A PRELIMINARY ANALYSIS OF INDICATED TORQUE RESPONSE REQUIREMENTS FOR AGGRESSIVE HELICOPTER HEAVE AXIS HANDLING

The National Research Council of Canada conducted an experiment to refine the displayed torque response requirements for aggressive helicopter heave axis handling. The presently accepted ADS-33D requirements for displayed torque response are expressed in terms of indicated overshoot ratio and rise time. To confirm and validate these boundaries, the NRC’s Bell 205 Airborne Simulator was configured with a heave axis control model incorporating a simulated engine-rotor governor. Selected second order engine response dynamics were simulated, defined by a range of frequency and damping values. The intention of the experiment was to investigate whether improved criteria could be developed that included both governor response and available power. The results of the flight tests indicated that modifications to the ADS-33D boundaries are warranted. The data showed general agreement regarding the shape of the ADS-33D boundaries, however variations in T/W ratio were found to influence their positions significantly. A more effective torque response requirement is proposed which would include both the influence of available power and torquemeter response, expressed in terms of a composite predictability metric incorporating both overshoot ratio and rise time.