Hiller YH-32 Hornet

The Hiller YH-32 Hornet (company designation HJ-1) was 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 13lbs each and deliver an equivalent of 45 h.p. for a total of 90 h.p. 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.

Design and development
The Hiller HJ-1 Hornet was an early attempt to build a jet-powered helicopter using ramjets. 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.

Operational history
The HJ-1 was evaluated by the United States Army as the YH-32, and the United States Navy as the XHOE-1. In 1957 two YH-32s were modified as the YH-32A for trials as armed helicopters. All the fibreglass cockpit fairings were removed and the tail was modified. The tests were successful in proving the viability of the helicopter as a weapons platform, but due to marginal performance, no further conversions or orders were placed. Also, versions were sent to the U.S. Army's DRC to be evaluated in one of their contests involving the research and development of a light weight, air droppable helicopter for air rescue and reconnaissance, and for a portable, easily put together, and fuel efficient 1 man observation and transport copter. It was competing against the Jet Jeep and its pulse jets. Overall the YH-32 won out over the Jet Jeep, but the concept was considered obsolete, and later the program was canceled.

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.

Aircraft on display

 * "XHOE-1 138652 is on display at the Udvar-Hazy Center of the National Air and Space Museum in Chantilly, Virginia
 * YH-32 55-4965 "Sally Rand" is on display at the US Army Aviation Museum at Fort Rucker in Ozark, Alabama
 * YH-32 55-4969 is on display at the Museum of Flight in Seattle, Washington
 * YH-32 53 4664 and 55-4976 are on display at the Hiller Aviation Museum in San Carlos, California
 * YH-32 Hornet is on display at Classic Rotors in Ramona, California
 * YH-32 Hornet is on display at Fantasy of Flight in Auburndale, Florida, claimed to be the only flyable example.