Airbus A220 operators are being instructed to install a new production baseline software for flight-control computers to remedy a number of deficiencies reported on in-service aircraft.
The upgrade is required for all three flight-control computers on the twinjet type, states a Transport Canada directive.
Its mandate follows occurrences of nuisance messages – including rudder, aileron or spoiler failure – resulting from erroneous transmissions from the remote electronic unit which handles flight computer commands.
Analysis of the problems also turned up “design deficiencies” in the software, says the directive.
These include weaknesses in built-in test and monitoring routines, it says, as well as a lack of “robustness” which might not prevent inadvertent autopilot engagement during take-off or unannunciated spoiler deployment.
The autopilot issue was the subject of previous regulatory action, with A220 operators ordered to alert pilots – through flight manual amendment – to the possibility of premature rotation if the autopilot was inadvertently engaged late in the take-off roll.
Transport Canada says the software issues could lead to increased crew workload and even a “large reduction of safety margins”.
It requires operators, within two years, to install the updated software – which will become the new production baseline – in accordance with a July 2024 service bulletin. Upgrading the software, it says, will remove the need for an autopilot warning in the flight manual.
