RADALT Notes
Some notes from the 737ng....if the #1 RADALT receiver/transmitter is inop do not use the associated FCC or autopilot for the approach. This would have allowed the autopilot to capture the LOC/GS if the FO was flying in CMD B. One of the major issues in this crash is a failure of the #1 RADALT you would lose modes 1-4 of the GPWS.
1) Excessive sink rate
2) "terrain..terrain..."
3) Do not sink after climb
4) unsafe altitude while not in the landing configuration.
RADALT failures in the NG can catch you by suprise especially the #2 RADALT failure with the FO flying. You get AutoPilot disengage with the LOC Capture with approach armend. Not applicable in this scenario but it does catch you off guard.