The Hiller OH-23 Raven was a four-place, light observation helicopter based on the Hiller Model 360. The Model 360 was designated by the company as the UH-12 ("UH" for United Helicopters), which was first flown in 1948.
built and flew his first helicopter, the Hiller XH-44, when he was 19. With the help of shipping mogul Henry Kaiser
, Hiller established the United Helicopters company in 1946. In 1947, United Helicopters developed the Model 360X, the prototype that would become the basis for the H-23. A year later, on 14 October 1948
issued a production certificate for the Model 360. United Helicopters began producing the Model 360 as the UH-12. In 1949, the UH-12 became the first helicopter to make a transcontinental flight from California to New York. When Hiller upgraded the engine and the rotor blades, the company designated the new model the UH-12A. It was the UH-12A that would be adopted by both the French and United States militaries.
The H-23 Raven performed as a utility, observation, and MedEvac helicopter during the Korean war
. Model numbers ranged A through D, F and G. The H-23A
had a sloping front windshield. The H-23B
was used as a primary helicopter trainer. Beginning with the UH-23C
, all later models featured the "Goldfish bowl" canopy similar to the Bell 47
, it also featured a unique cyclic control system, through two paddles offset 90 degrees to the main rotor blades. The OH-23 had a speed of 97 mph (84 knots). The Raven had a two-bladed main rotor, a metal two-bladed tail rotor. Both the OH-23B and the OH-23C were powered by one O-335-5D engine.
The OH-23D was a purely military version with a 0-435-23C engine and a more reliable transmission. Most OH-23Ds were replaced by the OH-23G, the most common version of the Raven, with a more powerful Lycoming O-540-9A six-cylinder, horizontally opposed, air cooled 305 hp engine. The OH-23G could seat four. The MEDEVAC version carried two external skid-mounted litters or pods. The Raven saw service as a scout during the early part of the Vietnam war before being replaced by the OH-6A Cayuse in early 1968. The Raven could be armed with twin M37C .30 Cal. machine guns on the XM1 armament subsystem or twin M60C 7.62 mm machine guns on the M2 armament subsystem. The XM76 sighting system was used for sighting the guns.
- One Model UH-12 for US Army evaluationH-23A
- Initial production version with 178 hp Franklin O-335-4 piston engine, 100 built for the US Army and 5 for evaluation by the US Air Force.H-23B
- H-23A with skid/wheel undercarriage and 200 hp 0-335-6 engine (some later re-engined with a 250 hp VO-435-23B), re-designated OH-23A in 1962, 273 built for the US Army and 81 for military export.H-23C
- Model UH-12C with three-seat cabin, one-piece canopy and metal rotor blades, redesignated OH-23C in 1962, 145 built for the US Army.H-23D
- H-23C with 250hp VO-435-23B engine, 348 built for US Army.H-23E
- Model UH-12E, not boughtH-23F
- Model UH-12E-4, four-seat model with 25-inch cabin extension and a 305hp VO-540-A1B engine, redesignated OH-23F in 1962, 33 built for US Army.H-23G
- Three-seat dual control version, redesignated OH-23G in 1962, 793 built.HTE-1
- US Navy version of the Model UH-12A with Franklin O-335 engine, two-seater with dual controls, 17 built.HTE-2
- US Navy version with Franklin 6V4-200C033 engine, 35 builtHT Mk 1
- Royal Navy designation for former US Navy HTE-2sHT Mk 2
- UH-12Es for Royal Navy.CH-112 Nomad
- Canadian military designation.
- Original production model for the US Army, powered by a 178hp Franklin O-335-4 piston engine. US Army designation H-23A.UH-12B
- Training version for the US Navy. US Navy designation HTE-1.UH-12C
- Three-seat version, equipped with all-metal rotor blades and one-piece 'goldfish bowl' canopy.
US Army designation H-23C
- Improved version of the H-23C for the US Army. US Army designation H-23D.UH-12E
- Three-seat dual-control version of the H-23D.UH-12ET
- Turbine-powered version of the UH-12E, fitted with an Allison 250 turboshaft engine.UH-12E3
- New three-seat production version.UH-12E3T
- New turbine-powered production version.UH-12E4
- Four-seat civilian version. US Army designation H-23F.UH-12E4T
- Four-seat turbine-powered production version.UH-12L-4
- Lengthed version with wider cabin windows.