Little known helicopters

Many of the helicopter models here mentioned were definitively abandoned after a test phase. Most of them were built in the United States between the 1940s and the 1950s. Luckily some of them were preserved and are now displayed in various museums.
It hasn’t been easy to find detailed technical and historical information concerning these models and their builders. Therefore, if you have more detailed information, or newspaper's articles, photographs or videos, or if you simply want to suggest other models that should be included in the list, do not hesitate to contact me. This way you will contribute to piece together the history of these helicopters.

Aeronautical Product Inc. – API (1944) - Two different models designed by Corwin Denny and Karl Schakel were built (registered NX-1270 respectively NX-1272). The first prototype was used experimentally to deliver merchandise for the Filene’s department store in Boston. Both models had accommodation for the pilot and one passenger. The engine was placed in front of the cabin.

American Helicopter Co. (1949-1952) - This company was founded in Inglewood by Corwin Denny in 1947 and built three models. The first of them was the two place XA-5 Top Sergeant (1948) followed by the sinlge place XA-6 Buck Private registered N6232C (1951). In 1952 a new prototype took the air as XA-26 Jet Jeep. This collapsible model could be used as an air-droppable rescue vehicle for downed aircrew and could be assemled in few minutes. All the models were tested extensively, but none of them reached the mass production. Actually one of the five XH-26 Jet Jeep produced is preserved at the National Museum of the U.S. Air Force at Wright-Patterson AFB in Ohio.

Bendix Helicopter Inc. (1945-1949) - The Model K was a monoplace registered NX41817. The famous test pilot Charles (Les)ter Morris (ex test-pilot of the Sikorsky), worked for a short period for this helicopter company. A larger model offering place for 4 occupants registered NX74101 was built in 1949 and is known as the Model J "Whirlaway". Both prototypes were equipped with a coaxial rotor system.

Brantly B.1 X69125 (1946) - First prototype built in 1946 by the Pennsylvania Elastic Company equipped with two coaxial rotors rotating in opposite directions. It was capable to transport a passenger and the pilot seated side-by-side.

Curtis-Wright CW-2 “Flymobile” Wek-copter (1945) - The Curtis Wright Industries Aircraft and trailer (nothing to do with the huge Curtiss-Wright Corporation) built a two place helicopter equipped with two coaxial rotors rotating in opposite directions. This model had a three wheels landing gear. The tail wheel could be drove. A part of the power was used to transform the helicopter in a automobile, that is why the Curtiss helicopter was also called “Flymobile”.

De Bothezat NX15699 (1940) - Single place helicopter tested in the early ’40 by the Russian pilot Cpt Boris Sergievsky. It was equipped with contra-rotating all metal fabric covered rotor blades. The engine and the transmission were mounted between the two coaxial rotors. The inventor died before the completition of this model which was then abandoned.

De Chappedelaine (1947) - Two seater model conceived by Jean Olivier De Chappedelaine a French that emigrates in the USA. The two seater helicopter was built by the American Die and Tool company based in Pennsylvania and had a two blades main rotor with tail rotor. In 1947 after an accident during the tests the project was abandoned.

De Lackner “Cloud-duster” NX14879 (1945) - The first helicopter built by the De Lackner Helicopters Inc. was a two place which had two rotors placed in tandem. It was known as “Cloud-duster” and was powered by a 125 hp Lycoming engine.

De Lackner DH-4 "Heli-Vector" and DH-5 "Aero-Cycle" N64W (1954/1955) - Much later De Lackner Helicopter Inc. built the DH-4 Heli-vector and the DH-5 Aerocycle also known as "individual lifting devices". Both these models were developed by L. C. Mc Carthy for this company on the basis of research work conducted at NACA in 1953/1954. These models had two coaxial rotors powered by a single outboard Mercury engine of variable power. The pilot stand on a platform located just above the two rotors.

Doman LZ-1A N74146 (1947), LZ-4 N74147 (1951), LZ-5, YH-31, D-10B - The first helicopter constructed by the Doman-Fraiser Helicopters Inc. was the two place LZ-1A, essentially a R-6A with a new rotor type. It was followed by the larger model LZ-4 and later the LZ-5 (tested by the US Army as the YH-31) which could accommodate 2 pilots and 6 passengers or 4 litters. In 1954 the company became Doman-Fleet Helicopters Inc. and constructed a civil model of the LZ-5 which obtained the FAA certification. Much later this model became the D-10B which however was not produced in series. One of the few YH-31 is now preserved in the Classic rotors museum in California.

