060-4241-000 • Rev. D - March 2000
MK V & MK VII EGPWS Pilot Guide
Altitude Calibrated Altitude (determined during approach), and
Barometric Altitude (if available). Estimates of the VFOM for
each of these are determined and applied in order to determine
its weight in the final altitude. The blending algorithm gives the
most weight to altitudes with a higher estimated accuracy,
reducing the effect of less accurate altitudes. Each component
altitude is also checked for reasonableness using a window
monitor computed from GPS Altitude and its VFOM. Altitudes
that are invalid, not available, or fall outside the reasonableness
window are not included in the final Geometric Altitude value.
The Geometric Altitude algorithm is designed to allow continued
operation when one or more of the altitude components are not
available. If all component altitudes are invalid or unreason-
able, the GPS Altitude is used directly. If GPS Altitude fails or is
not present, then the EGPWS reverts to using Corrected
Barometric Altitude alone.
The Geometric Altitude function is fully automatic and requires
no pilot action other than the proper setting of Corrected
Barometric Altitude on the Altimeter.
In -210-210 and later versions, the EGPWC computes a
optimum Weather Radar tilt angle based on the aircraft altitude
(ASL) and the terrain elevation ahead of the aircraft. This is
output and available to a compatible Weather Radar system so
that the tilt angle may be automatically set for optimum
Two or more messages may be activated simultaneously, so a
message priority has been established. The following table
reflects the priority for these message callouts. Messages at the
top of the list will start before or immediately override a lower
priority message even if it is already in progress.