The Douglas A-4 Skyhawk is a carrier-capable ground-attack aircraft designed for the United States Navy and U.S. Marine Corps. The delta winged, single turbojet-engined Skyhawk was designed and produced by Douglas Aircraft Company, and later McDonnell Douglas. It was originally designated the A4D under the US Navy's pre-1962 designation system.
Fifty years after the aircraft's first flight, and having played key roles in the Vietnam War, the Yom Kippur War, and the Falklands War, some of the nearly 3,000 Skyhawks produced remain in service with several air arms around the world, including active duty on the aircraft carrier São Paulo of the Brazilian Navy.
The Marine Corps A-4 Skyhawk is a lightweight, single engine attack aircraft. The mission of an A-4 attack squadron is to attack and to destroy surface targets in support of the landing force commander, escort helicopters, and conduct other operations as directed. Developed in the early 1950s, the A-4 Skyhawk was originally designated the A-4D as a lightweight, daylight only nuclear capable strike aircraft for use in large numbers from aircraft carriers. There are numerous models of the A-4 in use. The A-4M and the TA-4F are currently used by Marine Corps Reserve squadrons. All models have two internally mounted 20mm (.8 inch) cannons, and are capable of delivering conventional and nuclear weapons under day and night visual meteorological conditions. The A-4M uses a heads-up display and computer aided delivery of its bomb load with the angle rate bombing system. The Marine Reserve has two squadrons of A-4s with 12 aircraft each. Additionally, each squadron has two TA-4 aircraft.
The Skyhawk was designed by Douglas Aircraft's Ed Heinemann in response to a U.S. Navy call for a jet-powered attack aircraft to replace the older AD 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 diminutive Skyhawk soon received the nicknames "Scooter", "Kiddiecar", "Bantam Bomber", "Tinker Toy Bomber", and, on account of its nimble performance, "Heinemann's Hot-Rod".
The XA4D-1 prototype in 1954 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 200 rpg, 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 second production A4D-1 The choice of a delta wing, for example, combined speed and maneuverability with a large fuel capacity and small overall size, thus not requiring folding wings, albeit at the expense of cruising efficiency. 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. The wing structure itself could be lighter with the same overall strength and the absence of a wing folding mechanism further reduced weight. 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, leading to the need for more powerful, heavier engines and so on in a vicious cycle.