Airbus emphasizes that it will not be used to counter turbulent or vortex-induced rolls using ladder pedals, ensuring that high-load events are documented and reported quickly.
Air Flammer highlighted an incident involving an A320, which was unexpectedly caught up in the 52° right bank during the climb from 30,000 to 36,000 feet.
The pilot rebutted both the side stick and the rudder pedal.
With these combined inputs, the jet passed the bank to the left and, due to an opposing response by the pilot, the aircraft led the bank to the right “badly” on the right, says Air Flammer.
This cycle was repeated further on the left and right banks before the A320 stabilized. During the course of the occurrence, a “Stop the rudder” warning was triggered four times.
The aircraft continued climbing, cruised over altitude and advanced to its destination.
However, the crew reported the turbulent encounter to maintenance personnel, but did not mention the rudder input warning, Airbus first stated in the safety of its internal publications.
The jet was not equipped with a flight data interface unit that could trigger lateral load alerts.
Airbus says the event was “not reported immediately” by the crew and says it was not detected until routine data analysis (almost a year later) picked up unusual flight parameters.
Data revealed that the A320 is exposed to a maximum lateral acceleration of 0.41g. This is considered a “red level event” under maintenance guidance, but the jets were only inspected based on excessive turbulence.
Analysis of the data found that flight loads were “near design limits,” Airbus said, “did not exceed those.”
Airbus aircraft are equipped with two different rudders: either the mechanical systems found in older single-isle and wide body jets, or electric ladders such as the A321XLR, A220, A330Neo and A350.
The powerful alternating rudder-pedal inputs put structural damage at risk, Airbus said.
“The (electric ladder method) should not be considered as protection against structural damage or failure of the rudder due to such inputs.”
Airbus says the use of rudder pedals should be limited to taking off and landing, crossing control, and countering yaws from engine failures until the rudder is trimmed.
“Using rudders during other flight stages or turbulent encounters can cause unnecessary trajectory deviations and excessive loads on the rudder structure.”
Airbus adds that comprehensive information must be provided to maintenance personnel if the crew experiences a heavy load event, especially when a “stop ladder input” warning occurs, whether caused by turbulent flow or excessive maneuvering.
“This important information could allow maintenance personnel to properly assess lateral loads, perform the necessary inspections, and create more serious structural problems.”
