Back Hiller 360 / UH-12 / OH-23

Hiller OH-23

The Hiller UH-12, derived from the Model 360 two-seater of 1948 with a 180hp Franklin engine, occupies an important place in the history of the American helicopter industry in the fifties. Stanley Hiller Jr., who built the aircraft, was something of a whiz kid, in that he designed and built his first helicopter, the XH-44, in 1944 at the age of only 18. It was the first efficient American helicopter with coaxial, contra-rotating rotors. The later Hiller 360 leapt to fame in the summer of 1949 when it made the first transcontinental commercial flight. With an uprated engine and new UH-12A rotor blades, it was purchased by the US Army and Navy for battlefield evacuation and observation tasks, with the designation H-23 Raven, whilst the Navy ordered the same basic model as the HTE-1 for training.

Its successor, the H-23B, powered by a 200-210hp Franklin engine, was the first version used by the US Army as a trainer. A considerable number were built: 216 were assigned to the Primary Flying School at Fort Walters and another 237 were used for various tasks.

The UH-12B normally had skid or flotation gear, but a wheeled undercarriage was fitted to a batch ordered by the US Navy (the HTE-2). In 1955 a new variant, the UH-12C, appeared. It retained the 200hp Franklin engine, but had all-metal rotor blades and a "goldfish bowl" cockpit canopy. From 1956, 145 were delivered to the US Army as the H-23C. A purely military version, the OH-12D, flew on 3 April 1956 and 483 went to the US Army. The Franklin engine had been replaced by the more powerful 320hp Lycoming VO-540, and the transmission had also been changed to increase the service life of the helicopter.

The commonest version of this sturdy little helicopter was the UH-12E which had a more powerful engine. The US Army replaced nearly all the OH-23Ds by Hiller 12Es, designated OH-23G. In 1960 the Model E4 was developed from the Hiller 12E, with a longer cabin to seat four and an anhedral stabilizer on the tail boom. Twenty-two of these were acquired by the US Army as the OH-23F, for geodetic research.

The last civil variant, which appeared in 1963, was the Hiller 12L-4 which was also used as a test-bed for a PT6 turbine, but the project was taken no further.

Total sales of the Hiller 12E family exceeded 2000; more than 300 were exported. Operators of the Hiller included Argentina, Canada, Chile, Colombia, Great Britain, Guatemala, Japan, Morocco, Mexico, the Netherlands, Peru and Uruguay.

G.Apostolo "The Illustrated Encyclopedia of Helicopters", 1984

Hiller 360 / UH-12 / OH-23

Hiller Helicopters Inc. was formed in 1942 for the development and production of rotary-wing aircraft. Early work on the Hiller Model XH-44, UH-4 Commuter and the UH-5, which introduced a newly-developed 'Rotor-Matic' rotor control system, led to the Hiller Model 360 prototype. The company's first production helicopter followed and this, known as the Hiller UH-12 as Hiller had become part of United Helicopters, was of simple construction, incorporating a two-bladed main rotor and a two-bladed tail rotor on an upswept boom. The design was highly successful, being built extensively in two- and three-seat configurations for both civil and military use, and an early Model 12 was the first commercial helicopter to record a transcontinental flight across the United States. More than 2,000 were built before production ended in 1965, some 300 of this total being exported, and throughout this period the power and capability of the helicopter was steadily improved.

The commercial UH-12A to UH-12D became the OH-23A to OH-23D Raven respectively for service with the US Army, and the US Navy acquired UH-12As as HTE-1 and HTE-2. The UH-12E was basically a three-seat dual control version of the OH-23D and was built also as the military OH-23G. A lengthened-fuselage four-seat civil UH-12E4 was produced as the military OH-23F, and late civil versions with uprated powerplant included the UH-12E variants suffixed L3, L4, SL3 and SL4. OH-23s were exported to Argentina, Bolivia, Colombia, Chile, Cuba, Dominica, Guatemala, Guyana, Mexico, Morocco, the Netherlands, Paraguay, Switzerland, Thailand and Uruguay. The Canadian army acquired OH-23Gs which it operated with the designation CH-112 Nomad, and the Royal Navy used a number of ex-US Navy HTE-2s under the designation Hiller HT.Mk 2.

