Hiller XH-44

Hiller XH-44
Country	USA
Role	Coaxial-roto helicopter
First flight	1942-1944
Built	Unknow

Hiller Aircraft Company was founded in 1942 as Hiller Industries by Stanley Hiller to develop helicopters. Stanley Hiller, then seventeen, established the first helicopter factory on the West Coast of the United States, located in Berkeley, California, in 1942, under the name “Hiller Industries,” to develop his design for the coaxial-rotor XH-44 “Hiller-Copter” for the U.S. Army. The XH-44 became operational in 1944. In collaboration with Henry J. Kaiser, it became United Helicopters in 1945. In the postwar years, United Helicopter produced a number of innovative helicopter designs for military and civilian purposes, including coaxial-rotor and tailless designs, as well as more conventional models. In January, 1949, a Hiller 360 became the first civilian helicopter to cross the United States

Source: Hiller XH-44 on Wikipedia

Hiller XH-44 Walk Around
Photographer	Vladimir Yakubov
Localisation	Hiller Aviation Museum, San Carlos
Photos	57

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General Characteristics and Role

The Hiller XH-44 “Jet-Rotor” was an early and highly experimental American helicopter, developed by Stanley Hiller, Jr., during the 1940s. It was the first helicopter to use a unique propulsion system known as tip-jet drive, where compressed air mixed with fuel was ignited and expelled from the tips of the main rotor blades to provide thrust. The primary advantage of this “cold jet” or “hot jet” system was the elimination of the complex and heavy mechanical drivetrain and anti-torque tail rotor typically required by conventional helicopters. The XH-44 was an exceptionally simple and light aircraft for its time, and while it did successfully fly, demonstrating the tip-jet principle, the concept suffered from high fuel consumption and noise, leading to its eventual discontinuation for practical use. The XH-44 was the first helicopter produced by Hiller and helped launch the company’s career in aviation.

Property	Typical Value (XH-44 Prototype)
Role	Experimental Proof-of-Concept Helicopter
National Origin	United States
Manufacturer	Hiller Helicopters (Hiller-Copter)
First Flight	July 1944
Crew	1 (Pilot)
Rotor System	Two-bladed main rotor
Rotor Diameter (Approx.)	7.62 m (25 ft 0 in)
Length (Fuselage)	3.78 m (12 ft 5 in)
Empty Weight (Approx.)	145 kg (320 lb)
Gross Weight (Approx.)	300 kg (660 lb)

Powerplant and Propulsion

Engine: 1 x Franklin 4ACG-199 piston engine driving an air compressor (not driving the rotor directly).
Rotor Drive: Tip-jet system. The engine drove a compressor that sent compressed air through ducts in the rotor blades. Fuel was injected and ignited at the tip nozzles to generate propulsive jet thrust (a “hot cycle”).
Maximum Speed: Approximately 137 km/h (85 mph; 74 kn).
Range: Very short, due to the low fuel efficiency of the tip-jet concept.
Tail Rotor: None required. Torque reaction from the main rotor was eliminated because the thrust was applied at the blade tips, making the fuselage inherently stable in yaw.

Design Legacy

Significance: The XH-44 proved that the jet-powered rotor concept was feasible, attracting initial interest from the U.S. Navy.
Design Simplicity: The elimination of the heavy transmission, gears, and tail rotor simplified the design and reduced manufacturing complexity.
Successor: Hiller’s next and more successful designs, such as the Hiller 360, abandoned the jet-rotor in favor of a conventional mechanical drive but retained Hiller’s revolutionary use of a servocontrol paddle system for simplified control input.
Preservation: The original XH-44 prototype is preserved and on display at the Smithsonian National Air and Space Museum.