Sikorsky S-75 Sikorsky S-75 The Sikorsky S-75 was a proof-of-concept all-composite helicopter. Sikorsky Aircraft used all-composite materials to replace metal to provide greater strength, lighter weight, lower manufacturing costs, and reduce maintenance costs. The Sikorsky S-75 was developed under the US Army's Advanced Composite Airframe Program (ACAP), the goal of which was the development of an all-composite helicopter fuselage, lighter and less costly to build than predominantly metal airframes in support of the Light Helicopter Experimental (LHX) program. In February 1981, contracts were awarded to Sikorsky and Bell Helicopter, with Bell submitting its Model D292. The S-75 flew for the first time
Sikorsky S-28 was approved. The French ordered five examples and preparations were made to start construction, but the order was cancelled when World War I ended and no S-28s were completed. Sikorsky S-28 The Sikorsky S-28 was a proposed four engine biplane bomber aircraft designed by Igor Sikorsky to be built in France during World War I. Sikorsky moved to France in March 1918 and soon met with officers of the "Armée de l'Air" who asked him to design an aircraft capable of carrying a new 1,000 kg (2,200 lb) bomb. Although the aircraft was initially designed to be powered by two