01/31/2011. The S-61 was perhaps the most versatile airframe to emerge from Sikorsky. This started with a number of military version, including anti-submarine, search and rescue, transport, etc. Fitted with a boat hull and outrigger floats, it was a large helicopter with two turbine engines linked through an overrunning clutch system driving a single large five-bladed main rotor.
The rotor blades were designed for power folding for carrier stowage, and incorporated a unique spar pressurization system for detecting fatigue cracking.
The crew compartment was in the nose, and due to the positioning of the engines on the fuselage roof, it had an unobstructed cabin section.
Sikorsky produced a range of different variants of the S-61 using the standard nose and fuselage centre section together with the power pod - but incorporating additional stretch segments ahead of and behind the engines and, in the case of the S-61R, a new rear fuselage with a slimmer tail boom and a rear-loading ramp.
The civil S-61L was ordered by Los Angeles Airways and had a non-amphibious hull and a fixed strutted undercarriage. The later S-61N was a stretched passenger-carrying version which had the full water landing capability and was used extensively by BEA Helicopters and Bristow Helicopters on offshore oil operations in the North Sea.
In an apparent reversal of design philosophy, a number of S-61Ns have been rebuilt by Helipro Corporation as the S-61 Short (nicknamed Shortsky). This involves removal of the outrigger floats and a 50 in (1.27 m) plug from the forward fuselage in order to improve lifting capability, and six conversions have been completed to date. Shortly after the above photo was taken, N612RM also became an S-61 Short.