A-6 Intruder

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A-6 (A2F) Intruder

Type	Attack aircraft
Manufacturer	Grumman Aerospace Corporation
Maiden flight	19 April 1960
Introduced	1963
Retired	1997
Primary users	United States Navy United States Marine Corps
Number built	693
Unit cost	US$43 million as of 1998
Variants	EA-6B Prowler

The A-6 Intruder is a twin-engine, mid-wing attack aircraft built by Grumman Aerospace. In service between 1963 and 1997, the Intruder was designed as a replacement for the piston-engined A-1 Skyraider. A specialized electronic warfare derivative, the EA-6B Prowler, remains in service as of 2006. As the A-6 neared retirement, it was replaced at some reduction in combat radius by the multirole F/A-18 Hornet and fighter-bomber adaptations of the now also retired F-14 Tomcat.

[edit] Development

An A-6E Intruder prepares for launch aboard the USS Enterprise (CVN-65).

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. The jet nozzles were originally designed to swivel downwards, but this was dropped from production aircraft. The pilot sits in the left seat, while the bombardier/ navigator sits to the right and below. A unique CRT gives a synthetic display of terrain ahead which, with the additional crew member, enabled low-level flying in all weather conditions. The wing is very efficient at subsonic speeds compared to supersonic fighters such as the F-4 Phantom, which are also limited to subsonic speeds when carrying a paylod of iron bombs. A very similar wing would be put on pivots on Grumman's later supersonic swing-wing F-14 Tomcat, as well as the landing gear and inlet geometry.^[1]

The Intruder received a new standardized DOD designation of 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 and all-weather/night attack aircraft from the mid-1960s through the 1990s. This role was served in the USAF by the F-105 Thunderchief and later F-111 which was also later converted to a radar jammer. 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 that program was cancelled. The Intruder was left to soldier on for a few more years before retiring in favor of the F/A-18E/F Super Hornet, which had been scaled up to replace both the Intruder and F-14 Tomcat, though many questioned the shift to a shorter ranged strike force compared to the older generation planes.

The last Intruders were retired 28 February 1997. A number of retired A-6 airframes were sunk off the coast of St. Johns County, Florida to form a fish haven entitled Intruder Reef. However, 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 still unmatched by newer aircraft in the fleet.

[edit] Variants

[edit] YA-6A

This designation was given to eight prototypes and pre-production aircraft, used in the development of the A-6A Intruder.

[edit] 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.

[edit] 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 sites 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.

[edit] 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.

[edit] 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.

[edit] A-6E

An A-6E Intruder flying over Spain during Operation Matador.

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 addition, the Intruder used AMTI (Airborne Moving Target Indicator) which allowed the plane to track a moving target (such as a tank or truck) and drop ordnance on him even though the target was moving. Also, the computer system allowed the use of OAPs (Offset Aim Points) which gave the crew the ability to drop on a target if it was unseen on radar, simply by noting the coordinates of a known target nearby and entering the offset range and bearing to the unseen target.

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.

[edit] A-6F and A-6G

As crew members look on, Virginia Governor George Allen (center white vest) helps launch the final VA-34 A-6E Intruder aircraft from the flight deck of aircraft carrier USS George Washington (CVN-73), 1996.

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.

[edit] 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. In total, 170 were produced. The Prowler remains in service as of 2006, replacing the Air Force EF-111A Raven aka "Spark Vark" when the DOD decided to let the Navy handle the electronic warfare mission. It is scheduled to be replaced by the EA-18G Growler Super Hornet variant.

Prowlers have special markings on their nose to distinguish them from other Intruders for purposes of setting up launching catapults.

[edit] NA-6A

The redesignation of three YA-6As and three A-6As. The six aircraft were modified for special tests purposes.

[edit] YEA-6A

One YA-6A aircraft was converted into the EA-6A prototype.

[edit] YEA-6B

The designation of two EA-6B prototypes, which were modified for special test purposes.

