by David Kaminski-Morrow & David Learmount in London

Investigators call on Airbus and Boeing to develop procedures for coping with airborne loss of flightdeck power

UK investigators are recommending that Airbus and Boeing should develop operating procedures for coping with – respectively – A320 and 737 electrical problems that have, in two cases, left the pilots with a serious loss of cockpit instrumentation.


A320 ECAMS W445
© Airbus

The AAIB says both A320 ECAMs ( centre) should be working at departure

In the first event, an EasyJet Boeing 737-300, operating from Nice, France to London Luton airport on 22 March last year, suffered a loss of power from the battery busbar, which led to a gradual degradation of instruments, including the electronic attitude director indicator and the standby artificial horizon. While the EasyJet crew did not have a checklist for the situation, they correctly deduced that the main attitude display was being compromised by a loss of cooling, and switched to an alternative cooling system.

“The flightcrew in this incident dealt with the situation effectively,” says the UK Air Accidents Investigation Branch (AAIB). But it adds: “There is no doubt that a specific procedure for the problem, had one been available to them, would have made diagnosis more straightforward.”

The 737 diverted to Lyons, but the AAIB suggests that this might not have been necessary if the flight manual had provided the crew with the information they needed. It also points out: “A different crew may not have reacted to the situation in a similar manner, with an attendant risk that loss of all attitude information could have occurred.”

Boeing has stated that loss of the battery busbar is not hazardous, but the AAIB is challenging this because a similar event occurred in an Aer Lingus 737-500 at Copenhagen in 1997. The AAIB says that the various 737-300/400/500 models have many different electrical system configurations, which makes it difficult for Boeing to produce a generic procedure for such a failure – although it provides information enabling operators to write specific procedures for their own aircraft. EasyJet has developed such a procedure for 737s. The AAIB is recommending that the US Federal Aviation Administration should press Boeing to provide an operations manual procedure for handling power loss from the battery busbar that would work for all the variant configurations.

Meanwhile, in the Airbus incident, on 22 October last year, a British Airways A319 crew lost both pilots’ primary flight displays (PFD) and navigation displays (ND), plus the upper of two electronic centralised aircraft monitor (ECAM) screens. The crew also lost all cockpit lighting and communications, and were left with only one operating ECAM.

The AAIB has found that the same type of event has occurred five times before, and although it is continuing the investigation, it has made four interim recommendations to the manufacturer (see below).

Changing priorities

When the British Airways Airbus A319 crew were left with only one electronic centralised aircraft monitor (ECAM) display to show engine, systems and alerting/advisory text, there was only one line of text at a time shown at the base of the display. When that has been actioned, the next item scrolls up. The AAIB notes that the action by the co-pilot which restored power to almost all the cockpit displays was the ninth or tenth item on the list, so the board has recommended Airbus alter the action priorities so power is restored faster. In the case of the BA crew, power was restored within about 90s, says the AAIB.

At present the lower ECAM screen may be unserviceable and the aircraft may still depart. The AAIB has recommended Airbus consider requiring both ECAM screens to be serviceable for departure.

Finally, in some A320 series aircraft the standby artificial horizon has only one power source. In the BA A319 it had an alternative supply, but these differences are not reflected in crew manuals and the AAIB has recommended they should be. The AAIB says Airbus “has reacted positively” and is working on finding ways of actioning all the recommendations. A final report on the A319 incident will be published “when the investigation is complete”, the board says.

Source: Flight International

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