Tag Archives: Helicopter

6 May 1941

Igor Sikorsky with his VS-300A, Stratford, Connecticut, 6 May 1941. (Sikorsky Archives)
Igor Ivanovich Sikorsky 1888–1970. Sikorsky Archives)
Igor Ivanovich Sikorsky 1889–1972. (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.

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

© 2018, Bryan R. Swopes

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4 May 1924

Étienne Edmond Oehmichen, France, 1924
Étienne Edmond Oehmichen, France, 1924

At Valentigny, France, Étienne Edmond Oehmichen (1884–1955), an engineer for Peugeot, flew his tandem rotor L’hélicoptère Nº2 around a triangular closed circuit of approximately 1 kilometer (0.62 mile). The flight took 7 minutes, 40 seconds. It was observed by the public, members of the press and officials of the French air ministry. For his accomplishment, Oehmichen was awarded a prize of ₣90,000 by the government of France.

FLIGHT reported:

A Fresh Helicopter Record

     M. Oemichen has been continuing his experiments at Valentigny with his helicopter, and on Sunday, May 4, established a record for helicopters by accomplished a flight of more than one kilometre—1,100 yards—in a closed circuit. The flight lasted 7 mins. 40 secs. and during most of the time the machine maintained a height of about 3 feet, but sometimes rose to 10 feet. The flight was officially observed by a representative of the Department of Military Aeronautics. By this performance M. Oemichen wins an award of 90,000 francs given by the French Government.

FLIGHT, The Aircraft Engineer & Airships, No. 802 (No. 19, Vol. XVI.) May 8, 1924, Page 267, Column 1

Helicopter No. 2
Oehmichen’s helicopter. (Collection Phillipe Boulay)

The previous month, Oehmichen had set two FAI world rotorcraft records for distance in a straight line. On 14 April 1924, he flew 360 meters (1,181 feet)¹, and on 17 April, 525 meters (1,722 feet).²

On 14 September 1924, he would set two records for altitude, 1 meter (3.28 feet) with a 100 kilogram (220 pounds) and a 200 kilogram (441 pounds) payload.³

L'hélicoptère No. 2
One of the configurations of Oemichen’s helicopter.

Oehmichen’s helicopter (also referred to by some sources as the Peugeot Nº2) was a cross-shaped structure built of metal tubing. Lift was generated by two counter-rotating, two-bladed, main rotors. Five smaller rotors with reversible pitch were used to provide lateral control. Two pusher propellers gave the aircraft forward thrust and it was steered by another small rotor at the front.

L’hélicoptère Nº2 was powered by a single Société des Moteurs Gnome et Rhône Type R nine-cylinder rotary engine placed vertically near the center of the structure.

Le Rhône Type R (hydroretro)

The Le Rhône Type R, introduced in 1917, was an air-cooled, normally-aspirated, 15.892 liter (969.786 cubic inches) nine-cylinder overhead valve rotary engine with two valves per cylinder. The Type R produced 170 cheval vapeur (167.7 horsepower) at 1,360 r.p.m. The engine was 0.990 meters (3 feet, 2.9 inches) long, 0.995 meters (3 feet, 3.2 inches) in diameter, and weighed 166 kilograms (366 pounds).

Étienne Oehmichen's Helicopter No. 2
Étienne Oehmichen’s Helicopter No. 2

A technical description of the helicopter has proven elusive. Dimensions, weight, rotor diameters and rotating speeds are unknown.

¹ FAI Record File Number 13093

² FAI Record File Number 13095

³ FAI Record Files 13091 (100 kilograms) and 13092 (200 kilograms)

© 2018, Bryan R. Swopes

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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 on 17 April, he had the aircraft fitted with three inflatable pontoons and 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.

