Sikorsky S-59 / XH-39
In late 1953 the Army awarded Sikorsky a contract for the experimental conversion of two existing H-18 helicopters from piston to turbine power. The two aircraft selected for conversion were 49-2890 and -2891, the third and fourth H-18s built, with the former to be used for flight testing and the latter for static engineering evaluation. Sikorsky allotted the two craft the company designation S-59, and began the conversion work in early 1954.
On Jul 24, 1953 the S-52T (YH-18B) turbine powered version of the S-52 was first flown. It used a French Turbomeca Artouste I engine. A developed version designated YH-18B and powered by a T51-T-3 (Artouste) turbine is now re-designated XH-39.
The H-39 retained the H-18's basic pod-and-boom layout, but differed from the earlier machine in several ways. The H-39 was powered by a single 400shp XT51-T-3 Artouste II turbine engine, which drove a new, fully-articulated, four-bladed main rotor. Other changes included a modified tail rotor, strengthening of the fuselage, incorporation of retractable wheeled landing gear, and the addition of updated electronics.
The Model XH-39 (S-59), using a 400shp Continental XT51 turbine, was rejected by the US Army, despite its speed and the advantage of retractable landing gear, as being old-fashioned in design and unsuitable for further development. Instead, the Army chose the Bell XH-40 with a Lycoming XT53 turbine.
The H-39 was the Army's first turbine-powered helicopter, and was for a time the world's fastest rotorcraft.
On 29 August 1954 Army Warrant Officer Billy Wester flew a world speed record of 156 m.p.h / 251km/h over 3km was set up by Sikorsky XH-39.
Engine: 1 x Continental/Turbomeca Artouste XT51-T-3 turboshaft, 300kW / 400 hp
Rotors: 4-blade main 3-blade tail
Main rotor diameter: 10.0m / 35 ft
Fuselage length: 11.95m / 30 ft 3 in
Max take-off weight: 1226kg / 3,560 lb
Empty weight: 749kg
Max speed: 176km/h / 156 mph
Ceiling: 24,500 ft
Hovering ceiling, IGE: 2804m
Service ceiling: 4724m
Typical range: 253 miles at 138 mph
Seats: Pilot and 3 passengers, 800 lb. cargo or 2 stretchers and attendant.