S-59

Sikorsky S-59 N74150

Background

The Sikorsky S-59 was a highly modified S-52-2 helicopter. Modifications included the installation of a 400 hp Continental/Turbomeca, Artouste II, XT51-T-3 gas turbine engine, a fully articulated 4-bladed main rotor, and a 3-bladed tail rotor. Additional modifications included, a modified main gearbox, strengthened fuselage, incorporation of retractable, conventional configuration (tail wheel), landing gear, and updated electronics. Sikorsky modified a Company owned S-52-2 prototype and modified 2 U.S Army YH-18 helicopters to the S-59 configuration under a Government contract. The U.S. Army designation for the S-59 was XH-39. One of the U. S. Army XH-39 (Army Serial No. 49-2890) helicopters was a further modification of the YH-19B (S-52-5), which was the first installation of a gas turbine engine in a helicopter. The other was a modified YH-18A (S52-2) which was a non-flight model used for static testing.

Record setting XH-59 Serial No. 49-2890.

S-59 Development Timeline

June 1, 1954. First Flight

August 26, 1954. XH-39 Army Serial No. 49-2890, piloted by U.S. Army Warrant Officer Bill Wester, set a world speed record for a helicopter of 156.005 mph (135.6 knots, 251 km/hr.) over a 3 kilometer closed course at Bradley Field in Windsor Locks, Connecticut.

October 17, 1954. XH-39 Army Serial No. 49-2980, piloted by U.S. Army Warrant Officer Bill Wester, sets a world helicopter altitude record of 24,500 ft (7474 m.) at Bridgeport, Connecticut.

U. S. Army Warrant Officer Bill Wester and his record setting helicopter

Configuration Features

The Sikorsky S-59 design featured a “Quick Change Unit (QCU)” consisting of the engine, main gearbox, and main rotor head. It could be changed in 2 hours.

S-59 Side View

Main Rotor AssemblyA 4 blade fully articulated main rotor head was installed on the S-59 helicopter. The rotor diameter was 35 feet controlled by a hydraulic servo system.

EngineA Continental/Turbomeca, Artouste II, XT51-T-3 fixed shaft gas turbine engine was installed. This engine was a French Turbomeca designed engine manufactured in the United States under license by Continental Aviation and Engineering Corporation (CAE) in Detroit, Michigan. The engine with accessories weighed less than 250 lbs. and produced 400 shp. The engine was a fixed shaft design unlike any other turbine engine installed in Sikorsky helicopters. All succeeding turbine engines used were of the free power turbine design meaning that the rotor started turning on engine start unless restrained by a rotor brake. On the-S-59, the engine was started and when stable was connected to the main transmission with a hydro-mechanical clutch.

Main Rotor BladesThe all metal main rotor blades are made in two sections. The leading edge (spar)was made of a hollow one-piece extrusion of 61 ST aluminum alloy. The rear section (pockets) was made from thin dural sheets attached to the spar with rivets and cement held in contour by rib formers. The blades had a NACA 0012 air foil with constant cord and twisted 8 degrees. The all metal construction resulted in an extremely smooth surface and high efficiency due to a minimum of profile drag

Tail RotorThe all metal tail rotor blades were of a similar construction to the main rotor blades. The blades had a NACA 0012 air foil The 3 blade tail rotor was fully articulated.

FuselageThe fuselage was constructed of 3 sections:

Cabin and center section was monocoque, the tail cone and its mount was monocoque, and the main rotor pylon structure which was steel tube. The cabin section was the only reused component from the S-52 and that was heavily modified.

S-59(XH-39) Major Components

General Arrangement Drawing

S-59 (XH-39) 3-view Drawing

Mission Systems

The S-59(XH-39) was a single gas turbine, single main rotor type helicopter with an anti-torque tail rotor. The 4 main rotor blades were interchangeable as were the 3 tail rotor blades. All blades were of an all-metal construction. The engine was mounted horizontally above and aft of the cabin. The conventional type landing gear, two main and one tail wheel was fully retractable. The tail landing gear retracted forward and the main landing gear retracted inboard with the wheels exposed on the underside of the cabin. Litter patients were loaded through a large clam-shell type door in the cabin nose. Two large doors provided convenient entrance and loading of cargo into the cabin where ample space was provided for 3 passengers in seats or 2 litters and an

attendant.

