Grumman A-6 Intruder

Background As a result of the fair-weather limitation of the propeller-driven A-1 Skyraider in the Korean War and the advent of turbine engines, the United States Navy issued preliminary requirements in 1955 for an all-weather carrier-based attack aircraft. The U.S. Navy published an Operational Requirements Document (ORD) for it in October 1956. It released a Request For Proposals (RFP) in February 1957. The RFP called for a "close air support attack bomber capable of hitting the enemy at any time". The specification was shaped by the service's Korean War experiences, during which air support had been frequently unavailable unless fair weather conditions were present. In response to the RFP, a total of eleven design proposals were submitted by eight different companies, including Bell, Boeing, Douglas, Grumman, Lockheed, Martin, North American, and Vought. Grumman's submission was internally designated as the Type G-128. Grumman's design team was led by Robert Nafis and Lawrence Mead, Jr. The team was spread between two sites, the company's manufacturing plant at Bethpage, New York, and the testing facilities at Naval Weapons Industrial Reserve Plant, Calverton in Riverhead, New York. During September 1959, the design was approved by the Mock-Up Review Board. with the second prototype flying on 28 July 1960. The test program required to develop the aircraft was prolonged. The very advanced navigation and attack equipment required substantial development, and changes had to be made to correct aerodynamic deficiencies and remove unwanted features. Extending the air brakes, which were mounted on the rear fuselage, changed the downwash at the horizontal tailplane which overloaded its actuator so the tailplane was moved rearwards by . Later evaluation of the aircraft showed that the airbrakes were not effective enough in controlling the speed of the aircraft and they were moved to the wing-tips. Early production aircraft were fitted with both the fuselage and wingtip air brakes, although the fuselage-mounted ones were soon disabled, and were removed from later aircraft. The rudder needed a wider chord at its base to give greater exposed area to assist spin recovery. A major difference between the first six production aircraft and subsequent aircraft were the jet nozzles; the close-air support role sought by the U.S. Marine Corps required STOL performance to operate from forward airstrips. Jet deflection using tilting tailpipes was proposed. The performance benefits from varying the angle were not worthwhile, whether operating from short strips or carriers, thus they were fixed at a seven degree downward angle. Further development During February 1963, the A-6 was introduced to service with the US Navy; at this point, the type was, according to Gunston and Gilchrist, "the first genuinely all-weather attack bomber in history". However, early operating experiences found the aircraft to be imposing very high maintenance demands, particularly in the Asian theatre of operations, and serviceability figures were also low. In response, the Naval Avionics Lab launched a substantial and lengthy program to improve both the reliability and performance of the A-6's avionics suite. Various specialized variants of the A-6 were developed, often in response to urgent military requirements raised during the Vietnam War. The last A-6E was delivered in 1992. In the early 1980s, the Navy anticipated that an Advanced Carrier-Borne Multirole Fighter (VFMX) would eventually be the long term high-end replacement for both the F-14 and A-6, although this program was short-lived and was succeeded by separate efforts for fleet air defense and deep strike/attack; the latter became the Advanced Tactical Aircraft (ATA) program resulting in the development of the McDonnell Douglas A-12 Avenger II. Meanwhile, a further model, designated A-6F, was being planned. Intended to feature the General Electric F404 turbofan engine, as well as various avionics and airframe improvements, this variant was cancelled under the presumption that the A-12 would be entering production before long. Instead, a life-extension program involving the re-winging of existing A-6E aircraft was undertaken; initially a metal wing had been used before a graphite-epoxy composite wing was developed during the late 1980s. Other improvements were introduced to the fleet around this time, including GPS receivers, new computers and radar sets, more efficient J-52-409 engines, as well as increased compatibility with various additional missiles. ==Design==

, showing the split airbrakes on the tips of its left wing The Grumman A-6 Intruder is a two-seat twin-engined monoplane, equipped to perform carrier-based attack missions regardless of prevailing weather or light conditions. For its day, the Intruder had sophisticated avionics, with a high degree of integration. ==Operational history==

