The update to the software will revise the logic of the engine controls to prevent this type of shutdown from occurring again. The Federal Aviation Administration (FAA) has stated that the loss of engine power and hydraulic systems during the incident caused a compromised braking capability.
The investigation of the incident has revealed that a "transient disagreement" between actual and commanded thrust led to the shutdown of the engines of the aircraft. The disagreement occurred when the autothrottle increased thrust to maintain the speed but the pilot commanded a reduction to idle. This disagreement triggered the detection logic for thrust-control malfunction, which in turn shut down the engines when the aircraft's weight-on-wheels switch was activated upon touchdown.
In response to the incident, new procedures have been created for pilots to follow in order to reduce the risk of a similar incident happening in the future. These procedures direct pilots to take action before landing if they abruptly reduce the thrust levers towards idle above 16,000 feet. These actions include starting the auxiliary power unit and selecting the longest runway available, in order to reduce the potential for runway excursion.
The Federal Aviation Administration has issued a directive, effective from January 31, which focuses on updating the full-authority digital engine control software for the Pratt & Whitney PW1500G powerplants of the Airbus A220.
Airbus has identified situations that could mistakenly trigger the thrust-control malfunction logic and has revised the software to improve and correct the logic criteria. The FAA is now mandating that certain versions of the FADEC software, earlier than V2.11.14.1, be removed and replaced with the updated version within the next 12 months.
