Sikorsky downsized the basic S-38 design to create the S-39. The original prototype, NX813M / NX963M, was experimentally converted to two tractor-mounted 115hp Cirrus Hermes Mk I engines, was test flown in mid-1929 but crashed later that year after an engine failure.
Sikorsky followed with the S-39-A, flown in early 1930, with a single R-985 Wasp Junior engine mounted directly to the wing. The S-39-A was the first US aircraft to be certified with the R-985.
Twelve S-39-As (NC42V, NC802Y, NC803W/809W, NC887W), marketed at an average price of US$17,500 with ATC 340, were sold to civil owners by the end of 1930.
The S-39-B (ATC 375), introduced in 1931 with a larger fin and rudder, sold eight examples (NC50V and 51V, NC53V to 55V, NC58V, NC888W, and NC896W) to private owners at $20,000, plus one to the US Army Air Corps as the YIC-28 32-411, plus 9 conversions from S-39-A.
Two S-39-B, refitted with 400 hp R-1340 Wasp engines, were re-certified as S-39-C.
The final example, an S-39-CS Special named “Spirit of Africa”, was built in 1932 to an order from explorers and photographers Martin and Osa Johnson. In a giraffe paint scheme, the Spirit of Africa covered more than 60,000 miles across Africa and East Indies.
Several civilian S-39s were operated by the Civil Air Patrol during World War II on search and rescue missions.
A total of 21 were built.
S-39 / S-39-A
Engine: Pratt & Whitney R-985 Wasp Junior, 300 hp
Prop: 2 blade, ground adjustable, metal
Wingspan: 52 ft 0 in
Length: 38 ft 11 in
Wing area: 320 sq.ft
Empty weight: 2678 lb
MTOW: 4000 lb
Max speed: 115 mph
Cruise: 97 mph
Ceiling: 18,000 ft
Range: 375 miles
Seats: 4
S-39B
Engine: Pratt & Whitney R-985 Wasp Junior, 300 hp
Prop: 2 blade, ground adjustable, metal
Wingspan: 52 ft 0 in
Length: 38 ft 11 in
Wing area: 320 sq.ft
Seats: 5
All Aero 