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| CH-1 Skyhook YH-41 Seneca | |
|---|---|
 YH-41 prototype | |
| General information | |
| Type | Lighthelicopter |
| National origin | United States |
| Manufacturer | Cessna |
| Designer | Richard Ten Eyck |
| Status | Production ended December 1962 |
| Number built | ~50 |
| History | |
| Introduction date | 1956 |
| First flight | July 1953[1] |
| Developed from | Seibel S-4 |
TheCessna CH-1 Skyhook is the onlyhelicopter ever built by theCessna Aircraft Company. It was the first helicopter to land on the summit ofPike's Peak and the last piston-engined helicopter to set the helicopter altitude record. The CH-1 had a single, two-bladed main rotor, and a front-mounted reciprocating engine which gave the aircraft a stablecenter of gravity (CG). Itssemi-monocoque airframe greatly resembles its light airplane siblings built by Cessna. The CH-1 was named Skyhook for the civil market, similar to the marketing names used in the Cessna single engine airplane line, such asSkyhawk,Skylane andSkywagon.[2] TheUnited States Army designated the CH-1C as theYH-41 Seneca. While the CH-1 achieved several helicopter firsts and set a world record, it never became a commercial or military success.
Cessna Aircraft Company acquired theSeibel Helicopter Company ofWichita, Kansas on 14 January 1952[2] through a stock swap with Seibel investors. All equipment from the Seibel Helicopter Company, including theSeibel 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 engineer 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.[2]
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 as CH1-1, first hovered in July 1953, eventually making test flights as high as 10,000 feet (3,000 m).[2] 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.[2]
On 9 June 1955, the CH-1 receivedCAA type-certificate 3H10. Originally certified as a two-place helicopter, stability problems at higher gross weights required additional engineering solutions. A larger, free-floatinghorizontal stabilizer was introduced. During forward flight, the stabilizer pivoted to a variable mechanical stop, which was linked to the fore and aft cyclic control, thereby altering the stabilizerangle of incidence during flight. Reworking the stabilizer permitted the addition of a second row of seating, and the four-place ship, designated the CH-1A, was certificated on 28 February 1956.
In December 1955, Cessna was awaiting a contract to produce a limited number of CH-1s for evaluation by the Army. In preparation for the contract, Cessna began modifying the CH-1A with aContinental FSO-526 engine and other aerodynamic and structural changes in the possibility of eliciting a production contract. In spring 1956, the Army awarded Cessna with a US$1.1 million contract for 10 test aircraft, designated as the YH-41 Seneca. For marketing purposes, the CH-1A prototype (N5156) was painted in an olive drab Army scheme.
The aircraft incorporated a unique L-section hinges to attach the main rotor blades to the hub in place of more conventional pitch change bearings.[3]
The CH-1 external design was created byRichard 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,"[2] 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 prototype CH-1 was originally equipped with a superchargedContinental FSO-470 six-cylinder engine, producing 260 hp (190 kW) at 3,200 rpm. The engine's supercharger and cooling fans were driven by belts. Cessna had a long relationship with Continental who provided engines for the company's light airplanes, but the use of the Continental engine in a helicopter was as much of a test for the engine company, as Cessna's foray into the helicopter market, itself. This was especially true when considered that most other light helicopter manufacturers were usingFranklin andLycoming engines.
The CH-1 established many firsts. The CH-1A was the first helicopter to land onPikes Peak, at an altitude of 14,110 feet (4,300 m) on 15 September 1955,[2] it had a higher cruise speed than comparable machines, and a CH-1B, modified with an FSO-526-2X engine, set an officialFAI world altitude record for helicopters of 29,777 feet[note 1] on December 28, 1957, while being piloted by Army Captain James E. Bowman.[2] The previous record had been set by a turbine poweredAérospatiale 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.[4] The CH-1C was the first helicopter to receiveinstrument flight rules certification by theFederal Aviation Administration.[citation needed]
Production was ended in December 1962. The company indicated that this was due to the civil aviation market not being ready for this type of aircraft, although CH-1 ownerRex Trailer claimed that it was due to catastrophic transmission failures.[5][6]
Approximately 50 machines were built before Cessna ended their venture into helicopters. Most of the aircraft built were bought back and scrapped by Cessna, and thetype certificate was revoked, presumably to remove any liability to Cessna for continued operation of any helicopters they could not retrieve. The Army Aviation Museum atFort Novosel, Alabama has a YH-41 Seneca prototype (serial number 56-4244) as a part of its collection, although it is not currently on display.[7]
Data from Jane's All The World's Aircraft 1961–62[8]
General characteristics
Performance
Related development
Aircraft of comparable role, configuration, and era
Media related toCessna YH-41 Seneca at Wikimedia Commons
