An electromechanical actuator (EMA) is used to dynamically vary the blade pitch angle in response to power and thrust commands from the flight control computers for an advanced aircraft platform.
A common 270 VDC actuator is required to operate variable pitch blades within each ducted fan positioned at the canard and main wing. The actuators drive a set of blades mounted to a common rotor within each fan. The angle of attack of the suite of blades at each propulsor motor must respond quickly and accurately to meet aircraft flight performance demands for the 3-axes of motion. The actuator must incorporate a fail-safe design so that the blades move to a ‘feather’ position in the event of an EMA power failure. The installation envelope for the EMA was tight and is further complicated because the Circuit Card Assembly (CCA) was placed within the actuator. Balancing the internal and external thermal loads away from the EMA was also a key design parameter.
The in-line actuator is a unique design employing a very unique mounting configuration. A high-speed DC motor drives through a multistage geartrain to engage a ball screw assembly. The cam mechanism drives the fan blades in unison. A common CCA is built into each actuator so that the EMA can be used at any propulsion motor location. The EMAs were designed to be interchangeable between the propulsion canard and wing installation. Each EMA provides position feedback to the Flight Control Computer
Other design considerations included electromagnetic interference (EMI) and lightning strike requirements
Results & Outcome
Actuators have been supplied for aircraft certification tests regimen. Initial test results have matched closely to analysis and predictions.