Some models of Airbus A350 airliners still need to be hard rebooted after exactly 149 hours, despite warnings from the EU Aviation Safety Agency (EASA) first issued two years ago.
In a mandatory airworthiness directive (AD) reissued earlier this week, EASA urged operators to turn their A350s off and on again to prevent “partial or total loss of some avionics systems or functions”.
The revised AD, effective from tomorrow (26 July), exempts only those new A350-941s which have had modified software pre-loaded on the production line. For all other A350-941s, operators need to completely power the airliner down before it reaches 149 hours of continuous power-on time.
Airbus’ rival Boeing very publicly suffered from a similar time-related problem with its 787 Dreamliner: back in 2015 a memory overflow bug was discovered that caused the 787’s generators to shut themselves down after 248 days of continual power-on operation. A software counter in the generators’ firmware, it was found, would overflow after that precise length of time. The Register is aware that this is not the only software-related problem to have plagued the 787 during its earlier years.
It is common for airliners to be left powered on while parked at airport gates so maintainers can carry out routine systems checks between flights, especially if the aircraft is plugged into ground power.
The remedy for the A350-941 problem is straightforward according to the AD: install Airbus software updates for a permanent cure, or switch the aeroplane off and on again.