The Hiller YH-32 Hornet (company designation HJ-1) is an American ultralight helicopter built by Hiller Aircraft in the early 1950s. It was a small and unique design because it was powered by two Hiller 8RJ2B ramjet engines mounted on the rotor blade tips which weigh 13 lb (5.9 kg) each and deliver an equivalent of 45 hp (34 kW) for a total of 90 hp (67 kW). Versions of the HJ-1 Hornet were built for the United States Army and the United States Navy in the early 1950s. The Hiller Museum identifies the YH-32A, named the Sally Rand, as the first helicopter gunship. 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. The Hiller HJ-1 Hornet was an early attempt to build a jet-powered helicopter using ramjets, with work beginning in 1948. Before that there had been experiments with the XH-26 Jet Jeep tip rotor pulse jets.The HJ-1 ramjet tipped rotor propels the rotor and the aircraft. Unlike a conventional helicopter, this mechanically simple design avoids the need for a tail rotor. Unfortunately, the tip speeds on helicopter rotor blades are subsonic, and ramjets are inefficient at subsonic speeds due to low compression ratio of the inlets. Therefore, the Hornet suffered from high fuel consumption and poor range. Also, the vehicle suffered from low translational speeds, and the ramjet tips were extremely noisy. In the event of power loss, autorotation was found to be difficult due to the drag from the ramjet nacelles. The vehicle exhibited powerful lifting capacity, and there was some hope for military uses, but the high noise, poor range, and high night-time visibility of the ramjet flames failed to attract sales. The first Hiller Hornets were not ready for delivery until late 1954, due to Hiller certificating the aircraft to Civil Aviation Authority standards rather than military specifications. Variants HJ-1 Company designation, one prototype. YH-32 United States Army, Similar to HJ-1 with two small v-shaped stabilizers, 14 built (2 prototypes and 12 production aircraft). YH-32A Two YH-32s modified for trials as an armed helicopter. XHOE-1 Three HJ-1s for evaluation by the United States Navy in 1951. Number built 18.
