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C-75 / Boeing Model 307 Stratoliner

In the United States, federal support for Pan American Airways helped transform it into an intercontinental aerial system. By the late 1930s, Pan Am not only delivered mail and passengers throughout Latin America but also had inaugurated similar operations across the Pacific and Atlantic Oceans. Still, the majority of these efforts operated on a seasonal basis, required several days at a time, kept to a limited schedule of only one or two flights a week, and were beyond the means of all but the wealthiest travelers. Pan Am's longest routes relied on big, four-engine flying boats built by Martin and Boeing.

While conventional wisdom states that pre-World War II air travel in the United States was dominated by small, twin-engine airliners like the Boeing 247 and Douglas DC-3, the Boeing Model 307 Stratoliner was a notable exception. Entering service in 1940, it became the queen of the commercial skies ever so briefly. Transcontinental and Western Air-later Trans World Airlines-(TWA), had introduced four-engine Boeing Stratoliner passenger transports on important domestic routes. Pressurized for high-altitude flights, they were in the forefront of modern airliner design.

Transport airplanes began to appear that provided increases in speed, range, and payload as a result of continuing advances in research and technology particularly in engines, propellers, structures and materials, airfoils and flaps. The first American airplane utilizing these improvements was the Boeing 307 Stratoliner.

The Boeing Model 307 Stratoliner was the world's first high-altitude commercial transport and the first four-engine airliner in scheduled domestic service. With names like Rainbow, Comet, Flying Cloud and Apache, the Stratoliner set new standards for speed and comfort. Its pressurized cabin allowed the airplane to soar above rough weather at an altitude of 20,000 feet -- higher than any other transport of its time. Its circular fuselage provided maximum space for the five crew members and 33 passengers. The nearly 12-foot-wide cabin had space for comfortable berths for overnight travelers. The Stratoliner was the first airplane to have a flight engineer as a member of the crew. The engineer was responsible for maintaining power settings, pressurization and other subsystems, leaving the pilot free to concentrate on other aspects of flying the aircraft.

The airlines which had sponsored the DC-4E were not all entirely happy with what they were getting, but it was a considerable time before the project was finally dropped. In mid-1936, when construction of the prototype was still at an early stage, two of the sponsor airlines (Pan-American and T.W.A.) started discussions with Boeing about a possible civil transport development of the B-17 bomber, which had appeared in prototype form the previous year. The Boeing 307 Stratoliner was considerably smaller than the DC-4E-it had 30 per cent less wing area - and employed the wings, tail unit and tailwheel undercarriage of the B-17 but, like the Douglas, incorporated a large-diameter circular-section fuselage which was intended to be pressurized. The wing was a two-spar structure mainly of conventional aluminium alloy, as was the remainder of the airframe. Some use, however, was also made of steel.

Boeing built 10 Stratoliners. The first prototype used for flight testing crashed March 18, 1939, just 11 weeks after its maiden flight by Boeing test pilot Eddie Allen on Dec. 31, 1938. All 10 men aboard the plane perished. In July, Allen successfully flew the second prototype for the first test of cabin pressurization.

Five Stratoliners were produced for Transcontinental and Western Air, which later became Trans World Airlines, three for Pan Am and one for multimillionaire Howard Hughes. On July 8, 1940, TWA introduced the Boeing Stratoliner into service with a 12-hour, 18-minute flight from New York to Los Angeles. TWA's routes were to Chicago, Kansas City, Mo., and Albuquerque, N.M. Pan Am flew from Miami, New Orleans and Brownsville, Texas, into Mexico City and Central and South America. On 08 July 1940 the first commercial flight of the Boeing 307-B Stratoliner, from Burbank, Calif., to Long Island, N.Y., was the first commercial flight to use a pressurized cabin, in record time of 12 hours 18 minutes. Later in 1940, the 307s started flying routes to Latin America and from New York to Los Angeles, Calif. The Stratoliners attracted the attention of multimillionnaire Howard Hughes, who bought one for himself for $250,000 and transformed it into a "flying penthouse" with a master bedroom, two bathrooms, a galley, a bar and a large living room.

Sixteen months after the introduction of the Stratoliner World War II broke out and Boeing's hope of selling the plane to European customers diminished. Stratoliner production stopped at the onset of war, and with the end of Stratoliner production, commercial production was halted until the war's end. Boeing quickly became focused on building the B-17 Flying Fortress. In addition, Howard Hughes' desire to fly around the world in the Stratoliner disappeared. Howard Hughes retired his plane to a hangar. Later, his airplane would be purchased by a Texas oil millionaire and end its days as a palatial, Florida-based houseboat named Cosmic Muffin. It is available for charter in Florida. Photo courtesy Plane Boats Inc.

