Convair F2Y Sea Dart – The First and Only Supersonic Seaplane
The Sea Dart began as Convair's entry in a 1948 U.S. Navy contest for a supersonic interceptor aircraft. During the time, there was much scepticism about the ability to operating supersonic aircraft from carrier decks. So, in order to address this issue, U.S. Navy ordered many subsonic fighters. The concerns were valid, since many supersonic designs of the time required long take-off rolls, had high approach speeds, and were not very stable or easy to control—all factors that were troublesome on a carrier.
The Sea Dart was a prototype single-seat fighter designed and built by the Convair Division of General Dynamics Corporation at San Diego, California. It was equipped with retractable skis in place of ordinary landing gear to allow it to take off and land on water, snow or sand. When stationary or moving slowly in the water, the Sea Dart floated with the trailing edge of the wings touching the water. The skis were not extended until the aircraft reached about 10 miles per hour during its take-off run.
Convair's Sea Dart proposal gained an order for two prototypes in late 1951, twelve production aircraft were ordered before a prototype had even flown. No armament was ever fitted to any Sea Dart built, but the plan was to arm the production aircraft with four 20mm Colt Mk12 cannon and a battery of folding-fin unguided rockets. Four of this order were re-designated as service test vehicles, and an additional eight production aircraft were soon ordered as well.
Required power was put up by a pair of afterburning Westinghouse XJ46-WE-02 turbojets, fed from intakes mounted high above the wings to avoid ingesting spray. When these engines were not ready for the prototypes, twin Westinghouse J34-WE-32 engines of just over half the power were installed.
Westinghouse J34-WE-32 engine
The prototype was fitted with an experimental single ski, which proved to be more successful than the twin-ski design of the second service test aircraft. Testing with several other experimental ski configurations continued with the prototype through 1957, after which it was placed into storage.
The US was not the only country to consider the hydroski. The Saunders-Roe company of the United Kingdom, which had already built an experimental flying boat jet fighter, first flying in 1947 the SR.A/1, tendered a design for a ski-equipped fighter, but little came of it.
In the 1950s, the US Navy considered the internal arrangements of a submarine aircraft carrier that could carry three of these aircraft. Stored in pressure chambers that would not protrude from the hull, they would be raised by a portside elevator just aft of the sail and set to take off on their own on a smooth sea but catapulted aft in a higher sea. The program only reached the "writing on a napkin" stage, for two problems were not addressed: the hole for the elevator would have seriously weakened the hull and the load of a laden elevator would also be difficult to transmit to the hull structure.
The aircraft was built in Convair's San Diego facility at Lindbergh Field and was taken to San Diego Bay for testing in December 1952. On 14 January 1953, with E. D. "Sam" Shannon at the controls, the aircraft inadvertently made its first short flight during what was supposed to be a fast taxi run; its official maiden flight was on 9 April.
The underpowered engines made the fighter sluggish, and the hydro-skis were not as successful as hoped; they created violent vibration during take-off and landing, despite the shock-absorbing oleo legs they were extended on. Work on the skis and legs improved this situation somewhat, but they were unable to resolve the sluggish performance. The Sea Dart proved incapable of supersonic speed in level flight with the J34 engines; not helping was its pre-area rule shape, which meant higher transonic drag.
The second prototype was cancelled, so the first service test aircraft was built and flown. This was fitted with the J46 engines, which performed below specification. However, speeds in excess of Mach 1 were attained in a shallow dive with this aircraft, making it the only supersonic seaplane to date. On 4 November 1954, Sea Dart BuNo 135762 disintegrated in mid-air over San Diego Bay during a demonstration for naval officials and the press, killing Convair test pilot Charles E. Richbourg when he inadvertently exceeded the airframe's limitations. Richbourg was a 31-year-old Navy veteran of the Second World War, he was quickly pulled from the water but did not survive the airframe breakage. He was buried in St. Augustine National Cemetery in Florida.
Even before that, the Navy had been losing interest (problems with supersonic fighters on carrier decks having been overcome) and the crash relegated the Sea Dart program to experimental status. All production aircraft were cancelled, though the remaining three service test examples were completed. The two final prototypes never flew.