Tag Archives: Pratt & Whitney Twin Wasp S1C3-G

30 June 1975

The last operational U.S. Air Force C-47 Skytrain, 43-49507, on display at NMUSAF. (U.S. Air Force)

30 June 1975: The last operational Douglas C-47 Skytrain transport in service with the United States Air Force, 43-49507, was retired and flown to the National Museum of the United States Air Force at Wright-Patterson Air Force Base, Ohio.

A C-47D, it is on display in the World War II Gallery, painted and marked as C-47A-80-DL 43-15213 of the 91st Troop Carrier Squadron, 439th Troop Carrier Group, during World War II. At the time it was withdrawn from service, 43-49507 had flown a total of 20,831 hours.

43-49507 (Douglas serial number 26768) was built at Oklahoma City as a C-47B-15-DK Skytrain. The C-47B differed from the C-47A in that it was powered by Pratt & Whitney Twin Wasp S3C4-G (R-1830-90) engines. These engines were equipped with two-speed superchargers for improved high-altitude performance. Following World War II, the second speed (“high blower”) was either disabled or removed. Following this modification, the airplane was redesignated C-47D.

A group of new Douglas C-47 Skytrains. The airplane closest to the camera is C-47-DL 41-18415. (Douglas Aircraft Company)

The Douglas C-47 Skytrain is a military transport variant of the Douglas Aircraft Company DC-3 commercial airliner. It is an all-metal, twin-engine, low-wing monoplane with retractable landing gear. It was operated by a minimum flight crew of two pilots, navigator, radio operator and mechanic/load master. The airplane’s control surfaces are covered with doped-fabric. The primary differences between the civil DC-3 and military C-47 was the addition of a cargo door on the left side of the fuselage, a strengthened cargo floor, a navigator’s astrodome and provisions for glider towing.

The DC-3 made its first flight 17 December 1935, while the C-47 flew for the first time six years later, 23 December 1941.

Two Douglas C-47 Skytrains. Nearest the camera is C-47A-90-DL 43-15661. The further airplane is C-47A-65-DL 42-100550. (U.S. Air Force)

The C-47 is 64 feet, 5½ inches (19.647 meters) long with a wingspan of 95 feet (28.956 meters) and height of 17 feet (5.182 meters). The total wing area is 988.9 square feet (91.872 square meters). The angle of incidence is 2°. The wing center section is straight, but outboard of the engine nacelles there is 5º dihedral. The wings’ leading edges are swept aft 15.5°. The trailing edges have no sweep.  Empty weight of the C-47D is 17,865 pounds (8,103 kilograms) and the maximum takeoff weight is 33,000 pounds (14,969 kilograms).

The C-47A was powered by two 1,829.4-cubic-inch-displacement (29.978 liter) air-cooled, supercharged R-1830-92 (Pratt & Whitney Twin Wasp S1C3-G) two-row 14-cylinder radial engines with a compression ratio of 6.7:1. These were rated at 1,060 horsepower at 2,550 r.pm., up to 7,500 feet (2,286 meters), maximum continuous power, and 1,200 horsepower at 2,700 r.p.m. at Sea Level for takeoff. Each engine drives a three-bladed Hamilton Standard Hydromatic constant-speed full-feathering propeller with a diameter of 11 feet, 6 inches (3.505 meters) through a 16:9 gear reduction. The R-1830-92 is 48.19 inches (1.224 meters) long, 61.67 inches (1.566 meters) in diameter, and weighs 1,465 pounds (665 kilograms).

U.S. Army paratroopers jump from Douglas C-47-DL Skytrain 41-7805, over England, May 1944. (U.S. Air Force)

The specifications of the  Pratt & Whitney Twin Wasp S3C4-G (R-1830-90) installed on the C-47B and C-47D were nearly the same as the -92 engine of the C-47A. Displacement and compression ratio were identical. The engines’ diameters were the same, though the -90 was very slightly longer than the -92—1.85–2.74 inches (4.699–6.960 centimeters), depending on specific variant. Also, the -90 was heavier than the -92 by 25–30 pounds (11.34–13.61 kilograms), again, depending on the specific variant. The R-1830-90 could maintain 1,000 horsepower at 2,550 r.p.m. at 12,500 feet (3,810 meters), and 1,000 horsepower at 2,700 r.p.m. at 14,000 feet (4,267 meters), a significant increase over the -92.

