Faster-than-realtime inverse simulation method for tiltrotor handling qualities investigation

Abstract

The tiltrotor aircraft has unique flight dynamics characteristics because of the extensive aerodynamic interference and the unique control strategy. Inverse simulation offers an opportunity to study a vehicle's performance during manoeuvring flights. In this paper, an improved inverse simulation method is developed with an Automatic Differentiation (AD) approach embedded in the code based on the verified flight dynamics model of the tiltrotor aircraft. The AD algorithm would accelerate the computational rate of the inverse simulation process and make it achieve faster-than-realtime capability. Then, the XV-15 tiltrotor's control inputs and flight states encountered during a pop-up manoeuvre are investigated using this AD-augmented inverse simulation method, and the real-time capability of this method is also evaluated. The results indicate that the proposed method guarantees both accuracy and faster-than-realtime calculation performance. Lastly, the tiltrotor's manoeuvrability is assessed by executing this manoeuvre in different flight states and manoeuvre settings. Lastly, an envelope involving the velocity and nacelle incidence angle is calculated to indicate the safety region to achieve this pop-up manoeuvre.