Sikorsky H-19 Chickasaw

H-19 Chickasaw / S-55
An Army UH-19D Chickasaw
General information
Type	Utility helicopter
Manufacturer	Sikorsky Aircraft
Primary users	United States Army United States Air Force United States Navy United States Coast Guard
Number built	1,728[1]
History
Introduction date	16 April 1950 (U.S. Air Force)
First flight	10 November 1949
Retired	26 February 1969 (U.S. Navy)
Variants	Westland Whirlwind
Developed into	Sikorsky H-34 (S-58 / Wessex)

The Sikorsky H-19 Chickasaw (company model number S-55) is a multi-purpose piston-engined helicopter that was used by the United States Army and United States Air Force. It was also license-built by Westland Aircraft as the Westland Whirlwind in the United Kingdom. United States Navy and United States Coast Guard models were designated HO4S, while those of the U.S. Marine Corps were designated HRS. In 1962, the U.S. Navy, U.S. Coast Guard and U.S. Marine Corps versions were all redesignated as H-19s like their U.S. Army and U.S. Air Force counterparts.

The H-19 pioneered the use of a nose-mounted radial engine powering a single fully articulated main rotor located above the cabin, which helped maintain a proper center of gravity under varying loading conditions without requiring ballast to maintain longitudinal stability as with prior Sikorsky designs. This layout gave the H-19 series a characteristic bulbous-nosed appearance and made it one of the first truly successful single-rotor utility helicopters, leading to a number of derivative designs including the Sikorsky H-34, which was produced in even greater numbers. The H-19 had a long military career worldwide in the late 20th century and also proved popular with civil operators.