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The Hiller YH-32A Hornet with its missile armament.
In 1948, with the advent of jet engines, there was an idea of creating a jet-powered helicopters using ramjet technology. The Hiller YH-32A Hornet is one such case of an early attempt of creating a functional ramjet helicopter. So, today I would like to make a suggestion for this unique, tiny helicopter that is unlike anything built before or since.
History
The Hiller Hornet’s history can be traced back to 1948. After the US Army Air Corps were split from the US Army to form the US Air Force, there was a debate on which branch of the US Armed Forces should be responsible for operating helicopters, as during that time the US Army recognized the importance of helicopters for ground support, wheas the US Air Force maintained that any types of land-based aircraft should be operated by them. Therefore, while still waiting for the dispute to be resolved, the US Army chose to develop their own ultra-light helicopters to circumvent the then decision to assign all helicopters under the USAF command.
During this time, there is an interest in creating a jet-powered helicopters using rotor tip-mounted ramjet engines. The idea was that, in theory, these helicopters would be much more compact in size and is significantly faster than conventional helicopters, thus reducing the overall costs while increasing its effectiveness. The Hiller Aircraft Company is one of the companies who is interested in this concept, and would later on developed their first ramjet helicopter. Then named the HJ-1 Hornet. The HJ-1 would later made the first flight in 1950.
The HJ-1 Hornet on display at the Hiller Aviation Museum.
When the HJ-1 was first completed, certain flaws of its design were made apparent; the small ramjet engines is only capable of driving its propeller at a subsonic speed at best, resulting into inefficient air compression ratio which significantly increase its fuel consumption. This means the helicopter has a range of only 45 km in clear weather and a flight time of just 25 minutes. Another problem arose from the ramjet design, in which the aforementioned inefficient rotational speed of the propeller resulting into much lower top speed than expected, in addition of the engine being extremely loud and highly visible (especially at night). Nevertheless, the Hornet is noted to have a disproportionally high lifting capacity for its size, to which Hiller hoped that it would be useful for military applications.
The YH-32 underwent testing with the US Army. The bright “halo” resulting from the ramjet engines can be clearly seen here.
Due to Hiller initially registered the Hornet under Civil Aviation Authority instead of military, it is not until 1954 that Hiller was able to submit the design to the US Army and the US Navy, and received the designation YH-32 and XHOE-1, respectively. The US Army took an interest in the design, as they considered deploying the Hornet as an air-droppable helicopter for rescue missions.
The intended loadout for the YH-32A.
Later on, in 1957, the US Army modified two YH-32s into the YH-32A for trials as an armed helicopter. To make rooms for the loadout, the Hornet’s fiberglass was removed, its tail were modified, and a second seat for the weapon operator was added. Due to its barebone appearance, it was nicknamed “Sally Rand” after the dancer and stripper of the same name.
The YH-32A is armed with a payload of either eight “4-inch rockets” (I can’t find any info about the exact model of this weapon), a pair of 75 mm M20 recoilless rifle, or two SSM-A-23 Dart wire-guided ATGM (similar to the French SS.10 ATGM). Because of this, the Hornet is often considered the very first “helicopter gunship” of the US Army due to its anti-tank and fire support capabilities.
The YH-32A on display at the Hiller Aviation Museum.
Unfortunately, due to the aforementioned range and visibility problem, the YH-32A was not accepted for service. One of the two prototypes of the YH-32A survives to this day, and is on display at the Hiller Aviation Museum, San Carlos, California.
Specifications
- Crew: 2 (pilot and weapon operator)
- Capacity: 1 pax / 536 lb (243 kg) max. payload
- Length: 23 ft 8 in (7.21 m)
- Width: 3 ft 9 in (1.14 m) fuselage
- Height: 7 ft 10 in (2.39 m)
- Empty weight: 544 lb (247 kg)
- Gross weight: 1,080 lb (490 kg)
- Powerplant: 2 × Hiller 8RJ2B ramjet engines, 40 lbf (0.18 kN) thrust each
- Main rotor diameter: 23 ft (7.0 m)
- Main rotor area: 491 sq ft (45.6 m2)
- Blade section: NACA 0012
- Blade section: 8 x 4-inch rockets, or 2 x 75 mm M20 recoilless rifle, or 2 x SSM-A-23 Dart wire-guided ATGM
Sources
Hiller YH-32 Hornet - Wikipedia
U.S. Army Helicopter Evolution during the Vietnam War, Part II | Article | The United States Army
Andrade, John. U.S. Military Aircraft Designations and Serials since 1909. Hinckley, UK: Midland Counties Publications, 1979. ISBN 0-904597-22-9.
Apostolo, Giorgio. The Illustrated Encyclopedia of Helicopters. New York: Bonanza Books, 1984. ISBN 0-517-439352.
Hiller XHOE-1 Hornet | National Air and Space Museum
