The influence of elevator movement on the normal accelerations experienced by a transport aircraft in moderate turbulence

Abstract

Some excerpts from a record of data obtained in an encounter with moderate turbulence during routine operations by a transport aircraft are analysed in order to assess the contribution to the cg normal accelerations from the elevator movement produced by the automatic control system. It is found that this contribution is quite small and does not have a consistent effect on the amplitudes of the accelerations. The influence of an autostabilizer on the response in turbulent conditions is discussed for an idealised situation. From the analytical and numerical results obtained it is seen that the effectiveness of an autostabiliser will usually be strongly frequency-dependent. However, it is suggested that for the case considered here an autostabiliser with a pitch-rate law could gave a useful reduction in the cg normal accelerations experienced in turbulence: the most suitable value of the gearing appears to be that which produces a value of about 0.7 for the relative damping of the aircraft's short-period longitudinal mode.