[edit] NEA-6A

One EA-6A aircraft was modified for special test purposes.

[edit] Combat Experience

An air-to-air left side view of an A-6E Intruder aircraft assigned to the USS Dwight D. Eisenhower (CVN-69).

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 lb/8,170 kg) 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 performed strikes during the U.S. mission in Lebanon in 1983. One Intruder and one A-7 Corsair were downed by Syrian missiles on December 4. 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 USS America) and VA-55 "Warhorses" (from USS Coral Sea).

Intruders saw extensive action in Operation Desert Storm where they were the Navy's primary strike platform for delivering laser-guided bombs. The USN operated them from the aircraft carriers USS Saratoga, USS John. F Kennedy, USS Midway, USS Ranger, USS America, and USS Theodore Roosevelt. The USMC also operated two land-based squadrons of A-6E Intruders during the conflict. 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.

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 ^[2] "Drumstick" and "Pregnant Guppy".

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 early 1997.

[edit] Popular culture

The A-6 Intruder was featured in a 1986 novel by Stephen Coonts called Flight of the Intruder, with a plot line somewhat similar to the book Thud Ridge book about pilots flying into Hanoi restricted by militarily dubious rules of engagment. In 1991, the book 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. An Intruder is seen launching from a carrier deck in most opening credits of the series The West Wing. The air-to-air refueling capabilities of the KA-6D tanker variant were also seen in the film The Final Countdown.

[edit] Scale models

The A-6 Intruder is well represented in many plastic scale models by manufacturers such as Hasegawa and Fujimi in both A-6A/E form in various scales, and also as the EA-6B. Many inexpensive die-cast toys have been made by Maisto and other makers. Many are of the EA-6A, which can be distinguished by the large housing on top of the tail fin.

[edit] Operators

See also: List of A-6 Intruder squadrons

Several squadrons in both the United States Marine Corps and United States Navy operated the Intruder until its retirement in 1997.

[edit] Specifications (A-6E)

Data from Quest for Performance^[3]

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 ft² (49.1 m²)
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× Pratt & Whitney J52-P8B turbojets, 9,300 lbf (41.4 kN) each
Zero-lift drag coefficient: 0.0144
Drag area: 7.64 ft² (0.71 m²)
Aspect ratio: 5.31

Performance

Maximum speed: 563 knots (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

S-3A Viking, A-6E Intruder, and an EA-6B Prowler aircraft are parked on the flight deck of the aircraft carrier USS John F. Kennedy (CV-67) during a storm.

Armament

18,000 lb (8,170 kg) evenly distributed on five external hardpoints, with options including:

- 2.75" (70 mm) Rocket Pod
- 5" (127 mm) Zuni Rocket Pod
- Mk-20 Rockeye
- Mk-77 Napalm
- Mk-81 (250 lb) (113 kg)
- Mk-82 Snakeye
- Mk-83 (1,000 lb) (454 kg)
- Mk-84 (2,000 lb) (907 kg)
- Mk-117 (750 lb) (340 kg)
- CBU-78 Gator
- GBU-10E Paveway II Laser Guided Bomb
- GBU-12D Paveway II Laser Guided Bomb
- GBU-16B Paveway II Laser Guided Bomb
- AGM-123A Skipper II
- AGM-45 Shrike
- AGM-62 Walleye
- AIM-9 Sidewinder
- AGM-84D Harpoon
- AGM-88 HARM
- AGM-84E SLAM
- AGM-65 Maverick
- AIM-120A AMRAAM
- AGM-123 Skipper
- B-61 Special Weapon
- Various Land mines
- Various underwater mines
- Various practice bombs [Mk-76, BDU-45, LGTR, etc...]

[edit] References

^ Bill Gunston Modern Air Combat
^ [1]Flightline - US Military Aircraft Nicknames Compiled by Richard H. Caldwell
^ Loftin, LK, Jr.. Quest for performance: The evolution of modern aircraft. NASA SP-468. Retrieved on 2006-04-22.