Single action control for oleo-pneumatic shock absorbers in CS-23 aircraft

A novel open-loop semi-passive control concept for oleo-pneumatic shock absorbers of CS-23 aircraft is presented. This concept enables the control of the damping characteristics in diverse impact scenarios with a single configuration before touchdown. This approach maintains low energy consumption and allows for the application of slower actuators. The damping properties are optimized to achieve the best possible uniform deceleration during compression in various impact scenarios. Integration of this concept is focused on a trailing arm suspension, where the controller takes the interaction between the wheel and the ground at the point of impact as well as the orientation change of the shock absorber during deflection into account. This approach shows minimal maximum load in systems with uniform deceleration curves. For uncontrolled systems, the guaranteed overshoot causes the restoring forces to amplify the tendency for a bounced landing, if the recoil is not effectively damped, especially when ground forces or lift are present. Therefore, the shock absorber is augmented with a coned metering pin to provide increased damping at low deflections. To ensure a comparable analysis of the system regarding rebound tendency, a decompression efficiency criterion is introduced, which can be determined via drop tests. The influence of the metering pin and the single configuration control (separate and combined) on the system's performance (minimal load and rebounce tendency) is examined under varying load conditions. It is shown that the semi-passive concepts improve overall performance across various load scenarios.