Aircraft Level Steering Runaway Failure Analysis (2009-01-3136)

Integration of aircraft landing gear systems requires a high level of knowledge and understanding of these systems and how they contribute to aircraft performance. This paper considers a specific design requirement for the steering system. Failure of the steering system, resulting in the aircraft leaving the runway at high speed, can be considered hazardous or even catastrophic. The ability of the system to detect such a failure and take appropriate action is a key aspect of the design. This paper describes an aircraft level steering runaway failure analysis using an aircraft level mechanical and hydraulic control coupled simulation model.The aircraft level simulation model includes aircraft structure, weight and inertia. Appropriate loads and forces (engine thrust, aerodynamic forces, lift, drag) and moments are then applied. The model also includes nose and main landing gears, brakes and tires. The steering system model includes all hydraulic and control components, with failure triggers and steering failure detection logic.The aircraft level steering runaway failure analysis is carried out under different aircraft operations (taxi speeds, weights) in order to identify the most severe condition. In this model, differential braking is applied to simulate a pilot corrective action after the failure is detected.The analysis results show that the aircraft level steering model is able to determine the aircraft landing gear deviation from the runway centerline under failure conditions, with and without pilot corrective actions, and to assess the pilot reaction time required to bring the aircraft back to its runway centerline after the failure occurs.This analysis can be performed during early design stage to evaluate steering system sizing and other performance characteristics and the particular dynamic characteristics of the steering controller.This paper is addressed to the landing gear system performance specialists, who analyze similar conditions, to allow comparison of methods and results.