© 2017, Bryan R. Swopes

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11 April 1952

Piasecki YH-21-PH Work-Horse 50-1231, first flight at Morton Grove, PA. (San Diego Air and Space Museum Archives)
Piasecki YH-21-PH Work-Horse 50-1231, first flight at Morton Grove, PA. (San Diego Air and Space Museum Archives)

11 April 1952: At the Piasecki Helicopter Corporation factory at Morton Grove, Pennsylvania, the first YH-21 tandem-rotor helicopter, serial number 50-1231, made it’s first flight. The test pilots were Leonard Joseph (“Len”) LaVassar and Martin P. (“Marty”) Johnson, both former U.S. Navy aviators.

The Piasecki Helicopter Corporation built 18 pre-production YH-21-PH helicopters, followed by three production variants, the H-21A, H-21B and H-21C.

The U.S. Air Force immediately ordered 32 H-21A helicopters for Search and Rescue operations. The Workhorse was well suited to cold weather operations and it was widely used in Alaska, Canada, and the Antarctic. Another 163 H-21B models were ordered as a troop transports. The U.S. Army ordered a similar H-21C variant.

Piasecki YH-21, left profile.
Piasecki YH-21 Work Horse 50-1231, with rotors turning.

The H-21 was normally operated by two pilots, with a flight mechanic (crew chief), and could carry up to 20 soldiers under ideal conditions. With rotors turning, the ship’s overall length was 86 feet, 4 inches (26.314 meters). The fuselage was 52 feet, 7 inches (16.027 meters) long, and it was 15 feet, 9 inches (4.801 meters) high. Each three-bladed rotor had a diameter of 44 feet, 0 inches (13.411 meters). The angle in the fuselage was intended to provide adequate vertical clearance between the intermeshing fore and aft rotor assemblies. (Later tandem rotor helicopters use raised pylons.) The H-21C had an empty weight was 8,950 pounds (4,060 kilograms) and maximum takeoff weight was 15,200 pounds (6,895 kilograms).

The H-21 was powered by a single air-cooled, supercharged, 1,823.129-cubic-inch-displacement (29.875 liter) Wright Aeronautical Division Cyclone 9 863C9WD1 (R-1820-103) nine-cylinder radial, mounted inside the fuselage at midship, and drove the front and rear rotors in opposite directions through drive shafts and gear boxes.

Piasecki H-21B Workhorse 51-3433 at Elmendorf Air Force Base, Alaska, circa 1960. (U.S. Air Force)

The forward rotor turned counter-clockwise, as seen from above. (The advancing blade is on the helicopter’s right side.) The rear rotor turns the opposite direction. Normal operating speed for the main rotors was approximately 250 r.p.m. The counter-rotating rotors cancelled out engine torque, eliminating any need for a tail rotor. The angle in the fuselage was intended to provide adequate vertical clearance between the intermeshing fore and aft rotor assemblies. (Later tandem rotor helicopters use raised pylons.)

Piasecki HH-21B 51-15855 supported X-15 flight operations at Edwards Air Force Base. (NASA)

The Wright R-1820-103 engine was rated at 1,275 horsepower at 2,500 r.p.m., and 1,425 horsepower at 2,700 r.p.m., for takeoff. This direct-drive engine had a compression ratio of 6.80:1 and required 100/130 aviation gasoline. The engine was 4 feet, 0.50 inches (1.232 meters) long, 4 feet, 6.95 inches (1.396 meters) in diameter, and weighed 1,350 pounds (612 kilograms). Wright built 971 R-1820-103s from November 1950 through 1957.

The CH-21C had a maximum speed of 127 miles per hour (204 kilometers per hour) and a range of 265 miles (427 kilometers). Its service ceiling was 19,200 feet (5,852 meters).

In 1955, Piasecki became Vertol and eventually Boeing Vertol. The company would continue to produce tandem rotor helicopters such as the H-46 Sea Knight and the CH-47 Chinook, which is still in production.

