Kirks gusset, re #16.
There are situations where the Enhanced functions of EGPWS can / should be inhibited; as you state these are in the AFM. As the systems installations improve with GPS embedded in the EGPWS, the use of geometric altitude, and the terrain database expands and is updated, there are few if any situations where the terrain functions need to be inhibited.
A critical and mistaken belief is that EGPWS suffers nuisance warnings. Whilst any warning system might fail or react inappropriately in extreme situations, the proven reliability of EGPWS is now better than 0.03 alerts per 1000 flights (egpws.com), at least 100x better than GPWS (2003 data).
In some comparisons, this level of reliability is better than the error rate of most human performance. Thus, it could be more likely that the human has made a mistake and not the system.
Pilots should always react to a warning. The debate whether it was warranted or not, can and must be made at a safe altitude before continuing the flight. The essence of the situation is that you don’t know if a warning is valid or not.
The industry does not appear to suffer the same level of skepticism with ACAS or windshear alerting; perhaps this is because GPWS had a relatively poor history.
EGPWS should be considered as something completely new, highly reliable, and extremely effective.
Re:
As a rule, you can only override the warning if you know why it has occurred or you are visual, or both.
See
TAWS ‘Saves’ - some real life experiences, which indicate that ‘as a rule’ there should not be any rule – other than always pull up.