We have used these filters for years on the advanced engine failure warning logic of some of our models, such as the 76B and Comanche. The intelligent look at torque, rpm and N1 values and rates tells just what the pilot would if he were staring at these indicators constantly. Rate alone is misleading, since the rate might be triggered by normal events (big power pull) but the rate downward while torque/Manifold pressure was also going down is a big indicator of engine unhealth. Conversely, if the rotor is drooping due to a big power pull, the torque/MP will be going up rapidly as the Nr is dropping, and the warning would not be generated. If the Nr is going down, and so is the torque/MP, now its time to sound the warning.
These smart indicators are much faster than conventional speed switches.