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.
