Inputs to the
ground prox computer are radio altitude from the No1 radio altimeter,
barometric altitude rate and mach from an air data computer, glide
slope deviation signals from capt side, landing gear and flap positions.
The loss of one
of these inputs will deactivate only the affected mode or modes.
Aural alerts and warnings for modes 1 through 4 are accompanied by
red PULL UP lights
Modes
Explained (Note
that these diagrams are simplified)
Mode
1 - Excessive Decent Rate Has
two boundaries and is independent of airplane configuration. Penetration
of the first boundary generates the repeated aural alert of SINK RATE.
Penetrating the second boundary causes the repeated aural warning
of WOOP WOOP PULL UP, until the rte of decent has been corrected.
Mode
2 - Excessive Terrain Closure Rate Monitors
mach number, radio altitude and radio rate of change, barometric altitude
and airplane configuration. Has two boundaries, the first causes an
aural alert of TERRAIN repeated twice, followed by the repeated aural
warning of WOOP WOOP PULL UP. After leaving the PULL UP area the repeating
TERRAIN message will be herd while in that portion of the envelope..
If both boundaries are penetrated while in the landing configuration,
only the repeating TERRAIN aural alert will occur.
If the landing gear and wing flaps are not in the landing position
when leaving the PULL UP area, 300 ft of barometric altitude must
be gained before the aural TERRAIN alert is silenced.
As the mach number increases from .35 to .45 with the gear up, the
highest altitude at which a mode two alert warning will occur is increased
to 2450 ft. This higher portion is inhibited with the flap inhibit
switch in the FLAP INHIBIT position.
Mode - 3 Altitude Loss After Take off Or Go Around Provides
an alert if a decent is made during initial climb or go around. The
aural alert is a voice message "DON'T SINK", repeated until
the condition is corrected. It is effective between 50 and 700 feet
radio altitude and generates the alert when accumulated barometric
loss equals approx. 10% of the existing radio altitude.
Mode 3 does not arm during decent until below 200 ft radio altitude.
4A
- Unsafe Terrain Clearance With Landing Gear Not Down
This is the terrain clearance mode with the gear retracted, is armed
after take off upon climbing through 700 ft radio altitude. When this
envelope is penetrated at less than 0.35 mach the aural alert TOO
LOW, GEAR is sounded. When the envelope is penetrated at more than
0.35 mach, the aural alert TOO LOW TERRAIN is sounded and the upper
boundary of the envelope is increased to 1000 ft rad alt. The message
is repeated until the flight condition has been corrected.
4B
- Unsafe Terrain Clearance With The Flaps Not In Landing Position This
mode provides an alert when the gear is down and the flaps are not
in landing position. If the envelope is penetrated at less than 0.28
mach with the flaps not in the landing position, the aural alert TOO
LOW FLAPS is sounded. When the envelope is penetrated at more than
0.28 mach, the aural alert of TOO LOW TERRAIN is sounded and the upper
boundary is increased to 1000 ft rad alt. The voice messages continue
to occur until the flight condition has been corrected.
The TOO LOW GEAR alert take priority over TOO LOW FLAPS. The TOO LOW
FLAPS and associated TOO LOW TERRAIN alert are inhibited with the
flap inhibit switch when moved to the FLAP INHIBIT position
Mode
5 - Below Glideslope Deviation Alert This
mode alerts you of a descent of more than 1.3 dots below an ILS glideslope.
The envelope has two areas of alerting, soft and loud.
In both areas is a repeated aural warning of GLIDESLOPE and illumination
of the pilots BELOW G/S lights. The voice message amplitude is increased
when entering the loud area In both areas, the aural warning repetition
rate is increased as glideslope deviation increases and radio altitude
decreases.
The
mode is armed when a valid signal is being received by the capts glideslope
receiver and the radio altitude is 1000 feet or less.
This mode may be canceled or inhibited by pressing either pilots BELOW
G/S light while below 1000 ft radio altitude. The mode will re arm
when climbing above 1000 ft rad alt.
Mode
1 through 4 aural alerts and warnings have priority over mode 5 aural
alerts, though both PULL UP and BELOW G/S lights could be illuminated
at the same time.
