Airbus A350-900 operators will be ordered to inspect Rolls-Royce XWB front engine mount components after revised analysis by Rolls revealed that high stress in certain conditions could significantly reduce the parts’ service life.
The European Aviation Safety Agency (EASA) is proposing an airworthiness directive that would order inspections of low pressure compressor (LPC) outlet guide vane (OGV) outer mount ring assembly lug fillet areas. The directive, based on a Rolls service bulletin issued August 13, does not apply to the larger XWB-97s that power the A350-1000.
"Revised analysis of these parts, when the front engine mount is engaged in the fail-safe condition, has now been undertaken using more advanced modeling techniques,” EASA’s draft directive explained. “This analysis predicts that, once the [front mount] is in the fail-safe condition, the most highly stressed LPC OGV has a life that could be substantially less than one shop visit interval.”
The mount can enter a fail-safe condition if OGV outer-mount ring lugs fail, EASA explained. The checks are to pre-empt the failure.
Deadlines for the checks are based on service life. Engines with less than 1,700 cycles would be checked within 300 cycles, while engines with at least 1,700 cycles would need inspections within 300 cycles or eight months, whichever occurs first. Follow-up checks are required every 1,000 cycles.
Checks that turn up “discrepancies” may require replacing the outer mount ring assembly.
EASA is accepting comments on the directive through August 29.