Exel Model 100 NX9392H (1946) - Mr. George Exel of Clifton New Jersey built different helicopters. Among them the Exelicopter which flew in the second mid of the '40, very similar to the Sikorsky R-4. Very few information and pictures concerning the aviation activity of Exel are available.

Firestone XR-9, XR-9B and XR-14 - The Firestone Aircraft company (a subsidiary of the more famous Firestone Tire and Rubber company based in Akron Ohio) acquired in 1943 the G&A Aircraft Inc. and nearly 200 patents concerning autogyros and helicopters. The XR-9 (civil designation Model GA 45B) flew in 1944 as a one seater but was later transformed to accomodate a passenger. This version was known as the XR-9B (Model 45C). The civil Model GA 45D (registered NX58457) had a roomier cabin and a slightly modified rear fuselage. The pilot and his passenger seated side-by-side. This helicopter is now preserved in the Army Aviation Museum in Fort Rucker Alabama.

Gluhareff (1956) - One man helicopter “dressed” by the pilot and equipped with a mono-blade rotor with counter-weight powered with liquid propane fuel. Much later the rotor was converted in a two blades.

Hamilton NX41870 (194?) - Two place model built by the Hamilton Helicopter Inc. of Baltimore/Maryland in 1947-1948 equipped with two coaxial rotors and a tricycle landing gear. Acquired by Ag Rotors Inc. helicopter company as “gate guardian” in the ’60s. Lost in a barn fire where it was temporary placed while waiting a restoration.

Haig-K (1959) - Two place model of standard configuration constructed by the Haig K Aircraft Corporation of Malvern, Pennsylvania which was equipped with a Continental C-85 engine. It had the registration N9065H.

Helicopter Engineering H.100 NX69156 (1947) - Single seater of standard configuration constructed by Harold Lemont powered by a 56/75 kW/shp engine. The helicopter was of standard configuration with a 3 blades main rotor a two blade tail rotor and a quadricycle landing gear.

Higgins EB-1 (1943) - Higgins Industries of New Orleans, Luisiana, create an aircraft division where the EB-1 designed by the Italian emigrate Enea Bossi was constructed. Initially known as the Scorpion this two place model of standard configuration had two couple of rotors mounted on the same axis which were powered by a Warner Super Scarab engine placed behind the cabin.

Hoppi-copter (1945) - The first helicopter designed by Horace T. Pentecost of Seattle was a "back-strap" model intended for military use. Later the American Hoppi-Copters Inc. built other models which had two coaxial rotors and a small engine of variable power depending on the version.

Hoppicopter “Firefly” (1950) - Single place model equipped with a two blades tip powered rotor. It seems that this model did some hovering flights in 1950.

Humming Bird (1945) - This single place model built in China during WWII had two coaxial rotors. It was very simililar to the Hiller XH-44. It seems that the prototype was destroyed during a ground test flight in 1945.

CJC 3 (194?) - This two seater model built in China had two rotors placed in tandem, and was very similar to the Jov-3 and its successor the Mc Culloch MC-4. On the 18th of August 1953 this prototype was victim of an accident.

Jensen 21 "Silver Beetle" NX31224 (1948) - Martin Jensen, formerly vice-president and chief-engineer of the Bendix Helicopter, took with him a small group of personnel of the latter and founded his own helicopter company. Working secretly in an old ranch in Tonasket, Washington, he designed and built the Jensen 21 Silver Beetle, which was very similar to the Bendix Model K. The helicopter tested in flight by the pilot James Couperthwaite was powered by a 125 hp Continental C125 engine.

JOV-3 (1948) – Mc Culloch MC-4 (1951) - Jovair 4-E Sedan (1963)- The JOV-3 N9000H was a two place helicopter with a tandem rotor configuration which appeared in 1948 and was constructed by the Helicopter Engineering Research Corporation. Its president D. K. Jovanovich in 1949 joined the Mc Culloch Motors Corporation (Helicopter Division) as chief helicopter design and built the MC-4, an evolution of the JOV-3. The new two seat prototype was registered N4070K and did its first test flight on the 20th of March 1951. On the 17th of February 1953 this helicopter obtained the CAA certification. The Army acquired three Model MC-4C in 1952 for evaluation under the designation YH-30. Jovanovich founded much later the Jovair Corporation and built the Jovair 4-E Sedan, a four place helicopter with the same rotor configuration of its predecessors powered by a 156.5/210 kW/shp Franklin engine.

