Grumman A-6 Intruder

The A-6 Intruder is an American twin jet-engine, mid-wing attack aircraft built by Grumman Aerospace. In service between 1963 and 1997, the Intruder was designed as an all-weather replacement for the piston-engined A-1 Skyraider medium attack aircraft. A specialized electronic warfare derivative, the EA-6B Prowler, remains in service. 

The A-6 first saw combat in Vietnam and in later engagements in Lebanon and Libya. The Intruder saw further duty during Operation Desert Storm in 1991, as well as over Bosnia in 1994. The A-6 was phased out of service in the mid-1990s. The last Intruders were retired 28 February 1997.

Grumman A-6 Intruder
Class Aircraft
Type Attack
Manufacturer Grumman
Origin United States of America
Country Name Origin Year
United States of America 1960
ManufacturerName Production From Production To Quantity
Grumman 693 View

Following the good showing of the propeller-driven AD-6/7 Skyraider in the Korean War, the United States Navy issued preliminary requirements in 1955 for an all-weather carrier-based attack aircraft. The U.S. Navy published an operational requirement document for it in October 1956. It released a request for proposals (RFP) in February 1957. Proposals were submitted by Bell, Boeing, Douglas, Grumman, Lockheed, Martin, North American, and Vought. Following evaluation of the bids, the U.S. Navy announced the selection of Grumman on 2 January 1958. The company was awarded a contract for the development of the A2F-1 in February 1958.

The prototype YA2F-1 made the Intruder's first flight on 19 April 1960.

The A-6's design team was led by Lawrence Mead, Jr. He later played a lead role in the design of the Grumman F-14 Tomcat and the Lunar Excursion Module.

The jet nozzles were originally designed to swivel downwards for shorter takeoffs and landings. This feature was initially included on prototype aircraft, but was removed from the design during flight testing. The cockpit used an unusual double pane windscreen and side-by-side seating arrangement in which the pilot sat in the left seat, while the bombardier/navigator sat to the right and slightly below. The incorporation of an additional crew member with separate responsibilities, along with a unique cathode ray tube (CRT) display that provided a synthetic display of terrain ahead, enabled low-level attack in all weather conditions.

The A-6's wing was very efficient at subsonic speeds compared to supersonic fighters such as the McDonnell Douglas F-4 Phantom II, which are also limited to subsonic speeds when carrying a payload of bombs. The wing was also designed to provide good maneuverability with a sizable bomb load. A very similar wing would be put on pivots on Grumman's later supersonic swing-wing Grumman F-14 Tomcat, as well as similar landing gear. The Intruder was also equipped with the "Deceleron", a type of airbrake on the wings with two panels that opened in opposite directions; in this case, one panel went up, while another went down.

For its day, the Intruder had surprisingly sophisticated avionics (electronics systems), with a high degree of integration. It was felt that this could lead to extraordinary maintenance requirements, to identify and isolate equipment malfunctions. Hence, the aircraft was provided with automatic diagnostic systems, some of the earliest computer-based analytic equipment developed for aircraft. These were known as Basic Automated Checkout Equipment, or BACE (pronounced "base"). There were two levels, known as "Line BACE" to identify specific malfunctioning systems in the aircraft, while in the hangar or on the flight line; and "Shop BACE", to exercise and analyze individual malfunctioning systems in the maintenance shop. This equipment was manufactured by Litton Industries. Together, the BACE systems greatly reduced the Maintenance Man-Hours per Flight Hour, a key index of the cost and effort needed to keep military aircraft operating.

The Intruder was equipped to carry and launch a nuclear bomb and Navy crews regularly planned for assigned nuclear missions. Because the A-6 was a low-flying attack aircraft, an unusual method was developed for launching an atomic bomb, should that ever be required. Known as LABS-IP (Low Altitude Bombing System – Inverted Position) it called for a high-speed low-level approach. Nearing the target point, the pilot would put the aircraft into a steep climb. At a computer-calculated point in the climb, the weapon would be released, with momentum carrying it upwards and forwards. The pilot would continue the climb even more steeply, until near a vertical position the aircraft would be rolled and turned, heading back in the direction from which it came. It would then depart from the area at maximum acceleration. During this time, the bomb would rise to an apex, still heading in its original direction, then begin to fall towards the target while traveling further forward. At a pre-programmed height, it would detonate. By that time, the Intruder would be several miles away, traveling at top speed, and thus able to stay ahead of the shock wave from the explosion. This unusual maneuver was known as an "over the shoulder" bomb launch.

