May 2020

Vought-Sikorsky XR-4/HNS-1 First Shipboard Trials


Based on Igor Sikorsky’s successful VS-300 flight demonstrations, the XR-4 prototype of the US Army’s first production helicopter made its first flight on Jan. 14, 1942. Prior to the outbreak of World War II, the Army recognized the future potential of rotary-wing aircraft, including the helicopter. However, the US Navy and US Coast Guard were slow to act on developing a naval helicopter suitable for operations from ships at sea.

It was evident right after America’s entry into the war that the German U-Boat menace was achieving alarming results with the sinking of Allied shipping in the North Atlantic, the Mediterranean Sea, and right off the US eastern coastline. US-made war supplies shipped by convoys to England and other allies were critical to the success of the war. In the month of June 1942 alone, U-Boats accounted for 141 ships sunk.

The US coastline was partially protected by fixed-wing aircraft and blimps but their range into the North Atlantic was limited and the attendant US destroyer escorts only had partial effectiveness early in the war. US and British escort aircraft carriers were not available to assist every convoy crossing the seas. A ship-based helicopter was urgently needed to provide U-Boat observation and detection. The helicopter needed to be based on and safely operate from a platform on the freighter.

Using a borrowed Army XR-4 (Navy designation HNS-1), leading US Army Air Corps pilot Colonel Frank Gregory made the very first takeoffs and landings aboard the SS Bunker Hill, a tanker that was located off the coast of Connecticut for the trial. The demonstrations were especially challenging since the XR-4 rotor tips had only 14 feet of clearance from the nearest ship obstacle in the landing area. The tests, conducted with the cooperation of the Army Air Forces, the War Shipping Administration, and the Coast Guard, proved that the helicopter could operate safely from a ship at sea.

More successful shipboard tests followed in 1943 and by January 1944 the Navy’s first helicopter school had opened at Coast Guard Air Station Floyd Bennett Field, New York to train naval aviators as helicopter pilots. Also trained were mechanics and US Coast Guard and British pilots.


  • Main rotor diameter: 38 ft (11.6 m)
  • Engine: Warner Super Scarab R550-3 air-cooled 7-cylinder radial, takeoff rating: 200 hp (149 kW)
  • Max. takeoff gross weight: 2,540 lb (1152 kg) 
  • Empty weight: 2,020 lb (916 kg)


Text: Ken Bartie

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