The Intruder has one of the longest service records of any aircraft in the US Navy and the US Marine Corps. 42 years after the first prototype flight it is still up there, although very much has changed under its grey aluminium skin.
The Grumman A-6 Intruder was born out of the need to replace the Douglas AD (later A-1) Skyraider attack aircraft in both the US Navy and the US Marine Corps. In February 1957 the US Navy requested proposals for a two-seat all-weather capable aircraft that could operate from short runways and within a 300 nautical mile / 556km radius.
Proposals were submitted by Boeing, Grumman, Douglas, Lockheed, Bell, North American, Vought and Martin by the August 1957 deadline set by the US Department of Defense.
Grumman submitted their design number 128Q, a side-by-side two-seat jet-powered subsonic aircraft, utilizing two Pratt & Whitney J52 non-afterburning engines. Grumman's original design had one unique idea; the jet pipes could be deflected up to 23 degrees downwards in order to shorten take-off lengths. The design also had foldable wings to ease storage aboard carriers. Weapons would be carried on four wing pylons and one on the fuselage centreline. Because of the intended nature of Intruder missions, no provision for a cannon was fitted.
The three shortlisted proposals were from Vought, Douglas and Grumman. On January 2, 1958 Grumman's design was declared the winner, and on February 21, 1958 Grumman was awarded a contract for initial design work and a full-scale mock-up.
The very first Intruder rolled out of Grumman's factory in Bethpage, Long Island, on April 14, 1960. Since this was before the branches of the US military unified their numbering schemes, it was designated A2F-1 Intruder. The aircraft was fitted with only the equipment needed for safe flying. Five days later on April 19, 1960, the Intruder took to the skies for the first time, flown by Grumman test pilot Robert Smyth. The second prototype flew on July 28, 1960, again with Robert Smyth at the controls.
The Intruder had an impressive array of advanced features, not found in other aircraft up to that date, namely; a suite of electronics dubbed Digital Integrated Attack Navigation Equipment (DIANE). DIANE consisted of a separate search radar and track radar, an inertial navigation system, an air data computer, a ballistics computer, a radar altimeter and a Doppler navigation system.
In addition to the standard attack variant, Grumman was ordered by the USMC to build a supplement and later replacement for the EF-10A Skyknight. Its role was suppression of enemy air defenses during attacks, and a total of 28 EA-6As were built to fill this role. Originally, only the USMC operated the EA-6A, but once the EA-6B Prowler materialized in 1971, some EA-6A aircraft were handed over to the US Navy.
As the flight test program progressed, a number of problems with the fuselage mounted airbrakes and the down-tilt exhaust pipes manifested themselves. Directing engine exhausts downwards was found to help only marginally with regards to take-off length. As a result of this, the tilting exhaust pipes were removed from the design and the air brakes were moved to the wingtips.
Following the unification of equipment designation in September 1962, the A2F-1 Intruder became the A-6A Intruder.
In December 1962, the US Navy started testing the Intruder aboard the then brand new carrier USS Enterprise. In February 1963, early deliveries to training squadrons were made, and the first unit to receive the Intruder was the attack squadron VA-42 Green Pawns at NAS Oceania in Virginia.
A-6B, not quite a Prowler
The A-6A Intruder turned out to be a relatively versatile aircraft, and the Navy wanted to build a special defense suppression variant of it. In August 1967, the first A-6B variant was converted from the A-6A by stripping the A-variant off all its attack systems, replacing them with electronics capable of tracking down enemy SAM radars and attacking them with AGM-78 Standard anti-radiation missiles. This was in effect the Navy's take on the Air Force's Wild Weasel concept, and paved the way for one of the most sought after air assets in the entire US military inventory; the EA-6B Prowler.
A-6C, the truck hunter
During the Vietnam War, twelve A-6A variants were modified to detect, track and attack trucks on the Ho Chi Minh Trail. The twelve aircraft of the C variant were fitted with Forward Looking Infrared sensors and a camera designed to operate at low light levels. The DIANE system was retained. The attack squadron VA-165 Boomers were the sole operators of the C variant in Vietnam, losing one A-6C in combat. In the usual acronym-laden dryness, the A-6C's were officially known as TRIM (Trails, Roads Interdiction Multisensor).
The Prowler is seemingly just a conversion of the A-6B Intruder, but it is in fact a wholly different aircraft with an outward resemblance to an Intruder. The Prowler is a dedicated SEAD aircraft with a crew of four, utilizing a vast array of advanced electronics to find, track, jam and possibly attack air defenses. It is beyond the scope of this writeup to dwelve into all the differences between the Prowler and the Intruder, so it has its own node.
