Design of a Primary Fly-by-Light Control System with a Dissimilar Redundant Architecture

This paper presents the design of a quadruplex redundant fly-by-light flight control system with dissimilar hard- and software for an EC135 helicopter for use in a research and technology demonstration program (ACT/FHS). This purpose implies a dual pilot concept with a safety and evaluation pilot leaving interaction priority to the safety pilot. As the reliability proof of such a new fly-by-light system in a helicopter is part of the ACT/FHS mission, a mechanical emergency backup has been still kept. The basic FBL system consists of 8 quadruplex inceptor stick sensors (4 axes for each pilot), a 4-lane control signal processing computer, 4 smart actuators for the pitch/roll/yaw/collective axis each containing a 4- lane actuator control electronic. An optional flight control computer can be attached for extended experimental or operational modes. The components communicate through optical links. Most benefits of a fly-by-light helicopter control system are seen in the reduced electromagnetic interference susceptibility of datalinks as well as in the adaptation flexibility due to handling qualities or aircraft configuration change requirements.