The Convair F2Y Sea Dart was an American seaplane fighter aircraft that rode on twin hydro-skis during takeoff and landing. It flew only as a prototype, and never entered mass production. It is the only seaplane to have exceeded the speed of sound.
It was created in the 1950s, to overcome the problems with supersonic planes taking off and landing on aircraft carriers.
According to USNI, the Navy awarded Convair a contract for two XF2Y-1 prototype aircraft in January 1951. The first test flight occurred on 9 April 1953, in San Diego Bay, with the company’s E. D. “Sam” Shannon at the controls.
According to a contemporary Navy publication, “The intense interest [in the aircraft] is understandable, for this was an airplane which wrapped up in one package more new and untried features than any aeronautical design in many a day.”3 The delta-winged, tailless aircraft’s fuselage provided flotation at rest and low speeds. As the aircraft accelerated for takeoff, the fuselage, except for a small part of the tail, was lifted clear of the water by twin, fully retractable hydro-skis. This scheme brought the delta wing to the proper attitude for takeoff. The hydro-skis were planing skis, obtaining lift in the same manner as a person using water skis. Operations in waves up to five feet high were considered feasible.
No horizontal tail surfaces or flaps were provided. Control was by elevons and rudder. A rudder was provided for maneuvering at low speeds on the water. It was also employed in flight as a speed brake, being linked to the elevons to automatically coordinate banked turns.
The first aircraft—the XF2Y-1—was fitted with twin Westinghouse J34 turbojet non-afterburning engines in the upper fuselage that could develop 3,400 pounds static thrust each. Later aircraft would have twin Westinghouse XJ46-WE-2 turbojet engines with afterburners provided. Takeoff after a 30-second warm-up was estimated to be 15 seconds at military power plus afterburner—a total of more than 12,000 pounds static thrust. The definitive F2Y-2 was to have an empty weight of 12,652 pounds and a maximum takeoff weight of 16,527 pounds.
The relatively successful early trials of the Seadart prototypes led to tests with a dock landing ship (LSD) being employed to evaluate possible open-sea support of the aircraft. This was similar to the concept considered for the Navy’s Martin P6M Seamaster, a flying-boat strike/minelaying/reconnaissance aircraft. 4
Following the flight of the XF2Y-1, the Navy planned an initial production run of 17 aircraft to further evaluate the feasibility of a sea-based interceptor. However, the order that was placed was for an additional three prototypes, a total of five aircraft, with the latter four being designated YF2Y-1. The second aircraft was lost during a low-level flight at about 575 mph over San Diego Bay on 4 November 1954. Test pilot Charles E. “Chuck” Richbourg was killed in the crash.
Earlier in 1954, the XF2Y-1 was refitted with a single hydro-ski that was not fully retractable. Taxi tests of the new configuration began in the fall and the aircraft was found to lack hydrodynamic stability and control. Later tests of rigid non-retractable skis were conducted, with one of the skis having a hydrofoil shape. More than 100 ski configurations were considered for the aircraft.
The third aircraft—the second YF2Y-1—began flight tests on 4 March 1955. This aircraft had small wheels at the rear of its twin skis plus a small swivel-tail wheel to provide tail-down mobility when on a seaplane ramp or tarmac.
High-performance flight tests were canceled after the loss of the No. 2 Seadart, but taxi and flight trials continued. Four 1,000-pound-thrust rocket boosters were evaluated but were not successful, causing severe vibration and pounding loads on the aircraft and pilot. Additional modifications were made to the airplane, but in time it became clear that the hydro-ski configuration was not feasible for a high-performance operational aircraft.
Flight trials of various Seadart configurations continued until 1956, when the project was halted. Only three aircraft flew; engines were never installed in the last two YF2Y-1s. (The two surviving flight-test aircraft and two non-flying aircraft still exist in museums.) In a strange postscript to the Seadart story, in 1962—some six years after the project’s termination and the plane’s last flight—the YF2Y-1 Seadart was assigned the then-new tri-service unified aircraft designation of YF-7A.
The concept of a supersonic seaplane fighter—the F2Y Seadart—was another of the fascinating and envelope-pushing aircraft developed in the early jet age. And, like so many others of its time, it was not to be
The program was canceled after a series of unsatisfactory results and a tragic accident on 4 November 1954, when test pilot Charles E. Richbourg was killed when the Sea Dart he was piloting disintegrated in midair. The four surviving planes were retired in 1957, but some were kept in reserve until 1962.