Sikorsky S-43 / JRS / OA-8 / OA-11
The S-43 was originally designed for a Pan American requirement for a twin-engined amphibian for secondary Latin American routes.
Essentially a scaled-down version of the S-42, the S-43 employed a single-step hull and a single tail group. The wing rested on a central pylon, supported on either side by N-struts. Wing flaps covering 48% of the span reduced the stall speed to 65 mph.
The S-42 had twin vertical tails. Many of the S-43s had the same arrangement, but some had a single tail. Biggest difference other than size and the S-43's amphibious capabilities (although some S-43s were built as flying boats) were the powerplants, only two 750hp Pratt & Whitney Hornets on the S-43. The smaller airplane had a gross weight of 19,5001b (8,845kg) and could seat 16 to 24, depending on the legroom. Both transports were certificated in 1935.
After the first flight in June 1935, the first of fourteen S-43s delivered to Pan American entered Latin American service in April 1936, though most were subsequently turned over to Panair do Brasil and other subsidiary operations.
Sikorsky Aircraft built 53 S-43 twin engined amphibians in the mid1930s.
In 1938 Pan American used one of its S-43s on survey flights for planned route extensions to Alaska.
Additionally, four were sold Inter-Islan Airways Airways (later renamed Hawaiian, Airlines) in the Hawaiian Islands, four to Aeromaritime - an Air France affiliate, in West Africa, KLM's Netherlands East Indies associate, and one to DNL-Norwegian Airlines.
Twenty-two amphibians were delivered as S-43s, plus one S-43-A and three S-43-Bs with minor detail changes. Three delivered in 1937-8 for inter-island operations in the Phillipines were registered as S-43-W’s with a one-foot fuselage extension and Cyclone engines, plus one as the S-43-WB witthout amphibious landing gear. Two S-43s were custom built in 1937 as personal transports, one to Howard Hughes and another to Harold Vanderbuilt.
One 'Baby Clipper' was ordered in 1937 by Howard Hughes especially equipped to be flown around the world. It was fitted with larger 900hp Wright GR-1820 Cyclone radials and additional fuel tanks in the cabin. However, it proved too slow and Hughes made his flight in a Lockheed 14.
Hughes had a mishap with his S-43H, modified with twin tails in 1941, flying NC440 into Lake Mead, Nevada, in May 19413 while practicing alightings in preparation for flying the HK4 Hercules flying boat. Raised by a US Navy diving team, the airplane was rebuilt as a S-43W with a single tail, fitted out as a ten-seat executive transport. Manufacturer's serial number 4327 served only briefly in this capacity and spent most of its time in storage.
Ronald Van Kregten, an acquaintance of both Hughes and lgor Sikorsky, purchased the S-43 from the Hughes estate in 1977 and restored it essentially to its executive configuration, obtaining certification. The airplane was based at Houston. Van Kregten planed to flying it occasionally to air shows.
Between 1937 and 1939 the Navy acquired seventeen S-43s that entered service under the designation JSR-1, two being assigned to the Marine Corp. During the same time, five were delivered to the US Army Air Corp as the Y10A-8, and in 1942, a commercial S-43, after being re-equipped with 875 hp R-1690-S2C engines, was impressed into the USAAF as OA-11.
Military craft remained in service throught World War II. One S-43 was sold to the Soviet Union and several ex-Pan American examples were used in Brazil along the rubber river routes. Reeve Aleution Airways acquired an S-43 which it operated in Alaska and Catalina Island until the early 1960s.
One (a JRS) was in storage at the National Air & Space Museum's facility at Silver Hill, Maryland.