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Boeing 307 Stratoliner / C-75



In early 1934 Boeing began design studies for a multi-engine bomber and a basically similar civil transport. When, in June 1934, the USAAC invited proposals for a new bomber, Boeing's Model 299 was revamped to meet the Army specification and duly became built by the thousands as the B-17 Flying Fortress.

The Model 300 was also changed as ideas were developed and in its Model 307 form was similar to the B-17C, except for a very different fuselage. This was of circular cross-section with pressurisation for the crew of five and 33 passengers. The Model 307 introduced an extra crew member - known as the flight engineer - to relieve the captain of certain duties such as power plant, fuel and pressurisation management and monitoring.

The prototype Model 307 (named Stratoliner because of its high cruising ceiling) flew for the first time on 31 December 1938.



A total of ten were built: the prototype; five SA-307B for Transcontinental & Western Air; three S-3O7 for Pan American; and a single SB-307B for the late Howard Hughes.

First delivered to PanAm in 1940, the Boeing 307 went into service in 194, carrying passengers on long- haul American routes. The night-plane version had berths for 16 passengers and reclining chairs for a further 9.

TWA's SA-307B were impressed for service with the Army's Air Transport Command during World War II, being used as C-75 for VIP transport over the North and South Atlantic.


A special model SB-307B for Howard Hughes was built with more powerful engines and extra fuel tanks for an around-the-world flight that was cancelled due to the start of World War II. The flight was never made. It was the first Stratoliner delivered to a customer; its initial flight (with experimental license NX19904) occurred on July 13, 1939. Postwar it was fitted with a luxury interior, including a bedroom, and named The Flying Penthouse.

A 1964 hurricane severely damaged it and rendered it unflyable. In 1969 it was purchased as scrap for $61.99 -- the fuselage was salvaged (the aft rounded pressure bulkhead formed the cabin after end), then mounted on a boat hull and converted into a luxury yacht named The Londonaire. It was rebuilt beginning in 1994, and is a Florida based, operating yacht named Cosmic Muffin, with N19904 painted on its sides.


Engines: 4 x Wright GR-1820 Cyclone, 671kW
Take-off weight: 19050 kg / 41998 lb
Empty weight: 13608 kg / 30001 lb
Wingspan: 32.61 m / 106 ft 12 in
Length: 22.66 m / 74 ft 4 in
Height: 6.34 m / 20 ft 10 in
Wing area: 138.05 sq.m / 1485.96 sq ft
Max. speed: 396 km/h / 246 mph
Cruise speed: 354 km/h / 220 mph
Ceiling: 7985 m / 26200 ft
Range 50 % pwr: 1,635 miles / 2,616 km
Crew: 4
Pax cap: 33



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