The C-47D has a cruising speed of 161 knots (185 miles per hour/298 kilometers per hour) at 10,000 feet (3,048 meters), and maximum speed of 202 knots (232 miles per hour/374 kilometers per hour) at 3,500 feet (1,067 meters). Its service ceiling was 22,150 feet (6,751 meters). The Skytrain had a maximum range of 1,026 nautical miles (1,181 miles/1,900 kilometers) with full cargo.

The C-47 could carry 9,485 pounds (4,302 kilograms) of cargo, or 27 fully-equipped paratroopers. Alternatively, 24 patients on stretchers could be carried, along with two attendants.

C-47 Skytrains in Vee-of Vees formation.

On D-Day, The Sixth of June, 1944, a formation of C-47 Skytrains, nine airplanes abreast, 100 feet (30 meters) from wing tip to wing tip, 1,000 feet (305 meters) in trail, stretching for over 300 miles (483 kilometers), airdropped 13,348 paratroopers of the 82nd and 101st Airborne Divisions, United States Army, and another 7,900 men of the British Army 6th Airborne Division and the 1st Canadian Parachute Battalion, behind the beaches at Normandy, France.

During the Vietnam War, 53 C-47s were converted from their transport role to AC-47 Spooky gunships. These were armed with three fixed, electrically-powered General Electric  GAU-2/A .30-caliber (7.62 NATO) Gatling guns firing out the left side of the fuselage. These aircraft were highly effective at providing close air support. The three Miniguns could fire a total of 12,000 rounds per minute.

Douglas AC-47D Spooky gunship, 45-0927, 4th Special Operations Squadron, Nha Trang, Republic of Vietnam, September 1968. (U.S. Air Force)

Douglas Aircraft Company built 10,174 C-47 Skytrains at its factories in Santa Monica and Long Beach, California, and at Oklahoma City, Oklahoma.

Douglas DC-3 (C-47B) three-view drawing. (NASA)

© 2018, Bryan R. Swopes

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3 May 1952

LCOL William P. Benedict and LCOL Joseph O. Fletcher in cockpit of C-47 enroute the North Pole, 3 May 1952.

3 May 1952: A ski-equipped United States Air Force Douglas C-47A Skytrain, piloted by Lieutenant Colonels William P. Benedict and Joseph O. Fletcher, USAF, was the first airplane to land at the North Pole.¹ The navigator was 1st Lieutenant Herbert Thompson. Staff Sergeant Harold Turner was the flight engineer and Airman 1st Class Robert L. Wishard, the radio operator.

Also on board was Arctic research scientist Dr. Albert P. Crary and his assistant, Robert Cotell. Additional personnel were Fritza Ahl, Master Sergeant Edison T. Blair and Airman 2nd Class David R. Dobson.

Colonel Fletcher was commanding officer of the 58th Strategic Reconnaissance Squadron, Eielson Air Force Base, Fairbanks, Alaska. He was responsible for establishing Drift Ice Stations within the polar ice cap for remote weather observation bases. Ice Island T-3 was renamed Fletcher’s Ice Island in his honor. He became a world authority on Arctic weather and climate. Various geographic features, such as the Fletcher Abyssal Plain in the Arctic Ocean, and the Fletcher Ice Rise in the Antarctic are also named for him.

Crew and passengers of the C-47 at T-3, 3 May 1951 (fly.historicwings.com)
Crew and passengers of the C-47A Skytrain, 43-15665, at The North Pole, 3 May 1952. (A2C David R. Dobson, United States Air Force, via fly.historicwings.com)

The airplane flown on this expedition was Douglas C-47A-90-DL Skytrain 43-15665.

