MICHAEL PHELAN / CHELTENHAM
Smiths Aerospace is using highly accelerated life testing (HALT) methods to evaluate the performance of its Airbus A380 landing gear extension and retraction system (LGERS). It is also taking advantage of new materials to reduce the system's weight.Smiths' Cheltenham, UK-based Actuation Systems division believes this is the first time HALT has been used for hydromechanical systems.
Component testing of uplocks, valve housings, actuators and pitch trimmers is already under way at Cheltenham and Yakima, Washington, USA, and Smiths is due to begin testing electrically actuated gear and door uplocks on its in-house test rig from October. Rob Neal, Actuation Systems engineering director, says the use of electrical actuators will save 200kg (440lb) by eliminating mechanical pull cords on the emergency release system.
Smiths is supplying the complete A380 LGERS, including the controlling software and remote data concentrators as well as the hardware. "It allows us to tailor the operation of the system in the most appropriate location," says Neal. One of the major challenges for the A380 LGERS was the event sequencing, he says. "It's much more critical than on previous aircraft because the tolerances are smaller."
Paul Beazley-Long, Airbus programme manager for A380 landing gear, says the system was designed to cope with proposed larger 1.42m (56in) tyres on the A380 Freighter, "so there's a bit more space using the standard 1.37m tyres".
He adds: "As with previous aircraft, there is a crossover on the arcs of the gears and doors during retraction, but we've done much more modelling and simulation on this aircraft to ensure adequate clearance."
Smiths has designed the event sequencing to prevent such a conflict, while also eliminating the need for delay valves in the system.
The company is also testing polytetrafluoroethylene (PTFE) seal caps on its pitch trimmer seals to cope with high velocity oxy-fuel (HVOF) coatings. "HVOF can produce a better sealing surface than chromium plating, but because the coating is less porous there is less lubrication, which can wear traditional seals," says Neal.
Smiths aims to deliver its first LGERS hardware shipset to Airbus's landing gear test rig in Filton, UK, in December.
Source: Flight International
