Airbus A320 operators are to be instructed to install warning systems to prevent rudder inputs from overstressing the vertical fin.
The European Aviation Safety Agency is proposing the modification following design reviews and consideration of in-service incidents.
These reviews were prompted by the fatal accident involving an American Airlines Airbus A300-600 which lost its fin after departure from New York in November 2001.
The crew of the A300 had commanded five full alternating rudder inputs to counter roll disturbance from a wake vortex, and this had generated excessive aerodynamic loads on the fin.
While the A320 is a smaller, single-aisle aircraft, EASA says that the design review has determined that allowable loads on the fin “could be reached an possibly exceeded” under specific flight conditions.
Canadian investigators found that an Air Canada A319 had been subjected to fin overstress during an incident in January 2008, as the pilot attempted to counter wake turbulence generated by a Boeing 747-400.
Airbus has developed modifications to the flight augmentation computer, the system which handles rudder travel limitation, yaw damping and rudder trim.
EASA says this change is designed to reduce vertical fin stress and activate a conditional audible warning to protect against alternating rudder inputs from the pilot.
Its proposed airworthiness directive – open for consultation until 20 August – will require fitting and activation of the “stop rudder input” warning logic on the A320 family within 48 months.