Implications of Designing Unstable Aircraft from a Flight Control Perspective

Abstract: Designing a flight control system for an aircraft is a multifaceted task which has to take many requirements and constrints into account. Being able to quickly evaluate the feasibility of achieving design targets in terms of – for example – maneuvering capability and stability mar-gins is valuable when faced with the task of designing a flight control system for a new aircraft or aircraft configuration. This thesis presents methods to quickly assess the maneuverability capability of an aircraft with certain dynamics and control servo constraints by inverting the aircraft dynamics. Limitations related to the achievable robustness properties are also de-scribed with an emphasis on unstable aircraft configurations. The influence from variations of key flight mechanical parameters such as Cmα is investigated and the results are exempli-fied for a linearized model of the Admire aircraft.