Airbus A319 suffered previous electrical woes

 - October 1, 2009, 11:49 AM

On a Sept. 15, 2006 flight from Alicante, Spain, to Bristol, England, the captain of an Airbus A319 lost all his displays, auto-pilot and autothrust over Nantes, France. He handed control over to the copilot, who had all his displays, except the flight director, and would need to hand-fly using raw data. The commander tried to make contact with Brest Control using all radio facilities, but with no success. Attempts to reconfigure the electrical power supply were not successful.

At Brest Control all traces from of the Airbus had vanished from the radar controllers’ screens. Flight AAL63, which was a potential conflict, was instructed to descend and soon afterwards the crew reported seeing an “Easyjet 737” pass overhead northbound, although it was not displaying on AAL63’s TCAS.

Ten minutes after the incident the captain gave up trying to contact Brest and selected the emergency code on the number-two transponder. Shortly thereafter, the secondary radar trace for the Airbus reappeared on the radar controller’s display and one minute later the code changed to 7700. The airplane continued to Bristol and landed without incident, although on arrival at the parking area it was necessary to use the fire switches to shut down.

In-flight Power Troubles

The previous day, on a flight from London Stansted to Alicante, Spain, with a different crew, the airplane suffered a failure of the left generator control unit. The crew was unable to reset the system, so the pilots isolated the generator and started the APU to supply the left system. After arrival at Alicante, an engineer was unable to fix the defect but, in accordance with the company minimum equipment list, the aircraft was cleared to fly the next sector to Bristol, England, using the APU in place of the generator.

The airplane had a history of electrical-power supply problems in the eight weeks before the incident, but the maintenance department considered it unexceptional.

The UK Air Accidents Investigation Branch (AAIB) could not identify why the crew was unable to reconfigure the power supply system. However, it determined that the design of the aircraft electrical system–which required the crew to manually reconfigure the electrical feed to the essential AC system–was a contributing factor. Investigators also criticized the master minimum equip- ment list that allowed an aircraft to be dispatched without taking into account its previous electrical system history.

A further factor stemmed from inadequate record keeping at Hamilton Sundstrand, makers of the generator control unit. This unit had been returned to them three times in the previous five months. On each occasion it was returned to service as no fault found. Intermittency is the most difficult fault to pinpoint, but investigators determined that a better record of unit numbers and cross-referencing would have alerted the overhaul department to a service history.

The AAIB is aware of three similar electrical system failures in the A320 series. These are G-EUOB, October 2005 (AIN, January 2006); G-OZBE, 23 April 2007; and a U.S.-registered A320, currently under investigation by the NTSB.