Multi-motored Airplanes, 1933

Aircraft Models

Sikorsky named his developing aircraft models in a simple numerical series, S-1, S-2, S-3, etc., which represented all efforts—prototypes as well as models put into service. Those built in Russia from 1910 through 1916 were labeled S-1 through S-27G and his United States models were the series S-29A through S-44.

The S-21 LE GRAND or RUSSIAN KNIGHT, his first multi-engined airplane, had a 90 ft wingspan, and four 100-horsepower engines to power its 7400 lbs empty weight and was the world's first successful four-engined airplane. This biplane, built mostly of wood, had a backup steering apparatus, top-wing ailerons for stability, and traveled at a maximum speed of 55 miles per hour. The final Russian model, the 27G with 880 horsepower, was the largest seaplane in the world.

In the United States, the S-29A, manufactured by the new Sikorsky Aero Engineering Corporation, was the first twin-engined aircraft able to fly on a single engine. Pioneering improvements followed as commercial air routes were introduced and amphibian craft, able to touch down on sea or land, were introduced. Sikorsky's final airplane design, the S-44 built in 1937, showed the longest travel range of any available commercial aircraft. The next Sikorsky models, the R-4 and its successors through the present, are helicopters.

Letter from Robert Kemp, to George A. Hoadley, Supplying details to reinforce Sikorsky's achievement as the inventor of the multi-motored airplane, 9/16/1932 (and two duplicate copies), 9/16/1932 (2.8M) | Page 2 (2.8M) | Page 3 (1.9M)

Letter from Igor Sikorsky, to George A. Hoadley, Supplying references to contact for information on the value of the automatic control device, 11/14/1931 (2.1M) | Page 2 (1.2M)

Letter from Henry White, to George A. Hoadley, Detailing the operation of the automatic control device and its incalculable usefulness in airplane operation, 11/19/1931 (3.3M) | Page 2 (3.2M)