Entering service and Vietnam War

The Intruder received a new standardized US DOD designation of A-6A in the Autumn of 1962, and entered squadron service in February 1963. The A-6 became both the U.S. Navy's and U.S. Marine Corps's principal medium and all-weather/night attack aircraft from the mid-1960s through the 1990s and as an aerial tanker either in the dedicated KA-6D version or by use of a buddy store (D-704). Whereas the A-6 fulfilled the USN and USMC all-weather ground-attack/strike mission role, this mission in the USAF was served by the Republic F-105 Thunderchief and later the F-111, the latter which also saw its earlier F-111A variants converted to a radar jammer as the EF-111 Raven, analogous to the USN and USMC EA-6B Prowler.

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 (18,000 pounds or 8,200 kilograms) coupled with its ability to fly in all weather made it invaluable during the war. However, its typical mission profile of flying low to deliver its payload made it especially vulnerable to anti-aircraft fire, and in the eight years the Intruder was used during the Vietnam War, the U.S. Navy and U.S. Marine Corps lost a total of 84 A-6 aircraft of various series. The first loss occurred on 14 July 1965 when an Intruder from Attack Squadron 75 (VA-75) from the carrier USS Independence, flown by LT Donald Boecker and LT Donald Eaton, commenced a dive on a target near Laos. An explosion under the starboard wing damaged the starboard engine, causing the aircraft to catch fire and the hydraulics to fail. Seconds later the port engine failed, the controls froze, and the two crewmen ejected. Both crewmen survived.

Of the 84 Intruders lost to all causes during the war, ten were shot down by surface-to-air missiles (SAMs), two were shot down by MiGs, 16 were lost to operational causes, and 56 were lost to conventional ground fire and AAA. The last Intruder to be lost during the war was from Attack Squadron 35 (VA-35), flown by LT C. M. Graf and LT S. H. Hatfield, from the carrier USS America; they were shot down by ground fire on 24 January 1973 while providing close air support. The airmen ejected and were rescued by a Navy helicopter. Twenty U.S. Navy aircraft carriers rotated through the waters of Southeast Asia, providing air strikes, from the early 1960s through the early 1970s. Nine of those carriers lost A-6 Intruders: USS Constellation lost 11, USS Ranger lost eight, USS Coral Sea lost six, USS Midway lost two, USS Independence lost four, USS Kitty Hawk lost 14, USS Saratoga lost three, USS Enterprise lost eight, and USS America lost two. Although capable of embarking aboard aircraft carriers, most U.S. Marine Corps A-6 Intruders were shore based in South Vietnam at Chu Lai and Da Nang and in Nam Phong, Thailand.

Lebanon and later action

A-6 Intruders were later used in support of other operations, such as the Multinational Force in Lebanon in 1983. On 4 December, one LTV A-7 Corsair II and one Intruder were downed by Syrian missiles. The Intruder's pilot, Lieutenant Mark Lange, and bombardier/navigator Lieutenant Robert "Bobby" Goodman ejected immediately before the crash; Lange died of his injuries while Goodman was captured and taken by the Syrians to Damascus where he was released on 3 January 1984. Later in the 1980s, two Naval Reserve A-7 Corsair II light attack squadrons, VA-205 and VA-305, were reconstituted as medium attack squadrons with the A-6E at NAS Atlanta, Georgia and NAS Alameda, California, respectively.

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

During Operation Desert Storm in 1991, U.S. Navy and U.S. Marine Corps A-6s flew more than 4,700 combat sorties, providing close air support, destroying enemy air defenses, attacking Iraqi naval units, and hitting strategic targets. They were also the U.S. Navy's primary strike platform for delivering laser-guided bombs. The U.S. Navy operated them from the aircraft carriers Saratoga, John F. Kennedy, Midway, Ranger, America and Theodore Roosevelt, while U.S. Marine Corps A-6s operated ashore, primarily from Shaikh Isa Air Base in Bahrain. Three A-6s were shot down in combat by SAMs and AAA.

