Key Points:

  • Airbus is investigating new incidents of uncommanded altitude changes in A350 twinjets, despite implementing modifications intended to rectify a similar issue from two years ago.

  • The European Union Aviation Safety Agency (EASA) has reinstated a temporary altitude selection procedure for all A350 models as a precaution, including those with updated flight-control units.

  • EASA's directive follows reports from several operators of unexpected altitude changes in A350s, even after the application of the new flight-control unit standard.

Ongoing Challenges in Airbus A350 Altitude Control

Airbus is currently conducting investigations into recent reports of uncommanded altitude changes in its A350 twinjets. This development comes despite the implementation of specific modifications aimed at addressing a similar issue that first surfaced two years ago. The issue involves unintended changes in the aircraft's altitude, posing potential safety concerns. Originally, A350 crews were advised to follow a revised altitude-selection procedure after it was discovered that a failure in the altitude-selector dial, part of the flight control unit, could lead to unexpected changes in the aircraft's vertical trajectory. These changes could result in a deviation of either 100 feet or 1,000 feet from the set target altitude, depending on the interval setting of the aircraft.

In response to the initial problem, the European Union Aviation Safety Agency (EASA) issued a statement in 2021 identifying the root cause as a manufacturing flaw in the encoder of the altitude-selector knob. Subsequently, Airbus developed an upgraded flight-control unit standard, labeled H6.0. This upgrade was intended to allow operators to discontinue the use of the amended altitude-selection procedure on aircraft equipped with the new system. However, recent reports from several operators have indicated that uncommanded altitude changes are still occurring, even in A350s that have been modified with the new flight-control unit.

Precautionary Measures and Regulatory Actions

In light of these recent reports, EASA has taken immediate action. The regulator has confirmed that Airbus is thoroughly investigating the causes behind these newly reported incidents. As a precautionary measure, EASA has decided to reinstate the temporary procedure revision for altitude selection across all models of the A350 fleet, including both the A350-900 and A350-1000 variants. This decision applies even to those aircraft that have been updated with the new H6.0 flight-control unit. The reinstatement of these temporary measures underscores the ongoing efforts to ensure the safety and reliability of the A350 fleet.

EASA has emphasized that this directive is an interim solution. The agency has indicated that it might instruct operators to undertake further actions if necessary, based on the outcomes of the ongoing investigations. This situation highlights the complex nature of modern aircraft systems and the continuous vigilance required in maintaining operational safety. The ongoing issues with the Airbus A350's altitude control system not only underscore the challenges faced by aircraft manufacturers but also the importance of regulatory oversight in ensuring the safety of air travel.