Updated: Oct 23, 2021
After yesterday's trip to the 18th century, we go to a more recent date, although still nearly 70 years ago in today's look at aviation history. It was on the 23rd day of October 1952 that the first helicopter built by the Hughes Aircraft Company took to the skies for the first time! The Hughes XH-17.
The Hughes XH-17 in flight
The design of the XH 17 was based on a 1946 US Army Air Force Request for Proposal for the design of a heavy-lift helicopter. The actual design was started by the Kellett Aircraft Corporation of Upper Derby, Pennsylvania when they were awarded a design contract in May 1946. The initial designation was the XR-17. Some of the design requirements were:
External Load capable of 10.000 lbs (4536 kg)
Jet turbine propulsion
Wingtip jets on the rotors
After a stop in development due to financial issues at Kellet, the US Air Force allowed Hughes to purchase the project of Kellet and continue development. In March 1949 development was resumed, with the aircraft designation changed to XH-17.
The XH-17 was an assembly of components and sections of a collection of aircraft;
Front wheels were the main wheels of a North American B-25 Mitchell
Aft wheels were the main wheels of a Douglas C-54 Skymaster
The fuel tank was a bomb bay fuel tank from a Boeing B-29 Superfortress
The cockpit was from a Waco CG-15 glider
The tail rotor was from a Sikorsky H-19 Chickasaw
The first flight was the start of a three-year test flight and development program out of Culver City California, USA with the one aircraft built. During one of these flights, it lifted off with a gross weight in excess of 50.000 lbs (23.000 kg). The huge track of the aircraft allowed it to position over the cargo or have cargo positioned underneath the aircraft. Development was discontinued due to the aircraft inefficiency (it only had a range of 35 nm (64 km) and it was impracticable in size.
The propulsion system was something unique. It consisted of two General Electric J35 turbojet engines. They provided partial thrust. They also provided bleed air that was sent up through the rotor mast into the hollow blades.
At the tips, the blades were equipped with jets where fuel was mixed with the bleed air and ignition took place driving the rotors. This drove the rotors to a very low rotational speed, only 88 rpm.
This highly inefficient method of propulsion was the reason for the very short range although it had a fuel capacity of 635 US Gal (2400 liters).
Note the jets on the trailing edge of the rotor
A nice website with extensive development information on this unique aircraft can be found by clicking here. Specifications for the XH-17;
Crew: 3 (pilot, mechanic and in-flight test engineer)
Capacity: demonstrated loads up to 10,284 lb (4,665 kg) were carried
Length: 53 ft 3.6 in (16.246 m)
Height: 30 ft 1.2 in (9.174 m)
Empty weight: 28,562 lb (12,956 kg)
Gross weight: 31,270 lb (14,184 kg)
Max takeoff weight: 43,500 lb (19,731 kg)
Fuel capacity: 635 US gal (529 imp gal; 2,404 l)
Powerplant: 2 × General Electric 7E-TG-180-XR-17A gas generators, 3,480 hp (2,600 kW) each combined predicted gas power output, with the rotor turning at 88 rpm.
Main rotor diameter: 130 ft (40 m)
Main rotor area: 13,274.95 sq ft (1,233.283 m2)
Maximum speed: 90 mph (140 km/h, 78 kn) at 8,000 ft (2,438 m)
Cruise speed: 85 mph (137 km/h, 74 kn)
Range: 30 mi (48 km, 26 nmi) with 10,284 lb (4,665 kg) payload
Service ceiling: 13,100 ft (4,000 m)
Rate of climb: 1,650 ft/min (8.4 m/s)