Defining Pilot Gain

A common topic of discussion among members of the flight-test community is pilot gain. Every seasoned flight-test professional is capable of identifying test pilots that are considered to be either high-gain or low-gain pilots. It is considered a given in the testing world that high-gain pilots are better at exposing shortcomings in aircraft handling qualities, including the potential for explosive pilot-induced oscillation. By inference, low-gain pilots are often judged to be just the opposite. Despite this interpretation, the concept of pilot gain is itself not well understood. How do we define, quantify, and (perhaps most importantly) modify pilot gain? Using recent research data, pilot gain can be identified as an element in the pilot-vehicle closed-loop system. It is demonstrated that pilot gain, in closed-loop control, is a misnomer and that more proper terms might be pilot-vehicle bandwidth or crossover frequency.