Summary
We propose to adopt a new airworthiness directive (AD) for the products listed above that would supersede an existing AD. 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:
Several occurrences of untimely radio-altimeter lock-up have been reported, where the failed radio-altimeter indicated a negative distance to the ground despite the aircraft was flying at medium or high altitude.
A locked radio-altimeter 1 leads to untimely inhibition of warnings that could be displayed along with certain abnormal conditions while the avionic system switches into landing mode during altitude cruise. * * * * * [Untimely radio altimeter lock-up] may cause the crew to be unaware of possible system failures that could require urgent crew's actions. * * * * *
The proposed AD would require actions that are intended to address the unsafe condition described in the MCAI.