XR-6
prototype powered by a 225 h.p.
Lycoming O-435-7 (one)
XR-6A
as XR-6 but powered by the 240 h.p.
Franklin O-405-9 (five) of which three to the US Navy as XHOS-1
YR-6A
as XR-6A with small changes (26) built by Nash-Kelvinator
R-6A
production model (193) built by Nash-Kelvinator of which 36 to US Navy as HOS-1 and 27 to the RAF as Hoverfly II
R-6B
projected variant with 225 h.p.
 Lycoming O-435-7, but not proceeded with
XR-7
projected development of the XR-6 with a 240 hp Franklin O-405-9 engine, not built.

Doman LZ-1
One R-6A modified as a testbed
Doman LZ-1A
One R-6A modified as a testbed with a Doman-designed hingeless rotor blades and self-lubricating rotor hub.
XR-6
prototype powered by a 225 h.p. Lycoming O-435-7 (one)
XR-6A
as XR-6 but powered by the 240 h.p. Franklin O-405-9 (five) of which three to the US Navy as XHOS-1
YR-6A
as XR-6A with small changes (26) built by Nash-Kelvinator
R-6A
production model (193) built by Nash-Kelvinator of which 36 to US Navy as HOS-1 and 27 to the RAF as Hoverfly II
R-6B
projected variant with 225 h.p. Lycoming O-435-7, but not proceeded with
XR-7
projected development of the XR-6 with a 240 hp Franklin O-405-9 engine, not built.
Doman LZ-1
One R-6A modified as a testbed
Doman LZ-1A
One R-6A modified as a testbed with a Doman-designed hingeless rotor blades and self-lubricating rotor hub.
Sikorsky R-6