Vought-Sikorsky XR-4 41-18874 at Wright Field, Ohio, 17 May 1942. (Sikorsky Historical Archives)The Sikorsky XR-4 41-18874 at Wright Field, 17 May 1942. Left to right: E. Walsh, A. Planefisch, Igor Sikorsky, Orville Wright, R. Alex, Les Morris, B. Labensky. (Sikorsky Archives)
17 May 1942: After a 761 mile (1,224.7 kilometer) flight over five days, test pilot Charles Lester (“Les”) Morris and Igor Sikorsky arrived at Wright Field, Dayton, Ohio, to deliver the U.S. Army’s first helicopter, the Vought-Sikorsky XR-4. Morris hovered directly up to the base administration building and landed there. He and Sikorsky were greeted by a large group of people which included Lieutenant Colonel Hollingsworth Franklin (“Frank”) Gregory, the Army’s designated rotorcraft expert, and pioneer aviator Orville Wright.
From the Sikorsky factory at Stratford, Connecticut, to Wright Field, Ohio, was 761 miles (1,224.7 kilometers), direct. Because of the XR-4’s low speed and short range (weight limitations restricted the quantity of gasoline it could carry) the distance was covered in sixteen separate flights with a total flight time of 16 hours, 10 minutes. The longest single flight lasted 1 hour, 50 minutes, a new world’s record for helicopter flight endurance. Igor Sikorsky joined Les Morris for the final leg of the flight.
Sikorsky test pilot Charles Lester (“Les”) Morris in the cockpit of an earlier version of the Vought-Sikorsky VS-300. (Hans Groenhoff Photographic Collection, Smithsonian Institution National Air and Space Museum NASM-HGC-1408)
The Vought-Sikorsky VS-316A (which was designated XR-4 by the U.S. Army Air Corps and assigned serial number 41-18874), established the single main rotor/anti-torque tail rotor configuration. It was a two-place helicopter with side-by-side seating and dual flight controls. The fabric-covered three-blade main rotor was 38 feet (11.582 meters) in diameter and turned counter-clockwise as seen from above. (The advancing blade is on the helicopter’s right). The three-blade tail rotor was mounted to the right of the tail boom in a tractor configuration, and rotated clockwise when seen from the helicopter’s left side. (The advancing blade was below the axis of rotation.)
The XR-4 was 33 feet, 11.5 inches (10.351 meters) long and 12 feet, 5 inches (3.785 meters) high. It weighed 2,010 pounds (911.7 kilograms) empty and the maximum gross weight was 2,540 pounds (1,152.1 kilograms).
The VS-316A had originally been powered by a 499.8-cubic-inch-displacement (8.19 liter) air-cooled Warner Aircraft Corporation Scarab SS-50 (R-500-1) seven-cylinder radial engine, rated at 145 horsepower at 2,050 r.p.m. In the XR-4 configuration, the engine was upgraded to an air-cooled, direct-drive 555.298-cubic-inch-displacement (9.100 liter) Warner Super Scarab SS185 (R-550-3) seven-cylinder radial engine with a compression ration of 6.20:1. The R-550-3 was rated at 185 horsepower at 2,175 r.p.m. at Sea Level, and 200 horsepower at 2,475 r.p.m (five minute limit) for takeoff. The engine was placed backwards in the aircraft with the propeller shaft driving a short driveshaft through a clutch to a 90° gear box and the transmission. The R-550-3 weighed 344 pounds (156 kilograms).
The XR-4 was redesignated XR-4C. This would be the world’s first production helicopter. It is at the Steven F. Udvar-Hazy Center of the Smithsonian National Air and Space Museum.
Vought-Sikorsky XR-4C 41-18874 at the National Air and Space Museum. (NASM)
9 May 1962: The Sikorsky S-64 Skycrane, N325Y, prototype of a heavy-lift helicopter, made its first flight at Stratford, Connecticut. The Skycrane was a turbine-powered evolution of the piston-engined S-60. The United States Army bought six S-64s for evaluation, and then ordered 54 production aircraft, designated CH-54A Tarhe, and 35 CH-54Bs. Sikorsky produced 12 S-64E and Fs for the commercial helicopter market.
The Sikorsky CH-54A Tarhe is a large single-main-rotor/tail rotor helicopter, specifically designed to carry large external loads. In U.S. Army service, it had a crew of five: pilot, co-pilot, third pilot and two mechanics. The third pilot was in a rear-facing cockpit position and flew the helicopter while it was hovering to pick up or position an external load.
FAI record-setting Sikorsky CH-54A Tarhe (FAI)
The CH-54A is 88 feet, 5.9 inches (26.972 meters) long and 25 feet, 4.7 inches (7.739 meters) high. The main rotor has six blades and turns counter-clockwise, seen from above. (The advancing blade is on the helicopter’s right side.) The main rotor has a diameter of 72 feet (21.946 meters). The main rotor blades have a chord of 1.97 feet (0.601 meters) and incorporate a twist of -13°. The tail rotor has four blades and is placed on the left side of a vertical pylon in a pusher configuration. The tail rotor turns clockwise, as seen from the helicopter’s left side. (The advancing blade is below the axis of rotation.) The diameter of the tail rotor is 16 feet (4.877 meters). The chord of the tail rotor blade is 1.28 feet (0.390 meters).