Kaiser Fleetwings XH-10 Twirleybird NX41804 (1944) - Helicopter of standard configuration with a three blades main and tail rotor built in 1944 by the Kaiser Fleetwings Inc. of Bristol, Pennsylvania. This model was very similar to the Sikorsky R-4. It seems that two prototypes were built. Very few information about this helicopter are available.

Kellett XR-8 (1944), Kellett XH-10 (1947) - The XR-8 was a "synchropter", or better a helicopter with twin side-by-side intermeshing rotors as the Flettner FL282 Kolibri. For this characteristic it was soon nicknamed "egg-beater". Two prototypes of this militar two place model were built, the first of which flew for the first time on the 7th of August 1944. The twin-engine XH-10 was the successor of the XR-8 and could accomodate 10 passenger or six stretchers. Two prototypes were built the first of which made its first flight on the 24th of April 1947. Kellett built the mock-up of the KH-2, the 16-seat civil version of the XH-10. Unfortunately a dramatic incident occurred the 3rd of October 1949 caused the death of the test-pilot John David Driskill. Consequently the further development of this type of helicopter was abandoned.

Kellett KH-15 Stable Mable (1954) - Single place prototype provided with a two-blades rotor powered with two hydrogen peroxide rocket engines. The development of this "flying test bed" was financially sustained by the office of Naval Research. The KH-15 thanks its gyro-stabilizing system had excellent stick-fixed dynamic stability. After a series of test flight which were conducted in 1954 the helicopter was definitively abandoned.

Landgraf Helicopter company (1944-1945) - The H-2 NX21782 was an experimental single place model with side-by-side rotors built in California by Fred Landgraf. This helicopter powered by a 63/85 kW/shp Popjoy engine had a number of revolutionary design features as for example its tricycle retractable landing gear. The H-2 was developed and tested under contract with the Army Air Force and the Air Material Command. Landgraf designed bigger models for civil uses such the H-3 (for one pilot and two passengers) or the H-4 (one pilot and up to eight passengers). He later decided to sold his company to Firth Helicopters of London.

Marquardt M-14 (1948) - The Marquard Aircraft Company of Van Nuys/California built a two place model with a two blades rotor powered with two pulse jets. The prototype was registered N4107K.

Mc Donnell XHJD-1 "Whirlaway" (1946) - After WWII the Mc Donnell Aircraft Corporation of St. Louis, Missouri, founded a helicopter division to develop new models of helicopters. The first of them was the XHJD-1 a large helicopter with two rotors placed side-by-side powered by a 335.5/450 kW/shp Pratt&Whitney engine. This model capable to lift up to 10 passengers was tested by the US Navy but it was then abandoned.

Mc Donnell Model 38 “Little Henry” (1947) - Single place prototype built in 1947 powered with two ram-jets. This agile helicopter was tested under USAF contract.

Mc Donnell Model 79 "Big Henry" (1952) - This model registered N12M was designed as an utility helicopter for the civil market. Essentially the concept was identical to that of the model XH-20, even if it was larger. The two blades rotor was powered by two Mc Donnell 8RJ4 ramjets engines. The helicopter made its first flight on the 26th of March 1952. Due to the high fuel consuption and the high noise level this model was soon abandoned.

Mc Donnell Model 120 "Flying Crane" (1958) - This helicopter was powered by three Air Research GTC-85-35 turbo-compressors of 63/85 kW/shp each, but could fly if necessary using only two of them. After a series of flight tests (also as a "flying crane") it was abandoned.

