The Douglas A-4 Skyhawk is a single-seat subsonic carrier-capable light attack aircraftdesigned and produced by the American aerospace manufacturer Douglas Aircraft Company, and later by McDonnell Douglas. It was originally designated A4D under the United States Navy's pre-1962 designation system.
The Skyhawk was developed during the early 1950s on behalf of the US Navy and United States Marine Corps as a replacement for the propeller-driven Douglas AD Skyraider. It was a relatively compact, straightforward, and lightweight aircraft for the era, the aircraft's maximum takeoff weight of 24,500 pounds (11,100 kg) being roughly half of the Navy's weight specification. The Skyhawk has a short-span delta wing configuration, a tricycle undercarriage, and is powered by a single turbojet engine. The US Navy issued a contract for the aircraft on 12 June 1952. On 22 June 1954, the XA4D-1 prototype performed its maiden flight; it went on to set a world speed record of 695.163 mph on 15 October 1955.On 1 October 1956, the Skyhawk was introduced to operational service.
The Skyhawk's five hardpoints support a variety of missiles, bombs, and other munitions. It is capable of carrying a bomb load equivalent to that of a World War II–era Boeing B-17 bomber, and can deliver nuclear weapons using a low-altitude bombing system and a "loft" delivery technique. Furthermore, it pioneered the concept of "buddy" air-to-air refueling, enabling an aircraft to supply others and reduce the need for dedicated aerial tankers. The Skyhawk was originally powered by the Wright J65turbojet engine; from the A-4E onwards, the Pratt & Whitney J52 engine was used instead. The Skyhawk was in production through to February 1979, by which point 2,960 aircraft had been delivered to a variety of operators. 555 aircraft alone were built as dedicated two-seat trainers.
The Skyhawk saw active combat on several occasions. The US Navy operated the type as its principal light attack aircraft during the Vietnam War, carrying out some of the first air strikes by the US during the conflict. The Skyhawk was the Israeli Air Force's main ground attack aircraft during both the War of Attrition and the Yom Kippur War. In the Falklands War, Argentine Air Force Skyhawks bombed Royal Navy vessels, sinking the Type 42 destroyer Coventry and the Type 21 frigate Ardent. Kuwaiti Air Force Skyhawks saw action during Operation Desert Storm. In 2022, nearly seven decades after the aircraft's first flight in 1954, a number of Skyhawks remain in service with the Argentine Air Force and the Brazilian Naval Aviation.
Design and development
The Skyhawk was designed by Douglas Aircraft's Ed Heinemann in response to a United States Navy call for a jet-powered attack aircraft to replace the piston-powered Douglas AD Skyraider (later redesignated A-1 Skyraider). Heinemann opted for a design that would minimize its size, weight, and complexity. The result was an aircraft that weighed only half of the Navy's weight specification. It had a wing so compact that it did not need to be folded for carrier stowage. The first 500 production examples cost an average of $860,000 each, less than the Navy's one million dollar maximum. The diminutive Skyhawk soon received the nicknames “Scooter", "Kiddiecar", "Bantam Bomber", "Tinker Toy Bomber", and, on account of its speed and nimble performance, "Heinemann's Hot-Rod". The XA4D-1 prototype set a world speed record of 695.163 mph on 15 October 1955.
The aircraft is of conventional post-World War II design, with a low-mounted delta wing, tricycle undercarriage, and a single turbojet engine in the rear fuselage, with two air intakes on the fuselage sides. The tail is of cruciform design, with the horizontal stabilizer mounted above the fuselage. Armament consisted of two 20 mm (.79 in caliber) Colt Mk 12 cannons, one in each wing root, with 100 rounds per gun (the A-4M Skyhawk II and types based on the A-4M have 200 rounds per gun), plus a large variety of bombs, rockets, and missiles carried on a hardpoint under the fuselage centerline and hardpoints under each wing (originally one per wing, later two).
The short-span delta wing did not require the complexity of wingtip folding, saving an estimated 200 pounds (91 kg). Its spars were machined from a single forging that spanned across both wingtips. The leading edge slats were designed to drop automatically at the appropriate speed by gravity and air pressure, saving weight and space by omitting actuation motors and switches. Similarly the main undercarriage did not penetrate the main wing spar, designed so that when retracted only the wheel itself was inside the wing and the undercarriage struts were housed in a fairing below the wing. Thus the wing structure was lighter with the same overall strength. The rudder was constructed of a single panel reinforced with external ribs.
The turbojet engine was accessed for service or replacement by removing the aft section of the fuselage and sliding out the engine. This obviated the need for access doors with their hinges and latches further reducing weight and complexity. This is the opposite of what can often happen in aircraft design where a small weight increase in one area leads to a compounding increase in weight in other areas to compensate, creating a demand for more powerful, heavier engines, larger wing and empennage area, and so on in a vicious circle.
The A-4 pioneered the concept of "buddy" air-to-air refueling. This allows the aircraft to supply others of the same type, reducing the need for dedicated tanker aircraft—a particular advantage for small air arms or when operating in remote locations. This allows for greatly improved operational flexibility and reassurance against the loss or malfunction of tanker aircraft, though this procedure reduces the effective combat force on board the carrier.
A designated supply A-4 would mount a center-mounted "buddy store", a large external fuel tank with a hose reel in the aft section and an extensible drogue refueling bucket. This aircraft was fueled up without armament and launched first. Attack aircraft were armed to the maximum and were given as much fuel as was allowable by maximum takeoff weight limits, which was far less than a full tank.
Once airborne, they topped off their fuel tanks from the tanker using the A-4's fixed refueling probe on the starboard side of the aircraft nose. They could then sortie with both full armament and fuel loads. The A-4 was rarely used for refueling in U.S. service after the KA-3 Skywarrior tanker became available aboard the larger carriers.
The A-4 was also designed to be able to make an emergency landing, in the event of a hydraulic failure, on the two drop tanks nearly always carried by these aircraft. Such landings resulted in only minor damage to the nose of the aircraft which could be repaired in less than an hour.
The Navy issued a contract for the type on 12 June 1952, and the first prototype first flew from Edwards Air Force Base, California on 22 June 1954. Deliveries to Navy and Marine Corps squadrons (to VA-72 and VMA-224 respectively) commenced in late 1956.
The Skyhawk remained in production until 1979, with 2,960 aircraft built, including 555 two-seat trainers. The last production A-4, an A-4M of Marine squadron VMA-331 had the flags of all nations that operated the A-4 painted on its fuselage sides.