Effect of an active high-lift system failure during landing approaches

Simulation results of the longitudinal motion of a civil twin-engine aircraft with an active high-lift system are presented. The investigated system uses the lift-increasing effect of blowing over Coandă flaps along the wing. The core elements of the nonlinear model describing the dynamic behavior of an aircraft with this specific type of active high-lift system are explained. The main focus lies on the analysis of the aircraft’s reaction to an instant symmetric total failure of such a system. Initial investigations analyze the outcome of such failures, if throttle is set to maximum and elevator is controlled, without using stabilizer or flaps. Subsequently, an investigation has been performed estimating the effect of flap reconfigurations and stabilizer adjustments. The paper also considers a temporary failure of the system due to an engine failure combined with a too low power setting of the remaining engine which has to be increased first before the restart of the blowing system. The investigated situations vary from inconvenient to unrecoverable. Recommendations for backup systems and procedure changes are made to prevent such situations. A procedural approach is analyzed and respective simulations prove the efficiency of this solution.