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Hiller OH-23 Raven (Model UH-12)

United States (1948)
Picture of Hiller OH-23 Raven (Model UH-12) Light Utility Helicopter
Picture of Hiller OH-23 Raven (Model UH-12) Light Utility Helicopter Picture of Hiller OH-23 Raven (Model UH-12) Light Utility Helicopter
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Despite its rather simple appearance, the Hiller OH-23 Raven light helicopter line proved reliable even under the wartime stresses of Korea and Vietnam.


Detailing the development and operational history of the Hiller OH-23 Raven (Model UH-12) Light Utility Helicopter.  Entry last updated on 11/18/2017. Authored by Staff Writer. Content ©www.MilitaryFactory.com

Hiller Aircraft began during World War 2 in 1942 under the operating name of Hiller Industries. The company carried the surname of Stanley Hiller (1924-2006) whose provided much of the early work in the field of helicopter flight. Indeed his first coaxial helicopter design was completed at age 15 and his XH-44 impressed the US Army at age 17. Hiller headed the first helicopter factory in the world out of Berkeley, California. Among his early developments (now under the "United Helicopters" name) included the UH-4 "Commuter" and the UH-5B "Rotormatic" which led to the single-seat UH-12 light utility helicopter of the late 1940s.

The UH-12 held origins in the company Model 360 and saw a first flight in 1948. The UH-12A was a follow-up modification to the original UH-12 and included a more powerful engine to go along with a new, two-blade main rotor. The US Army liked what it saw and contracted for a militarized variant of the UH-12A and this became the evaluation prototype designated YH-23. For the military form, crew capacity was increased to two in a side-by-side seating arrangement underneath a largely transparent bubble-style windscreen. The aircraft was powered by a single Franklin piston engine of 178 horsepower.

The overall configuration consisted of a front-mounted cockpit (originally single-seat and then seating for two or more) with a mid-mounted engine and rear-set stem. The engine powered a two-bladed main rotor blade fitted high atop the mast and drove a two-bladed tail rotor used to offset torque. The cockpit offered generally excellent vision and the undercarriage was of a basic skid-type design. While typically unarmed, some war-time models were outfitted with 2 x 0.30 caliber medium machine guns for basic offense.

Following successful trials of the YH-23, the system was formally adopted by the US Army as the H-23A "Raven" across 100 examples. The powerplant became the Franklin O-335-4 piston engine outputting at 178 horsepower. The type also piqued the interest of the USAF whom ordered five examples for official evaluation. The H-23A was followed into service by the revised H-23B. This new model series incorporated a combined skid-and-wheel undercarriage and was powered by a Franklin O-335-6 series piston engine of 200 horsepower output. The US Army then took on a stock of 273 units while an additional 81 served the export market. Some later OH-23B models were upgraded to the more powerful Lycoming VO-435-23B series engine of 250 horsepower.


Picture of the Hiller OH-23 Raven (Model UH-12) Light Utility Helicopter
Picture of the Hiller OH-23 Raven (Model UH-12) Light Utility Helicopter


The H-23C proved unique upon its arrival for it featured seating for three personnel under a single-piece canopy cover and also instituted use of metal blades. Some 145 were procured by the US Army. The H-23D was given an all-new main rotor design and powerpack to include the Lycoming VO-435-23B engine of 250 horsepower. US Army procurement numbered 348 examples. The H-23E was offered but never purchased.

The H-23D seated two crew and showcased a maximum speed of 95 miles per hour with a cruise speed reaching 82 miles per hour. It fielded a range of 200 miles with a service ceiling of 13,200 feet. A rate-of-climb of 1,050 feet was reported.

The H-23F became a four-seat model with enlarged crew cabin. Additional changes included the use of the VO-540-A1B engine of 305 horsepower. The following H-23G offered seating for three personnel and dual-control features for both pilot positions. This mark was largely based on the preceding H-23F line.

The US Navy followed its own naming convention and tagged the UH-12A as the HTE-1. They were also two-seat airframes but offered dual-controls for both positions. Interestingly, this mark also showcased a tricycle-style wheeled undercarriage. Seventeen of the type were manufactured. The HTE-1 was then followed by the HTE-2 which was the H-23B and its Franklin O-335-6 piston engine of 200 horsepower. 35 examples were procured.

