2-840-046 - Heritage Art/Heritage Images

All aircraft designers attempt to maximize lifting power and reduce airframe weight. During the late 1940s, helicopter pioneers began to experiment with alternative propulsion methods that did not require heavy components such as tail rotor assemblies, drive shafts, main rotor clutches, transmissions, and engine cooling blowers. Without these items, a helicopter's useful load increases by a significant margin. These components are also potential failure points, making helicopters more fragile and more difficult to maintain. Yet another advantage is the substantial reduction in the cost to produce helicopters without this equipment. In 1948, Stanley Hiller began to experiment with ramjets mounted on the tips of the main rotor blade. He hoped to make small, ramjet-powered helicopters practical and affordable, and to eventually design and sell giant aerial cranes propelled by ramjets or jet turbine engines. The Hiller HOE-1 became the first production ramjet helicopter, and the Army and Navy flew a small number of these aircraft for a short time to test and evaluate the technology.