Once bitten, twice shy... or NOT?
We pointed earlier ( post no 899 ) that Amsterdam and Lion Air accidents were in part due to single channel/sensor.
In fact on 31 July 2009, Boeing informed airlines about a future Service Bulletin that they are going to rectify the situation in regard to Amsterdam rad alt problem by a comparator function between the measured heights of the left and right radio altimeter systems.
https://books.google.com.tr/books?id...terdam&f=false
P.S. related page 130 bottom part.