SIAI S.51

Design and development

The S.51 was a single-seat sesquiplane flying boat. Its 224-kilowatt (300-horsepower) Hispano-Suiza 8A V8 engine, mounted on two N struts above the hull and below the upper wing, drove a two-bladed propeller in a pusher configuration. The inclined interplane struts were mounted in a V configuration. The lower wings had small stabilizing floats mounted on inclined struts so that they hung below and outboard of the outer tips of the lower wing.

SIAI later based the design of the hull of its S.58 flying boat fighter of 1924 on that of the S.51's hull.

Operational history

All sources agree that Italy entered the S.51 in the 1922 Schneider Trophy race along with two Macchi M.17 flying boats, and that the three Italian aircraft competed against a British Supermarine Sea Lion II flying boat which won the race. Other than that, sources provide deeply inconsistent and mutually contradictory accounts of the S.51's career.

Some sources claim that the S.51 crashed during the race, killing its pilot. states that the S.51 suffered water damage when it capsized in a pre-race accident and that this damage forced it to retire from the competition after its engine nacelle began to separate from the upper wing during the race; however, this source does not say that the aircraft crashed. claim that the S.51 finished the race with an average speed of 230.93 kilometers per hour (143.41 miles per hour) and a finishing time of 1 hour 36 minutes 54 seconds, in second place behind the Sea Lion II but ahead of both M.17s.

Some sources claim that the S.51 had a career after the 1922 race. One source states that on 28 December 1922 the S.51 set a speed record for seaplanes of 280.155 kilometers (174.080 mi) per hour, and another claims that Italy considered entering the S.51 in the 1923 Schneider Trophy race but ultimately did not.

Operators

Specifications

General characteristics

Performance