Piasecki CH-21B Workhorse, 51-15857, at the National Museum of the United States Air Force. (U.S. Air Force)
Piasecki CH-21B Workhorse, 51-15857, at the National Museum of the United States Air Force. (U.S. Air Force)

© 2018, Bryan R. Swopes

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11 March–6 April 1949

Lieutenant Stewart R. Graham, USCG, in cockpit of Sikorsky HNS-1 near Gander, Newfoundland, September 1946. (U.S. Coast Guard)
Lieutenant Stewart R. Graham, USCG, in cockpit of Sikorsky HNS-1 near Gander, Newfoundland, September 1946. (U.S. Coast Guard)

April 6, 1949: Lieutenant Stewart Ross Graham, United States Coast Guard, and his crewman, Aviation Metalsmith 2nd Class (AM2) Robert McAuliffe, completed the longest unescorted helicopter flight on record. They flew a Sikorsky HO3S-1G, serial number 51-234, from the Coast Guard Air Station, Elizabeth, New Jersey, to Coast Guard Air Station Port Angeles, Washington, via San Diego, California, covering a distance of 3,750 miles (6,035 kilometers) in 57.6 flight hours over 11 days.

Lieutenant Graham was the first pilot to fly a helicopter from a ship. On 16 January 1944, he flew a Sikorsky YR-4B, serial number 46445, from the deck of a British freighter, SS Daghestan, while in convoy from New York to Liverpool. After 30 minutes, he returned to the freighter. He was a pioneer in the use of the helicopter by the Coast Guard and the Navy.

U.S. Coast Guard Sikorsky HO3S-1G 51-232. (U.S. Coast Guard)
U.S. Coast Guard Sikorsky HO3S-1G 51-232, sister ship of 51-234. (U.S. Coast Guard)

The HO3S (Sikorsky S-51) was a second-generation helicopter, capable of carrying a pilot and up to three passengers. The cabin was built of aluminum with Plexiglas windows. The fuselage was built of plastic-impregnated plywood, and the tail boom was wood monocoque construction.

The main rotor consisted of three fully-articulated blades built of metal spars and plywood ribs and covered with two layers of fabric. (All metal blades soon became available.) The three bladed semi-articulated tail rotor was built of laminated wood. The main rotor turned counter-clockwise, as seen from above. (The advancing blade is on the helicopter’s right.) The tail rotor was mounted on the helicopter’s left side in a pusher configuration. It turned clockwise as seen from the helicopter’s left.

The helicopter’s fuselage was 41 feet, 7.5 inches (12.687 meters). The main rotor had a diameter of 48 feet (14.630 meters) and tail rotor diameter was 8 feet, 5 inches (2.2.565 meters) giving the helicopter an overall length of 57 feet, 1 inch (17.399 meters). It was 13 feet, 1.5 inches (4.001 meters) high. The landing gear tread was 12 feet (3.7 meters).

The S-51 had an empty weight of 4,050 pounds (1,837.05 kilograms) and maximum takeoff weight of 5,500 pounds (2,494.76 kilograms). Fuel capacity was 100 gallons (378.5 liters).

The helicopter was powered by an air-cooled, supercharged, 986.749-cubic-inch-displacement (16.170 liter) Pratt & Whitney R-985 AN-5 (Wasp Jr. T1B4) direct-drive,  nine-cylinder radial engine which was placed vertically in the fuselage behind the crew compartment. This engine had a compression ratio of 6:1 and was rated at 450 horsepower at 2,300 r.p.m., Standard Day at Sea Level. The R-985 AN-5 was 48.00 inches (1.219 meters) long, 46.25 inches (1.175 meters) in diameter and weighed 684 pounds (310.3 kilograms) with a magnesium crankcase.

The S-51 had a maximum speed (Vne) of 107 knots (123.1 miles per hour/198.2 kilometers per hour). Range was 275 miles (442.6 kilometers). The service ceiling was 14,800 feet (4,511 meters). The absolute hover ceiling was 3,000 feet (914.4 meters).

Sikorsky built 220 helicopter of the S-51 series.

U.S. Coast Guard HO3S-1G, serial number 51-238, sister ship of Lieutenant Graham’s record-setting helicopter. (USCG/Smithsonian Institution)

© 2017, Bryan R. Swopes

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