The Douglas C-47 in the photograph below is similar to the Skytrain that Benedict and Fletcher landed at the North Pole, however it is a screen image from the RKO/Winchester Pictures Corporation motion picture, “The Thing from Another World,” which was released just one year earlier, 29 April 1951. Howard Hawks’ classic science fiction film involves an Air Force C-47 Skytrain crew that flies in support of a remote Arctic research station.

Screen Image of a ski-equipped Douglas C-47 Skytrain, “Tropical Tilly.” (RKO Pictures)

The Douglas C-47A Skytrain is an all-metal twin-engine, low wing monoplane transport with retractable landing gear. It was operated by a minimum flight crew of two pilots, a navigator and a radio operator. The wing is fully cantilevered and the fuselage is of semi-monocoque construction. Control surfaces are fabric-covered.

The C-47 is 64 feet, 5½ inches (19.647 meters) long with a wingspan of 95 feet (28.956 meters) and height of 17 feet (5.182 meters). Empty weight of the C-47A is 17,257 pounds (7,828 kilograms) and the maximum takeoff weight is 29,300 pounds (13,290 kilograms).²

The C-47A is powered by two 1,829.4-cubic-inch-displacement (29.978 liter) air-cooled, supercharged R-1830-92 (Pratt & Whitney Twin Wasp S1C3-G) two-row 14-cylinder radial engines. These were rated at 1,200 horsepower at 2,700 r.p.m. at Sea Level for takeoff. The maximum continuous rating for normal operation was 1,060 horsepower at 2,550 r.pm., up to 7,500 feet (2,286 meters). Each engine drives a three-bladed Hamilton Standard Hydromatic constant-speed full-feathering propeller with a diameter of 11 feet, 6 inches (3.505 meters) through a 16:9 gear reduction. The R-1830-92 is 48.19 inches (1.224 meters) long, 61.67 inches (1.566 meters) in diameter, and weighs 1,465 pounds (665 kilograms).

The C-47 has a cruising speed of 185 miles per hour (298 kilometers per hour) at 10,000 feet (3,048 meters) and service ceiling of 24,100 feet (7,346 meters).

The C-47-DL could carry 6,000 pounds (2,722 kilograms) of cargo, or 28 fully-equipped paratroopers. Alternatively, 14 patients on stretchers could be carried, along with three attendants.

43-15665 crashed on Fletcher’s Ice island 3 November 1952. It has since sunk to the floor of the Arctic Ocean.

Derelict C-47A 43-15665 at T-3, Fletcher's ice Island.
Derelict C-47A 43-15665 at T-3, Fletcher’s Ice Island.

¹ At least one source states that a Soviet expedition aboard three Lisunov Li-2 transports (a license-built Douglas DC-3) landed near the North Pole on 23 April 1948.

² Data from AAF Manual 51-129-2, Pilot Training Manual for the C-47 Skytrain

© 2019, Bryan R. Swopes

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31 December 1985

Eric Hilliard Nelson (8 May 1940–31 December 1985) (Guy Webster)

31 December 1985: At 5:14 p.m., Central Standard Time, a Douglas DC-3C, N711Y,¹ crash-landed in a field near DeKalb, Texas. The airplane struck a wire and several trees and was extensively damaged. The airplane, already on fire, was completely destroyed.

The pilot and co-pilot escaped through cockpit windows, but all seven passengers, including singer Rick Nelson, died.

N711Y was a Douglas C-47A-25-DK Skytrain twin-engine military transport, serial number 42-108981, built at the Midwest City Douglas Aircraft Company Plant, Oklahoma City, Oklahoma, circa 1943–1944. Following U.S. military service, the transport was operated in Brazil. The Skytrain had been converted to a civil DC-3C in 1959, and registered N136H. At one time the airplane had been owned by the DuPont family, and later by singer Jerry Lee Lewis. It was registered to the Century Equipment Co., Los Angeles, California, 13 March 1981.

