The American Helicopter XH-26 Jet Jeep (known as the XA-8 by its manufacturer) is an experimental

tip jet A tip jet is a jet nozzle at the tip of some helicopter rotor blades, used to spin the rotor, much like a Catherine wheel firework. Tip jets replace the normal shaft drive and have the advantage of placing no torque on the airframe, thus not re ...

helicopter A helicopter is a type of rotorcraft in which Lift (force), lift and thrust are supplied by horizontally spinning Helicopter rotor, rotors. This allows the helicopter to VTOL, take off and land vertically, to hover (helicopter), hover, and ...

developed in 1951 by the American Helicopter Company to meet a United States Army and Air Force (USAF) request for a collapsible and air-droppable observation helicopter. A few prototypes were evaluated and flown during the 1950s, but it was decided not to adopt this type. Several examples have survived as museum pieces into the present day.

Design and development

Design of the Model XA-8 began in 1951, following a specification for a one-man, collapsable helicopter that was capable of being assembled with simple tools; the intended roles of the aircraft were for observation and as an airdropped rescue vehicle. A contract for development was awarded in June 1951, and the prototype XH-26 flew in January 1952. The aircraft was made of aluminum with a

fiberglass Fiberglass (American English) or fibreglass (English in the Commonwealth of Nations, Commonwealth English) is a common type of fibre-reinforced plastic, fiber-reinforced plastic using glass fiber. The fibers may be randomly arranged, flattened i ...

rear fuselage. It could be collapsed to fit inside a container, and when stripped down weighed less than ; two men could assemble the aircraft in 20 minutes. Power was provided by two XPJ49

pulsejet file:Pulse Jet Engine.PNG, 300px, Diagram of a valved pulsejet. 1 - Air enters through valve and is mixed with fuel. 2 - The mixture is ignited, expands, closes the valve and exits through the tailpipe, creating thrust.3 - Low pressure in the engi ...

s serving as

tipjet A tip jet is a jet nozzle at the tip of some helicopter rotor blades, used to spin the rotor, much like a Catherine wheel firework. Tip jets replace the normal shaft drive and have the advantage of placing no torque on the airframe, thus not re ...

s; startup was by compressed air and the aircraft could take off within 30 seconds. The small tail rotor was used solely for directional control. American Helicopter chose the name "Jet Jeep", because the XH-26 could be used like a

Jeep Jeep is an American automobile brand, now owned by multi-national corporation Stellantis. Jeep has been part of Chrysler since 1987, when Chrysler acquired the Jeep brand, along with other assets, from its previous owner, American Motors Co ...

, but in the air. It could be transported by a Jeep, and even used the same fuel. The XH-26 could be dropped by air and assembled and be ready for flight in 20 minutes.

Operational history

Both the Army and USAF evaluated the five prototype Jet Jeeps. They proved to be rugged and durable vehicles with a top speed of and a ceiling of . Unfortunately, the pulse jets produced an unacceptable amount of noise and the drag of the engines in the event of power loss would prevent safe landings by

autorotation Autorotation is a state of flight in which the main rotor system of a helicopter or other rotary-wing aircraft turns by the action of air moving up through the rotor, as with an autogyro, rather than engine power driving the rotor. Bensen, Igor ...

. For these two reasons the Army found the pulse jet helicopters unsuitable as it had those with ramjets. Finally, cost considerations forced the cancellation of the program. The replacement of the XH-26's pulse jets with

ramjet A ramjet is a form of airbreathing jet engine that requires forward motion of the engine to provide air for combustion. Ramjets work most efficiently at supersonic speeds around and can operate up to . Ramjets can be particularly appropriat ...

s was suggested but never undertaken; however, the

Hiller YH-32 Hornet The Hiller YH-32 Hornet (company designation HJ-1) is an American Ultralight aircraft (United States), ultralight helicopter built by Hiller Aircraft in the early 1950s. It was a small and unique design because it was powered by two Hiller 8RJ2B ...

helicopter was built using blade tip ramjets.

Operators

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United States Air Force The United States Air Force (USAF) is the Air force, air service branch of the United States Department of Defense. It is one of the six United States Armed Forces and one of the eight uniformed services of the United States. Tracing its ori ...

United States Army The United States Army (USA) is the primary Land warfare, land service branch of the United States Department of Defense. It is designated as the Army of the United States in the United States Constitution.Article II, section 2, clause 1 of th ...

Surviving aircraft

* 50-1840 – XH-26 in storage at the

United States Army Aviation Museum The United States Army Aviation Museum is an aviation museum located on Fort Novosel near Daleville, Alabama. It has the largest collection of helicopters held by a museum in the world.Phillips 1992, p. 37.Purner 2004, p. 204. The museum feature ...

Ozark, Alabama Ozark is a city in and the county seat of Dale County, Alabama. As of the 2010 census, the population of the city was 14,907. Ozark is the principal city of the Ozark Micropolitan Statistical Area, as well as a part of the Dothan-Ozark Co ...

* 50-1841 – XH-26 on static display at the

National Museum of the United States Air Force The National Museum of the United States Air Force (formerly the United States Air Force Museum) is the official museum of the United States Air Force located at Wright-Patterson Air Force Base, northeast of Dayton, Ohio. The NMUSAF is ...

Dayton, Ohio Dayton () is a city in Montgomery County, Ohio, United States, and its county seat. It is the List of cities in Ohio, sixth-most populous city in Ohio, with a population of 137,644 at the 2020 United States census, 2020 census. The Dayton metro ...

Specifications (XH-26)

References