Abstract
The longitudinal motion of an aircraft is influenced by two oscillatory motion modes which are called short-period mode and phugoid mode. It is known that the pitch attitude handling qualities of an STOL (Short Take Off and Landing) airplane is degraded as the airspeed slows down. It is supposed as the main cause that the natural frequencies of the two modes come nearer. We have studied using a flight simulator, including the effect of other modal parameters. So we focused the initial amplitude ratio and the difference of the initial phase angles between short-period component and phugoid component in pitch attitude response to elevator step input. The result has showed that the difference of the initial phase angles plays a more important role in human pilot's pitch control than the proximity of two natural frequencies.