Rick Nelson's Douglas DC-3C, N711Y. © Thomas P. McManus
Rick Nelson’s Douglas DC-3C, N711Y. (Thomas P. McManus via lostflights)

At 5:08 p.m., the pilot informed Air Traffic Control  that he had a problem and was going to divert from the intended destination of Dallas, Texas, to Texarkana. At 5:11 p.m., ATC received a call from N711Y saying that there was smoke in the cockpit. At 5:12 p.m., it was seen on radar at an altitude of 600 feet (183 meters). The airplane disappeared from radar at 5:14 p.m.

Witnesses reported seeing the airplane descending in a left turn to line up with a farm field. It was trailing smoke. Small pieces of metal fell off which started several small fires. The DC-3 struck two power wires suspended about 30 feet (9 meters) above the ground, then a utility pole and several trees.

The pilot and co-pilot, who were both severely burned, gave differing statements as to what had occurred. The National Transportation Safety Board investigation found that there had been an in-flight fire in the passenger cabin which had probably started in the on-board cabin heater. The board concluded that the pilot in command did not follow proper procedures or check lists.

Burned-out wreckage of Douglas DC-3C N711Y. (Unattributed)

The Douglas C-47 Skytrain is an all-metal twin-engine, low wing monoplane transport with retractable landing gear. It was operated by a minimum flight crew of two pilots, a navigator and a radio operator. The wing is fully cantilevered and the fuselage is of semi-monocoque construction. Control surfaces are fabric-covered. The C-47A variant used a 24-volt electrical system.

The C-47 is 64 feet, 5½ inches (19.647 meters) long with a wingspan of 95 feet (28.956 meters) and height of 17 feet (5.182 meters). The wing center section is straight, but outboard of the engine nacelles there is 5º dihedral. The wings’ leading edges are swept aft 15.5°. The trailing edges have no sweep. Empty weight of the C-47A is 17,257 pounds (7,828 kilograms) and the maximum takeoff weight is 29,300 pounds (13,290 kilograms).

The C-47 is powered by two 1,829.4-cubic-inch-displacement (29.978 liter) air-cooled, supercharged R-1830-92 (Pratt & Whitney Twin Wasp S1C3-G) two-row 14-cylinder radial engines. These had a maximum continuous rating for normal operation was 1,060 horsepower at 2,550 r.pm., up to 7,500 feet (2,286 meters), and 1,200 horsepower at 2,700 r.p.m., at Sea Level, for takeoff. Each engine drives a three-bladed Hamilton Standard Hydromatic constant-speed full-feathering propeller with a diameter of 11 feet, 6 inches (3.505 meters) through a 16:9 gear reduction. The R-1830-92 is 48.19 inches (1.224 meters) long, 61.67 inches (1.566 meters) in diameter, and weighs 1,465 pounds (665 kilograms). (N711Y had been re-engined with Pratt & Whitney R-1830-75 engines, rated at 1,350 horsepower at 2,800 r.p.m.)

The C-47 has a cruising speed of 185 miles per hour (298 kilometers per hour) at 10,000 feet (3,048 meters) and service ceiling of 24,100 feet (7,346 meters).

The C-47 could carry 6,000 pounds (2,722 kilograms) of cargo, or 28 fully-equipped paratroopers. Alternatively, 14 patients on stretchers could be carried, along with three attendants.

The C-47A served with the United States Air Force until 1971. Hundreds of C-47s and DC-3s are still operational, worldwide.

Crash site of Douglas DC-3C N711Y, near DeKalb, Texas. (Unattributed)
Crash site of Douglas DC-3C N711Y, near DeKalb, Texas. (Unattributed)

¹ N711Y was  registered to Century Equipment, Inc., Los Angeles, California. The airplane was sold to Rick Nelson on 2 May 1985, but was never re-registered.

