Grumman A-6 Intruder

An A-6 Intruder landing aboard an Aircraft carrier.

The Grumman A-6 Intruder is a twin-engine, mid-wing attack aircraft manufactured by Northrop Grumman Aerospace Corporation. It was in service between 1962 and 1997, replaced by the F/A-18 Hornet.

Development

The Intruder was developed in response to a U.S. Navy specification for an all-weather carrier-based attack aircraft to serve as a replacement for the piston-powered, WWII-era A-1 Skyraider. Grumman was awarded the contract in 1957, and the resulting A2F-1 made its first flight on 19 April 1960. It was redesignated A-6A in the fall of 1962, and entered squadron service in February 1963.

The A-6 became the USN and USMC's principal medium attack aircraft from the mid-1960s through the 1990s. It served in combat in Vietnam and in later engagements in Lebanon and Libya. The Intruder saw further duty in the 1991 Gulf War, but it was phased out of service quickly in the mid-1990s. It was intended for replacement by the A-12 Avenger II, but following that troubled stealth aircraft's cancellation, the Intruder was left to soldier on for a few more years before retiring in favor of the F/A-18 Hornet.

The last Intruders were retired 19 December 1996. Contrary to popular belief, surviving aircraft fitted with the new wings were stored at the AMARC storage center at Davis-Monthan Air Force Base, and not sunk as artificial reefs. Although the Intruder could not match the F/A-18's speed or air-combat capability, the A-6's range and load-carrying ability are currently unmatched in the fleet.

Variants

A-6A

The initial version of the Intruder was built around the complex and advanced DIANE (Digital Integrated Attack/Navigation Equipment), intended to provide a high degree of bombing accuracy even at night and in poor weather. DIANE consisted of multiple radar systems: the Norden AN/APQ-92 search radar and a separate AN/APQ-112 for tracking, AN/APN-141 radar altimeter, and AN/APN-153 Doppler to provide position updates to the AN/ASN-31 inertial navigation system. An air-data computer and ballistics computer integrated the radar information for the bombardier/navigator (BN) in the right-hand seat. TACAN and ADF were also provided for navigational use. When it worked, DIANE was perhaps the most capable nav/attack system of its era, giving the Intruder the ability to fly and fight in even very poor conditions (particularly important over Vietnam and Thailand during the Vietnam War). It suffered numerous teething problems, though, and it was several years before its reliability was established.

Total A-6A production was 488, including six pre-production prototypes. Many of the surviving aircraft were converted to other variants.

A-6B

To provide Navy squadrons with a SEAD aircraft to attack enemy air defense and SAM systems--a mission dubbed "Iron Hand" in Navy parlance--19 A-6As were converted to A-6B standard from 1967 to 1970. The A-6B had many of its standard attack systems removed in favor of special equipment to detect and track enemy radar sights and to guide AGM-45 Shrike and AGM-78 Standard anti-radiation missiles. Five were lost in combat, and the rest were later converted to A-6E standard in the late 1970s.

A-6C

12 A-6As were converted in 1970 to A-6C standard for night attack missions against the Ho Chi Minh Trail in Vietnam. They were fitted with a TRIM (Trails/Roads Interdiction Multi-sensor) pod in the fuselage for FLIR and low-light TV cameras, as well as a "Black Crow" engine ignition detection system. One of these aircraft was lost in combat, the others were later converted to A-6E standard after the war.

KA-6D

In the early 1970s some 78 A-6As and 12 A-6Es were converted for use as tanker aircraft, providing aerial refueling support to other strike aircraft. The DIANE system was removed and an internal refueling system was added, sometimes supplemented by a D-704 refueling pod on the centerline pylon. The KA-6D theoretically could be used in the day/visual bombing role, but it apparently never was, with the standard load-out being four fuel tanks. A few KA-6Ds went to sea with each Intruder squadron, and the retirement of the aircraft left a gap in USN and USMC refueling tanker capability that was only later remedied by the new F/A-18E Super Hornet, which can act as a tanker.

A-6E

The definitive attack version of the Intruder, introduced in 1970, with its first deployment 9 December 1971, with vastly upgraded nav/attack systems. The original search and track radars of the A-6A were replaced by a single AN/APQ-148 Norden multi-mode radar, and the onboard computers with a more sophisticated (and generally more reliable) solid-state electronic system. A new AN/ASN-92 inertial navigation system was added, along with the CAINS (Carrier Aircraft Intertial Navigation System), for greater navigation accuracy. Beginning in 1979 all A-6Es were fitted with the AN/AAS-33 DRS (Detecting and Ranging Set), part of the TRAM (Target Recognition and Attack, Multi-Sensor) system, a small, gyroscopically stabilized turret, mounted under the nose of the aircraft, containing FLIR boresighted with a laser spot-tracker/designator. TRAM was matched with a new AN/APQ-156 Norden radar. The BN could use both TRAM imagery and radar data for extremely accurate attacks, or use the TRAM sensors alone to attack without using the Intruder's radar (which might warn the target). TRAM also allowed the Intruder to autonomously designate and drop laser-guided bombs.

In the early 1990s some surviving A-6Es were upgraded under SWIP (Systems/Weapons Improvement Program) to enable them to use the latest precision-guided munitions, including AGM-65 Maverick, AGM-84 Harpoon, AGM-84E SLAM, and the AGM-88 HARM anti-radiation missile. After a series of wing-fatigue problems, about 85% of the fleet was fitted with new graphite/epoxy/titanium/aluminum composite wings.

