Airbus has asked FAA for a waiver that would permit operators of Rolls-Royce Trent 500- and 700-powered A330s and A340s to install improved but not-yet-certified fuel oil heat exchangers (FOHEs) to help eliminate the risk of ice inhibiting engine fuel flow. The request (.pdf)
is based on findings from the probe into the January 17, 2008 crash
of a Trent 800-powered British Airways Boeing 777 at London Heathrow. Investigators determined that the engine's FOHE design, while meeting all regulations, could be susceptible to clogging by ice released from the fuel system under certain conditions. EASA
issued an airworthiness directive requiring new FOHEs on Trent 800s as a result, Airbus noted, and the agency is planning on a similar directive covering the Trent-powered Airbuses because the FOHE designs are common on the 500, 700, and 800.
While no Airbus aircraft have reported the ice-clogging condition, the OEM feels that "a rapid introduction of the modified FOHE within the Airbus A330 and A340 fleet is a valid precaution."
Airbus is working on justifying the benefit of the new FOHE as part of the certification requirements. Getting final data "will take months," Airbus notes--hence the request to press on with a "good precautionary measure."