Tag Archives: Lycoming O-145-C3

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

14 September 1939

The prototype VS-300 helicopter clears the ground for the first time, 14 September 1939. Igor Sikorsky is at the controls. (Sikorsky Historical Archives)
The prototype VS-300 helicopter clears the ground for the first time, 14 September 1939. Igor Sikorsky is at the controls. His right foot rests on the anti-torque pedal. (Sikorsky Historical Archives)

14 September 1939: At Stratford, Connecticut, Igor Sikorsky made the first tethered flight of the Vought-Sikorsky VS-300 prototype helicopter. The duration of the flight was just 10 seconds but demonstrated that the helicopter could be controlled.

The Vought-Sikorsky VS-300 was the first successful single main rotor, single tail rotor helicopter.

The three-bladed main rotor had a diameter of 28 feet (8.534 meters) and turned approximately 255 r.p.m. The rotor turned clockwise as seen from above (the advancing blade is on the left). This would later be reversed. A counter-weighted single blade anti-torque rotor with a length of 3 feet, 4 inches (1.016 meters) is mounted on the left side of the monocoque beam tail boom in a pusher configuration and turns counter-clockwise as seen from the helicopter’s left (the advancing blade is above the axis of rotation).

Vought-Sikorsky VS-300 under construction, 8 September 1939. (Sikorsky Historical Archives)
Vought-Sikorsky VS-300 under construction, 8 September 1939. (Sikorsky Historical Archives)

In the initial configuration, the VS-300 was powered by an air-cooled, normally-aspirated, 144.489-cubic-inch-displacement (2.368 liter) Lycoming O-145-C3 horizontally-opposed, four-cylinder, direct-drive engine with a compression ratio of 6.5:1. It was rated at 75 horsepower at 3,100 r.p.m., using 73-octane gasoline. It was equipped with a single Stromberg carburetor and dual Scintilla magnetos. The dry weight of the O-145-C3 was 167 pounds (75.75 kilograms). Later in the VS-300’s development, the Lycoming was replaced by a 90-horsepower Franklin 4AC-199 engine.

On 19 December 1939, the VS-300 was rolled over by a gust of wind and damaged. It was rebuilt, however, and developed through a series of configurations. It made its first free (untethered) flight 13 May 1940.

Test flights continued for several years. After 102 hours, 32 minutes, 26 seconds of flight, the VS-300 was donated to the Henry Ford Museum, Dearborn, Michigan.

Igor Sikorsky adjusts is fedora while at teh controls of the VS-300. (Sikorsky Historical Archives)
Igor Sikorsky adjusts his fedora while at the controls of the VS-300. (Sikorsky Historical Archives)

© 2018, Bryan R. Swopes