The Microprocessor and the Airplane: The Evolution of an Intelligent Trim System 830728

In this paper, the writer will review the need for, and the importance of a powered and intelligently-controlled aircraft pitch trim system. Two types of trim motors and their respective advantages and disadvantages will be presented along with motor to microprocessor interface techniques. Input command monitoring features for protecting the integrity of wiring and switches will he discussed. A variety of pitch-trim operating modes will be described, along with a discussion of the sensors needed to feed flight dynamics data to the pitch-trim controller. A fail-passive design philosophy will be presented with the goal of achieving more useful operation along with less rigorous certification requirements; and, finally, electronic hardware and redundant software will be described which will take advantage of microprocessor technology to provide an impressive cost/performance ratio in complex system design.


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