January 2019

Vought-Sikorsky XR-4 / YR-4A / R-4A

World’s first production helicopter and world’s first helicopter to perform a medical evacuation in a combat zone (April 1944)

The Sikorsky R-4 was the first helicopter in the world that was built in production qualities, with a total of 131 being manufactured during World War II. It was based on the proven configuration of the Vought-Sikorsky VS-300 demonstrator.


The XR-4 prototype made its first flight on Jan. 14, 1942, with Les Morris as pilot. The helicopter did not have the desired performance, so a number of changes were made, including increasing the main rotor radius from 36 to 38 ft (11 to 11.6 m), increasing the tail rotor diameter, and using a more powerful version of the Warner Scarab engine with 200 hp (150 kW). The tail cone was also modified to reduce weight and this, along with other changes, were incorporated into the YR-4A, provided to the Army for service trials. After a few more minor changes, it was put into production as the R-4A.


The first helicopter rescue was made by 2nd Lt. Carter Harman, who made the first medical evacuation on April 23, 1944, in Burma. Other rescues were subsequently made with the R-4, its limited payload only allowing one person to be carried at a time. The R-4 also was used to demonstrate flights to and from ship decks and develop use of rescue hoists. Later, it delivered small parts from maintenance ships to shore, helping to speed the vital repair process. The R-4 established the helicopter as a new but very useful addition to the aviation family and paved the way for the many that followed.

Text: Tom Lawrence

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