At the height of UH-12/OH-23 production Hiller was taken over by the Fairchild Corporation, but in 1973 a new company, Hiller Aviation, acquired design rights and production tooling for the UH-12E, and for some years provided support for the world-wide fleet of UH-12 variants. In April 1984 Hiller became a subsidiary of Rogerson Aircraft of Port Angeles, Washington. Renamed Hiller Helicopters and later Rogerson Helicopters, the company, now known as Rogerson Hiller, relaunched the piston-engined UH-12E in 1991 as the Hauler, and a number have been exported. The company is also proposing the Allison turbine-powered UH-12ET development for the US Army's NHT (New Training Helicopter) requirement.

D.Donald "The Complete Encyclopedia of World Aircraft", 1997


Two-seat helicopter based on UH-5 of all-metal construction with fixed tricycle u/c, fully enclosed cabin and rear fuselage, overhead mounted control stick attached to Hiller rotor control, powered by one 175hp Franklin 6V4-178-B32 engine. Prot. N68940.


Developed 360 with framed 'bubble'-type cabin, no fuselage structure round engine, skid u/c and 175hp Franklin 6V4-178-B33 engine. 1015kg TOGW.

UH-12A Raven


Production two-seat UH-12 with collective pitch ballast system and wooden rotor blades for civil and military customers. 1082kg TOGW.


UH-12A with skid/wheel u/c, 200hp Franklin 6V4-200-C33 engine and 1128kg TOGW.


UH-12B for USN with wheel u/c. Also HT Mk.1 for Royal Navy.


UH-12B with moulded bubble canopy, 3 seats and metal rotor blades.



Military UH-12C with 250hp Textron Lycoming VO-435-A1C engine, new transmission system, 1240kg TOGW. Prot. FF 3 Apr. 1956.



UH-12D with 305hp Textron Lycoming VO-540-A 1 A engine. OH-23G is 3-seat dual control trainer.



UH-12E retro-fitted with Ham-Standard rotor stability augmentation system, stainless steel rotor blades and 1400kg TOGW.



Revised designation for Hiller Aircraft Corp. production UH-12E with 3 seats.



Revised designation for Hiller Aircraft Corp. 3-seat UH-12ET.


UH-12E with inverted rear tail planes and lengthened cabin to accommodate pilot plus rear bench seat for 3 pax.



UH-12E fitted with Soloy conversion to 400shp Allison 250-C20B turboshaft.



UH-12E4 fitted with Soloy conversion to 400shp Allison 250-C20B turboshaft.


UH-12E4 fitted with five seats and 340hp Textron Lycoming VO-540 piston engine. Prot. flown but design not further developed.



Proposed turbine-powered UH-12E5 with Allison 250-C20B. Not built.



Unofficial designation for Soloy-converted UH-12E.



UH-12E with supercharged Textron Lycoming TIVO-540 engine and 'L' series rotor head with gyro-controlled stability augmentation system.



UH-12SL with unsupercharged VO-540 engine.


UH-12L with E4 four-seat cabin.

*     *     *
Stanley Hiller Jr designed the Model 360 which has enjoyed considerable commercial success since its first flight in 1948. It was derived from the UH-5 which had proved very unstable during trials and had subsequently been fitted with a new stability system patented as the Hiller 'Rotormatic'. It entailed fitting the two-blade rotor with two small paddles which acted as a control rotor and were also connected to a hanging stick. This servo 'paddle control' system tilts the rotor head and actuates the cyclic pitch control.

It received its FAA (Federal Aviation Administration) approval in October 1948 and a year later a production model designated Model 12 made the first transcontinental helicopter flight across the USA. At that time it still had an open cockpit, and the 178hp Franklin 6V4-178-B33 was in an open engine bay.

