Airbus is considering implementing a cockpit-warning system for the A320neo which would alert pilots if the engine fan-cowl doors are not secure.
The system would monitor the condition of the cowl locks and provide a warning to the crew if they are unlatched.
Airbus is looking at making such a system available from service entry of the re-engined aircraft type, which is scheduled to take place before the end of this year.
It would form part of a rethink on the problem of cowl-loss, particularly in the wake of the British Airways Airbus A319 event in May 2013 in which both engines shed their cowls on take-off. The right-hand engine’s fuel system was damaged, resulting in a fuel leak and fire.
UK investigators remarked that this was “by far the most serious” of the 38 cowl-loss incidents to date involving A320-family aircraft.
The airframer has previously resisted pressure from investigators to devise a warning system, citing complexity, weight and cost, and believing that the solution to unlatched cowls lay in simpler measures centred on the locks.
But such measures – including high-visibility paint on the latches and mechanisms designed to keep unlocked cowls slightly open – have not proven as effective as desired.
While the rate of incidents has halved since 2002, to around one in 2.4 million cycles, the proliferation of the A320 has resulted in twice as many cowl losses involving aircraft with these measures in place.
Airbus says it is adopting a multi-faceted approach to preventing the problem which will encompass design, operational and training aspects.
As well as the cockpit-warning system being considered for the A320neo, the airframer has been developing a new latch system for the current A320 models.
This involves a dedicated key to open the latch, to which is attached a red warning flag. The key cannot be removed while the latch is open, so the flag will dangle visibly below the engine nacelle if the cowl has been closed but not locked.
Airbus says it intends to make this latch a line-fit on production aircraft and the mechanism will be available as a retrofit from early 2016.
Mechanical solutions will be “incorporated in parallel” on the A320neo, the airframer adds. The manufacturer has also revised maintenance procedures to require an entry in the aircraft’s logbook when the cowls are open, which has to be closed off once the cowls have been shut and latched.
Investigators have attempted to determine the contributing elements to A320 cowl-loss events by analysing the circumstances of the recorded incidents.
Both engine types – the International Aero Engines V2500 and CFM International CFM56 – have been affected. But the UK Air Accidents Investigation Branch says there is a “marked correlation” between the cowl loss and the position, inboard or outboard, of the specific engine’s latches.
The V2500 cowl is latched on the right side of the engine while the CFM56 cowl is latched on the left.
An engine with its latch positioned on the inboard side was three times more likely to be the subject of a cowl loss than the engine mounted on the other wing, the analysis found.
More than two-thirds of the events examined for the analysis followed the opening of the cowl for checking or servicing of the oil level in the engine’s integrated drive generator.
Airbus has doubled the oil-level check interval, says the inquiry into the BA event, in order to reduce the number of occasions that the cowl needs to be opened. It has also introduced an optional viewing window on CFM56 engines enabling the generator’s oil level to be checked without opening the cowl at all.
Source: Cirium Dashboard