060-4241-000 • Rev. D - March 2000
MK V & MK VII EGPWS Pilot Guide
The EGPWS uses various input signals from other on-board
systems. The full compliment of these other systems is
dependent on the EGPWS configuration and options selected.
Systems providing Altitude, Airspeed, Attitude, Glideslope, and
position are required for basic and enhanced functions.
Accelerations, Angle-of-Attack (AOA), and Flap position is
required for Windshear. Inputs are also required for discrete
signal and control input.
The EGPWS utilizes signals from the following systems:
Uncorrected and corrected Barometric Altitude, Altitude rate,
Computed Airspeed, True Airspeed, and Static Air Temperature
are provided by Air Data system.
Radio Altitude is provided by a Radio Altimeter system.
Decision Height or Decision Height Altitude is provided by a
Radio Altimeter system or ancillary system.
In -210-210 and later versions, the EGPWC performs Radio
Altitude reasonableness checks based on the Computed
Terrain Clearance (pseudo-radio altitude). Computed Terrain
Clearance is computed by subtracting the elevation of the
(database) terrain below the aircraft from Geometric Altitude
(ASL). Radio Altitude is considered unreasonable when it
indicates a terrain clearance that is less than the Computed
Terrain Clearance by more than 2000 feet. For example, if the
Computed Terrain Clearance is 10,000 feet and the Radio
Altitude is any value (0-2500) then the Radio Altitude is
considered unreasonable. This is only performed if TAD is
enabled, high integrity terrain and position data is available
(based on GPS/Geometric Altitude), and the Computed Terrain
Clearance is greater than 4000 feet.