CORDIS - EU research results

Drivetrain Rolling Elements in Aeronautics, Design and Sizing for

Final Report Summary - DREADS (Drivetrain Rolling Elements in Aeronautics, Design and Sizing for)

Executive Summary:
A new sizing method for rolling elements in application where small oscillation strokes and high frequency loads are to be considered has been developed, improved and validated.
A study case with the application of the sizing method has been performed, showing the benefits in terms of envelope and weight.
In the frame of the project, high frequency test rigs and ballscrew specimens for test have been built and tested.
The purpose of the project has been completely achieved.

Project Context and Objectives:
The development of a more electrical aircraft is a technological transition applied or envisioned for almost all the systems in the aircrafts and helicopters.
In order to achieve such a goal, a plurality of innovations is needed, included a robust sizing method for components of an Electro-Mechanical Actuator, designed and sized to minimize the probability of a mechanical jam. There is actually no proof that the standard sizing method is also applicable to specific condition of operation, as they are usually find on primary flight actuators for Fixed Wing and Rotary Wing aircrafts.
The goal of the project is to develop, validate and apply a sizing approach that addresses the conditions of operation indicated. The improvement is necessary with respect to the ISO 281 and 3408 sizing criteria, that are commonly considered not applicable to the operating conditions of many flight control surfaces actuators.
In this frame the sizing method I validated generally, and the application is referred to a study case concerning the flight control actuators of a helicopter swashplate.

Project Results:
The project has been split in the work packages below:
- WP2 is dedicated to the analysis and evaluation of the state of the art. In the first part of this work package a survey has been performed covering literature studies and other project activities about the state of the art of sizing methods for electro-mechanical actuator in aerospace applications. Literature, Research and Manufacturers’ guidelines are considered in the scope of work. The definition of requirements of the innovative sizing method has been part of the WP.
- WP3 was dedicated to the development of the sizing method and of the corresponding Validation Plan. Starting from theoretical evaluation of possible modes of failure for the rolling elements, and joined with manufacturer’s experience in the field, life calculations have been modified from the standard to include all ranges of motion and high frequency loads. Some criteria have been defined for safe operation.
For each identified range of operation, a corresponding validation test has been designed.
- WP4 was dedicated to the application of the new sizing method to the study case identified in the proposal, a helicopter swashplate actuator. The comparison of the improved design versus a standard design showed benefits in terms of envelope and weight, with the same calculated life.
The validation plan of the improved design delivers an accelerated test approach.
- WP5 was dedicated to the manufacturing of test facilities and test specimens. With respect to the original plan, an additional facility was necessary to parallelize tests, and additional test specimens were necessary to reach statistical confidence.
- In WP6 all validation test results are reported and evaluation of results is provided. The results gave indication for validation of the sizing method, for design improvements and robustness, for failure identification.
The main milestones have been:
- the development of a robust sizing method for the operating conditions requested and of design criteria needed to avoid the identified most critical failure modes;
- the validation of the life calculation with significant statistical confidence, for the most common operating range, and the validation of design criteria for the other operating range, for full coverage.
- the application of the sizing calculation and of the design robustness criteria to a study case, with significant improvement of envelope and weight.

Potential Impact:
The results of DrEADS project can extend the application of electromechanical actuators in aviation. Such technology is considered to provide environmental benefits in comparison to the current actuation technology based on hydraulic actuators.
The promising results of the project can be considered conclusive, for the configuration and materials tested. Further tests should be implemented in order to extend the results to further materials and architectures used in aerospace applications.

List of Websites:
The public website is not foreseen.