The Royal Navy followed suit and purchased the Hiller design under two marks - Hiller HT.Mk 1 and HT.Mk 2. The Mk 1 were ex-US Navy mounts (HTE-2 models) while the Mk 2 were UH-12E production models. Numbers totaled 20 and 21 respectively and primarily held as trainers out of RNAS Culdrose (Cornwall). The Canadian Army utilized the Hiller design as well, this under the C-112 "Noman" designation.

In 1962, the United States military underwent a branches-wide designation revision which changed all H-23 designations to the "OH" format. H-23B became OH-23B, H-23C became OH-23C and so on (see variants section for complete list). Many OH-23 variants were based on existing civilian-minded Hiller marks including the original UH-12A. The UH-12B was the basis for the US Navy HTE-1 while the UH-12C was the H-23C. The UH-12 was the H-23D and so forth.

The OH-23 proved exceedingly popular on the world market beyond its use by the United States, United Kingdom and Canada. The list included Argentina, Chile, Indonesia, Israel, Mexico, the Netherlands, South Korea, Thailand and Uruguay among others.

The OH-23 served American forces during the Korean War (1950-1953) as one of the handful of helicopters present in the conflict. The conflict marked the first practical use of rotary-wing aircraft in a modern war despite their (limited) use in the latter years of World War 2. The Hiller aircraft was used in the mission liaison, scouting, observation, general service, trainer and MEDEVAC role in the war, operated alongside the similar Bell Model 47/H-13 "Sioux" helicopter lines. The primary military variant became the OH-23D. As with the H-13 line, the OH-23 saw some combat service in the early years of the Vietnam War. They were replaced, in time, by the much improved Hughes OH-6A "Cayuse" light helicopter.






Our Data Modules allow for quick visual reference when comparing a single entry against contemporary designs. Areas covered include general ratings, speed assessments, and relative ranges based on distances between major cities.

Image of collection of graph types

Relative Maximum Speed Rating
Hi: 100mph
Lo: 50mph
    This entry's maximum listed speed (95mph).

    Graph average of 75 miles-per-hour.
City-to-City Ranges
NYC
 
  LON
LON
 
  PAR
PAR
 
  BER
BER
 
  MOS
MOS
 
  TOK
TOK
 
  SYD
SYD
 
  LAX
LAX
 
  NYC
Graph showcases the Hiller H-23D Raven's operational range (on internal fuel) when compared to distances between major cities.
Aviation Era
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Useful in showcasing the era cross-over of particular aircraft/aerospace designs.
Unit Production Comparison
Comm. Market HI*: 44,000 units
Military Market HI**: 36,183 units
1820
1820


  * Commercial Market High belongs to Cessna 172.

  ** Military Market High belongs to Ilyushin Il-2.


Altitude Visualization
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National Flag Graphic
Origin: United States
Year: 1948
Type: Light Utility Helicopter
Manufacturer(s): Hiller Aircraft Corporation - USA
Production: 1,820
Status: Retired, Out-of-Service
Global Operators:
Argentina; Canada; Chile; Colombia; Dominican Republic; Guatemala; Indonesia; Israel; Mexico; Netherlands; Paraguay; Peru; South Korea; Thailand; United Kingdom; United States; Uruguay
Historical Commitments / Honors:

