LUCASAEROSPACE hopes to have identified an initial application for its power-by-wire technology by the time a 1,000h in-service evaluation of electric flight-control actuation on a US Air Force Lockheed C-141 StarLifter is completed early in 1998.

The company is pursuing military retrofit opportunities for its integrated actuation package (IAP) for the Rockwell B-1B and Lockheed C-5, as well as new commercial-aircraft applications, such as the planned Airbus Industrie A3XX large airliner, says Steve Croke, director of technology at Lucas Aerospace Power Transmission in Utica, New York.

Lucas believes that its IAP is particularly suited to retrofit applications because it uses standard 115V AC aircraft power, whereas competing electric-actuation technologies require 270V DC power. There are also safety concerns with using 270V DC power on commercial aircraft, Croke says.

The IAP consists of a constant-speed AC motor driving a variable-displacement hydraulic pump. Flow though the pump is controlled by a swashplate, or tilt block, and is reversible to extend or retract the actuator. Croke says that the design results in more-constant electrical loads, without the peaks caused by stopping and starting a DC motor driving a fixed-displacement pump or ballscrew actuator.

The hydraulic aileron-control system of the "Electric StarLifter" testbed has been removed and replaced with dual-channel electric actuation, driven off the existing aircraft power system. Signals from sensors attached to the C-141's mechanical flight-controls are sent to dual electronic control-units which drive two dual-channel IAPs, one for each aileron.

Croke says that operation of the electrically actuated ailerons is "transparent" to the pilot. Some 520h have been accumulated since the first flight in June 1996. "Experience in the field has proved that the maintenance required to remove, install, troubleshoot and rig is very much less [than with the conventional hydraulic system]," he says. The Lucas system has health-monitoring capabilities.

Electric actuation is attracting attention as a way to overcome reliability problems with in-service aircraft, adds Croke.

Source: Flight International