A Novel Hydraulic Solution to Simulate Inertial Forces on a Landing Gear Qualification Test Rig

The proposed test rig consists of a multi-functional intelligent test facility with the objective to perform all the tests and analyses required to assess the maturity of an electro-mechanical landing gear and demonstrate the feasibility of Prognostics and Health Management (PHM) functionalities for the electrical brake system. One of the most critical elements in the design of such iron-bird is the definition of the system replicating the aircraft inertia, which presence is necessary to properly assess the behavior of both the brake and its anti-skid logic during landing. The most common solution foresees to bring the landing gear leg in contact against a rotating cylinder, or runway simulator, which moment of inertia is equivalent to the aircraft mass. Although it is possible to reduce the system encumbrance through the introduction of a geared reducer, such architecture is usually extremely heavy and requires significant space in the test facilities. This architecture is also difficult to adapt to different aircrafts, since it would require the addition or replacement of these heavy flywheels, which is both difficult and dangerous. This paper deals with the definition of a possible alternative, based on a hydraulic solution, where two variable-displacement hydraulic motors, connected to a light rotating cylinder, are used to replicate most of the aircraft inertial forces during braking. The paper opens with the preliminary sizing of such system, presents the high-fidelity simulation environment used to assess its expected performances and compare the behavior of the hydraulic solution with that of the traditional configuration, finally presenting both the benefits and the disadvantages of the proposed architecture.