Compare the fixed costs, variable cost, and performance of Sikorsky S-61N to over 500 jets, turboprops, helicopters and piston aircraft, with accurate data from Conklin & de Decker.
In the 1950’s Sikorsky developed a heavy twin-engine turbine helicopter that became both a successful military helicopter (the H 3 series) and a successful commercial helicopter – the S61. The S 61 came in several versions. The two primary ones are the S 61L and the S 61N. Both have a boat like lower hull, but only on the “N” model is the lower fuselage sealed to provide a true amphibious hull. The “N” model also has sponsons. The sponsons enclose the main gear and provide stabilization when the helicopter is on the water. The “L” model is not sealed and does not have the sponsons. The S61 has the distinction of being in service with three of the scheduled helicopter airlines that operated in New York, Los Angeles and San Francisco in the 1960’s and early 1970’s. Later in the 1970’s it became one of the mainstays of the offshore oilfield support fleet in the North Sea. The performance of the S 61N and S 61L is identical.
The S 61N is a heavy twin-engine turbine helicopter. It has a five-bladed, fully articulated rotor with metal blades. It uses a bifilar vibration absorber, mounted above the rotor head to decrease vibration levels. Two General Electric CT 58-140 engines are used for this helicopter. A five-bladed tail rotor provides directional control. The fuselage is made of conventional aluminum alloys and is mounted on a fixed three-wheeled landing gear. The cabin features two pilot seats up front. Below and behind them is the passenger/cargo cabin. It has a flat floor and stand-up headroom (6.25 Ft). When used for passenger transport, it can seat up to 39 although typically the cabin seats 24 to 26. When used for external lift, it can carry up to 8000 pounds.
Certification of the S 61L was obtained in 1961 and certification of the S 61N was obtained in 1963. Both aircraft also are certificated for Category A and IFR operations. The S 61 and military H 3 series was in production until about 1980. The bulk of some 125 commercial deliveries took place between 1968 and 1980. In addition, about 30 H 3 helicopters appear to have been converted to S 61 status.
General Electric CT58-140 2