XH-26 Jet Jeep | |
---|---|
![]() | |
Role | Experimental observation helicopter |
National origin | United States |
Manufacturer | American Helicopter |
First flight | January 1952 |
Primary users | United States Army United States Air Force |
Number built | 5 |
The American Helicopter XH-26 Jet Jeep (known as the XA-8 by its manufacturer) was an experimental tip jet helicopter 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.
The design of the original Model XA-8 single-seat lightweight helicopter began in 1951 under the sponsorship of the US Army Transportation Corps and the USAF. The Army's specification in 1950 called for a lightweight, one-man unarmed helicopter that was collapsible, capable of aerial delivery to troops in rugged terrain, and assembled quickly with simple tools. The helicopter was to be used for both light observation and as an air-droppable rescue vehicle for downed aircrews. After a review of all proposals American Helicopter was awarded the development contract in June 1951, based on its XA-8 design proposal. The first of five prototype XH-26s flew in January 1952.
The XH-26 was constructed of aluminium, except for the aft fuselage, which was laminated fiberglass, and possessed a well-glazed, pyramidal-shaped cockpit. When collapsed, its 5 by 5 by 14 feet (1.5 by 1.5 by 4.3 m) container fit on a trailer that could be towed by a military Jeep. If stripped for air drop, the Jet Jeep weighed less than 300 pounds (140 kg). It could be assembled by two men in 20 minutes. The XH-26 did not use any gears, or an internal engine like other helicopters. Rather, the Jet Jeep was powered by two 6.75-inch (17.1 cm) XPJ49 pulse jet engines mounted on the end of each rotor blade tip as tip jets. Also designed by American Helicopter, each pulse jet weighed 16 pounds (7.3 kg) and produced 35 pounds-force (160 N) of thrust, and were started with an internal compressed air system. Since the engines did not have to be warmed up, the XH-26 could take off in 30 seconds. The pulse jets produced no torque, and the tiny, belt-driven tail rotor was used only to improve directional control. The only mechanical item that had to be replaced after so many hours of flight was the intake air vanes, which were small and inexpensive and could be replaced with a small tool in minutes.
American Helicopter chose the name "Jet Jeep", because the XH-26 could be used like a Jeep, 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. [1]
Both the Army and USAF evaluated the five prototype Jet Jeeps. They proved to be rugged and durable vehicles with a top speed of 80 mph (130 km/h) and a ceiling of 7,000 feet (2,100 m). 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. 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 ramjets was suggested but never undertaken; however, the Hiller YH-32 Hornet helicopter was built using blade tip ramjets. [2]
Data fromThe Illustrated Encyclopedia of Helicopters [7]
General characteristics
Performance
Aircraft of comparable role, configuration, and era
Related lists
The Bell UH-1 Iroquois is a utility military helicopter designed and produced by the American aerospace company Bell Helicopter. It is the first member of the prolific Huey family, as well as the first turbine-powered helicopter in service with the United States military.
A pulsejet engine is a type of jet engine in which combustion occurs in pulses. A pulsejet engine can be made with few or no moving parts, and is capable of running statically. The best known example is the Argus As 109-014 used to propel Nazi Germany's V-1 flying bomb.
The Sikorsky H-19 Chickasaw is a multi-purpose piston-engined helicopter that was used by the United States Army and United States Air Force. It was also license-built by Westland Aircraft as the Westland Whirlwind in the United Kingdom. United States Navy and United States Coast Guard models were designated HO4S, while those of the U.S. Marine Corps were designated HRS. In 1962, the U.S. Navy, U.S. Coast Guard and U.S. Marine Corps versions were all redesignated as H-19s like their U.S. Army and U.S. Air Force counterparts.
The Piasecki H-21 Workhorse/Shawnee is an American helicopter, the fourth of a line of tandem rotor helicopters designed and built by Piasecki Helicopter. Commonly called "the flying banana", it was a multi-mission helicopter, capable of being fitted with wheels, skis or floats.