Models 12A, B and C were powered by a 200hp 6V4-200-C33 or a 210hp 6V-335-B Franklin piston engine. The 12C was the first version with a goldfish bowl canopy.

The Korean War gave an added impetus to improvements and when the Hiller 12E appeared in 1959 it came either as the L3 with a 305hp Lycoming VO-540-C2A or as the SL3 with a supercharged 315hp TIVO-540-A2A engine.

The 12E has been used for the usual range of civil work, like fire-fighting, crop and forestry control, and as a private and business transport.

A Model E4 was built with a longer fuselage to take a bench for three passengers and it introduced stabilized tail surfaces. All new helicopters now have these features and they can be retrofitted on Model 12Es. A turbine-powered retrofit kit is available as the UH-12E4. This engine pack was jointly developed with Soloy Conversions of Chehalis, Washington who began work on it in 1976.

The Model 12 has the usual equipment for helicopter safety and civil work, but can also be fitted with a night-lighting kit, a 454kg capacity cargo hook, twin heavy duty cargo racks, and auxiliary fuel tanks. Equipped with extra tanks the 12E has a maximum range of 676km. Production of both the 12E and 12E-4 is running at about five a month and with over 2200 helicopters built since the introduction of the Model E there is a world-wide maintenance service.

Bill Gunston "The Illustrated Encyclopedia of Commercial Aircraft", 1980

*     *     *


- An early UH-12 was the first commercial helicopter to log a transcontinental flight across the United States.

- Over 1,600 UH-12s went to the US Army and were used in Korea and Vietnam.

- As a flying ambulance, the UH-12 can carry two stretcher cases.

- UH-12s were exported to at least 18 countries, many via the Mutual Defense Aid Program.

- The Hiller UH-12 was the US Army's primary trainer until 1965.

- UH-12s were manufactured by Hiller in Palo Alto, near San Francisco, California.

Technical data for Hiller OH-23D "Raven"

Engine: 1 x Avco Lycoming VO-540-A1B 6-cylinder pistone engine, rated at 241kW, main rotor diameter: 10.82m, length: 8.53m, height: 2.97m, take-off weight: 1225kg, empty weight: 824kg, max speed: 153km/h, cruising speed: 132km/h, service ceiling: 4025m, range: 330km

Comments1-20 21-40
James Carlisi, e-mail, 04.03.2024reply

I worked for Hiller, on the assembly line, and later Engineering, flight testing Hillers Stainless Steal Composite rotor blades, and Flight Testing, before the company went Bankruptcy. Was the first mechanic on the Tuna Boats for Reston Purina, as a flight mechanic..

James Carlisi, e-mail, 04.03.2024reply

I worked for Hiller, on the assembly line, and later Engineering, flight testing Hillers Stainless Steal Composite rotor blades, and Flight Testing, before the company went Bankruptcy. Was the first mechanic on the Tuna Boats for Reston Purina, as a flight mechanic..

James Carlisi, e-mail, 04.03.2024reply

I worked for Hiller, on the assembly line, and later Engineering, flight testing Hillers Stainless Steal Composite rotor blades, and Flight Testing, before the company went Bankruptcy. Was the first mechanic on the Tuna Boats for Reston Purina, as a flight mechanic..

:Karson-M: Branham., e-mail, 13.12.2023reply

I have worked on Hiller Helicopters since 1992, was familiarized in aircraft maintenance school in 1987-88 on the school UH12E. experienced with the B,C,D and E3 /E4 /E5, ihave rebuilt every component on them and have a decent spare parts stash. my favorite model is the C with wood blades and the franklin O-335-B or Franklin V-350-B. excellent helicopter, none is more economical or as safe as the Hiller, best light helicopter you can fly even today in 2023!

Marshall Schmit, e-mail, 16.12.2023 :Karson-M: Branham.

