakenheath in Suffolk. They were supported by EF-111As from the 42nd ECS which worked in harmony with the navy’s Grumman EA-6B Prowlers to jam Libyan radar systems. Twenty-four F-111Fs and six EF-111As took off in the late afternoon of April 14 accompanied by a tanker force of McDonnell Douglas KC-10A Extenders and Boeing KC-135 Stratotankers. France denied over­flight rights so a large supporting tanker force was required.

After the first refuelling, six F-111F airspares and one EF-111A returned to their bases. The air armada was due to strike Libyan targets at around 2am on April 15. Ten minutes beforehand the EF-111As and the EA-6Bs began jamming Libyan air defence radars and communications. It was not until the ground attack aircraft egressed the area that the EF-111s left their jamming orbits and headed for their tankers.

During Operation Desert Storm, between January and February 1991, the 42nd ECS ­ flew missions from Incirlik in Turkey and Taif air base, Saudi Arabia. The aircraft at Incirlik were already on an exercise at the Turkish base when Iraqi forces invaded Kuwait on August 2. They remained there until Desert Storm started, with six aircraft, taking part in operations. The four EF-111As had deployed to Taif on December 21, 1990.

The EF-111As provided jamming support for a wide range of coalition aircraft in Desert Storm, for example on the first day of the campaign (January 17) three Ravens supported Lockheed F-117A Nighthawks when they attacked targets in Baghdad. The same day one of the unit’s Ravens was credited with the first aerial `kill’ of the campaign by causing a pursuing Iraqi Dassault Mirage F1 to crash. The EF-111A had been one of two supporting 22 F-15E Strike Eagles conducting a raid on an Iraqi airfield when it was attacked by the Mirage. Evading a missile by deploying chaff and ­ flares, the Raven then descended rapidly to low level, and the enemy fighter ­ flew into the desert while trying to follow. During the campaign the EF-111As of the 42nd ECS ­ flew 471 combat missions, totalling 1,859 hours.

One 42nd ECS EF-111A crew was lost when aircraft 66-0023, belonging to the 390th ECS, crashed into the desert just over the Iraqi border in Saudi Arabia. The precise reason for this incident is not known. The

Ravens stayed on at Incirlik after the end of Desert Storm as part of Operation Provide Comfort to assist with the protection and give reassurance to the Kurds of Northern Iraq from persecution by Saddam Hussein’s forces. They returned to the UK in March 1992.

PHASE OUT

By the early 1990s, the days of the Raven were numbered. The 42nd ECS was reassigned to the 20th TFW on January 25, 1991 and was finally inactivated on July 10, 1992, with its Ravens being returned to the 429th ECS at Cannon AFB, New Mexico. Finally, in May 1998, the EF-111 was retired from the USAF inventory and replaced in the electronic combat role by the EA-6B Prowler in a co-operative venture with the US Navy and the US Marine Corps.

Country of origin: United States of America

Type: Electronic warfare aircraft

Powerplants: Two 82.3kN (18,500lb) with afterburning Pratt & Whitney TF30-P-3 turbofans.

Performance:

Max speed 2272km/h (1226W), max combat speed 2215km/h (1195kt), average speed in combat area 940km/h (507kt).

Max initial rate of climb 3300ft/min.

Service ceiling 45,000ft.

Combat radius 1495km (807nm).

Endurance unrefuelled over 4hr.

Weights: Operating empty 25,073kg (55,275lb), max takeoff 40,347kg (88,948lb).

Dimensions: Wing span fully extended 19.20m (63ft 0in), wing span fully swept 9.74m (31ft 11 in), length 23.16m (76ft 0in), height 6.10m (20ft 0in). Wing area with wings fully spread 48.8m2 (525.0sq ft), wing area with wings swept 61.6m2 (657.1sq ft).

Accommodation: Pilot and Electronic Warfare Officer side-by-side.

Armament: Usually none, although can carry two AIM-9 Sidewinders for self defence.

Operators: USA

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