Sikorsky plans to begin flight testing a modified S-92 Helibus civil helicopter in August, incorporating the first in a series of significant design changes to the rotorcraft's empennage, fuselage and cockpit avionics suite.
The lead S-92 flying prototype is being modified and will resume testing this summer fitted with a redesigned tail pylon. The main change has been to reduce the height of the vertical stabiliser by 355mm (41in) and reposition the horizontal stabiliser from the upper left side of the tail forward and to the lower right.
Reducing the weight and size of the tail allows Sikorsky to add a 400mm plug to the fuselage just aft of the cockpit and correct a slight nose-up pitch angle in flight (Flight International, 18-24 April). "This moves the centre of gravity forward to get a flatter hover attitude," says Tommy Thomason, Sikorsky vice-president for civil programmes.
The fifth utility-configured prototype, which has been completed but not yet flown, will incorporate the stretched fuselage as well as the new tail pylon. It will enter the flight test programme at the end of the year. The smaller tail has the added benefit of easier shipboard storage, which is a requirement for the Nordic Standard Helicopter Programme (NSHP), for which the S-92 is competing.
The NSHP could total up to 90 machines for Denmark, Finland, Norway and Sweden, which are seeking a common helicopter to replace a range of models for transport, anti-submarine warfare, search and rescue and shipborne roles.
Sikorsky's revised flight schedule calls for the fourth and final civil-configured prototype to follow early next year equipped with the recently selected Rockwell Collins Pro Line 21 avionics suite incorporating four 150 x 243mm liquid crystal displays. Certification will be pushed back from late 2001 to early the following year, while first delivery is on schedule for April 2002 to Canadian offshore oil operator Cougar Helicopters.
The redesigned fuselage will produce a small increase in empty weight, but the standard maximum take-off weight remains constant at 11,440kg (25,200lb), with the option to go to 13,620kg with auxiliary fuel.
The fuselage plug will add two seats to the 22-seat military version and give the option of an extra row of seats to 19-seat civil operators.