|S42 NC-822M, "Brazilian Clipper", 1934|
|Role||Flying boat airliner|
|National origin||United States|
|First flight||March 29, 1934 (prototype)|
|Status||Retired, none remaining|
|Primary user||Pan American Airways|
|Developed from||Sikorsky S-40|
The Sikorsky S-42 was a commercial flying boat designed and built by Sikorsky Aircraft to meet a 1931 requirement from Pan American World Airways (Pan Am) for long-range trans-Atlantic service. The innovative design included wing flaps, variable-pitch propellers, and a tail-carrying full-length hull. The prototype established ten world records for payload to height within a short period of development and test flying following the first flight on 29 March 1934. The "Flying Clipper" and the "Pan Am Clipper" were other names for the S-42.
Design and development
Based on the earlier Sikorsky S-40 that flew in 1931, Igor Sikorsky and Charles Lindbergh (who was working at the time as a consultant to Pan American Airways) laid out plans for a new, larger flying boat. During the S-40's inaugural flight on November 19, 1931, the two visionaries began preliminary sketches on the back of a menu in the S-40's lounge.  In addition to the many aerodynamic improvements over the S-40, the S-42 had a surprisingly heavy wing loading. A novel wing flap fixed the resulting problem in high take-off and landing speed. 
Pan Am's president, Juan Trippe, had a similar vision of an aircraft able to span oceans. The new design provided for an increased lifting capacity to carry enough fuel for a 2,500 mi (4,000 km) nonstop flight against a 30 mph (48 km/h) wind, at a cruising speed far in excess of the average operating speed of any flying boat at that time. Pan Am was also courted by Glenn Martin, but Sikorsky's S-42 was delivered first, as the Martin M-130 was still almost a year away from completion.
British Marine Aircraft Ltd. was formed in February 1936 to produce S-42-A flying boats under license in the United Kingdom but nothing came of this. The company built a factory on the western side of the Hamble peninsula with a slipway to Southampton Water. When the deal fell through the company was sold to Henry Folland, who renamed it Folland Aircraft Limited.
Flying for Pan American Airways, a total of 10 S-42s were built, manufactured by the Vought-Sikorsky Aircraft Division of the United Aircraft Corporation in Stratford, Connecticut. The prototype first flew on March 30, 1934.
The S-42 only flew 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 Harbor, Hawaii in April 1935. (It never flew scheduled passengers from California to Hawaii.)
In March 1939 a Pan Am S-42 was scheduled to leave Miami at 0730, stop overnight in San Juan, Port of Spain, Belem and Recife, and arrive Rio de Janeiro at 1530 on the fifth day. (It returned to Miami, and passengers to Buenos Aires continued on DC2/DC3s.)
All Sikorsky S-42s were either scrapped or destroyed in accidents.
- Production aircraft with four 700 hp (522 kW) Pratt & Whitney Hornet S5D1G radial engines, three built: NC 822M, NC 823M, NC 824M.
- Production aircraft with four 750 hp (559 kW) Pratt & Whitney Hornet S1EG radial engines, longer wings and a 2,000 lb (907 kg) increase in maximum takeoff weight, four built: NC 15373, NC 15374, NC 15375, NC 15376.
- Production aircraft with aerodynamic improvements, constant-speed Hamilton Standard propellers and a further 2,000 lb (907 kg) increase in maximum takeoff weight, three built: NC 16734, NC 16735, NC 16736.
- British Marine BM-1
- Proposed licence-built variant of the S-42A, not built.
Accidents and incidents
On April 11, 1936, a Pan Am S-42 named Puerto Rican Clipper crashed on takeoff from Port of Spain, killing three of 25 on board. The pilot swerved to avoid a fishing boat that was in his path but one pontoon struck the boat and the aircraft overturned.
On January 11, 1938, Pan Am Flight 1, an S-42 named Samoan Clipper (formerly Pan American Clipper II), exploded near Pago Pago. The flying boat developed an engine problem shortly after takeoff. The pilot elected to dump fuel before making an emergency landing, but the aircraft exploded while fuel dumping was in progress. All seven crew members (including famous aviator, Captain Ed Musick), died in the crash.
On October 3, 1941, Pam Am Flight 203, an S-42A named Dominican Clipper, crashed on landing in the harbour at San Juan, Puerto Rico, killing two of 27 on board. After the approach to San Juan, the aircraft hit the water in a nose-low attitude while moving sideways; after the first contact the aircraft swerved violently to the right and broke apart.
On December 8, 1941, a Pan Am S-42B named Hong Kong Clipper II (formerly Bermuda Clipper and Alaska Clipper) was destroyed on the ground at Kai Tak Airport, Hong Kong, during a Japanese bombing raid.