Two Mk8 Mod 2 bomb shackles each capable of carrying 500 pounds were provided. Provisions for a wire laying dispenser for field telephone connections were provided.

Standard instruments included a vertical gyro and gyro magnetic compass. This instrumentation made the XH-39 capable of blind flying (IFR).

Heating and ventilating systems were provided in the cabin. Photos show that this included flying with the door open.

XH-39 Helicopter in flight with door open

Quickly detachable components, (a Quick Change Unit (QCU)” consisting of engine, main gearbox, and main rotor head) permitted quick overhauls by interchanging component parts and the XH-39 was air transportability in the C-82, C-119, and C-124 aircraft

General Characteristics and Performance S-59 (XH-39)

PERFORMANCEStandard Day, Sea Level at 3,361 lbs (1,528 kg) gross weight

Maximum speed (Vne) 136 kts 251 km/hrRange 243 nm 451 km

Service ceiling 23,700 ft 7,2234 mRate of Climb 2,000 ft/min 610 m/sAbsolute hover ceiling 6,800 ft 2,073 m

WEIGHTS

Maximum takeoff gross weight 3,361 lbs. 1,528 kgWeight empty 2,105 lbs. 957 kgMaximum fuel load (135 gal.) 918 lbs. 416.4 kg

GENERAL DATA

Crew seating capacity 2Seating capacity 2 passengersFuel capacity 135 US gal 511 L

POWERPLANT RATINGSStandard Day at Sea Level

Continental/Turbomeca Artouste II (XT-51-T-3) 400 hp 298 kw

AIRCRAFT DIMENSIONS

Main rotor diameter (blade tip circle) 35’ 0” 10.67 mTail rotor diameter (blade tip circle) 3' 2" .914 mFuselage length 30’0" 9.144 mFuselage width 5' 0" 1.52 mLength over-all (including rotors) 41’9.5" 12.5 mHeight over-all 9’ 7” 2.74mMain landing gear tread 8' 0" 2.44 mCabin length 7' 7" 2.13 mCabin width 4' 6" 1.22 mCabin height 5’ 0” 1.52 m

Production History

S-59 (XH-39) production consisted of 3 helicopters, one S-59, N74150, was used for company demonstration flights and two XH-39 helicopters.

S-59 N74150 hovers at the Sikorsky Plant

One XH-39, Army Serial No.49-2891 was a static test article which never flew. The second XH-39, Army Serial No. 49-2890 was the flight test helicopter. The XH-39 was in competition with the bell XH-40. The Army chose the XH-40 which became the UH-1, Huey. The Army continued to fly the XH-39 for a few years gaining extensive data on turbine powered helicopters.

Bell XH-40 helicopter

S-59 N74150 was restored and displayed at the World’s Fair in New York in 1964. It is now in the collection at the New England Air Museum, Windsor Locks, Connecticut.

S-59 N74150 on static display at World’s Fair 1964

XH-39, Army Serial No. 42-2890, is in the collection of the U.S. Army aviation Museum at Fort Rucker, Alabama. The museum acquired this record setting helicopter in 1957. It was restored in 1986 by volunteers from the Sikorsky Support Services Incorporated (SSSI) Aircraft Maintenance Team at Fort Rucker.

XH-39 Army Serial No. 49-2890 in retirement at the Army Aviation Museum

Additional Information:

A National Archives 3:27 minute video of the Sikorsky XH-39 in flight is available on YouTube with the following description:National Archives Identifier: 67283 (B&W, Silent)XH-39 (Serial No. 92890) hovering and extending, then retracting landing gear. XH-39 take off and approach to landing. XH-39 flying about twenty feet off ground. XH-39 taking off and doing a loop. XH- 39 maneuvering in flight. XH-39 landing. XH-39 taxiing and turning right.The link is below:http://www.youtube.com/watch?v=ROjYV0wxT4U

Prepared by Vinny DevineJuly 2012