Entering service and Vietnam War , A-6E Intruder, and an EA-6B Prowler aircraft are parked on the flight deck of aircraft carrier during a storm. The Intruder received a new standardized US DoD designation of A-6A on 18 September 1962, with deliveries to VA-42, the medium attack training squadron, in February 1963. The first operational fleet squadron, VA-75 re-equipped with A-6s from October 1963. 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, Libya and Persian Gulf 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-304, 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 USS America) and VA-55 "Warhorses" (from USS Coral Sea). On 19 October 1987, Intruders of VA-145 operating from USS Ranger attacked Iranian oil platforms during Operation Nimble Archer. On 19 April 1988, VA-95 Intruders operating from USS Enterprise sank the Iranian frigate, Sahand and severely damaged the Iranian frigate, Sabalan during Operation Praying Mantis. Gulf War and later action During the Gulf War 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 , , USS Midway, USS Ranger, USS America and , 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 the Gulf War, 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. Navy A-6s saw further duty over Bosnia in 1994. On 4 June 1996, during RIMPAC a US Navy A-6E performing the unusual target towing task to train Japanese Navy air defense crews was mistakenly engaged and shot down by the Japanese destroyer JS Yūgiri with its Phalanx CIWS gun. Both the pilot and BN ejected and were recovered by a motor launch from the destroyer. Retirement Despite the production of new airframes in the 164XXX Bureau Number (BuNo) series just before and after the Gulf War, 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. After the A-12's cancellation, the Navy initiated a new attack aircraft program, the Advanced Attack (A-X), to replace the Intruder; A-X would shortly become the Advanced Attack/Fighter (A/F-X) due to added fighter capabilities to eventually replace the F-14 Tomcat as well, but the program would be canceled in the 1993 Bottom Up Review due to post-Cold War budget pressures. The Intruder remained in service for a few more years before being retired in favor of the LANTIRN-equipped F-14D Tomcat, which was in turn replaced by the 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. During the 2010s, the Unmanned Carrier-Launched Airborne Surveillance and Strike program was at one point intended to produce an unmanned aerial vehicle (UAV) successor to the Intruder's long-distance strike role, but the initiative has since changed priorities towards the tanker mission instead. 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 tankers modified to accommodate USN, USMC and NATO tactical aircraft in all recent conflicts was considered 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. Surviving aircraft fitted with the new wings, and 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. ==Variants==

