Airbus’s initial reading of the Digital Flight Data Recorder (black box) of the A-320 jetliner, which violently dropped 300 feet on a flight from Phuket to New Delhi, indicated that there was a total, simultaneous loss of key control surfaces, including the elevators and ailerons, for a period of 4 seconds – with the spoilers also lost as a consequence of the same hydraulic failure.

During those 4 seconds, the elevators and ailerons of the A-320 NEO drifted on their own without any pilot command following multiple failures of the jet’s three hydraulic systems, unprecedented in operations of this type of airliner. Hydraulics are critical to the operation of flight control surfaces, namely the elevators which pitch the nose up or down, the ailerons which roll the aircraft left or right by tilting the wingtips, and spoilers which reduce lift, add drag to help the aircraft descend or slow down (including braking on landing).