Originally Posted by TBL Warrior
Shaggs, there is no reference in any Boeing manuals to ‘Terrain Clearance Floor’
This is what's in mine:
Enhanced Operation
Terrain Clearance Floor
The Terrain Clearance Floor (TCF) alert function adds an additional element of
protection to the basic GPWS by creating an increasing terrain clearance envelope
around the airport runway. TCF alerts are based on current airplane location,
destination runway center point position and radio altitude. When the TCF
envelope is penetrated:
* TOO LOW TERRAIN voice warning is generated twice.
* Amber GROUND PROX message is displayed on PFD.
* Additional TOO LOW TERRAIN voice warning will be generated for every
additional loss of radio altitude of approximately 20%.
TCF is active during takeoff, cruise, and final approach. The TCF alerts add to the
existing Mode 4 protection by providing alerts based on insufficient terrain
clearance including landing configuration.