Airbus Investigates Continued Uncommanded Altitude Deviations on A350 Despite Control Unit Update

Airbus is currently probing recurring instances of uncommanded altitude changes on its A350 twinjets, even after implementing modifications following a similar issue two years ago.

Previously, A350 flight crews received a revised altitude-selection procedure in response to investigations that revealed a potential failure of the altitude-selector dial on the flight control unit, resulting in changes to the target altitude. These changes could range from 100ft to 1,000ft, leading to unexpected deviations from the planned vertical trajectory.

The European Union Aviation Safety Agency (EASA) determined in 2021 that these incidents were linked to a manufacturing flaw in the altitude-selector knob’s encoder. Airbus had subsequently introduced an updated flight-control unit (H6.0) to rectify the problem.

However, EASA has recently disclosed that “several operators” have reported uncommanded altitude changes on aircraft that had undergone the modification. Airbus is actively investigating the causes of these reported events, according to the regulatory authority.

As a precautionary measure, EASA is reinstating the temporary procedure revision for altitude selection, which will apply to all A350-900s and -1000s, including those with the updated flight-control unit.

EASA emphasizes that its directive is an interim step, leaving the possibility open for further action to be mandated for operators. The investigation into these altitude deviations on the A350 remains ongoing.

Sources: AirGuide Business airguide.info, bing.com, flightglobal.com