The Hiller YH-32 Hornet was an American 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 ramjet engines mounted on the rotor blade tips which weigh 13 lb (5.9 kg) each and deliver an equivalent of 45 hp (34 kW) for a total of 90 hp (67 kW). Versions of the HJ-1 Hornet were built for the United States Army and the United States Navy in the early 1950s.
The Kaman HH-43 Huskie is a helicopter developed and produced by the American rotorcraft manufacturer Kaman Aircraft. It is perhaps most distinctive for its use of twin intermeshing rotors, having been largely designed by the German aeronautical engineer Anton Flettner.
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 requiring the presence of a tail rotor. Some simple monocopters are composed of nothing but a single blade with a tip rocket.
The Sikorsky S-69 is an American experimental compound helicopter developed by Sikorsky Aircraft as the demonstrator of the co-axial Advancing Blade Concept (ABC) with United States Army and NASA funding.
The Bell R-12 was an American 1940s military utility helicopter built by the Bell Helicopter company. The design did not go into full production, but over a dozen prototypes were used for various tests and projects.
The Bell Model 201 was created using a modified Model 47G and was the first Bell helicopter to use a turbine engine.
The NHI H-3 Kolibrie was a small helicopter developed in the Netherlands in the 1950s by Nederlandse Helikopter Industrie. It first flew in May 1956.
The McDonnell XV-1 is an experimental Convertiplane developed by McDonnell Aircraft for a joint research program between the United States Air Force and the United States Army to explore technologies to develop an aircraft that could take off and land like a helicopter but fly at faster airspeeds, similar to a conventional airplane. The XV-1 would reach a speed of 200 mph, faster than any previous rotorcraft, but the program was terminated due to the tip-jet noise and complexity of the technology which gave only a modest gain in performance.
The Sud-Ouest SO.1221 Djinn is a French two-seat light helicopter designed and manufactured by aircraft manufacturer Sud-Ouest (SNCASO), which was later merged into Sud Aviation. It was the first production French helicopter, as well as being one of the first practical European helicopters to be produced. The Djinn was also the first rotorcraft to harness tip-jet propulsion to enter production, and the first production turbine powered helicopter.
The Sikorsky S-52 is a utility helicopter developed by Sikorsky Aircraft in the late 1940s. It was used by the U.S. Navy, Marine Corps, and Coast Guard. The S-52 was the first US helicopter with all-metal rotor blades. Initially a two-seater, it was developed into the four-seat S-52-2 and S-52-3. It was designated HO5S-1 by the U.S. Navy and Marine Corps, HO5S-1G by the Coast Guard, and YH-18A by the U.S. Army, and was used extensively by civil operators after being retired by the military.
The Piasecki H-16 Transporter was a tandem-rotor transport or rescue helicopter designed by Frank Piasecki and built by Piasecki Helicopter. The prototypes were evaluated by the United States Air Force and Army, but the crash of the second test aircraft led to cancelling the project.
The Doblhoff/WNF 342 was an early experimental tip jet helicopter designed and produced by Wiener-Neustädter Flugzeugwerke. It was the first helicopter to take off and land using tip jets to drive the rotor.
The Bell XH-15 was an American two-seat utility helicopter designed and built by Bell Helicopter, to meet a requirement for a liaison and utility helicopter for the United States Army and United States Air Force.
The McDonnell XH-20 Little Henry was a 1940s American experimental lightweight helicopter designed and built by McDonnell Aircraft.
The Dornier Do 32E was a simple, collapsible one-man helicopter, designed for military use in Germany in the 1960s. Despite initial hopes of large orders and some proposed civilian roles, only three flew.
The McDonnell 120 Flying Crane, also V-1 Jeep, was a lightweight utility flying crane helicopter designed and built by the McDonnell Aircraft Corporation during the 1950s. The open frame fuselage supported the three gas-producers and main rotor mast, with a small single-seat cockpit in the nose, which was originally open, but later enclosed.