Boeing 307 - Operational History

Operational History

The maiden flight of the first Boeing 307 Stratoliner (not a prototype, as it was planned to be delivered to Pan Am following testing and certification), registration NX 19901 took place from Boeing Field, Seattle on December 31, 1938. It crashed, however, on March 18, 1939, while being demonstrated to representatives of KLM. At the time, the 307's performance with two engines inoperative on one wing was being demonstrated. When the engines were shut down, the pilot moved the rudder to maximum deflection to counter the resulting yaw. The Stratoliner then experienced rudder lock, where the control loads prevented the rudder from being re-centered. As a result, the 307 went into a spin and crashed. The 10 people aboard, including KLM test pilot Albert von Baumhauer, Boeing test pilot Julius Barr, Boeing Chief Aerodynamcist Ralph Cram, Boeing Chief Engineer Earl Ferguson, and a TWA representative were killed. Subsequent wind tunnel testing showed that the addition of an extended dorsal fin ahead of and attached to the vertical tail prevented rudder lock from happening. This was incorporated into the 307's rudder redesign, while also being incorporated in Boeing's rear fuselage redesign for their models "E" through "G" B-17 long-range bomber.

The first delivery to a customer was to multi-millionaire Howard Hughes, who purchased one 307 for a round-the-world flight, hoping to break his own record of 91 hours 14 minutes set between July 10–14, 1938 in a Lockheed 14. Hughes' Boeing Stratoliner was fitted with extra fuel tanks and was ready to set out on the first leg of the round-the-world attempt when Nazi Germany invaded Poland on September 1, 1939, causing the attempt to be abandoned. This 307 later had the extra fuel tanks removed, was fitted with much more powerful Wright R-2600 engines, and was transformed into a luxurious "flying penthouse" for Hughes, although it was little used, eventually being sold to oil tycoon Glenn McCarthy in 1949.

Deliveries to Pan-Am started in March 1940, with TWA receiving its first 307 in April. TWA's Stratoliners flew three-stop flights between Los Angeles and New York while Pan-Am's flew from Miami to Latin America. Ten 307s were built, three being delivered to Pan-Am (Clipper Flying Cloud, Clipper Comet, and Clipper Rainbow) and five to TWA (Comanche,Cherokee,Zuni,Navajo and Apache) with the one aircraft for Howard Hughes.The first airplane crashed in testing.

On the entry of the United States into World War II following the Attack on Pearl Harbor, Pan-Am continued operating its Stratoliners on routes to Central and South America, but under direction of the Army Air Force, while TWA's 307s were sold to the U. S. government, being designated Boeing C-75 and operated by the United States Army Air Forces (although normally still flown by TWA crews).

The U.S. Army returned the five C-75s to TWA in 1944 and they were sent to Boeing for extensive overhauls and rebuilding. Boeing replaced the wings and horizontal tail with those from the improved B-17G model, while more powerful engines were fitted and the electrical system was replaced by one based on the Boeing B-29 Superfortress. Passenger capacity was increased from 33 to 38. The rebuild cost TWA a total of $2 million for the five aircraft, which re-entered passenger service on April 1, 1945. Although TWA was now committed to the larger and faster Lockheed Constellation the Stratoliners remained in use on regional services until withdrawn and sold in April 1951.

TWA's sold its Stratoliners to the French airline Aigle Azur, who used them for scheduled flights from France to North and Central Africa, and later to French Indo-China. These 307s were later transferred to Aigle Azur's Vietnamese subsidiary and were used by a number of airlines in South East Asia, with at least one aircraft remaining in commercial use until 1974. Pan-Am disposed of its unmodified Stratoliners earlier than TWA, with them being sold to a number of small operators. One aircraft was purchased by the Haitian Air Force, being fitted out as a Presidential transport for Papa Doc Duvalier. This aircraft was later returned to the United States and was purchased by the Smithsonian Museum.