A-6E models totaled 445 aircraft, about 240 of which were converted from earlier A-6A/B/C models.

A-6F and A-6G

An advanced A-6F Intruder II was proposed in the mid-1980s that would have replaced the Intruder's elderly Pratt & Whitney J52 turbojets with non-afterburning versions of the General Electric F404 turbofan used in the F/A-18 Hornet, providing substantial improvements in both power and fuel economy. The A-6F would have had totally new avionics, including a Norden AN/APQ-173 synthetic aperture radar and multi-function cockpit displays--the APQ-173 would have given the Intruder air-to-air capacity with provision for the AIM-120 AMRAAM. Two additional wing pylons were added, for a total of seven stations.

Although five development aircraft were built, the Navy ultimately chose not to authorize the A-6F, preferring to concentrate on the A-12 Avenger II. This left the service in a quandary when the A-12 was cancelled in 1991.

Grumman proposed a cheaper alternative in the A-6G, which had most of the A-6F's advanced electronics, but retained the existing engines. This, too, was cancelled.

Electronic warfare versions

See also: EA-6B Prowler

An electronic warfare/ECM version of the Intruder was developed early in the aircraft's life for the USMC, which needed a new ECM platform to replace its elderly F3D-2Q Skyknights. An EW version of the Intruder, initially designated A2F-1Q and subsequently redesignated EA-6A, first flew on 26 April 1963. It had a Bunker-Ramo AN/ALQ-86 ECM suite, with most electronics contained on the walnut-shaped pod atop the vertical fin. They were theoretically capable of firing the AGM-45 Shrike anti-radiation missile, although they were apparently not used in that role.

Only 28 EA-6As were built (two prototypes, 15 new-build, and 11 conversions from A-6As), serving with Marine Corps squadrons in Vietnam. It was phased out of front-line service in the mid-1970s, remaining in use in reserve units with the USMC and then the US Navy primarily for training purposes. The last had been retired completely by 1993.

A much more highly specialized derivative of the Intruder was the EA-6B Prowler, a 'stretched' airframe with two additional systems operators, and more comprehensive systems for the electronic warfare and SEAD roles. 170 were produced. The Prowler remains in service as of 2006.

Combat Experience

A-6 Intruders first saw action during the Vietnam War, where the craft were used extensively against targets in Vietnam. The aircraft's long range and heavy payload coupled with its ability to fly in all weather made it invaluable during the war. However, its effectiveness in flying low and delivering its payload made it especially vulnerable to anti-aircraft fire and in the eight years the Intruder was used, the U.S. Navy and Marines lost 68 of the aircraft in combat.

Intruders saw action in strikes against the Bekaa Valley in Lebanon in 1983. One Intruder and one A-7 Corsair were lost during the Lebanon campaign. The BN could use both TRAM imagery and radar data for extremely accurate attacks, or use the TRAM sensors alone to attack without using the Intruder's radar (which might warn the target). TRAM also allowed the Intruder to autonomously designate and drop laser-guided bombs.

Intruders also saw action operating from the aircraft carriers America CV-66 and Coral Sea CV-43 during Operation "El Dorado Canyon"in April of 1986. The squadrons involved were VA-34 "Blue Blasters" from CV-66 USS America and VA-55 "Warhorses" from the CV-43 USS Coral Sea.

In the early 1990s some surviving A-6Es were upgraded under SWIP (Systems/Weapons Improvement Program) to enable them to use the latest precision-guided munitions, including AGM-65 Maverick, AGM-84 Harpoon, AGM-84E SLAM, and the AGM-88 HARM anti-radiation missile.

Intruders saw extensive action in Operation Desert Storm where they were the Navy's primary strike platform for delivering laser-guided bombs. Following Desert Storm, Intruders were used to patrol the no-fly zone in Iraq and provided air support for Marines during Operation Restore Hope in Somalia.

After a series of wing-fatigue problems, about 85% of the fleet was fitted with new graphite/epoxy/titanium/aluminum composite wings. They were all retired by the end of 1996.

Books & Films

The A-6 Intruder was featured in a 1986 novel by Stephen Coonts called Flight of the Intruder, which in 1991 was adapted as movie and a flight simulator video game in the early 1990s, as well as the novel's 1995 sequel, The Intruders. Footage of the A-6 is used to represent an unspecified fighter in the comedy Hot Shots, a spoof of Top Gun.

Specifications (A-6E)

General characteristics

• Crew: 2, pilot and bombardier/navigator

Performance Armament

• One centerline and four wing pylons each rated at 3,600 lb (1,630 kg) for a total payload of 18,000 lb (8,160 kg), including:
  • Bombs
  • laser-guided bombs
  • land mines
  • AGM-12 Bullpup and later AGM-62 Walleye / AGM-65 Maverick
  • AGM-84 Harpoon anti-ship missiles
  • AGM-84E SLAM
  • AGM-45 Shrike and later AGM-88 HARM missiles
  • B57 or B61 nuclear weapons.
  • Various ECM pods
  • M260 unguided 2.75 in (70 mm) rocket pods
  • Refueling pods

Related content

Related development

• EA-6B Prowler

Aircraft of comparable role, configuration, and era

• A-7 Corsair II, F-111

Related lists

• List of military aircraft of the United States