Technical data

Product Specification
HIF-2121/R5 CAGE CODE: 97896 SCALE: NONE SIZE: A DWG NO: 965-1176-601 REV: D SHEET 58
6.2.3 Mode 3 -- Descent After Takeoff
Mode 3 provides alerts for excessive altitude loss after takeoff
Mode 3 is based primarily on radio altitude, barometric altitude, and barometric altitude rate. Mode 3 is shown in the block
diagram of Figure 6.2.3-1.
LANDING GEAR
LANDING FLAPS
ALTITUDE
ALTITUDE RATE
SAMPLE
& HOLD
RADIO ALTITUDE
ALTITUDE
ALTITUDE LOSS
MODE 3 BIAS
ALERT/WARNING
COMPARATOR
A
B
A
B
RADIO
ALTITUDE
ALTITUDE RATE
RADIO ALTITUDE
TAKEOFF MODE
MODE 3 ENABLE
ENHANCED MODES
MODE 3
VOICE CONTROL
MODE 3 LAMP
MODE 3 VOICE
LANDING GEAR
LANDING FLAPS
ALTITUDE
ABOVE
FIELD
RADIO ALTITUDE
ALTITUDE
MODE 3 BIAS
INTEGRATOR
ENHANCED MODES
ALTITUDE
FIGURE 6.2.3-1: MODE 3 FUNCTIONAL BLOCK DIAGRAM
Penetration of the Mode 3 alert condition will result in the message “Don’t Sink” and is based on altitude loss and radio
altitude. This alert is only provided during takeoff when the aircraft loses a predetermined amount of altitude. Figure 6.2.3-2
illustrates the Mode 3 envelope for turboprop aircraft. Figure 6.2.3-2A illustrates the Mode 3 envelope for turbofan aircraft,
available on MKVIII EGPWS only and selectable upon installation. The sloped portion of the static alert envelope depicted
is defined by the following equation.
ALTITUDE LOSS (FT) = 5.4 + 0.092 [RADIO ALTITUDE (FT)]
With flap override active (not applicable to turbofan aircraft):
ALTITUDE LOSS (FT) = 9.0 + 0.184 [RADIO ALTITUDE (FT)]