The Boeing 314 Clipper was an American long-range flying boat produced by Boeing from 1938 to 1941. One of the largest aircraft of its time, it had the range to cross the Atlantic and Pacific oceans. For its wing, Boeing re-used the design from the earlier XB-15 bomber prototype. Twelve Clippers were built, nine of which served with Pan Am.
Design and development
Pan American had requested a truly trans-Pacific flying boat with unprecedented range and double the passenger payload of the airline's Martin M-130. Boeing's bid was successful and on July 21, 1936, Pan American signed a contract for six. Boeing engineers adapted the cancelled XB-15's wing, and replaced the Pratt & Whitney Twin Wasp radial engines with the Wright Twin Cyclone. Pan Am ordered six more aircraft with increased engine power and capacity for 77 daytime passengers as the Boeing 314A.
The huge flying boat was assembled at Boeing's Plant 1 on the Duwamish River in Seattle, and towed to Elliott Bay for taxi and flight tests. The first flight was on June 7, 1938, piloted by Edmund T. "Eddie" Allen. At first the aircraft had a single vertical tail, and Allen found he had inadequate directional control. The aircraft returned to the factory and was fitted with the endplates on the ends of the horizontal tail in place of the single vertical fin. This too was found to be insufficient and finally the centerline vertical fin was restored, after which the aircraft flew satisfactorily.
The 314 used a series of heavy ribs and spars to create a robust fuselage and cantilevered wing, eliminating the need for external drag-inducing struts to brace the wings. Boeing also incorporated Dornier-style sponsons into the hull structure. The sponsons, broad lateral extensions at the waterline on both sides of the hull, served several purposes: They provided a wide platform to stabilize the craft while floating, they acted as a gangway for boarding and exiting, and they possessed intentional shaping to contribute additional aerodynamic lift in flight.
To fly the long ranges needed for trans-Pacific service, the 314 carried of gasoline. The later 314A model carried a further . A capacity of of oil was required for operation of the radial engines.
Pan Am's "Clippers" were built for "one-class" luxury air travel, a necessity given the long duration of transoceanic flights. The seats could be converted into 36 bunks for overnight accommodation; with a cruising speed of (typically flights at maximum gross weight were flown at ) in 1940, Pan Am's schedule San Francisco to Honolulu was 19 hours. Clipper service catered to elite businessmen and the wealthy traveler. The 314s had a lounge and dining area, and the galleys were crewed by chefs from four-star hotels. Men and women were provided with separate dressing rooms, and white-coated stewards served five and six-course meals with gleaming silver service. The standard of luxury on Pan American's Boeing 314s has rarely been matched on heavier-than-air transport since then. A round trip from New York to Southampton was $675 (), while a one-way ticket from San Francisco to Hong Kong via the "stepping-stone" islands posted at $760 (). The Pan Am Boeing 314 Clippers brought exotic destinations like the Far East within reach of air travelers and came to represent the romance of flight. Most of the flights were transpacific, while transatlantic flights to neutral Lisbon and Ireland continued after war broke out in Europe in September 1939 (and until 1945), but military passengers and cargoes necessarily got priority, and the service was more spartan.
Equally critical to the 314's success was the proficiency of its Pan Am flight crews, who were extremely skilled at long-distance, over-water flight operations and navigation. For training, many of the transpacific flights carried a second crew. Only the very best and most experienced flight crews were assigned Boeing 314 flying boat duty. Before coming aboard, all Pan Am captains as well as first and second officers had thousands of hours of flight time in other seaplanes and flying boats. Rigorous training in dead reckoning, timed turns, judging drift from sea current, celestial navigation, and radio navigation were conducted. In conditions of poor or no visibility, pilots sometimes made successful landings at fogged-in harbors by landing out to sea, then taxiing the 314 into port.