Pan American Airways' Sikorsky Flying Boats
Three Sikorsky S-40 aircraft were built for, and delivered to, Pan American Airways in 1931. They served without incident, flying passengers and mail throughout the Caribbean routes until WWII when the U.S. Navy used them for training purposes. Pictured above, from the museum collection, is NC81V "Caribbean Clipper".
Juan Trippe and his aviation consultant, Charles Lindbergh, pressed for improvements in the S-40 design and capabilities. Starting in 1934, the first three Sikorsky S-42 were delivered to Pan American Airways. These offered better aerodynamics through wing flaps, variable pitch propellers, and a full length hull. Overall, ten Sikorsky aircraft were added to the fleet.
Iconic Airliners from the Past: Sikorsky S-42
submitted by Keith Hitchman, aviation author and historian
The Sikorsky S-42 was a commercial flying boat designed and built by Sikorsky Aircraft to meet requirements for a long-range flying boat laid out by Pan American World Airways (Pan Am) in 1931. The innovative design included wing flaps, variable-pitch propellers, and a tail-carrying full-length hull. The prototype first flew on 29th March 1934, and, in the period of development and test flying that followed, quickly established ten world records for payload-to-height. The "Flying Clipper" and the "Pan Am Clipper" were other names for the S-42.
During the inaugural flight of Sikorsky's previous flying boat, the S-40, on November 19th 1931, the pilot and Pan American Airways consultant, Charles Lindbergh, who considered the S-40 a monstrosity, engaged designer Igor Sikorsky in a conversation about what he thought the next airplane should look like. Sikorsky argued that design development should be incremental and that the safe approach would be a larger S-40. Lindbergh argued that a sleeker design, with a range in still air of 2,500 miles, was needed.
In June 1931 Pan Am president Juan Trippe had requested designs from six aircraft companies for an aircraft able to span the oceans. The new design would need increased lifting capacity to carry enough fuel and 300 pounds of mail, but no passengers, for a 2,500 miles nonstop flight against a 30-mph wind, at a higher cruising speed than the norm for similar flying boats at that time. Of the six companies’ tenders had been sent to, only Sikorsky and Martin provided submissions. Sikorsky offered the S-42. The other offer was the more ambitious Martin M-130.
The new Sikorsky design, the S-42, had major aerodynamic improvements over the S-40. Diverting sharply from the past Sikorsky designs, external bracings have been reduced to a minimum. The tail, instead of being supported by outriggers, is attached directly to the hull. The S-42 had a high wing loading which required flaps to provide acceptable take-off and landing speeds. Though Lindbergh approved of the S-42, it fell far short of his proposed range Stripped of all accommodations, with extra fuel tanks in the fuselage, the S-42 was just able to fly proving flights across the Atlantic and Pacific oceans. Pan Am would have to wait for the Martin M-130 to have an airliner capable of flying the Pacific with a payload.
Pan Am's S-42s were used primarily on the Miami - Rio de Janeiro route. In 1937 S-42s also operated a New York-to-Bermuda service. 1940 saw S-42 flights between Seattle and Alaska. An S-42 was also used between Manila and Hong Kong.
Flying for Pan American Airways, a total of ten S-42s were built, manufactured by the Vought-Sikorsky Aircraft Division of the United Aircraft Corporation. The prototype first flew on March 30th 1934.
The S-42 flew only for Pan American Airways. The S-42 Pan Am Clipper surveyed the route from the US West Coast to China, making the first survey flight from Alameda, California to Pearl Harbour, Hawaii in April 1935. (It never flew scheduled passengers from California to Hawaii.)
All Sikorsky S-42s were either scrapped or destroyed in accidents.