Sikorsky Product History
Sikorsky S-35
Background
The Sikorsky S-35 model was a 3 engine sesquiplane designed specifically in 1926 to try to win the $25,000 Orteig prize for the first nonstop flight from New York to Paris. The original design was a 2 engine transport but it was redesigned to the 3 engine configuration while still in the drawing phase of development.
Igor Sikorsky knew that a successful crossing would, with the world wide press coverage, generate much interest in Sikorsky designed airplanes and increase sales. Capt. Rene Fonck, a World War One Ace and hero, was chosen by the buyers (Argonauts Inc.) to fly the trans-Atlantic flight.
The S-35 was completed on August 21, 1926 and had its first test by ground taxiing. This test proved that the airplane had full rigidity but required an air pressure adjustment on the left wheel and a reduction of the rubber doughnuts on the tail skid shock absorber. The first flight was made on August 23, 1926 with a duration of 35 minutes. A second flight was made the same day with a flight over New York City. The aircraft proved satisfactory in every way and no modifications were made to the aircraft after this date. Three additional test flights were conducted: A speed test on August 27, 1926, an altitude test on August 28, 1926, and a load test on September 7, 1926. A flight was made from Roosevelt Field on September 9, 1926 to Bolling Field, Washington D.C. and return on September 10th. The purpose of the flight was to test fuel consumption and navigation equipment. In Washington, a demonstration flight was made for representatives of the Bureau of Aeronautics with Bureau Chief, Commander H.C. Richardson at the controls. Another flight was made for U.S. Army pilots.
During the 23 test flights of the S-35 ten different expert pilots from the U.S. Navy, U.S. Army, and Sikorsky and all unanimously expressed the opinion that the plane was exceptionally light on the controls and had remarkable maneuverability and stability in the air including flights with only one side motor operating. Several of the expert pilots expressed the opinion that the easiness on the controls of the S-35 was more characteristic of a pursuit type plane than a heavy multiengine plane.
The video below entitled “Sikorsky S-35: The plane that should have beat Lindberg” shows the S-35 in flight.
S-35 Development Timeline
S-35 Design Details
An all metal structure covered by fabric, the entire frame-work of the body was composed of duralumin channels, tubes and plates assembled with steel bolts and rivets. There was no welding on any part of the structure and there were no wires or structural cross members in the cabin area. The entirely enclosed cockpit had shatterproof, sliding glass windows at the top and sides, and dual controls had been provided for the pilots. Behind the cockpit the passenger cabin contained space for 450 cu. ft. of cargo or 12 passengers. This cabin was four ft. wide, six ft. high, and fifteen and one half ft. long. Radio equipment was also installed for regular or short wave transmission.
The S-35 had self-compensating rudders, so the plane could fly level with any two of its three engines in operation. The wing structure was made up entirely of duralumin, with the main spar built up to I-section by four duralumin angles, riveted to the central web of flat sheet duralumin. These ribs were formed from light sheet duralumin channels and angles, and high tensile strength tie rods were used in the internal drift bracing system.
The ailerons were hinged on an auxiliary spar behind the main spar. They tapered at the tip and blended into the wing at point of attachment. Tail surfaces were built similar to the construction of the wings and were fabric covered. The stabilizer was adjustable for trim during flight, while the landing gear, of the divided axle type, was made entirely of steel and bolted together; the wheel spread of the gear was 18 ft. 4 in.
Engine
Power was supplied by three Gnome Rhone Jupiter nine cylinder air cooled radial engines with 425 hp at 1600 rpm.
Landing Gear
The landing gear was of the conventional type, with a tail skid. To compensate for the extreme weight for the transatlantic flight auxiliary landing gear were attached which would be jettisoned after takeoff.
Cockpit
The cockpit was covered with Plexiglas with emergency escape hatches.
Furnishings
The cabin was configured for 10 passengers and 2 mechanics during test flights and then reconfigured for the transatlantic flight.
General Arrangement Drawing
General Characteristics and Performance
| Performance – Standard Day at Sea Level | |
|---|---|
| High Speed | 145 mph / 126 kts / 233 km/hr |
| Low Speed | 65 mph / 56 kts / 105 km/hr |
| Maximum Rate of Climb | 1,100 ft/min / 5.6 m/s |
| Service Ceiling | 17,000 ft / 5,182 m |
| Time to Climb to Service Ceiling | 45 minutes |
| Weights | |
|---|---|
| Maximum Takeoff Gross Weight | 20,000 lbs / 9072 kg |
| Weight Empty | 9,700 Lbs / 4,400 kg |
| Maximum Fuel Load | 2,290 Gal / 8,668.6 ltr |
| General Data | |
|---|---|
| Crew Seating Capacity | 2 |
| Seating Capacity | 12 passengers |
| Powerplant Ratings Standard Day at Sea Level | |
|---|---|
| Gnome Rhone Jupiter 9A | 425 hp (316.9 kw) @1,600 rpm |
| Aircraft Dimensions | |
|---|---|
| Span, Upper Wing | 101 ft / 30.8 m |
| Span, Lower Wing | 76 ft / 23.2 m |
| Length Overall | 46 ft / 13.4 m |
| Height Overall | 16 ft / 4.9 m |
| Total Wing Area | 1,095 sq. ft / 33.2 sq. m |
| Loading per Horsepower | 19 lbs / 8.6 kg |
Production History
S-35 production consisted of 1 aircraft. Igor Sikorsky anticipated many orders would follow after the publicity of a successful Atlantic crossing.
by Vinny Devine
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