Technical data
Product Specification
HIF-2121/R5 CAGE CODE: 97896 SCALE: NONE SIZE: A DWG NO: 965-1176-601 REV: D SHEET 63
0 100 200 300 400
COMPUTED AIRSPEED (KTS)
M
IN
T
E
R
R
A
IN
C
L
E
A
R
A
N
C
E
(F
T
)
1800
1600
1400
1200
1000
800
600
400
200
0
500 FT
1000 FT
190 KTS
250 KTS
30 FT
ALERT AREA
EXPANDED
ALERT AREA
800 FT LIMIT DURING OVERFLIGHT
FIGURE 6.2.4.1-2B: MODE 4A STATIC ALERT ENVELOPE FOR TURBOFAN (MODE 4 TYPE 1)
AIRSPEED (KTS)
M
IN
T
E
R
R
A
IN
C
L
E
A
R
A
N
C
E
(F
T
)
1200
1000
800
600
400
200
0
500 FT
750 FT
148 KTS
170 KTS
30 FT
ALERT AREA
TOO LOW GEAR
EXPANDED ALERT AREA
TOO LOW TERRAIN
0 100 200 300
FIGURE 6.2.4.1-3: MODE 4A STATIC ALERT ENVELOPE (ALTERNATE AIRSPEED EXPANSION, MODE 4 TYPES 7,9)
Figure 6.2.4.1-2, 6.2.4.1-2A, and 6.2.4.1-3 detail the three Mode 4A options for the MKVI EGPWS. The MKVIII EGPWS
has these options as well as the turbofan boundaries as shown in Figure 6.2.4.1-2B. Figures 6.2.4.1-2 and 6.2.4.1-2A depicts
the normal airspeed expansion, Figure 6.2.4.1-3 the alternate airspeed expansion and Figure 6.2.4.1-2B the curve for turbofan
aircraft, only. The alternate airspeed expansion may be used by any aircraft capable of flying the slow approach speeds as a
matter of routine. If alternate airspeed expansion is used for Mode 4A it must also be used for Mode 4B. The turbofan
curves are only available on the MKVIII EGPWS. If this is the selection for Mode 4A, it must be selected for all Mode 4
curves.
When the landing gear is lowered, the Mode 4B alert envelope is selected. The upper boundary decreases to 170 feet (Mode
4 Types 6 and 7) or 245 feet on turbofan aircraft (Mode 4 Type 1). This is reduced to 150 feet on those aircraft types that
routinely delay full flap deployment (Mode 4 Types 8 and 9). The action of lowering the gear is recorded in nonvolatile
memory to prevent inadvertent reactivation of the 500 foot Mode 4A boundary after a power loss. To satisfy customer
requirements, Mode 4B has been modified to produce Mode 4 Type 5. For this type only, the upper boundary decreases to
200 feet.
The following paragraph explains the Mode 4B behavior for turboprop aircraft. Penetration of the Mode 4B envelope below
150 knots (Mode 4 Type 6), or alternatively 120 knots (Mode 4 Type 7) with gear up results in “Too Low Gear” (per Mode