YA-6A and A-6A The eight prototypes and pre-production Intruder aircraft were sometimes referred to with the YA-6A designation. These were used in the development and testing of the A-6A Intruder. The initial version of the Intruder was built around the complex and advanced DIANE (Digital Integrated Attack/Navigation Equipment) suite, intended to provide a high degree of bombing accuracy even at night and in poor weather. DIANE consisted of multiple radar systems: the Norden Systems AN/APQ-92 search radar replacing the YA-6A's AN/APQ-88, and a separate AN/APG-46 for tracking, the AN/APN-141 radar altimeter, and an AN/APN-122 Doppler navigational radar to provide position updates to the Litton AN/ASN-31 inertial navigation system. An air-data computer and the AN/ASQ-61 ballistics computer integrated the radar information for the bombardier/navigator in the right-hand seat. TACAN and ADF systems were also provided for navigation. When it worked, DIANE was perhaps the most capable navigation/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, and it was several years before its reliability was established. Total A-6A production was 480, excluding the prototype and pre-production aircraft. The A-6B had many of its standard attack systems removed in favor of specialized equipment to detect and track enemy radar sites and to guide AGM-45 Shrike and AGM-78 Standard anti-radiation missiles, with AN/APQ-103 radar replacing earlier AN/APQ-92 used in the A-6A, plus AN/APN-153 navigational radar replacing earlier AN/APN-122, again used in the A-6A. Between 1968 and 1977, several Intruder squadrons operated A-6Bs alongside their regular A-6As. Five were lost to all causes, and the surviving aircraft 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 "Trails/Roads Interdiction Multi-sensor" (TRIM) pod in the fuselage for FLIR and low-light TV cameras, as well as a "Black Crow" engine ignition detection system. Radars were also upgraded, with the AN/APQ-112 replacing the earlier AN/APQ-103, and an AN/APN-186 navigational radar replacing the earlier AN/APN-153. A vastly improved Sperry Corporation AN/APQ-127 radar replaced the AN/APG-46 fire control radar. One of these aircraft was lost in an accident; the others were later refitted to A-6E standard after the war. KA-6D To replace both the KA-3B and EA-3B Skywarrior during the early 1970s, 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. Because it was based on a tactical aircraft platform, the KA-6D provided a capability for mission tanking, the ability to keep up with strike aircraft and refuel them in the course of a mission. A few KA-6Ds went to sea with each Intruder squadron. Their operation was integrated into the Intruder squadrons, as A-6 crew were trained to operate both aircraft and the NATOPS covered both the A6 and KA-6D. These aircraft were always in short supply, and frequently were "cross decked" from a returning carrier to an outgoing one. Many KA-6 airframes had severe G restrictions, as well as fuselage stretching due to almost continual use and high number of catapults and traps. The retirement of the aircraft left a gap in US Navy and Marine Corps refueling tanker capability. At least 16 KA-6Ds served in the Gulf War. The Navy Lockheed S-3 Viking filled that gap until the new F/A-18E/F Super Hornet became operational. A-6E The definitive attack version of the Intruder with vastly upgraded navigation and attack systems, introduced in 1970 and first deployed on 9 December 1971. The earlier separate search and track (fire control) radars of the A-6A/B/C were replaced by a single Norden AN/APQ-148 multi-mode radar, and onboard computers with a more sophisticated (and generally more reliable) IC based system, as opposed to the A-6A's DIANE discrete transistor-based technology. A new AN/ASN-92 inertial navigation system was added, along with the CAINS (Carrier Aircraft Inertial 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 'Target Recognition and Attack Multi-Sensor' (TRAM) system, a small, gyroscopically stabilized turret, mounted under the nose of the aircraft, containing a forward-looking infra-red (FLIR) boresighted with a laser spot-tracker/designator and IBM AN/ASQ-155 computer. TRAM was matched with a new Norden AN/APQ-156 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 an Airborne Moving Target Indicator (AMTI), which allowed the aircraft to track a moving target (such as a tank or truck) and drop ordnance on it even though the target was moving. Also, the computer system allowed the use of Offset Aim Point (OAP), giving the crew the ability to drop on a target unseen on radar by noting coordinates of a known target nearby and entering the offset range and bearing to the unseen target. In the 1980s, the A-6E TRAM aircraft were converted to the A-6E 'Weapons Control System Improvement' (WCSI) version to extend weapons capability. This added the ability to carry and target some of the first generation precision guided weapons, like the AGM-84 Harpoon missile, and AGM-123 Skipper. WCSI equipped aircraft were eventually modified to have a limited capability to use the AGM-84E SLAM standoff land attack missile. Since the Harpoon and SLAM missiles had common communication interfaces, WCSI aircraft could carry and fire SLAM missiles, but needed a nearby A-6E SWIP to guide them to target. Radar 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 Mavericks, AGM-84E SLAMs, AGM-62 Walleyes and the AGM-88 HARM anti-radiation missile as well as additional capability with the AGM-84 Harpoon. A co-processor was added to the AN/ASQ-155 computer system to implement the needed MIL-STD-1553 digital interfaces to the pylons, as well as an additional control panel. After a series of wing-fatigue problems, about 85% of the fleet was fitted with new graphite/epoxy/titanium/aluminum composite wings. The new wings proved to be a mixed blessing, as a composite wing is stiffer and transmits more force to the fuselage, accelerating fatigue in the fuselage. In 1990, the decision was made to terminate production of the A-6. Through the 1970s and 1980s, the A-6 had been in low-rate production of four or five new aircraft a year, enough to replace mostly accidental losses. The final production order was for 20 aircraft of the SWIP configuration with composite wings, delivered in 1993. 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 U.S. 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 canceled 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 canceled. Electronic warfare versions . An electronic warfare (EW)/Electronic countermeasures (ECW) 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-1H (rather than A2F-1Q, as "Q" was being split to relegate it to passive electronic warfare and "H" to active) 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 equipped with AN/APQ-129 fire control radar, and theoretically capable of firing the AGM-45 Shrike anti-radiation missile, although they were apparently not used in that role. The navigational radar is AN/APN-153. Only 28 EA-6As were built (two prototypes, 15 new-build, and 11 conversions from A-6As), serving with U.S. Marine Corps squadrons in Vietnam. It was phased out of front line service in the mid-1970s, remaining in use in reserve VMCJ units with the USMC and then the United States Navy in specialized VAQ units, primarily for training purposes. The last EA-6A had been retired by 1993. A much more highly specialized derivative of the Intruder was the EA-6B Prowler, having a "stretched" airframe with two additional systems operators, and more comprehensive systems for the electronic warfare and SEAD roles. A derivative of AN/APQ-156, AN/APS-130 was installed as the main radar for EA-6B. The navigational radar was upgraded to AN/APS-133 from the AN/APN-153 on EA-6A. In total, 170 were produced. The EA-6B took on the duties of the U.S. Air Force EF-111 Raven when the DoD decided to let the U.S. Navy handle all electronic warfare missions. The Prowler has been replaced by the EA-18G Growler in the U.S. Navy and was retired from USMC service in 2019. Variant list ;YA2F-1 :Pre-production aircraft, eight built with the first four with rotating jet exhaust pipes, redesignated YA-6A in 1962. ;A2F-1 :First production variant with fixed tailpipe, 484 built, redesignated A-6A in 1962. ;A-6E SWIP :A-6E TRAM upgraded with the AN/ALR-67 RWR and ability to carry the AGM-88 HARM, AGM-62 Walleye, AGM-84E SLAM and AGM-65 Maverick. Several versions had new composite wings. ==Operators==

