July 28, 2007

Cessna CH-1 helicopter

Cessna Aircraft Company acquired the Seibel Helicopter Company (pronounced "See-bull") of Wichita, Kansas on 14 January 1952 through a stock swap with Seibel investors. All equipment from the Seibel Helicopter Company, including the Seibel S-4B, was moved to Cessna's Pawnee Plant in Wichita and work began on the CH-1 design during the summer of 1952. Charles Seibel, who became the new Helicopter Division's chief designer as part of the acquisition, believed that the S-4B with a Cessna body would make an excellent helicopter. Cessna pilots test flew Seibel's S-4B for several months to familiarize the engineers with helicopters, and then it was scrapped.

A quarter-size wind tunnel model of the CH-1 was created and tests were conducted at Wichita State University. The first full-size machine did not have an enclosed fuselage or cowling, nor a horizontal stabilizer. This test bed skeleton (referred to by the company as CH1-1) first hovered in July, 1953, eventually making test flights as high as 10,000 feet. The actual prototype CH-1 was built based on modifications made to the test bed aircraft and this second ship made its first flight in 1954, at the Prospect plant.

The CH-1 Skyhook is the only helicopter ever built by the Cessna Aircraft Company. The single, twin-bladed main rotor helicopter used a front-mounted reciprocating engine which gave the aircraft a stable center-of-gravity (CG). Its semi-monocoque airframe greatly resembles its light airplane siblings built by Cessna. The helicopter was named Skyhook for the civil market, similar to the marketing names used in the Cessna single engine airplane line, such as Skyhawk, Skylane and Skywagon. The CH-1's military designation for the United States Army was the YH-41 Seneca. The Skyhook would achieve several helicopter "firsts" and set a world record, but ultimately, it would never be a commercial or military success.

The prototype CH-1 had a turbocharged Continental FSO-470 engine rated at 260 h.p. at 3200 rpm. The turbocharger and cooling fans were driven by belts. Cessna had a long relationship with Continental who provided engines for their light airplanes, but the use of the Continental engine in a helicopter was considered as much of a test as Cessna's foray into the helicopter market itself, especially in a time when most other light helicopter manufacturers were using Lycoming engines.

The CH-1 external design was created by Richard Ten Eyck, an industrial designer for Cessna. It was a low profile streamlined aircraft-style body, featuring the engine in front and cabin seating behind the powerplant. The forward engine location provided "ease of access,...efficient cooling, and frees the center of gravity behind the cockpit for use in disposable load," but also presented a problem for how to vent the exhaust which would prove to be a problem throughout the aircraft's life. Additionally, the tail boom size, resulting from the airplane-style fuselage, created aerodynamic problems in hover and forward flight that would have to be solved by later aerodynamic structural changes.

The CH-1 established many firsts. The CH-1A was the first helicopter to land on Pikes Peak, at an altitude of 14,110 feet on 15 September 1955,[2] it had a higher cruise speed than comparable machines, and a CH-1B, modified with a FSO-526-2X engine, set an official FAI world altitude record for helicopters of 29,777 feet (Cessna's instrumentation showed 30,355 feet) on December 27, 1957.[2] The previous record had been set by a turbine powered AĆ©rospatiale Alouette II and was later broken by another Alouette II, but the record set by the CH-1B remains the highest altitude ever achieved by a piston-powered helicopter.[1] The CH-1C was the first helicopter to receive IFR certification by the FAA.

Source: Wikipedia

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