On August 8, 1944, Pan Am Flight 218, an S-42 named Hong Kong Clipper (formerly West Indies Clipper and Pan Am Clipper I) on a return trip from San Juan to Miami with intermediate stops at Port-au-Prince and Antilla, Cuba, crashed shortly after taking off from Antilla. After striking, bow first, the flying boat left the water in a slightly nose-high attitude, then returned, and by the third time, stalled. There were 17 fatalities (all passengers) out of the 26 passengers and five crew.
Sikorsky S-42 NC823M is fully submerged near Antilla airport (MUAT) in Cuba. It crashed in 1944 during takeoff, the aircraft striking the water fracture the hull just aft of the pilot's compartment. There are no plans to recover the wreck.
Another sunken wreck is located near Botwood, Canada, which was one of the stops on Pan Am's trans-Atlantic Clipper service. The Avalon Historical Aircraft Recovery Association is looking for this S-42.
Data from Sikorsky S-42 Clipper Data SheetFlying Boat, 1934
- Crew: 4
- Capacity: up to 37 day passengers or 14 sleeper berths
- Length: 68 ft (20.73 m)
- Wingspan: 118 ft 2 in (36.03 m)
- Height: 17 ft 5 in (5.3 m)
- Wing area: 1,329 ft² (123.5 m²)
- Empty weight: 19,764 lb (8,984 kg)
- Loaded weight: 38,000 lb (17,273 kg)
- Powerplant: 4 × Pratt & Whitney R-1690 Hornet, supercharged radial engine, 660 hp (492 kW) each
- Maximum speed: 188 mph (300 km/h)
- Range: 1,930 miles (3,088 km)
- Service ceiling: 15,704 ft (4,788 m)
- Rate of climb: 1,000 ft/min (305 m/min)
- Wing loading: 28.6 lb/ft² (140 kg/m²)
- Power/mass: 0.07 hp/lb (0.11 kW/kg)
- Related development
- Aircraft of comparable role, configuration and era
- King, H.F. (1969). Milestones of the Air (McGraw-Hill ed.). New York: Jane's All the World's Aircraft Publishing Company. p. 80.
- Delear, Igor Sikorsky: His Three Careers in Aviation, Dodd, Mead & Co., 1969
- Delear, Igor Sikorsky: His Three Careers in Aviation, Dodd, Mead & Co., 1969
- Fagan, Dave. "Hamble." Aviation in Hampshire UK 1900 to 2000. Retrieved: July 5, 2009.
- "Clipper Conquers Pacific on Hawaiian Hops." Popular Mechanics, July 1935.
- Donnelley, James E. "The Crash of NC 15376." webstart.com. Retrieved: April 3, 2010.
- Accident description for NC824M at the Aviation Safety Network. Retrieved on 2014-6-24.
- "Clipper wrecked, all 7 fliers dead in sea after fire; Fragments of Big Flying Boat Are Found in Pacific 14 Miles From Her Pago Pago Base." The New York Times, 1938. Retrieved: December 12, 2011.
- Accident description for NC15376 at the Aviation Safety Network. Retrieved on 2014-6-24.
- Accident description for NC16735 at the Aviation Safety Network. Retrieved on 2014-6-24.
- Accident description for NC16736 at the Aviation Safety Network. Retrieved on 2011-12-12.
- Accident description for NC823M at the Aviation Safety Network. Retrieved on 2011-9-5.
- Randell, Adam. "Taking history to the skies." The Labradorian, July 20, 2009.
- McKinney, Michael. "The First Clippers: The 'Sikorsky S-42." flyingclippers.com. Retrieved: April 3, 2010.
|Wikimedia Commons has media related to Sikorsky S-42.|
- Sikorsky S-42 photos and history
- Sikorsky S-42
- "Atlantic Routine," Flight 1937, contemporary article on S42 and British Caledonian operating across Atlantic
- "The Long-Range Flying Boat, Its Development and Characteristics: A Precis of a Lecture Delivered by Igor Sikorsky," in Flight, 1934 article on the S-42 design
- "Thirty-Two Passenger Flying Boat Meets First Tests," Popular Science Monthly, June 1934, article bottom of p. 37
- "Giant Plane to Cut U.S. - Argentine Time" Popular Mechanics, October 1934, cutaway drawings of purposed S-42, pp. 488–489
- "Sikorsky Sees Dawn to Dusk Trans-Atlantic Flight by Airliners" Popular Mechanics, January 1935, pp. 44-46
- "Pan Americans Flying Boat the Sikorsky S-42", YouTube 3.33 minutes, excellent rare photos of S-42 in service