Summary
We propose to adopt a new airworthiness directive (AD) for the products listed above. This proposed AD results from mandatory continuing airworthiness information (MCAI) originated by an aviation authority of another country to identify and correct an unsafe condition on an aviation product. The MCAI describes the unsafe condition as:
During a Back-up Control Module (BCM) retrofit campaign * * *, some BCMs have been found with loose gyrometer screws.
* * * When the aeroplane is in control back up configuration (considered to be an extremely remote case), an oscillation of the BCM output order may cause degradation of the BCM piloting laws, potentially leading to erratic motion of the rudder and possible subsequent impact on the Dutch Roll, which constitutes an unsafe condition.
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* * * [S]everal Pedal Feel Trim Units (PFTU) have been found with loose or broken screws during the accomplishment of maintenance tasks on A330 fitted with electrical rudderand A340-600. The loose or failed screws could lead to the loss of the coupling between the Rotary Variable Differential Transducer (RVDT) shaft and the PFTU shaft, and consequently to a potential rudder runaway when the BCM is activated.
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The unsafe condition is loss of control of the airplane. The proposed AD would require actions that are intended to address the unsafe condition described in the MCAI.