Power by Wire for Aircraft - The All-Electric Airplane 771006
The achievement of a single-power generation distribution and utilization system on future high-performance aircraft will yield many benefits in the form of improved maintainability, reliability, and logistics. It will also reduce aircraft weight and the number of skill catagories required in maintenance training programs. Current aircraft have two parallel and nearly equal-sized secondary power systems (electrical and hydraulic). Of the two, only electrical has the potential for powering all significant functions on the aircraft from radio to landing gear. However, even though electrical power generation and distribution has always been competitive with hydraulic, electrical actuators (utilization) have been heavy and slow. For this reason, hydraulics have for many years monopolized all actuation applications in which power and/or frequency response requirements were moderately high.
With the advent of high specific output, low inertia, rare-earth permanent magnet-type electric motors, the aircraft actuation field was reopened to electric motors. This, in turn, made possible the “all-electric” airplane, and significant power system (generation and distribution system) weight savings. For the B-1 aircraft, used as a typical example in this paper, these savings were on the order of 566 pounds.
Servo-motor versions of these new electric motors will be adequate for most actuation functions. However, certain specific functions on advanced high-performance aircraft will still exceed the motor's capability in terms of power and/or frequency response. It is shown in this paper that the application of a mechanical servo-power package (MSPP) to these functions will meet the power and frequency response requirements, and will save additional weight. The MSPP consists of an electric motor, an adapter gearbox, a flywheel, a mechanical controller, and a mechanical hinge. The MSPP is shown to be capable of meeting high power demands while achieving a frequency response nearly an order of magnitude higher than the electric motor servo design goal. Through the energy storage features of the flywheel, the MSSP is able to save additional weight. On the B-1 aircraft, this weight saving is 1,046 pounds. It is also shown that the total weight savings on the B-1 aircraft, as a result of converting to the “all electric” airplane configuration, is 1,642 pounds.