© 2018, Bryan R. Swopes

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23 December 1941

A group of new Douglas C-47 Skytrains. The airplane closest to the camera is C-47-DL 41-18415. (Douglas Aircraft Company)

23 December 1941: Although hundreds of Douglas DC-3 commercial transports had been impressed into military service directly from the production line and designated C-48, C-49 and C-50, the first airplane of the type specifically built as a military transport, C-47 Skytrain, 41-7722, made its first flight at Daugherty Field, Long Beach, California, on this date. More than 10,000 C-47s would follow. In service with the United States Navy, the Skytrain was designated R4D-1. In British service, it was called the Dakota Mk.I.

The first DC-3-type airplane to be purchased by the Army Air Corps was this Douglas C-41A, serial number 40-070, (DC-3-253A s/n 2145) delivered 11 September 1939. It was used by General Hap Arnold, Chief of Staff, Air Corps.

The primary differences between the civil and military airframes was the addition of a cargo door on the left side of the fuselage, a strengthened cargo floor, a navigator’s astrodome and provisions for glider towing.

Douglas DC-3 (C-47B) three-view drawing. (NASA)

The Douglas C-47 Skytrain is an all-metal twin-engine, low wing monoplane transport with retractable landing gear. It was operated by a minimum flight crew of two pilots, a navigator and a radio operator. The wing is fully cantilevered and the fuselage is of semi-monocoque construction. Control surfaces are fabric-covered.

Early production C-47 Skytrain transports under construction at the Douglas Aircraft Company plant at Long Beach, California. (Library of Congress)

The C-47 is 64 feet, 5½ inches (19.647 meters) long with a wingspan of 95 feet (28.956 meters) and height of 17 feet (5.182 meters). The wing center section is straight, but outboard of the engine nacelles there is 5º dihedral. The wings’ leading edges are swept aft 15.5°. The trailing edges have no sweep. Empty weight of the C-47A is 17,257 pounds (7,828 kilograms) and the maximum takeoff weight is 29,300 pounds (13,290 kilograms).

A Douglas employee at Long Beach, California works on a C-47’s Pratt & Whitney Twin Wasp R-1830-92 radial engine. Stenciling shows that the propellers were inspected 10 October 1942. (Albert T. Palmer/Office of War Information)

The C-47 is powered by two 1,829.4-cubic-inch-displacement (29.978 liter) air-cooled, supercharged R-1830-92 (Pratt & Whitney Twin Wasp S1C3-G) two-row 14-cylinder radial engines. These had a maximum continuous rating for normal operation was 1,060 horsepower at 2,550 r.pm., up to 7,500 feet (2,286 meters), and 1,200 horsepower at 2,700 r.p.m., at Sea Level, for takeoff. Each engine drives a three-bladed Hamilton Standard Hydromatic constant-speed full-feathering propeller with a diameter of 11 feet, 6 inches (3.505 meters) through a 16:9 gear reduction. The R-1830-92 is 48.19 inches (1.224 meters) long, 61.67 inches (1.566 meters) in diameter, and weighs 1,465 pounds (665 kilograms).

The C-47 has a cruising speed of 185 miles per hour (298 kilometers per hour) at 10,000 feet (3,048 meters) and service ceiling of 24,100 feet (7,346 meters).

U.S. Army paratroopers jump from Douglas C-47-DL Skytrain 41-7805. This airplane was in the first production block of C-47s built at Long Beach, California. (U.S. Air Force)

The C-47 could carry 6,000 pounds (2,722 kilograms) of cargo, or 28 fully-equipped paratroopers. Alternatively, 14 patients on stretchers could be carried, along with three attendants.

U.S. Paratroopers board a Douglas C-47 Skytrain for Operation Husky, 9 July 1943. (U.S. Army)
U.S. Paratroopers board a Douglas C-47 Skytrain for Operation Husky, 9 July 1943. This airplane, Douglas C-47-DL 41-18341, was built at Long Beach, California. (U.S. Army)
Douglas C-47 Skytrains at the Midwest City Douglas Aircraft Plant. Douglas produced 13 C-47s a day at this facility. (U.S. Air Force)

© 2018, Bryan R. Swopes

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