Tag Archives: Sikorsky a Lockheed Martin Company

9 May 1962

Sikorsky S-64 Skycrane N325Y, s/n 64001. (John Daniel)

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.

© 2021, Bryan R. Swopes

6 May 1941

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.

² FAI Record File Number 13147

© 2019, Bryan R. Swopes

17 April 1941

Igor Sikorsky piloting his pontoon-equipped VS-300, 17 April 1941. (Sikorsky Historical Archives)
Igor Sikorsky piloting his pontoon-equipped VS-300, 17 April 1941. (Sikorsky Historical Archives)

17 April 1941: Igor Sikorsky’s Vought-Sikorsky VS-300 helicopter went through various rotor configurations during development as he searched for a combination that would give stability, anti-torque control, as well as lateral and yaw control. By April 1941, the VS-300 was configured with a single main rotor for lift and three smaller tail rotors to provide anti-torque and directional control.

This was not the ultimate solution, but he had the aircraft fitted with three inflatable pontoons and on 17 April, made a successful water landing, demonstrating that the helicopter could be a practical amphibious aircraft. During a lecture to the Rotating Wing Section of the Tenth Annual Meeting of the Institute of Aeronautical Sciences, Igor Sikorsky gave a brief description of the flight:

Igor Ivanovich Sikorsky 1888–1970. Sikorsky Archives)
Igor Ivanovich Sikorsky (Sikorsky Archives)

“On April 17 the helicopter, mounted on rubber floats, was repeatedly taken off from water and landed on water and then landed on ground, demonstrating for the first time a direct lift aircraft with excellent amphibian characteristics on which no adjustments whatsoever are needed when going from water to land and vice versa.”

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.

Igor Sikorsky banks the VS-300 through assymetric pitch of the horizontal tail rotors. (Sikorsky Historical Archives)
Igor Sikorsky banks the VS-300 through assymetric pitch of the horizontal tail rotors. (Sikorsky Historical Archives)

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 17 April.

© 2019, Bryan R. Swopes