Sikorsky S61L & S61N

United States of America

Medium lift utility helicopter

The Sikorsky S61N and S61L are based on SH3/S61A/B Sea King series originally developed in the late 1950s. They are two of the most widely used airliner and oil rig support helicopters built. In September 1957 the US Navy awarded Sikorsky a development contract to produce an amphibious anti submarine warfare helicopter capable of detecting and attacking submarines. The prototype Sea King flew on March 11 1959, while production deliveries took place from September 1961. Power for initial production aircraft was supplied by two 930kW (1250shp) General Electric T58GE8B turboshafts. Development of a civil version was undertaken almost concurrently, with the commercial S61L flying for the first time on November 2 1961. While based on the Sea King, the S61L is 1.27m (4ft 3in) longer allowing it to carry a substantial payload of freight or passengers. Power for initial production S61Ls was supplied by two 1005kW (1350shp) GE CT58140 turboshafts, the civil equivalent of the T58. Unlike the Sea King, the S61L features a modified landing gear without float stabilisers. The otherwise identical S61N, which first flew on August 7 1962, retains the floats, making it suitable for overwater operations, particularly oil rig support. Both the S61L and S61N were subsequently updated to Mk II standard with improvements including more powerful CT58110 engines giving better hot and high performance, vibration damping and other detail refinements. A third civil development of the S61 series to be offered was the Payloader, a stripped down machine optimised for aerial crane work. The Payloader features the fixed undercarriage of the S61L, but with an empty weight almost 900kg (2000lb) less than the standard S61N. The S61 Shortsky is a unique shortened (1.6m/50in) conversion of the S61N and L, designed to increase single engine performance and external payload. The conversion first flew in February 1996 and

S61N Mk II - Two 1120kW (1500shp) General Electric CT581401 or 1402 turboshafts driving five blade main and tail rotors.

S61N Mk II - Economical cruising speed 222km/h (120kt). Service ceiling 12,500ft. Hovering ceiling out of ground effect 8700ft. Range with max fuel and reserves 833km (450nm).

S61N Mk II - Empty 5595kg (12,336lb), max takeoff 8620kg (19,000lb). S61L Mk II - Empty 5,308kg (11,701lb).

Main rotor diameter 18.90m (62ft 0in), length overall rotors turning 22.20m (72ft 10in), fuselage length 17.96m (58ft 11in), height 5.32m (17ft 6in). Main rotor disc area 280.5m2 (3019.0sq ft).

Flightcrew of two. Main cabin seating for up to 26 in early production aircraft and 30 in later production aircraft. Payloader can lift a 4990kg (11,000lb) external sling load.

Production ceased in 1979 when 116 S61Ns and S61Ls had been delivered.

Sikorsky S61L & S61N