Monte-Copter Inc. - The Monte Copter Inc. of Seattle, Washington, managed by Maurice Ramme was incorporated in 1953 to develop a small two seat helicopter known as the Model 10. For its sustentation this model registered N68P used a cold tip jet rotor. The first test flights were done in 1955 using a Lycoming 0-290-D2 engine driving a compressor. In 1958 this model was modified and flown with two turbines under a new designation (Model 10A). It was then again modified into the Model 12, which had a new rear fuselage. The Model 15 registered N69P "Tri-phibian" was similar to its predecessor but could accomodate the pilot and two passengers. The power of its 149/200 kW/shp Continental Model 141 gas turbine supplied compressed air to the rotor. The residual thrust was sufficient for taxying on land or water. Actually this helicopter is preserved in the Classic Rotors museum in California.

Nemeth “Anti-torque” (1946) - After a long period of experimentation at the Georgia Technical school Stephen P. Nemeth of Chicago built a two place helicopter of his own conception. His model had a two blades rotor system. The inventor claimed that his blades were 28% more efficient than any others constructed. These were rotated by two small 26/35 kW/shp engines carried on booms set at 90° to the lifting blades. It is probable that this helicopter never took the air.

PB-61 (1949) / PB-63 (1953) / PB-64 (1957) - At the end on WWII the Austrian inventor Paul Baumgartl left Austria and went in Brasil. Here he continued his work in the vertical flight field designing the PB-61 a one seater helicopter with two coaxial rotors powered with a 48/65 kW/shp Continental engine. This helicopter was tested in 1950. The results obtained with this prototype were not encouraging. For this reason Baumgartl decided to change the formula for his next helicopter. The PB-63 was an ultra-light of standard configuration powered with a 63/85 kW/hp Continental engine tested in 1953. The PB-64 was an ultra-light one seater helicopter powered by two pulse-jet.

Roteron X-100 (1946) - Single place helicopter designed by William Thomas, the president of the Roteron Corporation. The outstanding feature of this mini-helicopter was the position of the the 18/25 kW/shp Noble engine which was placed between the two contra-rotating coaxial rotors. It is very improbable that this helicopter flew with the reduced power installed.

Rotor-Craft XR-11 Dragonfly (1946) - RH-1 Pinwheel (1951) - In 1945 the Rotor-Craft Corporation of Glandale, California, began the development of a helicopter with a tandem rotor configuration designed by Gilbert W. Magill and designated XR-11 "Dragonfly". This two place model was powered by a 74.6/100 kW/shp Continental C100 engine and used a rigid-rotor system patented by Fred Landgraf. The RH-1 Pinwheel was a "strap on" monoplace developed for the US Navy. Its rotor was driven by two liquid-fuel rockets which used peroxide as fuel. The RH-1 made its first test flights in 1954 but was then later abandoned.

Safti-copter X-502 (194?) - Single place model constructed by Leonard E. Mueller. It had two coaxial rotors rotating in opposite direction and was equipped with a 30/40 kW/shp engine. A two place model with similar characteristics was designed but probably was never built

Seibel S-3, S-4A and S-4B (1947-1952) - Three different models of standard configuration were built by the Seibel Helicopter Company. The monoplace S-3 registered NX735B was powered by a 48/65 kW/shp engine had initially an unusual control system. The lateral and longitudinal control were obtained changing the centre of gravity. This was acccomplished by moving the cabin at the pilot's will. However this system was not practical and was consequently replaced with conventional controls. The S-4 N5152 built in two units was its successor and could accomodate a passeger behind the pilot. This helicopter obtained the CAA certification on the 2nd of January 1951 and was tested by the US Army under the designation YH-24 Skyhawk. The S-4B N5154 had a more powerful engine and could accomodate two pilots seated side-by-side. The wheeled landing gear on this helicopter was replaced with skids.

Sun Helicopter Model 1 (1950) - One seater of standard configuration registered N8411H powered with a 70.8/95 kW/shp engine. This model had an inusual mono blade rotor counterbalanced on the other side with a steel weight.

Teicher-Hunt Humming Bird (1947) - This two place model was originally designed by William (Bill) E. Hunt, an engineer who worked on the early Sikorsky helicopters. Hunt left the Sikorsky Aircraft Division and designed a conventional helicopter initially known as the Teicher-Hunt Humming Bird. Initial test flights were done at the end of 1947. The Aircraft Division of the Glenview Metal Products of Delanco, New Jersey decided to acquire the prototype. Consequently the name of the helicopter registered N544A was changed in GMP-1 Flyride. The tests continued for a while, then the helicopter was definitively abandoned.