Pagina 2

Background

Worldwide civil aviation safety statistics indicate that ‘in-flight loss of control’ is currently the main cause of aircraft accidents (followed by ‘controlled flight into terrain’ (CFIT)). Recent loss of flight control accidents and incidents, in which mechanical and atmospheric hazards were the main contributing factors, show that a small number of aircraft were recovered successfully despite severe failure conditions and controllability problems. In other cases, awareness by the onboard crew of the remaining performance and control capabilities in the degraded flight conditions could have improved the survivability of the aircraft.

Emergency landing sequence and wing damage due to surface-to-air missile impact, DHL Cargo A300B4-203F, Baghdad, 2003.

Fault tolerant flight control (FTFC) allows improved survivability and recovery from adverse flight conditions induced by faults, damage and associated upsets. This can be achieved by “intelligent” utilisation of the control authority of the remaining control effectors in all axes consisting of the control surfaces and engines or a combination of both. In this technique, control strategies are applied to restore stability and maneuverability of the vehicle for continued safe operation and a survivable landing.

An increasing number of measures are currently being taken by the international aviation community to prevent loss of flight control accidents. This not only includes improvements in procedures training and human factors, but also finding approaches to better mitigate system failures and increase aircraft survivability in the case of an accident or in degraded flight conditions. Acceptance of innovative fault tolerant flight control and reconfiguration techniques in the commercial and military aircraft field has still not been achieved. However, improved situational awareness or guidance would have increased the odds for pilots of aircraft that have encountered severe and exceptional mechanical failures, resulting in aircraft upsets or hull loss, or the impact of intentional hostile actions. Improving the resilience of flight control systems will support the pilot in bringing crippled aircraft safely back home after facing the improbable.

Cargo accident aircraft prior to takeoff at Amsterdam Schiphol Airport (left). Reconstructed loss of control based on flight data following separation of the right-wing engines (right), EL AL Flight 1862, B747-200F, Amsterdam, 1992.