Piasecki Helicopter Co. | This Day in Aviation

ARVN soldiers run to board U.S. Army CH-21C Shawnee helicopters. (LIFE Magazine)

12 January 1962: The first helicopter assault of th Vietnam War, Operation Chopper, took place when 33 United States Army CH-21C Shawnee transport helicopters of the 8th and 57th Transportation Companies airlifted 1,036 soldiers of the Army of the Republic of Vietnam (ARVN) into battle against an insurgent Việt cộng (National Liberation Front) stronghold, approximately 10 miles (16.1 kilometers) west of Saigon. The landing zone was 150 yards by 300 yards and surrounded by tall trees.

A flight of U.S. Army CH-21C Shawnee helicopters over South Vietnam, 1962. (LIFE Magazine)

The Piasecki Helicopter Company CH-21C Shawnee was a single-engine, tandem rotor transport helicopter. It had a flight crew of three with one or two gunners, 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) and it was 15 feet, 9 inches (4.801 meters) high. The rotors were 44 feet (13.411 meters) in diameter and the fuselage was 52 feet, 7 inches (16.027 meters) long. The empty weight was 8,950 pounds (4,059.7 kilograms) and maximum takeoff weight was 15,200 pounds (6,894.6 kilograms).

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 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. 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). It’s service ceiling was 19,200 feet (5,852.2 meters).

A U.S. Army CH-21C Shawnee over the Landing Zone west of Saigon, 12 January 1962. (U.S. Army)

The Piasecki H-21 Workhorse was developed for the U.S. Air Force as an air base support and search and rescue helicopter in cold weather operations. A total of 707 were built for the U.S., France and Germany, as well as civil operators. 334 were built for the U.S. Army as the H-21C Shawnee, redesignated CH-21C in 1962.

Its performance in the hot and humid climate of Southeast Asia was limited, restricting the troop load to 9 soldiers. It was withdrawn from service in 1964 when the Bell HU-1A Iroquois began to replace it. All CH-21Cs were retired when the CH-47 Chinook assumed its role in 1965.

ARVN troops wait while a U.S. Army CH-21C Shawnee lands. (LIFE Magazine)

Piasecki YH-16A-PH Transporter 50-1270 hovers in ground effect. (Piasecki Aircraft Corporation)

5 January 1956: The prototype Piasecki Helicopter Company YH-16A-PH Transporter twin-turboshaft, tandem-rotor helicopter, serial number 50-1270, was returning to Philadelphia from a test flight, when, at approximately 3:55 p.m., the aft rotor desynchronized, collided with the forward rotor and the aircraft broke up in flight. It crashed at the Mattson Farm on Oldman’s Creek Road, near Swedesboro, New Jersey, and was completely destroyed.

Test pilots Harold W. Peterson and George Callahan were killed.

It was determined that a bearing associated with an internal coaxial shaft supporting test data equipment had seized, causing the rotor shaft to fail.

Harold W. Peterson (left) and George Callahan, with the prototype Piasecki YH-16A Turbo Transporter, 50-1270. (Photograph courtesy of Neil Corbett, Test and Research Pilots, Flight Test Engineers)

At the time, the YH-16 was the largest helicopter in the world. The United States Air Force intended it as a very-long-range rescue helicopter, while the U.S. Army expected it to serve as a heavy lift cargo and troop transport.

The YH-16A had a fuselage length of 78 feet (23.774 meters), and both main rotors were 82 feet (24.994 meters) in diameter. With rotors turning, the overall length was 134 feet (40.843 meters). Their operating speed was 125 r.p.m. Overall height of the helicopter was 25 feet (7.62 meters). The helicopter’s empty weight was 22,506 pounds (10,209 kilograms) and the gross weight was 33,577 pounds (15,230 kilograms).

YH-16 50-1269 was powered by two 2,181.2-cubic-inch-displacement (35.74 liter) air-cooled, supercharged Pratt & Whitney Twin Wasp E2 (R-2180-11) two-row, fourteen-cylinder radial engines with a Normal Power Rating of 1,300 horsepower at 2,600 r.p.m. at 8,000 feet (2,438 meters), and 1,650 horsepower at 2,600 r.p.m., for Takeoff.

Piasecki YH-16A 50-1270 during a test fight.

The second YH-16A, 50-1270, was modified while under construction and was powered by two Allison Division YT38-A-10 turboshaft engines which produced 1,800 shaft horsepower, each. This made the YH-16A the world’s first twin-engine turbine-powered helicopter.

The Piasecki YH-16A Transporter was the world's largest helicopter in 1956. (Piasecki Aircraft Corporation) — The Piasecki YH-16A Transporter was the world’s largest helicopter in 1956. (Piasecki Aircraft Corporation)

The cruise speed of the YH-16A was 146 miles per hour (235 kilometers per hour). In July 1955, Peterson and Callahan had flown 50-1270 to an unofficial record speed of 165.8 miles per hour (266.83 kilometers per hour). The service ceiling was 19,100 feet (5,822 meters) and the maximum range for a rescue mission was planned at 1,432 miles (2,305 kilometers).

After the accident, the H-16 project was cancelled.

Prototype Piasecki YH-16A Transporter 50-1270, hovering in ground effect at Philadelphia Airport, 1955. (Piasecki Aircraft Corporation)

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12 January 1962

5 January 1956