The stability and control characteristics of the neutrally bouyant non-rigid airship

The response to controls of a neutrally buoyant non-rigid airship was investigated for a range of speeds from the hover to 30 m/s using a non-linear simulation model. The responses shown include both flight path and a range of motion variables. The latter show the influence of the stability modes on control. The controls included in the airship model comprise equivalent elevator, equivalent rudder, thrust magnitude and thrust vector direction.

A linearised state model of the airship was obtained from the simulation model for a range of speeds from the hover to 30 m/s. The validity of the linearised model for short term evaluation of stability and control was confirmed by matching linear response plots with those obtained from the simulation model. By making assumptions about the nature of response, the state equations were simplified to enable algebraic approximations for the stability modes to be derived by analysis. The approximate models were shown to compare favourably with the actual modes obtained in the solution of the equations of motion.