I am rebuilding a b model in Hawaii and you sound like an awesome resource. I would like to talk to you more please email me back
Thank you


Michael Clary, e-mail, 22.07.2022reply

I am in the current process of restoring back to permanent non-flyable static display a former United States Army (HILLER) OH-23D raven Helicopter s /n 61-3169 here in Anderson, South Carolina. I believe it was stationed there at Fort Wolters from 1962 to 1972, but I am not sure, I sent away for the historical records to the U.S. Army and they could not help me so I am currently looking for any former Army student aviators that might have trained /flown in 61-3169 or may have worked on it in the maintenance shop, I would greatly appreciate it.

Nick Hurley, e-mail, 28.09.2022 Michael Clary

Michael, I am the curator of the New England Air Museum in Windsor Locks, CT. I recently came across a group of Hiller OH-23 parts including some still in the original packaging. We will be selling all of it as a parts lot. If you are in need of parts, I'd love to send you a list of what we have to see if you are interested. Please let me know. Thanks!


Ryan, e-mail, 23.12.2023 Nick Hurley

Hi Nick,
I just came across your old post on a website saying you had a bunch of Hiller parts. Do you still have them, and if so, could I get the list of what you have?


James Palmer, e-mail, 02.04.2021reply

The American Helicopter Museum in West Chester, PA,. USA seeks a bubble in fair condition or better for an OH-23D being restored for static display. Any information about bubble prices and whereabouts would be appreciated. Donations, of course, would be gratefully accepted.
Jim Palmer, ORWAC Class 67-22

Tom Morrissey, e-mail, 27.06.2021 James Palmer

In 1978-9 I had a job flying Hillers inMiami FA for Dade and Tropical helicopter companies. The owner had bought several as I recall from the army and they were at Opa Locka airport. Still may be some there. I flew them in flight school. Good luck.


Lynn S Beedle Jr, e-mail, 23.04.2021 James Palmer

I just got back from a visit to Fort Wolters. I wont begin to explain what a astounding trip that was. Everything is the same...only 52 years gone by...I spent the day there and drove over to the Main Heliport on the road between the briefing rooms and the hangars, Grant Road, and told my wife "There has GOT to be a 23 here someplace besides the main gate" (restored I might add) I saw the old hangars where the engine shops used to be. I drove around back and there was a "B" model. The hangar doors were open. I saw an A&E type and his junkyard dog. and inside his boss and.....rows of 23s in every state and condition. and racks of spares. So there is a guy who works on these things!. Pat Pockrus 888-925-5971. 940.325.5971 fax: "Fort Wolters Helicopters" 517 Grant Road, Mineral Wells, TX....if anybody has a bubble its Mister Pockrus. He's a for-profit old-timer. Good Luck. LBeedle 10th WOC 69-49 B-1


Tom Morrissey, e-mail, 27.06.2021 Lynn S Beedle Jr

I was in 69-49 10th woc


Tom Morrissey, e-mail, 27.06.2021 Lynn S Beedle Jr

I was in 69-49 10th woc


John Mateyko, e-mail, 22.02.2018reply

My flight class 65-7 flew these in primary helicopter flight training at Ft. Wolthers Nov '64-Feb '65. My primary flight instructor had been a B-24 pilot. I cannot believe he could sit there with his arms folded while we practiced touchdown autorotations from a hover.

Dewey Chapman, e-mail, 29.02.2016reply

Most of my fellow chopper mechs were trained in San Marcos TX. in 1955. After completing training 12 of us went to an airport in CA. Livermore,CA. We trained there on Bell H13s.After training our group was sent to Libya,as part of an Engr. Battalion, my memory is not as good as it used to be . I think it was the 3099th I think. Libya was a Kingdom at that time . We were stationed on the USAF base called Wheels Fld . If you are young and want to go in the military join the USAF. great food easy duty . At that time 1956 most of us found the beach that was loaded with English ,italian German young ladies NICE Surprise .to shorten this somewhat , I will only say that inspire of it being classed a hardship Post We enjoyed our 18 Mos there.Our helps were Hiller ho23s Great machine . The extra 50..00 flight pay came in very handy Nuff said Bless all the GI s

Ron Neely, e-mail, 04.06.2015reply

flew 23,s 69 70 at Wolterslater redid some in Amarillo, Tx .My best memory was the old saying give me 15 acres and I,ll turn this thing around. I carry a lot of fond memories

mehic omer, e-mail, 16.12.2012reply

I want buy Hiller UH 12 ET?
Please help me...

