Primary Flight Control System Research Articles

Magnetostrictively actuated control flaps for vibration reduction in helicopter rotors—design considerations for implementation

Vibration reduction using blade root pitch control introduces a significant power penalty and may adversely affect the airworthiness of the flight control system. Comparable levels of vibration reduction can be achieved using considerably less power through an actively controlled trailing edge flap mounted on the blade. Such a device would have no effect on helicopter airworthiness since it is controlled by a loop separate from the primary flight control system which utilizes the swashplate. Control flap actuation using the magnetostrictive material Terfenol-D is studied in this paper by designing a minimum weight actuator, subject to a set of actuation and stress constraints. An important ingredient in this design process is the precise characterization of the constitutive relations for the magnetostrictive material which provides valuable guidelines on the practical implementation of magnetostrictive actuators. It is shown that the magnetostrictively actuated flap is capable of producing vibration reduction in high speed forward flight in excess of 90%.

Simulation of a prototype electrically powered integrated actuator for civil aircraft

Developments in the design and proposed operation of large civil aircraft have resulted in aircraft manufacturers and equipment suppliers developing new system concepts, one of which is the all or more electric aircraft. In the all or more electric aircraft the distribution of power for flight actuation will be through the electrical system, as opposed to the currently used bulk hydraulic system. In order to implement power-by-wire, high-performance electrically powered actuators will be required. The paper discusses the design details, and the simulation of an electrohydrostatic actuator suitable for use in primary flight control systems of a civil aircraft. The paper presents experimental and simulation results, and identifies the parameters that will critically affect the performance of an actuator.

777 flight controls validation process

The validation process used in support of certification of the Boeing 777 full fly-by-wire Primary Flight Control System (PFCS) and Autopilot Flight Director System (AFDS) is summarized. This process includes development of the system and component level requirements, ensuring the requirements are correct and complete, and ensuring the integrated systems and airplane comply with the system and airplane level requirements. Validation methods, traceability, problem tracking, and organizational management of the process are described.

X-29 flight control system: lessons learned

Two X-29A aircraft were flown at the NASA Dryden Flight Research Facility over a period of eight years. The airplanes' unique features are the forward-swept wing, variable incidence close-coupled canard and highly relaxed longitudinal static stability (up to 35% negative static margin at subsonic conditions). This paper describes the primary flight control system and significant modifications made to this system, flight test techniques used during envelope expansion, and results for the low and high angle-of-attack programmes. Throughout the paper, lessons learned will be discussed to illustrate the problems associated with the implementation of complex flight control systems.

Surface control system

THE VFW 614 has been designed around a manual primary flight control system for rudder elevator and aileron. It follows then that within the flight envelope encountered conditions will exist where, due to thermal lag and different rates of expansion between the steel cables and the aluminium structure and also due to normal in flight structural deflection, the cable run will be either slackened or stretched. The cable tension regulator is introduced into the cable loop system in order to maintain correct rig tension.