Olivier Dereure

Experimental Assessment of Low Noise Landing Gear Component Design

Landing gear related airframe noise is one of the dominant aircraft noise components at approach, so continued research efforts to reduce landing gear noise are essential. This paper describes further development of an advanced low noise main landing gear that was previously designed and tested in the European SILENCER project. The work was carried out under the current European co-financed TIMPAN project (Technologies to IMProve Airframe Noise) using a ¼ scaled landing gear model that was tested in the German-Dutch Wind Tunnel. A variety of gear configurations were tested including a new side-stay design and various modifications to the bogie inclination, wheel spacing, bogie fairings with different flow transparency, leg-door configurations and brake fairings. The farfield noise data from the tests are compared with results from a landing gear noise prediction model, transposed to full scale flight conditions and compared with the full scale test data obtained for the original SILENCER advanced A340 style 4-wheel main landing gear. An optimal combination of tested gear modifications led to a further noise reduction of up to 8 dB(A) in terms of overall A-weighted noise levels relative to the original advanced gear configuration.

Non-Linear Dynamics of a Complex Aircraft Brake System: Experimental and Theoretical Approaches

Stability and non-linear dynamics in a complex aircraft brake model are investigated. The non-linear contact between the rotors ands the stators, and mechanisms between components of the brake system are considered. The stability analysis is performed by determining the eigenvalues of the jacobian matrix of the linearized system at the equilibrium point. Parametric studies with linear stability theory is conducted in order to determine the effect of system parameters on stability. In order to obtain time-history responses, the complete set of nonlinear dynamic equations may be integrated numerically. But this procedure is both time consuming and costly to perform when parametric design studies are needed. So it is necessary to use nonlinear analysis : the center manifold approach and the rational approximants are used to obtain the limit cycle of the non-linear system and to study the behaviour of the system in the unstable region. Results from these nonlinear methods are compared with results obtained by integrating the full original system. These non-linear methods appear very interesting in regard to computational time and also necessitate very few computer resources.Copyright