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A4 Skyhawk

The Douglas A-4 Skyhawk is a single seat subsonic carrier-capable attack aircraft developed for the United States Navy and United States Marine Corps in the early 1950s. The delta winged, single turbojet engine Skyhawk was designed and produced by Douglas Aircraft Company, and later by McDonnell Douglas. It was originally designated A4D under the U.S. Navy's pre-1962 designation system.

The Skyhawk is a relatively lightweight aircraft with a maximum take-off weight of 24,500 pounds (11,100 kg) and has a top speed of more than 670 miles per hour (1,080 km/h). The aircraft's five hardpoints support a variety of missiles, bombs and other munitions. It was capable of carrying a bomb load equivalent to that of a World War II-era Boeing B-17 bomber, and could deliver nuclear weapons using a low altitude bombing system and a loft delivery technique. The A-4 was originally powered by the Wright J65 turbojet engine; from the A-4E onwards, the Pratt & Whitney J52 was used.

Image: An 805 Squadron A4 Skyhawk landing on HMAS Melbourne in 1980.

Skyhawks played key roles in the Vietnam War, the Yom Kippur War, and the Falklands War. Sixty years after the aircraft's first flight, some of the nearly 3,000 produced remain in service with several air arms around the world, including from the Brazilian Navy's aircraft carrier, São Paulo.

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 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 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 choice of a delta wing combined speed and manoeuvrability 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.

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 aircraft 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 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 refuelling. This allows the aircraft to supply others of the same type, eliminating 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 refuelling bucket. This aircraft was fuelled up without armament and launched first. Attack aircraft would be armed to the maximum and given as much fuel as was allowable by maximum take-off weight limits, far less than a full tank. Once airborne, they would then proceed to top off their fuel tanks from the tanker using the A-4's fixed refuelling probe on the starboard side of the aircraft nose. They could then sortie with both full armament and fuel loads.

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 Skyhawk remained in production until 1979, with 2,960 aircraft built, including 555 two-seat trainers.

Twenty A-4G Skyhawks were operated by the Royal Australian Navy for operation from HMAS Melbourne. These aircraft were acquired in two batches of 10 Skyhawks in 1967 and 1971, and were primarily used to provide air defence for the fleet.

Ten of the A-4Gs were destroyed in accidents, and all of the survivors were sold to the Royal New Zealand Air Force in 1984.

Eight aircraft built new for the Royal Australian Navy with minor variations from the A-4F; in particular, they were not fitted with the avionics hump. Subsequently, eight more A-4Fs were modified to this standard for the RAN. Significantly the A-4G were modified to carry four underwing Sidewinder AIM-9B missiles increasing their Fleet Defence capability.

The A-4F was a refinement of the A-4E, with extra avionics housed in a hump on the fuselage spine, and more powerful J52-P-8A engine with 9,300 lbf (41 kN) of thrust, of which 147 built in total.

Crew was generally one, but some variants had a crew of two. It was 40 ft 3 in or 12.22 m long, its wingspan: 26 ft 6 in or 8.38 m and its height was 15 ft or 4.57 m.

Its maximum speed was 673 mph or 1,083 km/h. It had a range of 1,700 nautical miles or 3,220 km. Its service ceiling was 42,250 feet or 12,880 m, and its rate of climb was 8,440 ft/min or 43 m/s.

They were fitted with Bendix AN/APN-141 low altitude radar altimeter s and Stewart-Warner AN/APQ-145 Mapping & Ranging radar.

They were also capable of carrying up to three 1,400 litre drop tanks for ferry and extended range flight, and to increase their loitering time capabilities.

The A4 had four under-wing and one under-fuselage hardpoints (weapon stations) holding up to 9,900 lb or 4,490 kg of payload. It was also a nuclear capable aircraft capable of carrying B43, B47 or B61 nuclear bombs.

Its other armament consisted of 2× 20 mm Colt Mk 12 cannons with 100 rounds per gun, 4× LAU-10 rocket pods, each with 4× 127 mm Mk 32 Zuni rockets, 4× AIM-9B Air-to-air missiles, two AGM-12 Bullpup, two AGM-45 Shrike anti-radiation missiles, two AGM-62 Walleye missiles, two AGM-65 Maverick air-to-surface missiles, and TV-guided glide bombs, as well as six Rockeye-II Mark 7 and Mark 20 Cluster Bomb Units (CBU), as well as Mark 80 series unguided bombs.


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