The Intruder's large blunt nose and slender tail inspired a number of nicknames, including "Double Ugly", "The Mighty Alpha Six", "Iron Tadpole" and also "Drumstick".

Following Desert Storm, Intruders were used to patrol the no-fly zone in Iraq and provided air support for U.S. Marines during Operation Restore Hope in Somalia. The last A-6E Intruder left U.S. Marine Corps service on 28 April 1993.

The A-6 also saw further duty over Bosnia in 1994.

Retirement

Despite the production of new airframes in the 164XXX Bureau Number (BuNo) series just before and after Operation Desert Storm, augmented by a rewinging program of older airframes, the A-6E and KA-6D were quickly phased out of service in the mid-1990s in a U.S. Navy cost-cutting move driven by the Office of the Secretary of Defense to reduce the number of different type/model/series (T/M/S) of aircraft in carrier air wings and U.S. Marine aircraft groups.

The A-6 was intended to be replaced by the McDonnell Douglas A-12 Avenger II, but that program was canceled due to cost overruns. The Intruder remained in service for a few more years before being retired in favor of the LANTIRN-equipped Grumman F-14 Tomcat, which was in turn replaced by the Boeing F/A-18E/F Super Hornet in the U.S. Navy and the twin-seat F/A-18D Hornet in the U.S. Marine Corps. The last Intruders were retired on 28 February 1997.

Many in the US defense establishment in general, and Naval Aviation in particular, questioned the wisdom of a shift to a shorter range carrier-based strike force, as represented by the Hornet and Super Hornet, compared to the older generation aircraft such as the Intruder and Tomcat. However, the availability of USAF Boeing KC-135 Stratotanker and McDonnell Douglas KC-10 Extender tanking assets modified to accommodate USN, USMC and NATO tactical aircraft in all recent conflicts was perceived by certain senior decision makers in the Department of Defense to put a lesser premium on organic aerial refueling capability in the U.S. Navy's carrier air wings and self-contained range among carrier-based strike aircraft. Although the Intruder could not match the F-14's or the F/A-18's speed or air-combat capability, the A-6's range and load-carrying ability are still unmatched by newer aircraft in the fleet.

At the time of retirement, several retired A-6 airframes were awaiting rewinging at the Northrop Grumman facility at St. Augustine Airport, Florida; these were later sunk off the coast of St. Johns County, Florida to form a fish haven named "Intruder Reef". Surviving aircraft fitted with the new wings, as well as later production aircraft (i.e., BuNo 164XXX series) not earmarked for museum or non-flying static display were stored at the AMARG storage center at Davis-Monthan Air Force Base, Arizona.

Role Attack aircraft
National origin United States
Manufacturer Grumman
First flight 19 April 1960
Introduction 1963
Retired 28 April 1993 (USMC)
28 February 1997 (USN)
Status Retired
Primary users United States Navy
United States Marine Corps
Number built 693
Unit cost US$43 million (1998)
Variants Northrop Grumman EA-6B Prowler


General characteristics

  • Crew: 2 (pilot, bombardier/navigator)
  • Length: 54 ft 7 in (16.6 m)
  • Wingspan: 53 ft (16.2 m)
  • Height: 15 ft 7 in (4.75 m)
  • Wing area: 529 ft (49.1 m)
  • Airfoil: NACA 64A009 mod root, NACA 64A005.9 tip
  • Empty weight: 25,630 lb (11,630 kg)
  • Useful load: 34,996 lb (15,870 kg)
  • Max takeoff weight: 60,626 lb (27,500 kg)
  • Powerplant: 2 x Pratt & Whitney J52-P8B turbojets, 9,300 lbf (41.4 kN) each
  • * Zero-lift drag coefficient: 0.0144
  • Drag area: 7.64 ft (0.71 m)
  • Aspect ratio: 5.31

Performance

  • Maximum speed: 563 kn (648 mph, 1,040 km/h)
  • Range: 2,819 NM (3,245 mi, 5,222 km)
  • Service ceiling 40,600 ft (12,400 m)
  • Rate of climb: 7,620 ft/min (38.7 m/s)
  • Lift-to-drag ratio: 15.2

Armament

  • The Intruder carries no internal armament, but can carry 18,000 lb (8,170 kg) evenly distributed on five external hardpoints.

End notes