Hiller OH-23 Raven

https://en.wikipedia.org/wiki/Hiller_OH-23_Raven

The Hiller OH-23 Raven was a three-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. The OH-23 trainer
was jokingly nicknamed the "Hiller Killer" by US Army Aviation student pilots
who had to fly it.

In 1947, United Helicopters (later renamed Hiller Aircraft) developed the
prototype Model 360X helicopter. A year later, on 14 October 1948 the CAA issued
a production certificate for the Model 360. United Helicopters began producing
the Model 360 as the UH-12 (UH-12 in French, UH-12 in German). 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 as the UH-12A. It was the UH-12A that would
be adopted by both the French and United States militaries, as well as being
used by civil commercial operators in several countries.


Role
Multipurpose light helicopter

Manufacturer
Hiller Aircraft Corporation

Introduction
1948

Status
Retired

Primary user
United States Army, Colombian Air Force

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.

The Raven used Hiller's "Rotor-Matic" cyclic control system, with two small
servo rotor paddles offset 90 degrees to the main rotor blades. The paddles were
attached to the control column, so that movement of the column would cause the
pitch of the servo paddles to change, loading the main rotor blade so that the
desired cyclic changes to the rotor occurred. The OH-23 had a top 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 Franklin 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 three. 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. A Raven piloted by Hugh
Thompson, Jr. played a crucial role in curtailing the My Lai Massacre. When a
Raven of the 59th Aviation Company strayed north of the Korean DMZ in August
1969 it was shot down and the crew were kept prisoner until released on December
2.

The Raven could be armed with twin M37C .30-caliber 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.

The Royal Navy's No. 705 Training Squadron used Hiller HTE-2s for several years
from 1953 and later operated Hiller 12E's for many further years as its basic
helicopter trainer based at RNAS Culdrose located in Cornwall, England.

Specifications (H-23D)

General characteristics
Crew: 2
Length: 27 ft ?9 1/2 in (8.47 m)
Rotor diameter: 35 ft 5 in (10.80 m)
Height: 9 ft ?9 1/2 in (2.99 m)
Disc area: 985 sq ft (91.5 m²)
Empty weight: 1,816 lb (825 kg)
Max. takeoff weight: 2,700 lb (1,227 kg)
Powerplant: 1 × Lycoming VO-435-23B 6-cylinder piston engine, 250 hp (187 kW)

Performance
Maximum speed: 95 mph (153 km/h, 83 knots) at sea level
Cruise speed: 82 mph (132 km/h, 71 knots)
Range: 197 mi (317 km, 171 nmi)
Service ceiling: 13,200 ft (4,025 m)
Rate of climb: 1,050 ft/min (5.3 m/s)




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