Same on the 777. The alert height is 200ft RA. Below that height the AFDS will NOT change from LAND 3 to LAND 2 in the event of a failure, and all unrelated EICAS cautions are inhibited. The idea is that the flight crew should not interfere at that late stage, unless it is obvious that intervention is required. In the event of a critical failure that affects the autoland system, a NO AUTOLAND EICAS caution would be annunciated and the flight crew should go around unless they are in a position to continue visually.
On our aircraft there is no EICAS alert for a rad alt failure, only 'NO LAND 3'; don't know if that's a customer option or not. The only way you would know that a rad alt has failed is by looking at the status page, and there's no requirement to do that in-flight.
Last edited by BuzzBox; 25th April 2009 at 11:31.