The helicopter has an empty weight of 19,120 pounds (8,673 kilograms) a design gross weight of 38,000 pounds (17,237 kilograms) and overload gross weight of 42,000 pounds (19,051 kilograms).
The prototype S-64A Skycrane, N325Y, lifts an M-113 armored personnel carrier during a demonstration at Fort Benning, Georgia. (NASM-84-8161)
The CH-54A is powered by two Pratt & Whitney JFTD12A-4A (T73-P-1) turboshaft engines, each rated at 4,000 shaft horsepower at 9,000 r.p.m. (N2) maximum continuous power at Sea Level, and 4,500 shaft horsepower at 9,500 r.p.m. (N2) for takeoff, 5-minute limit, or 30 minutes, with one engine inoperative (OEI). The maximum gas generator speed (N1) is 16,700 r.p.m. The T73-P-1 is an axial-flow free-turbine turboshaft engine with a 9-stage compressor section, 8 combustion chambers and a 4-stage turbine section (2-stage gas generator and 2-stage free turbine). It is 107.0 inches (2.718 meters) long, 30.0 inches (0.762 meters) in diameter, and weighs 966 pounds (438 kilograms). The helicopter’s main transmission is limited to a maximum 6,600 horsepower.
It has a useful load of 22,880 pounds (10,342 kilograms) and can carry a payload of 20,000 pounds (9,072 kilograms) from a single point cargo hoist.
The CH-54A has a maximum cruise speed of 115 knots (132 miles per hour, 213 kilometers per hour). It’s range is 217 nautical miles (250 miles, 402 kilometers). The CH-54A has a hover ceiling in ground effect (HIGE) of 10,600 feet (3,231 meters) and its service ceiling is 13,000 feet (3,962 meters).
The United States Army has a tradition of using Native American names for its aircraft. Tarhe (pronounced tar-HAY) was a famous chief, or sachem, of the Wyandot People of North America, who lived from 1742–1818. He was very tall and the French settlers called him “The Crane.”
Sikorsky CH-54A Tarhe 68-18448, Nevada National Guard, 16 November 1989. (Mike Freer/Wikipedia)
N325Y, the prototype Sikorsky S-64, was damaged beyond repair in an accident near Arboletes, Columbia, 19 August 1968. The FAA registration was cancelled.
Igor Sikorsky with his VS-300A, Stratford, Connecticut, 6 May 1941. (Sikorsky Archives)
6 May 1941: At Stratford, Connecticut, Igor Sikorsky piloted his Vought-Sikorsky VS-300 helicopter to a new world’s record for endurance. He flew for 1 hour, 32 minutes, 26 seconds. ¹ The previous record—1 hour, 20 minutes, 49 seconds—had been set by Ewald Rohlfs with the Focke-Wulf Fw 61 tandem-rotor helicopter, 25 June 1937. ²
During its development, the VS-300 went through at least 18 changes in its rotor configuration. This photograph, taken after the record-setting flight, shows an intermediate version, with one main rotor for lift and three auxiliary rotors for anti-torque and directional control.
Igor Ivanovich Sikorsky 1888–1970. Sikorsky Archives)
In the final configuration, Sikorsky arrived at what we now recognize as a helicopter, with the main rotor providing lift, thrust and roll control through variable collective and cyclic pitch, and a single tail rotor for anti-torque and yaw control.
The VS-300 had a welded tubular steel airframe and used a 28-foot (5.34 meters) diameter, fully-articulated, three-bladed main rotor, which turned clockwise (as seen from above) at 260 r.p.m. (The advancing blade was on the left. This would later be reversed.) The main rotor had collective pitch control for vertical control, but cyclic pitch (Sikorsky referred to this as “sectional control”) for directional control would not be developed for another several months.
The tail “propellers” (what we now consider to be rotors—one vertical and two horizontal) each had two blades with a diameter of 7 feet, 8 inches (2.337 meters) and turned approximately 1,300 r.p.m. The vertical rotor provided “torque compensation” (anti-torque) and the blade pitch was fully reversible. The horizontal rotors were mounted on 10-foot (3.048 meters) outriggers at the aft end of the fuselage. For lateral control, the pitch on one rotor was increased and the other decreased. For longitudinal control, the pitch of both rotors was increased or decreased together.
The VS-300 was originally equipped with an air-cooled, normally-aspirated 144.489-cubic-inch-displacement (2.368 liter) Lycoming O-145C-3 four-cylinder horizontally-opposed engine which was rated at 75 horsepower at 3,100 r.p.m. According to Mr. Sikorsky, “early in 1941,” the Lycoming engine was replaced by an air-cooled, normally-aspirated 198.608 cubic inch (3.255 liter) Franklin 4AC-199-E, a four-cylinder horizontally-opposed overhead valve (OHV) direct-drive engine with a compression ratio of 7:1, rated at 90 horsepower at 2,500 r.p.m. It is not known if this change was made prior to 6 May.
¹ During World War II, only a very few ballooning and gliding world records were certified by the Fédération Aéronautique Internationale. Although Sikorsky’s flight duration exceeded that of Rohlfs, it is not listed as an official world record.
