Investigators are recommending that pilots be trained more rigorously to fly with sole reference to standby instruments following a serious incident in which a British Airways Airbus A319 suffered an extensive loss of electrical power.
The UK Air Accidents Investigation Branch has also advised BA to review its reporting procedures after the inquiry team only learned about the incident six days later, the jet having remained in service in the meantime.
After a two-year investigation the AAIB has been unable to determine the reason for the power loss, which affected the jet’s left-hand electrical network, shortly after the aircraft departed London Heathrow for Budapest on 22 October 2005. But it suspects one of the generator control units detected a false electrical current differential-protection condition.
Failure of the network caused the loss of both pilots’ primary flight and navigation displays, the upper electronic centralised aircraft monitor (ECAM) display, cockpit lighting, the radio and the intercom. In addition the auto-thrust and autopilot disconnected.
“This and other similar incidents show that there is at least one unforeseen failure mode on A320 family aircraft which can cause the simultaneous loss of the captain’s and co-pilot’s electronic flight instruments and the upper ECAM display,” says the AAIB.
If the primary displays are unavailable the A319 can be flown on standby instruments – including a horizon, altimeter, airspeed indicator and compass – but the AAIB says: “The flight crew had not received any formal training on how to operate A320-family aircraft by sole reference to the standby instruments.”
Most of the systems were recovered after about 90s. The captain incorrectly believed that the fault lay in a transformer rectifier and, despite the alarming nature of the initial failure, opted to continue to Budapest.
While the AAIB questions whether particular procedures listed on the lower ECAM could have been prioritised differently to speed recovery, Airbus rejects the suggestion.
It says the ECAM prioritisation was drawn up after analysis of many different safety issues and changing them would require complex follow-up verification and approval. It has, however, addressed concerns over power supply to standby instruments.
The AAIB states that an air safety report form was posted from Budapest, arriving days after the event, while faxed copies did not arrive at BA’s flight operations safety department.
Technical log entries contained hardly any details of the event and, as a result, failed to trigger any investigation. “A substantial period of time passed before the significance of this incident was recognised by the airline,” says the AAIB, which is recommending that BA review its reporting procedures to ensure timely delivery of safety-related information.
Circumstances of the BA incident bear strong resemblance to an electrical failure on board an EasyJet A319 in September 2006 which also became the subject of a AAIB investigation.
Source: flightglobal.com's premium news site Air Transport Intelligence news