By Dec. 24, 1941, TWA removed its five Stratoliners for service in preparation for their mobilization by the Army's Air Transport Command. According to some accounts, Pan Am followed suit, while other accounts maintain that the Pan Am aircraft remained in commercial service. So a total of at least five and maybe eight [but surely not all 10] were drafted into the Army Transport Command. In 1942 these Stratoliners were stripped of their luxurious décor and drafted into service by the Army as C-75 military transports.

The last remaining Stratoliner, the Flying Cloud, was purchased by the Smithsonian's National Air and Space Museum in 1969. The airplane was "discovered" by several Boeing employees while visiting the Pima Air Museum in Tucson, Ariz., to recover the Dash 80 airplane, which was the prototype for the Boeing 707. They investigated who owned the Stratoliner and learned it belonged to the Smithsonian. The Smithsonian had obtained it from a private owner, who converted it for use as a crop duster.

Realizing it was the last Stratoliner in existence - only 10 were built - the employees met with the Smithsonian and offered to take the airplane out of the desert and restore it with all of its original parts. Upon a simple handshake, the Smithsonian agreed, and Boeing began restoring the airplane so it could fly back to Seattle. The journey was made in June 1994. In March 1995, the airplane was moved to Boeing Plant 2 in the same area where it was originally built, and the Boeing team began work on locating and securing original parts. After being stored in the Arizona desert for 20 years, it was restored at Boeing in Seattle, Wash.

F. Schumacher & Co. of New York, N.Y., used a vintage loom to produce the original picturesque Pan Am wall fabric showing the Pan Am logo, world map and animals native to various continents. The fabric design was the same as that of the Boeing 314 Clipper and Boeing Archives fortunately had preserved some of the Clipper fabric. The color of the cloth was determined from remnants trapped between structures of the airplane. Douglass Interior Products of Bellevue, Wash., donated the flooring in the galley and cockpit, the carpet in the main cabin interior, the paneling in the cabin and lavatory, and the imported Scottish leather for the single-aisle and crew seats. BE Aerospace of Miami, Fla., donated its time and materials to upholster the five flight deck crew seats, nine passenger seats and eight divans. Only six of the original seat frames were still in the airplane when it was discovered. All of the light fixtures, bulkheads and trims were manufactured from original engineering drawings.

After a six-year restoration process, Boeing employees rolled out the last existing 307 Stratoliner airplane - the world's first pressurized commercial airliner - on 23 June 2002, in Seattle. First delivered to Pan American Airways in 1940 and named the Clipper Flying Cloud, the airplane was restored to original condition with the help of approximately 30 retiree volunteers. In addition, Boeing employees and suppliers built parts and structures according to original drawings preserved by Boeing Archives.

On March 28, 2002, a Boeing S-307 Stratoliner, N19903, registered to the National Air & Space Museum and operated by The Boeing Company as a 14 CFR Part 91 maintenance check and proficiency flight, ditched in the waters of Elliott Bay near Seattle, Washington, following a loss of engine power on all four engines. The newly restored 1939 Boeing Stratoliner was on its first test flight when it ran out of fuel and couldn't make it back to Boeing Field. The plane arched past the Seattle skyline and nosedived into Elliot Bay. The four passengers were unharmed and able to climb out onto the wing. SPD Harbor Patrol and the Seattle Fire Dive Team responded within minutes to rescue the crew and stabilize the plane.

The airplane was substantially damaged but the two airline transport pilots, and two airframe and powerplant mechanics seated at the flight engineer and avionics stations were not injured. The flight had departed Everett, Washington and was destined for Seattle, Washington. The crew had originally planned to practice landings at an airport about 20 minutes away, then stop, refuel the airplane, and return to the original departure airport. Prior to the flight, the crew discussed fuel endurance, which was calculated to be two hours based on the captain's knowledge of the airplane's fuel consumption, and the quantity of fuel indicated on the gauges. The fuel tanks were not dipped. On approach back to the original departure airport, power was lost in all four engines and the aircraft was ditched in Elliott Bay near Seattle. The Safety Board determined that the probable cause of the accident was the loss of all engine power due to fuel exhaustion that resulted from the flight crew's failure to accurately determine onboard fuel during the pre-flight inspection. A factor contributing to the accident was a lack of adequate crew communication regarding the fuel status.

In June of 2003, the plane was restored for its final destination at the Smithsonian. In August 2003, it flew to its new home on permanent display at the museum's new companion facility, the Steven F. Udvar-Hazy Center near Washington, D.C.'s Dulles International Airport.

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Page last modified: 07-07-2011 02:27:27 ZULU