Results of an elevator servo-control mechanism survey on Airbus A320-family aircraft required by an August 2009 airworthiness directive have led the US FAA to issue a more stringent version of the original one-time inspection.
According to a notice of proposed rulemaking (NPRM) to be issued on 8 November, the FAA is requesting that operators of approximately 770 US-registered Airbus A320-family aircraft perform repetitive inspections (every 5,000 cycles) of the mechanisms, starting earlier than the 10,000 flight cycle threshold set in the August 2009 airworthiness directive (AD).
Both the initial AD and the proposed new AD mirror mandates issued by the European Aviation Safety Agency (EASA), the certification authority for the Airbus aircraft.
"As a result of this one-time inspection campaign, a significant number of rod eye-ends have been found cracked," says the FAA. "In addition, some cracks have been reported on rod eye-ends that had not yet accumulated the 10,000 [flight cycles] of the established threshold."
The FAA notes that a dual servo-control disconnection on the same elevator could result in "an uncontrolled surface, the elevator surface being neither actuated nor damped, which could lead to reduced control of the aeroplane".
The original inspection campaign was prompted by an aircraft on which the elevator servo-control had disconnected. An investigation revealed that the failure occurred at the servo-control rod eye-end, two of which are used to control each side of the A320's elevator.
Inspections on other aircraft "revealed cracking at the location on a number of other servo-control rod eye-ends. In several cases, both actuators of the same elevator surface were affected," says the FAA, who states the root cause of the cracks is not yet known.