The gas station Intruder
In 1968 Grumman got a go-ahead from the US navy to build a tanker variant of the Intruder. It became designated KA-6D and flew for the first time on April 16, 1970. The DIANE system was taken out, the aircraft was completely rewired, the internal fuel tanks were replaced and the wings were reworked. For navigation, an Omega navigation system was put in. The transferrable fuel was stored in four underwing tanks and sometimes in a large backup fuel pod under the fuselage. The second crewmember was responsible for filling up the receiving aircraft by reeling out a hose from the back of the aircraft. The receiving aircraft would then fly its refuelling probe into a basket-like funnel at the end of the hose. This is known as the probe-and-drogue system.
A total of 90 A-6As were converted into KA-6D tanker Intruders.
The definitive Intruder
As the electronics industry progressed with regards to radars, radios and computers, so did the Intruder. In 1966 Grumman began work on what was to become the final variant of the A-6; the A-6E. The main goal for the E variant was to reduce the need for Intruder maintenance by increasing the reliability of its equipment and make it easier to service.
The A variant had two radars; one for searching and one for tracking. The E variant combined them into one multimode radar. In addition, the old early 1960's style computer was replaced with a "solid state computer" and the Intruder was given a new set of slightly more powerful Pratt & Whitney J52-P-8B engines. An A-6A converted into an E variant first took to the air on February 27, 1970. On December 9, 1971, the VA-85 Black Falcons attack squadron got the Navy's first E variant.
During the production run of the E variant, a lot of improvements were made to the design. So many improvements have been made, that a recently manufactured A-6E is a very much more capable attack aircraft than one from the earlier batches.
A rundown on systems used in the A-6E:
CAINS: Carrier Aircraft Inertial Navigation System. Introduced in the 1970's and fitted to almost every carrier aircraft, not just the Intruder. It gave the crew greater accuracy and reliability than what was possible with the old A-6A navigation system. At the heart of CAINS is a Litton AN/ASN-92 INS unit.
TRAM: Target Recognition Attack Multi-sensor. In 1976 the A-6E with TRAM was introduced. The TRAM system consisted of a turret under the aircraft's nose, providing the ability to detect and track targets by their infrared emissions, as well as the ability to illuminate targets with a laser. TRAM Intruders also had an updated radar and computer compared to original A-6E's. One of the more advanced features of the TRAM Intruder was the Approach Power Compensator. This system gave the pilot the opportunity to undertake completely automatic carrier landings. I am unsure whether it's in daily use or saved for one of those "rainy days".
The first TRAM capable Intruders were deployed aboard the USS Nimitz in September 1979 with attack squadron VA-35 Black Panthers. The famous footage from Desert Storm which depicted what General Norman Schwartzkopf described as "the luckiest man in Iraq", shows a TRAM view during an A-6E attack on a bridge.
TRAM/DRS: TRAM with Detection and Ranging Set. Introduced in 1979 as an improvement on the original TRAM.
SWIP: Systems and Weapons Improvement Program. SWIP gave the Intruder the ability to carry the AGM-65E and F Maverick missiles (aimed by laser or infrared), the AGM-84 Harpoon anti-shipping missile, the AGM-84E SLAM (Stand-off Land Attack Missile) and the AGM-88 HARM (High-speed Anti Radiation Missile).
In the 1980's, the Intruders were diagnosed with a problem. By now many airframes had put in 25 years of service, and the metal in the wings became the victim of what every aircraft sooner or later succumbs to: metal fatigue. A program to replace the wings with composite graphite/epoxy/titanium/aluminum ones was started, and by 1995, 85 percent of the A-6E aircraft in service had new wings.
As with any other piece of equipment in military service, the Intruder had its fair share of nicknames, some affectionate and some not-so-affectionate:
- Tadpole, because it looks like one
- Q-bird (EA-6B Prowler)
- Queer (EA-6B Prowler)
- Double Ugly (EA-6B Prowler, even uglier than the basic A-6, and with twice the crew)
- Sterile Arrow (EA-6B Prowler, "Sterile" because of its lack of weapons)
- Gliding Electric Show (EA-6B Prowler, because of its huge amounts of onboard electronics)
The Intruder in combat
From the day the Intruder entered service with the United States military it was destined to see combat. This is a list of places where the Intruder took part in the fight, as well as any losses incurred:
In addition, EA-6B Prowlers took part in the NATO operation Allied Force over Kosovo in 1999.
End of service
In 1990, the United States Marine Corps decided to replace their Intruders with the F/A-18 Hornet. The EA-6B Prowler is however still the main electronic warfare platform for the US Marines and is likely to remain so for a long time to come. The US Navy started phasing out their Intruders immediately following Desert Storm in favour of F/A-18 Hornets and ground attack capable F-14 Tomcats. The last A-6 Intruder catapult launch took place on USS Enterprise on December 19, 1996.
The Navy finally retired the A-6E in February 1997 after more than 30 years of service. Some 130 A-6E aircraft are currently in storage at AMARC and have been designated for Foreign Military Sales (FMS).
A total of 687 Intruders were built by Grumman between 1960 and the late 1980's.
This text was proofread by princess loulou
"American Warplanes", Salamander Books, 1987.