Analysis of the Wizz Air CFDS revealed no previous gear door fault messages.
In probing the incident, Airbus discovered that airplanes outfitted with a certain combination of LGCIUs and actuators were “masking” the relevant CFDS messages, creating the possibility of actuators unknowingly getting worse.
Investigators determined that, left unchecked, the debris build-up can restrict an actuator enough to delay gear deployment, which automatically triggers a flight crew warning that the gear is not down and locked. When pilots switch to the manual gear extension mode, a faulty actuator could keep the gear door from “free-falling” open and the gear from extending, even if the crew follows the correct procedures.
Airbus issued an All-Operators Telex on June 24, alerting operators to the newly discovered CFDS anomaly and potential ramifications. EASA’s emergency directive followed a day later.
FAA’s AD is based on the EASA directive. The problem’s urgency prompted FAA to go directly to final AD status without prior public comment.