Sikorsky has begun ground testing a fly-by-wire (FBW) flight-control system in its S-92 medium helicopter to support development of the H-92 maritime variant for the Canadian Forces. The company plans to introduce FBW on the commercial S-92 at a later stage.
An S-92 development aircraft has been modified with the BAE Systems-supplied triple-redundant digital flight-control computers, and will be used for flight testing to obtain US Federal Aviation Administration certification of the FBW system. FAA approval is planned for mid-2008, with delivery of 28 H-92s to Canada to begin early in 2009.
The S-92 will be the first civil-certificated fly-by-wire helicopter, says Stan Hunter, Sikorsky's Canadian Maritime Helicopter Programme manager.
Replacing the mechanical control linkages between the cockpit controls and rotor actuators saves about 70kg (150lb) and provides more space for mission systems, he says, as well as improving reliability and enabling advanced flight-control modes.
Control laws for the FBW system come in four categories, Hunter says: basic, flight director search-and-rescue modes replicating the latest S-92's capability, plus mission modes specific to the Canadian H-92 for anti-submarine warfare and other tasks. "Fly-by-wire will allow us to extend the modes and add different ones for the next customer," he says.
The first H-92 shipboard helicopter for Canada is entering final assembly at Sikorsky, and will fly early next year, says Hunter.
In addition to FBW, changes from the S-92 include automatic rotor and tail fold and increased gross weight. The second aircraft, to fly a month later, will be the first equipped with the mission system.
Source: Flight International