Experimental Determination of Hydromechanical Constant Speed Drive Precise Frequency Control Accuracy

The paper presents a discussion of the measured speed control accuracy of a Hydro-Mechanical constant speed drive with precise speed trim. The error between the generator output frequency and the precise reference oscillator frequency is measured during generating system operation representing a greatly accelerated flight schedule. The digital instrumentation used to measure the error was developed specifically for this test and is described. The tests were made possible by the availability of a Programmed Test Area (PTA) which allows the test conditions to be repeated accurately through the application of Digital Programming. The test results indicate that frequency control accuracy is essentially determined by the reference.