Originally Posted by
KelvinD
I wonder: at what altitude above ground does the GPWS issue a warning? Looking at the approach plate, there seems to be nothing above 4,000 to 5,000ft along that arc. So, if the aircraft was at 7,800ft, why the alert?
Also, the pie chart shows 10,700ft if approaching from the East, which this flight presumably was.
Puzzling!
By the way, the approach plate shows the arc with a note "NoPT". What does that mean?
There is a spot height @7655' immediately to the north east of the right hand turn to finals. The aircraft had already descended to 7800' prior to reaching the lead in to the final radial. There was around 150' vertical separation, assuming standard pressure and standard temperature at that point, with rapidly rising terrain within a mile of their track. The EGPWS would have been going nuts, as would the GPWS system with a likely Mode II and a possible but not likely Mode IV modes. That terrain is steep, and would have been pretty challenging for the reactive system to give adequate warnings. EGPWS is a blessing, when it is available, not temp limited etc...