Hybrid Control System for a Future Small Aircraft

Abstract

A Fly-by-Wire like Flight Control System for small general aviation aircraft designed for excellent flying qualities and pilot assistance with particular emphasis on acceptable development and especially certification efforts (cost-benefit ratio) is considered. The manifold benefits of advanced Active Fly-by-Wire Flight Control Systems within modern transport aircraft featuring a wide range of functionalities and applications are undisputable. They represent an effective means of reducing pilot's workload significantly, monitoring pilot’s inputs, providing warnings and protections and hence, increasing the passenger, crew and aircraft safety (carefree handling). However, the general aviation aircraft sector is still missing such Active Flight Control Systems because of their tremendous (development, system/hardware and certification) cost which can easily exceed the actual airframe cost of the small aircraft several times. Affordable Fly-by-Wire technology for small aircraft can be achieved by using a Hybrid Control System which combines additional (limited) electrical actuated control surface deflections commanded by the Flight Control Computer together with retaining a (full-authority) permanent mechanical direct link between pilot inceptor and the control surface via a mechanical mixing unit. This approach offers the opportunity of utilizing the benefits of state of the art Fly-by-Wire control technology simultaneously enhanced by the reliability of conventional control systems and thus, reducing certification effort and cost dramatically. The Hybrid Fly-by-Wire like control concept discussed is integral part of a joint Technology Research project concerning upcoming future small aircraft representing a cooperation of an Austrian aircraft manufacturer and Technische Universitat Munchen.