Boeing 314 - Design and Development

Design and Development

Pan American had requested a flying boat with unprecedented range that could augment the airline's trans-Pacific 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 149 feet (45 m) wing, and replaced the 850 horsepower (630 kW) Pratt & Whitney Twin Wasp radial engines with the 1,600 horsepower (1,200 kW) 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 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 fitted with the endplates on the ends of the horizontal tail in place of the single vertical fin. This too was found to be lacking 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, obviating 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 water line on both sides of the hull, served several purposes: they provided a wide platform to stabilize the craft while floating on water, they acted as an entryway for passengers boarding the flying boat and they were shaped to contribute additional lift in flight. With weight an extremely sensitive concern, passengers and their baggage were weighed, with each passenger allowed up to 77 pounds (35 kg) free baggage allowance (in the later 314 series) but then charged $3.25 per lb ($7.15/kg) for exceeding the limit. To fly the long ranges needed for trans-Pacific service, the 314 carried 4,246 US gallons (16,070 l; 3,536 imp gal) of gasoline. The later 314A model carried a further 1,200 US gallons (4,500 l; 1,000 imp gal). To quench the radial engines’ thirst for oil, a capacity of 300 US gallons (1,100 l; 250 imp gal) was required.

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 cruise speed of only 188 miles per hour (303 km/h) (typically flights at maximum gross weight were carried out at 155 miles per hour (249 km/h)), many flights lasted over 12 hours. 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; they were a form of travel for the super-rich, at $675 return from New York to Southampton, comparable to a round trip aboard Concorde in 2006. Most of the flights were transpacific with a one-way ticket from San Francisco to Hong Kong, via the "stepping-stone" islands posted at $760 (or $1,368 round-trip). The transatlantic flights continued to neutral Lisbon and Eire 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, astral 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 Clipper into port.