Brian Buttrum, e-mail, 06.12.2012reply

Hi, my name is Brian and I am a civilian contractor at FT. Campbell KY. The AVIM unit that my crew supports is restoring a OH-23A, 1955 model for the Warrior Transition Battalion. This Battalion helps our wounded soldiers return to a normal life. My crew and I are asking for any help restoring this aircraft. We are in great need of a Tail rotor drive shaft from the eng gearbox to the tail boom, a used bubble with doors (as the ACFT will be displayed outdoors), a complete tail rotor assy (blades, yoke, and hardware) also 2 seats, belts etc... any help would be appreciated, Thanks Brian Buttrum 931-561-4232

Mike Cress Sr, e-mail, 25.07.2010reply

A couple of years ago there was a guy in Early County Georgia (Blakely area) that was flying an H-23 with a spray boom for crop dusting. That acft might not still be flying and could potentially be available

Vic, e-mail, 17.09.2010reply

As I remember the the G model had two carbs? And maybe an extra damper on the rotor system? Flying a Huey in '69 in Nam I was cooling it a a field over in the Michelin when I heard a 23 coming in. The pilot landed, frictioned down the collective, disappeared over a berm and came back with a fuel hose. Heard a gas engine crank up (fuel pump) and he filled up the 23, put everything away and left. It belonged to the 23rd Arty Gp. My Crew Chief tapped me on the shoulder and asked if I had paid attention. I said yes. He said "Good, I'm taking tomorrow off".

Don Bailey, e-mail, 15.11.2010reply

I flew the OH-23D at Camp Wolters,TX-circa'62.(ORWAC-62-10A)
Flew the OH-23C at Ft. Eustis,VA.["bootleg" time]
Flew the OH-23B for 3 years- '63-'66 Ohio Army Guard-107th ACR.
Flew the OH-23F [4 place] in Iran-'66-'67. 64th ENG. Bn.
Flew the OH-23G & JOH-23L(315 BHP turbocharged) in AZ-NM-UT-NV '68-'71-30th ENG Bn.
Flew the UH-12A for Civilian contractor. '63.
My flight records indicate about 2,300 hours logged in Hillers. Sturdy birds!
Don Bailey-CW4-USA (Ret)

fabian, e-mail, 21.11.2010reply

hola quiciera saber el precio del kit , helicopter 360 /UH-12 / IL 23 puesto en argentina o en brasil gracias saludo a usted muy atte. fabian

Ron Hartleroad, e-mail, 17.12.2010reply

Well the restoration has taken a full year but the OH-23 Hiller in Lexington,OK is back on the pole. We put countless off duty hours into a static display. It looks great. If anyone wants to see it email me and I will send you pics.

Paul E.Nichols, e-mail, 17.01.2011reply

The Uh12D had a Lycoming VO 435 engine in it. Not a VO 540
Your referance is correct in blocked area with pictures and specs, but is incorrect in many other areas.
I did the dual carb design thing on the E-model. It reminded me of my hot rod days

Jim Crawford, e-mail, 28.02.2011reply

I learned to fly in a OH-23 at Ft Wolters, TX in 1969.

OSCAR PIMENTEL, e-mail, 22.03.2011reply


Roger D. Huffaker, e-mail, 02.08.2011reply

I learned to fly helicopters in the OH-23D at Fort Wolters, TX in June 1962.

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