Ian Sheppard/LONDON

Messier-Bugatti has installed a prototype electro-hydraulic actuator (EHA) in an Airbus Industrie "iron bird" test rig at Aerospatiale's Toulouse systems development centre, as part of an industry drive to replace cumbersome hydraulics with electric cables.

The EHA is a key technology for all electric, or power by wire, aircraft. The traditional centralised hydraulic pump is replaced with a decentralised electric power generation system, which supplies electric power to drive a hydraulic pump at the actuator. This avoids the need for complex hydraulic pumping and saves weight.

Messier is developing versions of the EHA for landing gear extension and retraction, nosewheel steering, braking and flight controls. The major challenge, says the Snecma subsidiary, was developing a universal pump "compatible with all EHAs", for which it used a flight control actuator as a baseline.

The design selected is an axial-piston type, reversible with fixed displacement. Three, five, seven and nine-piston versions have been designed, with weight varying between 0.1kg and 1.5kg and displacement of up to 50mm³ (0.305in³). Messier has carried out "static development" and start-up tests at its laboratory in Vélizy, France, on a 24.2mm³ pump running at speeds of up to 10,000RPM.

An endurance test with a Messier-Bugatti customer, within a simulated airborne environment, demonstrated a life of 20,000h.

The company says the results meet manufacturers' requirements and the pump is undergoing demonstration tests on one braking and two servo-control EHAs.

Other EHAs are being tested by Lucas Aerospace, which is developing a primary servo-control EHA for the Airbus A330's inboard aileron, and Belgium's Sabca, developing a similar unit for the Airbus A320.

Source: Flight International