The Grumman A-6 "Intruder" was a dedicated strike platform designed to a United States Navy (USN) requirement for an all-weather, carrier-based attack aircraft capable of carrying and delivering large, potent payloads on inland enemy targets. To this point, the USN had found success for such a platform through the multi-faceted Douglas "Skyraider" prop-driven attack aircraft line used in the Korea War (1950-1953) and looked to expand on such capabilities through a jet-powered mount. The USN delivered their request in 1955 and finalized their wish-list by 1957. This resulted in the usual American defense players being solicited (no fewer than eleven bids from eight companies forthcoming) and in January of 1958, the Grumman model "G-128" was selected for further development under the USN designation of "A2F-1" (using the pre-1962 USN marking convention). This continued the Grumman-USN partnership that dated back to World War 2 and the storied F4F Wildcat fighter line.
Work revealed a flyable prototype which first took to the skies on April 19th, 1960. The prototype YA2F-1 would largely resemble the finalized A-6 Intruder known today but featured a unique quality with its swiveling jet pipe nozzles which were to allow for short runway take-offs when pointing downwards. The rest of the aircraft constituted tear drop-shaped fuselage with bulbous frontal section and severely tapering aft section, high-mounted and rearward-swept monoplane wing assemblies, and a wide two-man, side-by-side cockpit arrangement (pilot at left with the bombardier at right). Indeed the aircraft took on the shape of a turkey leg and was thus nicknamed that over the course of its career. The aircraft was powered by two turbojet engines seated along the sides of the lower fuselage, aspirated through semi-circle intakes found along the forward fuselage sides and exhausted through individual nozzles under the sides of the tail unit. The undercarriage was typically carrier-like - two single-wheeled main legs and a dual-wheeled nose leg, all three legs retractable into the frame. The all-weather requirement was aided by a terrain display CRT system to which the navigator/bombardier utilized for their low-level attack runs. A permanently fixed in-flight refueling probe was fitted over the nose between the forward cockpit windscreens and used to further extend the operational reach of the aircraft. The tail unit consisted of a single vertical tail fin with swept-back horizontal planes.
From the outset, the A2F-1/A-6 was designed around a large bomb load out and this necessitated a specialized approach to the wings which could enable the aircraft to carry potent payloads while maintaining the necessary strength and capabilities for subsonic flight. With a high-mounted installation, the underwing hardpoints were cleared from any ground interference and offered the needed performance handling during low-level runs while retaining agility against ground-based fire. Airbrakes were integrated into the wings for additional stabilizing support. The avionics suite was of an advanced nature for the period with automation built-in as well as diagnostic measures to aid technicians and the flight crew. This sort of sophisticated design nature made the A-6 a high maintenance machine.
Armament was set across five total hardpoints that included four underwing and one under fuselage position for a total of 18,000lb of externally-held stores. The A-6 would eventually see a career carrying everything from air-to-air missiles, air-to-surface missiles, anti-radar missiles, rocket pods, and a plethora of general purpose drop bombs. Precision-guided munitions followed in time and a nuclear-drop capability was always a part of her design. There was no internal gun fitted. Additionally, the aircraft could carry external drop tanks across any of its five hardpoints for all positions were plumbed.
Grumman completed eight airframes for the preliminary and developmental testing phases. These led to the initial A-6A production models which would eventually number 480 units (USN designations moved to a new standard in 1962). The first operational squadron to be issued the A-6A was VA-42 on February 1st, 1963 and the type was adopted for service with both the USN and the United States Marine Corps (USMC) serving as the primary strike arm of USN carrier groups.
As a carrier-based aircraft, the A-6 was given the usual carrier-minded qualities to assist in its operation in an over-water environment. Its undercarriage was reinforced for the rigors of deck service (complete with the double-tired nose landing gear leg) and an arrestor (tail) hook was added under the empennage to snag awaiting deck cables when landing. For storage on the space-strapped carriers of the day, the A-6's wing mainplanes folded upwards at about their midway length to promote a more contained profile when held below deck.
The A-6's baptism of fire occurred in the long-running Vietnam War (1955-1975). By the mid-1960s, America's commitment in the region had grown to the point that any and all available military hardware was sent to the region in an attempt to turn the tide against the invading Soviet-supported North. The A-6 was up to the challenge with well-trained crews and long-ranged capabilities while carrying an incredible amount of ordnance against enemy ground targets. Of course, the low-altitude runs expected of the aircraft opened it up to intense enemy ground fire (including Surface-to-Air Missile (SAM) strikes) from all quarters and some eighty-four A-6s were lost in the war. Nevertheless, the A-6 became just one of the many American military symbols of the Vietnam War - joining the storied McDonnell Douglas F-4 Phantom II fighter, the Bell UH-1 "Huey", and others in the fray.
During the war, the A-6A was selected for modification to an anti-radar platform for suppression of North Vietnam air defense systems. Nineteen A-6As were converted by replacing their traditional ground attack equipment (AN/APQ-103 radar) with anti-radar systems (AN/APQ-92) to be used in conjunction with AGM-78 "Standard ARM" and the AGM-45 "Shrike" anti-radiation missiles. The missiles rode to their target on the emissions generated from a seeking/tracking enemy radar system upon their launching from the A-6 wing hardpoints. Navigation was also replaced with the AN/APN-153 series radar and these revised Intruders were designated "A-6B", beginning service in 1968.
