Navy variant with 600-hp Pratt & Whitney R-1340-AN-l engine
(as HRP-l); weight empty 5;205 Ibs, loaded 7,500 Ibs; 41-ft
rotor diameter; 4 built (factory designation PV-17).
pre-production aircraft; 18 built (factory PD-22).
USAF production SAR helicopter with 1,250-hp Wright R-1820-103
engine de- rated to 1,150 hp; loaded 11,500 Ibs; first flight
October 1953; 38 built including 5 for Canada (factory 42);
changed to CH-21A in 1962.
USAF production assault transport with 1,425-hp R-1820-103;
loaded 15,000 Ibs; auto-pilot, external fuel tanks, armor; first
flight November 1955; 163 built for USAF (factory 421); some
employed in SAR role designated SH-21B; changed to CH-21B and
then to HH-21B in 1962.
U.S. Army production cargo/transport helicopter; similar to
H-21B; first flight June 1953; 334 built for U.S. Army and
foreign service (factory 43); changed to CH-21C in 1962.
H-21C fitted with 2 GeneralElectricT58 turbo shaft engines;
first flight September 1957; 2 converted.
Swedish naval variant with 1,425-hp Wright 977C9HDl Cyclone
engines; 11 built (factory 44A).