PJ2,
On our Airbii the Terr pb being off on the overhead would disable the EGPWS and the NDs would not receive the terrain ahead caution/warning. The pop up feature is only available if the overhead pb is on and the TERR on NDs pbs are off.
The TAWS pb might have been switched off routinely as the system had no terrain clearance info for that airfield and runway.
Last edited by Right Way Up; 10th May 2012 at 16:07.