The European Aviation Safety Agency (EASA) is trying to eliminate incidents caused by engine fan cowl doors left unlatched during routine maintenance, urging operators to change procedures while it ponders formal mandates.
EASA wants operators to begin requiring mechanics to make logbook entries when fan cowl doors are unlatched for any reason. The agency also suggests that manufacturers amend their aircraft maintenance manual (AMM) procedures to include logbook entries listing fan cowl door openings.
While many aircraft types have been involved in fan cowl door-loss incidents, they have been especially prevalent on Airbus narrowbodies. EASA’s latest push is driven by a U.K. Air Accidents Investigation Branch (AAIB) report on a May 24, 2013, accident involving a British Airways (BA) Airbus A319.
The report, released in July, found that a series of oversights allowed the A319 to depart London Heathrow Airport (LHR), with both fan cowl doors unlatched. The doors ripped away shortly after takeoff, causing a fuel leak, prompting the crew to shut down one engine and make an emergency landing at LHR, without any serious injuries.
The probe concluded that two BA technicians left the A319’s fan cowl doors unlatched when they had to interrupt routine maintenance to get needed materials. The technicians, working on six aircraft during an overnight maintenance shift, later returned to the wrong aircraft to finish the job. A series of mishaps and procedural weaknesses—many of which have been addressed by BA as a result of the probe—meant that their mistakes were not detected, even during pre-flight walk-arounds by a pilot and a ground service worker.
“There has been much effort to improve the detectability to ensure preventing such events,” EASA explains in safety information bulletin. “However, at this time, all measures rely largely upon the human factor that an unsecured fan cowl door should be detected by ground personnel or the flight crew during walk-around.”
The BA accident is one of about 40 in which an Airbus narrowbody has departed with at least one fan cowl door unlatched, AAIB said. Analysis found that the system’s design leads mechanics to leave the doors unlatched in a certain configuration that makes them safer to work around by providing more clearance between the ground and the latches, which hang down below the engine when not secured. But the configuration also makes unlatched doors more difficult to notice.
Airbus has updated its AMM to include logbook entries when fan cowl doors are opened. The company also is developing a modification for A320ceo-family aircraft that will make latching the doors a more deliberate process. The change will be line-fit into production next year and available as a retrofit.
Airbus is going further on the A320-neo family, adding a flight deck warning to flag unlatched fan cowl doors. Regulators rejected past calls for such systems, in part to avoid nuisance warnings triggering dangerous scenarios such as unnecessary aborted takeoffs.
The A320’s certification basis considers fan cowl doors structural, not systems elements. While systems elements—such as passenger and cargo doors—require system safety assessments to identify risks and suggest features like cockpit warnings, structures elements only must show they can withstand certain loads. Once the standard is met, a failure’s ramifications are not considered.
AAIB included a call to reclassify fan cowl doors as systems elements among its five recommendations from the BA A319 probe, while also calling for modifications to the A320-family system. EASA says it will likely mandate the modification that Airbus is developing.