In 1970, a dozen A-6A models were modified for the night attack role and outfitted with the TRIM pod ("Trails/Roads Interdiction Multi-Sensor") which allowed for enhanced night time function of the aircraft in low light / poor weather over the crucial Ho Chi Minh Trail supply route. Again, attack systems and navigational radar were replaced for the role.
While no definitive "D" Intruder model emerged, the "KA-6D" was developed as a successor to the outgoing KA-3B "Skywarriors" in the in-flight refueling role. The KA-6D retained some of its basic bombing capabilities but was a support platform through and through. It could service other attack aircraft by carrying a specialize refueling kit which made the base A-6A a "fuel bus" of sorts, providing fuel to awaiting allies during missions. As the USN lacked a dedicated in-flight refueling tanker, the KA-6D filled this role through a the "K" conversion process and some 78 A-models and a further 12 E-models were converted to this standard.
Also in 1970 emerged the A-6E variant which introduced a new attack suite and navigation system. This mark became the final - and somewhat definitive - Intruder of the Vietnam War years. A 1980 conversion program increased weapons support to include precision-guided ordnance. A large portion of the fleet were also given new wing assemblies due to combat and service life fatigue over the ensuing decade. E-models eventually totaled 445 units of which 240 were brought along from existing A-, B-, C-model stocks.
The A-6F became an ultimately failed bid to augment the A-6 fleet through an improved "Intruder II" concept with new, more powerful engines and onboard processing systems. Five prototypes were completed but USN authorities decided against the costly endeavor. The A-6G was, therefore, a Grumman-sponsored "budget alternative" of the F-model but went nowhere as well.
The EA-6A was a USMC Electronic Warfare Aircraft (EWA) variant which numbered 28 airframes (distinguished by their vertical fin bulge housing the antennas). The type first flew on April 26th, 1963 and eventually was made from a stock of 15 new-build models and 11 converted A-6A airframes. The USMC used these specially outfitted aircraft over Vietnam where they replaced the aging stock of Douglas F3D "Skyknights" in the same role. Equipment included the AN/APQ-129 Fire Control Radar (FCR) and AN/APN-153 series navigation system and EA-6As soldiered on up to the late 1970s before being given up.
A more dedicated EWA version of the Intruder family became the EA-6B "Prowler" which was given a lengthened fuselage to accommodate an additional two side-by-side crewmen (electronic warfare officers). More advanced radar, navigation, and processing systems greeted this type and gave the USN a potent alternative to the USAF-sponsored EF-111 "Ravens" that it relied on in combat zones. One other identifying quality about these aircraft was the pod fitted to the tail fin which housed the necessary antennas and underwing pods for the jammer equipment. Prowler procurement numbered 170 units for service with both the USN and USMC and were introduced during 1971 with production spanning into 1991.
The Prowler has since been replaced by the modern EA-18G "Growler" series, this specialized airframe based on the twin-seat Boeing F/A-18 "Super Hornet" line.
For the 1980s, American attention had turned away from Southeast Asia and centered more and more on involvement in Middle East affairs. In 1983, the A-6 was called to service over Lebanon in support of an international peacekeeping measure under the banner of the United Nations. Combat found the series once more when they launched in anger against targets in Libya. In 1991, Intruders formed the carrier-based strike arm of the U.S.-led coalition in the Persian Gulf as it laid waste to the Iraqi air force and army during Operation Desert Storm where precision-guided capabilities were put to tremendous use. Both USN and USMC Intruders were used in the war with only three lost to enemy fire. After the war, Intruders served with coalition forces in maintaining the UN-imposed "No Fly Zones" over northern and southern Iraq. Its next actions in the region brought it over Somalia during Operation Restore Hope (1992-1993) while final sorties were in eastern Europe against enemy targets in Bosnia during 1994.
By the middle of the decade, the Intruder design had all but run its course as a frontline USN player, having seen consistent combat service throughout most of the major American engagements of the latter 20th Century. Time and technology advances eventually crept into a decision to begin a drawdown of the A-6 fleet. The McDonnell Douglas A-12 "Avenger II" - a triangle-shaped naval stealth bomber - was, at one point, envisioned to be the A-6's high-tech replacement but the project went nowhere and ended as an over-funded black eye for the USN. Once the Grumman F-14 Tomcat air defense interceptor was given a long-awaited ground attack capability, the A-6 was formally retired to help better streamline and standardize the types of aircraft serving aboard American carriers. The F-14 was then, itself, retired and replaced by the multirole F/A-18 "Hornet" which, in turn, gave rise to a two-seat platform as the "Super Hornet". The Super Hornet handles both the role of fleet defense (as the F-14 did) while taking on strike sorties as needed (as in the A-6).
The A-6 Intruder was never exported beyond American shores. Total production netted 693 aircraft of all variant types mentioned.