Model 6 Cloudboy
The YBT-3
Role	Training biplane Type of aircraft
Manufacturer	Stearman Aircraft Company
First flight	1931
Primary user	United States Army Air Corps
Produced	1930-1931
Number built	7

The Stearman Model 6 Cloudboy was a 1930s American training biplane designed and built by the Stearman Aircraft Company of Wichita, Kansas.

History

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).^[1]

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, four built (one converted to YPT-9A, one to YPT-9B, one to YBT-3 and one YBT-5).

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.

Operators

 United States

United States Army Air Corps

Surviving aircraft

• 6002 – 6L airworthy at the Candler Field Museum in Williamson, Georgia.^[2][3]
• 6003 – 6L airworthy at the Western Antique Aeroplane & Automobile Museum in Hood River, Oregon.^[4] It was previously owned by the Golden Wings Flying Museum.^[5]
• 6004 – YPT-9B on display at the Yanks Air Museum in Chino, California. It was previously owned by the Boeing School of Aeronautics and was acquired by the museum in 1987.^[6][7]
• 6010 – 6C airworthy with Robert Lock of Lakeland, Florida.^[8]

Specifications (YPT-9B)

Data from United States Military Aircraft since 1909^[9]

General characteristics

• 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)