Military lapel ribbon for Operation Allied Force
Military lapel ribbon for the Arab-Israeli War
Military lapel ribbon for the Battle of Britain
Military lapel ribbon for the Battle of Midway
Military lapel ribbon for the Berlin Airlift
Military lapel ribbon for the Chaco War
Military lapel ribbon for the Cold War
Military lapel ribbon for the Cuban Missile Crisis
Military lapel ribbon for the Falklands War
Military lapel ribbon for the French-Indochina War
Military lapel ribbon for the Golden Age of Flight
Military lapel ribbon for the 1991 Gulf War
Military lapel ribbon for the Indo-Pak Wars
Military lapel ribbon for the Iran-Iraq War
Military lapel ribbon for the Korean War
Military lapel ribbon for the 1982 Lebanon War
Military lapel ribbon for the Malayan Emergency
Military lapel ribbon for the attack on Pearl Harbor
Military lapel ribbon for the Six Day War
Military lapel ribbon for the Soviet-Afghan War
Military lapel ribbon for the Spanish Civil War
Military lapel ribbon for the Suez Crisis
Military lapel ribbon for the Vietnam War
Military lapel ribbon for Warsaw Pact of the Cold War-era
Military lapel ribbon for the WASP (WW2)
Military lapel ribbon for the World War 1
Military lapel ribbon for the World War 2
Military lapel ribbon for the Yom Kippur
* Ribbons not necessarily indicative of actual historical campaign ribbons. Ribbons are clickable to their respective campaigns/operations.
Measurements and Weights icon
Structural - Crew, Dimensions, and Weights:
Unless otherwise noted the presented statistics below pertain to the Hiller H-23D Raven model. Common measurements, and their respective conversions, are shown when possible.

Operational
CREW


Personnel
1


Dimension
LENGTH


Feet
27.79 ft


Meters
8.47 m


Dimension
WIDTH


Feet
35.43 ft


Meters
10.8 m


Dimension
HEIGHT


Feet
9.84 ft


Meters
3 m


Weight
EMPTY


Pounds
1,819 lb


Kilograms
825 kg


Weight
LOADED


Pounds
2,712 lb


Kilograms
1,230 kg

Engine icon
Installed Power - Standard Day Performance:
1 x Lycoming VO-435-23B 6-cylinder engine developing 250 horsepower.

Performance
SPEED


Miles-per-Hour
95 mph


Kilometers-per-Hour
153 kph


Knots
83 kts


Performance
RANGE


Miles
197 mi


Kilometers
317 km


Nautical Miles
171 nm


Performance
CEILING


Feet
13,205 ft


Meters
4,025 m


Miles
2.50 mi


Performance
CLIMB RATE


Feet-per-Minute
1,050 ft/min


Meters-per-Minute
320 m/min

Supported Weapon Systems:

Graphical image of an aircraft medium machine gun
Armament - Hardpoints (0):

Usually none though some wartime models were outfitted with 2 x 0.30 caliber medium machine guns in special mountings.
Variants: Series Model Variants
• H-23 "Raven" - Base Hiller company model designation
• YH-23 - U.S. Army evaluation model; single example
• H-23A - Initial production model; powered by Franklin O-335-4 engine; two-seat; 105 produced.
• H-23B - Powered by Franklin O-335-6 engine of 200 horsepower; 354 produced.
• H-23C - Three-seater; metal main rotor blade; 145 examples.
• H-23D - All-new main rotor; powered by Lycoming VO-435-23B engine of 250 horsepower; new transmission; 348 produced.
• H-23E - Proposed variant; not adopted
• H-23F - Four-seater; Lycoming VO-540-A1B engine of 305 horsepower; 22 produced.
• H-23G - Three-seater with dual control scheme; 793 examples produced.
• HTE-1 - USN model; Franklin O-335 engine; dual control scheme in two-seat cockpit arrangement; wheeled undercarriage; 17 examples produced.
• HTE-2 - USN model; Franklin O-335-6 engine; 35 examples produced.
• HT Mk 1 - British Navy designation; 20 examples from USN stock.
• HT Mk 2 - British Navy designation; 22 examples
• CH-112 "Nomad" - Canadian Army designation
• U-12A (H-23A) - Civilian model; Franklin O-335-4 engine of 178 horsepower.
• UH-12B - USN trainer
• UH-12C - Three-seat variant
• UH-12D - Improved H-23C for US Army service
• UH-12E - Three-seater with dual control scheme
• UH-12ET - UH-12E with Allison 250 series turboshaft engine.
• UH-12E3 - Improved three-seat form
• UH-12E3T - Improved turboshaft version
• UH-12E4 - Four-seater; Lycoming VO-540 engine
• UH-12E4T - Four-seater with turboshaft engine
• UH-12L-4 - Extended fuselage; enlarged cabin windows