Title: Sikorsky R-4 Hoverfly I and R-6 Hoverfly II

The Sikorsky R-4 was the first mass-produced helicopter and the first used in service by the US military. Examples were used by the RAF and known as the Hoverfly I. 131 were built between 1942 and 1944.

The Sikorsky Model 49 (designated R-6 by the USAAF, HOS-1 by the USN, and Hoverfly II by the RAF), was developed from the R-4 with a new streamlined fuselage and lengthened tailboom and first flew in 1943. 225 examples were built, mostly by the Nash-Kelvinator company. Re-designated H-6A in 1948, most had been retired from service by the end of the 1940’s.

This title contains the US military flight manuals for the R-4 HNS-1, and the R-6 HOS-1 and the RAF Pilot’s Notes for the Hoverfly I (R-4) and Hoverfly II (R-6). The files have been scanned from the original flight manuals and retain any colour pages.



This title contains:

  • USAAF/N Pilot’s Flight Operating Instructions for the Sikorsky R-4B and HNS-1, AN 01-230HA-1 dated 1-6-44 with approx. 36 pages.
  • USAAF/N Pilot’s Flight Operating Instructions for the Sikorsky R-6A and HOS-1, AN 01-230HC-1 dated 5-7-45 with approx. 28 pages.
  • RAF Pilot’s Notes for the Sikorsky Hoverfly I and II, AP 4104A & B-PN dated Jan 1947 with approx. 30 pages.