|Primary user||United States Army|
|Developed from||Sikorsky S-52|
The Sikorsky XH-39 (manufacturer designation S-59), developed by Sikorsky Aircraft in 1954, was the U.S. Army’s first turbine-powered helicopter. It was fast and innovative, but ultimately rejected by the United States Army in favor of the Bell UH-1 Iroquois.
Design and development
The four-seat XH-39 was powered by one Continental CAE XT51-T-3 400 shp (298 kW) turboshaft engine, a license-built development of the Turbomeca Artouste. It was developed from a previous Sikorsky model, the H-18 (company model S-52), and had the same layout. It differed in using retractable landing gear, modified tail rotor, and four-blade main rotor. In the end, the U.S. Army selected the Bell XH-40, prototype of the UH-1 Huey. Two YH-18As were modified into XH-39s; one for flight testing and the other for static test.
On 26 August 1954, the XH-39 set a world helicopter speed record of 156.005 mph (251 km/h) over a three kilometer closed course at Bradley Field (now Bradley International Airport) in Windsor Locks, CT. The same year, on October 17, 1954, it set an unofficial world helicopter altitude record of 24,500 ft (7,474 m) at Bridgeport, CT.
In addition to the two XH-39's, one S-59, serial number 52004, registration number N74150, was produced for use for company demonstration flights. It has been restored and is now on display at the New England Air Museum, Windsor Locks, CT 
- Former YH-18A modified for static testing, not flown and later modified back to YH-18A standard.
- Former YH-18A modified for flight testing.
Data from U.S. Army Aircraft Since 1947
- Crew: Four
- Length: 41 ft 0 in (12.50 m)
- Rotor diameter: 35 ft 0 in (10.67 m)
- Height: 9 ft 7 in (2.92 m)
- Disc area: 962 ft² (89.4 m²)
- Empty weight: 2,105 lb (957 kg)
- Loaded weight: 3,361 lb (1,528 kg)
- Powerplant: 1 × Continental CAE XT51-T-3 turboshaft, 400 shp (298 kW)
- Maximum speed: 136 knots (156 mph, 251 km/h)
- Cruise speed: 120 knots (138 mph, 222 km/h)
- Range: 243 NM (280 mi, 451 km)
- Service ceiling: 17,900 ft (5,460 m)
- Disc loading: 3.49 lb/ft² (17.1 kg/m²)
- Power/mass: 0.12 hp/lb (0.20 kW/kg)
- Related development
- Aircraft of comparable role, configuration and era
- Related lists
- Polmar and Kennedy 1981, p. 288.
- "Sets Helicopter Record." Popular Mechanics, February 1955, p. 113, bottom of page.
- Harding 1990, p. 233.
|Wikimedia Commons has media related to Sikorsky S-59.|
- "Sikorsky Model XH-39 (S-59)." at Global Security (accessed 12 May 2008)