Stearman Cloudboy

1st Flight 1931

The Stearman Model 6 Cloudboy was a 1930s American training biplane.

The Cloudboy was designed as a commercial or military trainer.

Due to economic pressure during the Great Depression, only a few aircraft were built.

Three civil models were built, followed by four similar aircraft for evaluation by the United States Army Air Corps.

Designated YPT-9 by the Army, it failed to gain any orders.

All models went through a number of engine changes (resulting in new designations for both the military and civil aircraft).

Variants

Model 6A Cloudboy

Initial civil production with a 165 hp (123 kW) Wright J-6 Whirlwind 5 engine, three built.

Model 6C Cloudboy

Re-engined with a 300 hp (220 kW) Wright J-6-9 Whirlwind (R-975-1), also designated YBT-3.

Model 6D Cloudboy

Re-engined with a 300 hp (220 kW) Pratt & Whitney Wasp Junior, also designated YBT-5

Model 6F Cloudboy

Re-engined with a 165 hp (123 kW) Continental A70 engine, also designated YBT-9A.

Model 6H Cloudboy

Re-engined with a 170 hp (130 kW) Kinner YR-720A engine, also designated YBT-9C.

Model 6L Cloudboy

Re-engined with a 200 hp (150 kW) Lycoming R-680-3 engine, also designated YBT-9B

Model 6P Cloudboy

One 6F re-engined with 1 220 hp (160 kW) Wright J-5 engine

YPT-9

Military production variant of the Model 6A with a 165 hp (123 kW) Wright J-6 Whirlwind 5 engine.

YPT-9A

One YPT-9 re-engined with a 165 hp (123 kW) Continental A70 (YR-545-1) engine, later converted to YPT-9B.

YPT-9B

One YPT-9 and one YPT-9A re-engined with a 200 hp (150 kW) Lycoming R-680-3 engine.

YPT-9C

YBT-3 re-engined with a 170 hp (130 kW) Kinner YR-720A engine.

YBT-3

One YPT-9 re-engined with a 300 hp (220 kW) Wright J-6-9 Whirlwind, later converted to a YPT-9C.

YBT-5

One YPT-9 re-engined with a 300 hp (220 kW) Pratt & Whitney R-985-1 Wasp Junior engine.

XPT-943

A primary trainer derived from the 6A for evaluation at Wright Field.

Formed the origins of the Stearman NS and PT-13 for the US Navy and USAAC respectively.

X-70

Alternative company designation for the XPT-943.

Specifications

YPT-9B

Crew

2

Length

24 ft 8 in (7.52 m)

Wingspan

32 ft 0 in (9.76 m)

Height

9 ft 7 in (2.92 m)

Wing area

272 sq ft (25.3 m2)

Gross weight

2,814 lb (1,279 kg)

Powerplant

1 × Lycoming R-680-3 , 200 hp (149 kW)

Performance

Maximum speed

135 mph (217 km/h, 117 kn)

Range

490 mi (789 km, 430 nmi)

Service ceiling

17,000 ft (5,183 m)

Rate of climb

1,050 ft/min (5.3 m/s)

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