; • United States Navy (1963–1997) • United States Marine Corps (1963–1993) ==Aircraft on display==

. ;YA-6A • 147865 – Cherry Point Historical Aircraft Park, Havelock, North Carolina; displayed as an EA-6A. • 147867 – Alleghany Arms & Armory Museum, Smethport, Pennsylvania. ;KA-6D • 149482 – NAS Whidbey, Oak Harbor, Washington; displayed as an A-6E. • 151826 – Battleship Memorial Park, Mobile, Alabama; • 152910 – Oakland Aviation Museum, Oakland, California. ;A-6E • 151782 – USS Midway Museum, San Diego, California • 152599 – Patriots Point Naval & Maritime Museum, Mount Pleasant, South Carolina • 152603 – Richmond Municipal Airport, Richmond, Indiana. • 152907 – NAS Whidbey, Oak Harbor, Washington. • 152923 – Norfolk Naval Station/Chambers Field (former NAS Norfolk), Norfolk, Virginia. • 152935 – Empire State Aerosciences Museum, Glenville, New York • 152936 – United States Naval Museum of Armament and Technology, NCC China Lake (North), Ridgecrest, California. • 154131 – Walker Field Colorado Park, Grand Junction, Colorado. • 154162 – Palm Springs Air Museum, Palm Springs, California • 154167 – Steven F. Udvar-Hazy Center, NASM, Washington, D.C. • 154170 – Flying Leatherneck Aviation Museum, MCAS Miramar, San Diego, California • 154171 – Estrella Warbird Museum, Paso Robles, California • 155595 – Pacific Coast Air Museum, Santa Rosa, California • 155610 – National Naval Aviation Museum, NAS Pensacola, Pensacola, Florida • 155627 – NAS Fallon, Fallon, Nevada. • 155629 – Hickory Aviation Museum, Hickory NC • 155644 – Yanks Air Museum, Chino, California • 155648 – Aviation History & Technology Center, Dobbins ARB (formerly Atlanta NAS), Atlanta, Georgia. • 155661 – Camp Blanding Museum and Memorial Park, Camp Blanding, Florida. • 155713 – Pima Air & Space Museum (adjacent to Davis-Monthan AFB), Tucson, Arizona • 156997 – Patuxent River Naval Air Museum, NAS Patuxent River, Lexington Park, Maryland. • 157001 – Naval Inventory Control Point, Philadelphia, Pennsylvania. • 157024 – Defense General Supply Center, Richmond, Virginia. • 158532 – USS Lexington Museum, Corpus Christi, Texas • 158794 – Museum of Flight, Seattle, Washington • 159567 – Naval Surface Warfare Center Dahlgren Division, Dahlgren, Virginia. • 159568 – Patuxent River NAS, Lexington Park, Maryland. • 159579 – Castle Air Museum, Atwater, California • 159901 – NAF El Centro, El Centro, California. • 160995 – Yanks Air Museum, Chino, California • 161676 – Lycoming County Veterans Memorial Park, Williamsport, Pennsylvania. • 162182 – Valiant Air Command Warbird Museum, Space Coast Regional Airport, Titusville, Florida • 162195 – San Diego Aerospace Museum, San Diego, California. • 162206 – Oregon Air and Space Museum, Eugene, Oregon • 164378 – Eastern Carolina Aviation Exhibit, Havelock, North Carolina. • 164384 – Grumman Memorial Park, Long Island, New York. ;A-6F • 162184 – Cradle of Aviation Museum, Garden City, New York • 162185 – Intrepid Sea-Air-Space Museum, New York City, New York ==Specifications (A-6E)==

==Notable appearances in media==