ASSISTANCE IN DEVELOPMENT AND EVALUATION OF BEARING, DISTANCE AND HEADING INDICATOR (BDHI) INSTRUMENTATION.
NAVAL AIR DEVELOPMENT CENTER JOHNSVILLE PA AERO MECHANICS DEPT
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CONCLUSIONS BDHI instrumentation in current aircraft cannot perform to one-degree accuracy. Large errors occur during change of heading of the aircraft, and an indication lag of from four to eight degrees is common. Specifications for the equipments which are the source of signal inputs for the BDHI are wholly inadequate in defining the synchros that are to be used in the system. The BDHI specification, MIL-1-22075, does not require that the indicator be tested using the inputs that are the same as those to which it would be connected in an aircraft. Consequently indicators can pass all the requirements of the specification and still not perform satisfactorily when installed in an aircraft. If torque receiver synchros are to be used in the BDHI, then the systems which drive the BDHI must contain torque transmitter synchros. With the proper type of torque synchros installed, a satisfactory BDHI instrumentation system can be had without requiring the indicator pointers to be servo driven. Author
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