11/30/2009. Remarks by Johan Visschedijk: "The only Cessna helicopter known to exist was designed and engineered by Charles M. Siebel.

While working for Bell Aircraft in Buffalo, New York, Seibel had designed the S-1 twin-tilt rotor helicopter in 1943, and the S-2 co-axial rotor helicopter. He left Bell for Boeing at Wichita, Kansas in 1946 and designed the experimental single-seat S-3 (N735B c/n 1, flown September 4, 1947), and formed Seibel Helicopters Company Inc. at Wichita, Kansas, in early 1948.

Next came the tandem two-seat S-4 (N5152 c/n 1, certificated in 1950), and the similar S-4A (N5153 c/n 2, both to the US Army as YH-24 Sky Hawk), and the side-by-side two-seat S-4B (N5154 c/n 4) training helicopter.

In 1952, Cessna Aircraft Company, also at Wichita, wanted to enter the helicopter market, and impressed with Seibel's technological achievement, acquired the Seibel Helicopter Company on March 1, 1952.

To carry through the appearance of Cessna's single-engined aircraft, Seibel developed the open frame S-4B into the high-performance two-seat all-metal monocoque fuselage CH-1. It had a conventional tail plane and fin, and a streamlined cabin section with the engine positioned in the nose.

Registered N5155 (c/n 45001) and powered by a 260 hp Continental FSO-470-A piston engine, it was flown in July 1954, receiving its type certificate in June 1955. Three months later, September 13, it gained fame as the first helicopter landing at summit of the 14,110 ft (4,300 m) Pike's Peak in Colorado.

Cessna CH-1A (N5156) (Ron Dupas Collection)

A few months later, the sole CH-1 was converted into the four-seat CH-1A, flown as N5156 (new c/n 45002). It was followed by a CH-1A for boundary layer research (N5157c/n 45003), while c/n 45004 was a static test example.

CH-1B YH-41 Seneca (56-4237) (Ray Watkins Collection)

Cessna received an evaluation order from the US Army for ten CH-1Bs, fitted with a 270 hp Continental FSO-526-A engine. Allotted the s/n 56-4236 to 56-4245 (c/n 45005 to 45014), and designated YH-41Seneca, they were delivered between December 1957 an June 1958.

The CH-1C Skyhook had revised systems and structure and was introduced in 1960. The USAF ordered eleven CH-1Cs, those received the paper designation UH-41A and were MAP deliveries to Guatemala (6), s/n 62-5845 to 62-5848, 62-12350, 63-9793, and to Iran (5) s/n 63-8067 to 63-8071.

During December 1962, Cessna discontinued production of the Skyhook after a thorough market study indicated that the use of the helicopter for business and utility purposes had not developed as anticipated earlier. The pictured example is the sole Cessna helicopter still in existence."