Boeing 307 Stratoliner four-engine commercial monoplane

Boeing 307 Stratoliner
United States — four-engine commercial monoplane

Archive Photos ²

Boeing 307 "Stratoliner" "Clipper Flying Cloud" (NC19903) at the National Air and Space Museum Steven F. Udvar-Hazy Center, Chantilly, Virginia (Photos by Jim Hough)

Overview ²

Boeing 307 "Stratoliner"
Role: Airliner
Manufacturer: Boeing
First flight: 31 December 1938
Introduced: 8 July 1940
Retired: 1970s
Primary users: TWA, Pan Am
Number built: 10
Unit cost: $315,000 (1937)
Developed from: Boeing B-17 "Flying Fortress"
Variants: Boeing C-75

The Boeing Model 307 Stratoliner was the first commercial transport aircraft with a pressurized cabin. This feature allowed the plane to cruise at an altitude of 20,000 ft (6,000 m), well above weather disturbances. The pressure differential was 2.5 psi (17 kPa), so at 14,700 ft (4,480 m) the cabin altitude was 8,000 ft (2,440 m). The Model 307 had capacity for a crew of five and 33 passengers. The cabin was nearly 12 ft (3.6 m) across. It was the first plane to include a flight engineer as a crew member.

Operational History ²

A total of 10 Stratoliners were built. The first flight was on December 31, 1938. Boeing 307 prototype NX 19901 crashed on March 18, 1939 during a test flight. By 1940 it was flying routes between Los Angeles and New York, as well as to locations in Latin America. Multi-millionaire Howard Hughes purchased a model for his personal use, and had it transformed into a luxurious "flying penthouse". This plane was later sold to oil tycoon Glenn McCarthy in 1949. Haiti and the United States have used the 307 in military operations.

Variants ²

307 — Wright Cyclone GR-1820-G102 engines with single speed supercharger. Crew of 5.
307B — Wright Cyclone GR-1820-G105A engines with two speed supercharger for better high altitude performance. Crew of 7.
C-75 — Five Trans World 307Bs impressed into service with the USAAF as military transports and converted to 307B-1 standard with B-17G wings, a larger tailplane, four Wright Cyclone GR-1820-G606 engines and cabin pressurization removed.

Operators ²

Civilian Operators

France: Aigle Azur bought in 1951 ex-TWA aircraft with new engines and wings replaced with B-17G ones.
Laos: Air Laos received ex-Aigle Azur aircraft.
United States: Pan Am received 3 aircraft; TWA received 5 aircraft; Howard Hughes bought 1 aircraft.

Military Operators

Haiti: Haitan Air Force
United States: United States Army Air Force operated Boeing 307s designated as the C-75.

Survivors ²

The only surviving Boeing Model 307 (NC19903), operated by Pan Am, is preserved in flying condition at the Smithsonian Museum’s Steven F. Udvar-Hazy Center. On March 28, 2002 this particular aircraft was subject to a dramatic crash in which it ditched into Elliott Bay in Seattle, Washington on what was to be its last flight before heading to the Smithsonian. Despite the incident, it was again restored, flew to the Smithsonian and is now on display.
The fuselage of Howard Hughes’ personal 307 survives, although it has been converted into a boat.

Boeing Model 307 Specifications ⁴

Type

Four-engined commercial monoplane.

Wings

All-metal low-wing monoplane.
Wing in six sections, consisting of two inter sections, two outer sections, and two tips.
Structure mainly of aluminum-alloy, built up of two spars, ribs and stressed-skin covering.
Split trilling-edge flaps.
Flaps and ailerons are fabric-covered.
Trimming-tabs in ailerons.

Fuselage

Semi-monocoque structure of circular cross-section.
Structure consists of aluminum-alloy ring and partition bulkheads, longitudinal stiffeners and circumferentials, the whole covered with smooth Alclad skin.

Tail Unit

Cantilever monoplane type.
Aluminum-alloy framework, fixed surfaces covered with smooth metal skin and movable surfaces with fabric.
Trimming-tabs in elevators and rudder.

Undercarriage

Retractable type.
Auxiliary manual control for landing-gear retraction and wheel-brakes, which are normally electrically-operated.
Retractable tail-wheel.

Power Plant

Four 1,100 hp Wright Cyclone Series G-102 or 1,200 hp Pratt & Whitney Wasp Series 1830-C radial air-cooled engines in semi-monocoque nacelles in the leading-edge of the wings.
Hamilton-Standard three-bladed constant-speed airscrews with brakes.
Fuel tanks and interweaving sections.
No tanks in fuselage.

Accommodation

Crew of four or five (including steward and stewardess) and thirty-three passengers.
Capacity for approximately 3,700 lb (1,680 kg) of mail and cargo.
For night-flying there will be upper and lower berths for 16 passengers, with reclining sleeper chairs for a further nine passengers.
Separate dressing rooms and lavatories for men and women.
Fully-equipped galley.
Air-conditioning for Summer and Winter.
Soundproofed throughout.
Structural provision for moderate super-charging with sealed cabin and cockpit.

Dimensions

Span: 107 ft (32.63 m)
Length: 74 ft (22.57 m)
Height: 17 ft 6 in (5.33 m)

Weights (Wright Cyclone G-102 Engines)

Weight empty (Day-plane): 27,649 lb (12,553 kg)
Weight empty (Night-plane): 27,869 lb (12,653 kg)
Weight loaded: 41,729 lb (18,955 kg)

Weights (Pratt & Whitney Wasp 1830-C Engines)

Weight empty (Day-plane): 28,446 lb (12,914 kg)
Weight empty (Night-plane): 28,666 lb (13,014 kg)
Weight loaded: 42,600 lb (19,340 kg)

Performance (Wright Cyclone G-102 engines)

Maximum speed at 6,000 ft (1,830 m): 241 mph (385.6 km/h)
Cruising speed: at 6,000 ft (1,830 m): 241 mph (395.6 km/h)
Cruising speed: at 10,000 ft (3,050 m) on 2,500 hp: 215 mph (344 km/h)
Service ceiling: 23,300 ft (7,110 m)
Service ceiling on three engines: 18,200 ft (5,550 m)
Absolute ceiling with any two engines: 10,500 ft (3,200 m)
Maximum range at 10,000 ft (3,050 m) at 50% power: 1,635 miles (2,616 km) at 184 mph (294.4 km/h)

Performance (Pratt & Whitney Wasp 1830-C engines)

Maximum speed at 6,000 ft (1,830 m): 250 mph (400 km/h)
Cruising speed: at 10,000 ft (3,050 m) on 2,500 hp: 214 mph (342.4 km/h)
Service ceiling: 24,600 ft (8,700 m)
Service ceiling on three engines: 19,900 ft (6,070 m)
Absolute ceiling with any two engines: 12,300 ft (3,750 m)
Maximum range at 10,000 ft (3,050 m) at 50% power: 1,700 miles (2,720 km) at 184 mph (294.4 km/h)

References

Wikipedia, the free encyclopedia. Boeing 307
Grey, C. G. and Leonard Bridgman. The Boeing 307. Jane’s all the World’s Aircraft 1937. London: Sampson Low, Marston & Company, Ltd., 1937, p. 279c-280c. Print.