Drivetrain Rolling Elements in Aeronautics, Design and Sizing for

In the scope of the development of a more electrical aircraft, this subject aimed at the development and the experimental validation of a reliable sizing method for mechanical transmission elements, specifically screw drives and thrust bearings of aeronautic flight control actuation system. In fact, the replacement of the hydraulic with electric devices promises many advantages but we have to pay attention to the compliance with the operational reliability and safety requirements of these essential components.

Main critical requirements for the sizing method of rolling drivetrain contact elements are related to oscillation loads and reversal of the direction of load, low frequencies oscillating movements, proper lubrication conditions at critical temperatures (low and extreme high temperatures). These critical issues are typical of aeronautic applications, specifically of the helicopter swashplate actuation system, and they are not covered by the standard norms.

At first, the project activities concerned a deep survey of state of the art, including norms, patents and proprietary methods of sizing. Moreover, a targeted analysis to the exact definition of the operating conditions were conducted. These first steps were essential steps for the development of the sizing method. Then, the third step was the analysis of the stress at the contact area between the balls/rollers and the tracks on both bearings and screws in dynamic conditions that were performed by dedicated software.

The case of the helicopter swashplate was considered as a benchmark and a dedicated sets of rolling contact thrust bearing and balls screws transmission was designed, manufactured and tested in order to validate the developed new method of sizing.