Boeing 307 Stratoliner

Boeing 307 Stratoliner
Country	USA
Role	Airliner
First flight	December 31, 1938
Built	10

The Boeing Model 307 Stratoliner was the first commercial transport aircraft to enter service with a pressurized cabin. This feature allowed the aircraft to cruise at an altitude of 20,000 ft (6,000 m), well above many weather disturbances. The pressure differential was 2.5 psi (17 kPa), so at 14,700 ft (4,480 m) the cabin air pressure was equivalent to an altitude of 8,000 ft (2,440 m). The Model 307 had capacity for a crew of six and 33 passengers. In addition to its civilian service it was also flown as the Boeing C-75 Stratoliner by the United States Army Air Forces, who used it as a long-range cargolift aircraft.

Source: Boeing 307 Stratoliner on Wikipedia

Boeing Model 307 Stratoliner Walk Around
Photographer	Vladimir Yakubov
Localisation	National Air & Space Museum
Photos	107

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Boeing Model 307 Stratoliner Walk Around
Photographer	Michael Benolkin
Localisation	Unknow
Photos	27

A Revolution in Civil Aviation

The Boeing Model 307 Stratoliner was a milestone in aviation history. Introduced in 1938, it was the first commercial transport aircraft to feature a pressurized cabin. This allowed the Stratoliner to fly at 20,000 feet, far above the turbulent weather that plagued earlier airliners like the DC-3. By utilizing the wings, tail, and engines of the B-17 Flying Fortress, Boeing created a robust, high-altitude cruiser that changed the definition of luxury and speed in the “Golden Age” of flight.

Attribute	Technical Specification (Boeing 307)
Role	Long-Range Commercial Airliner / Military Transport
Crew	5 (Pilot, Co-pilot, Flight Engineer, 2 Flight Attendants)
First Flight	December 31, 1938
Powerplant	4 × Wright GR-1820-G102 Cyclone radials
Horsepower	1,100 hp (820 kW) per engine
Maximum Speed	241 mph (388 km/h)
Cruising Altitude	20,000 feet (6,100 m)
Passenger Capacity	33 (Day) / 25 (Night Sleeper)

Engineering the High-Altitude Cabin

Circular Fuselage: Unlike the flat-sided aircraft of the era, the 307 featured a perfectly circular cross-section. This shape was necessary to evenly distribute the internal pressure stresses required to maintain a breathable atmosphere at high altitudes.
Pressurization System: The Stratoliner used engine-driven superchargers to pump air into the cabin. This allowed passengers to enjoy an “8,000-foot” environment while the aircraft cruised at 20,000 feet, effectively avoiding the “bumps” of low-level air.
B-17 DNA: To save on development costs and improve reliability, Boeing used the flight surfaces of the B-17C Flying Fortress. The wings, landing gear, and horizontal stabilizers were nearly identical to the bomber, giving the 307 legendary structural strength.
Sleeper Comfort: The wide fuselage allowed for reclining seats and berths, making it one of the first true “sleeper” transports for transcontinental travel.

The “C-75” and Notable History

Military Service (C-75): During WWII, the five Stratoliners operated by TWA were pressed into service for the Army Air Transport Command. Designated as C-75s, they were used for high-priority transatlantic flights because their pressurization allowed them to fly above most interception threats.
Howard Hughes and the “Flying Penthouse”: The famous billionaire bought a Stratoliner and converted it into a lavish private office and home. After being damaged in a hurricane, the fuselage was eventually converted into a “Cosmic Muffin” house boat.
Rare Survival: Only 10 Stratoliners were ever built. The only surviving example, the “Flying Cloud” (formerly of Pan Am), was meticulously restored by Boeing volunteers and is now at the Steven F. Udvar-Hazy Center.