Technical data

Product Specification
HIF-2121/R5 CAGE CODE: 97896 SCALE: NONE SIZE: A DWG NO: 965-1176-601 REV: D SHEET 21
1.3.1.9 Mode 7 - Windshear Alerting
Mode 7 produces optional alerts for flight into an excessive windshear condition during takeoff or final approach in
accordance with TSO-C117a. The windshear caution, or pre-alert as it is sometimes referred to, provides visual, ARINC 429
and optional aural output indications. The windshear warning also produces visual, ARINC 429 and aural output indications.
Windshear detection is active between 10 and 1500 feet AGL during the initial takeoff and final approach phases of flight.
Alerts are provided when the level of windshear exceeds predetermined threshold values. The actual windshear value
measured represents the vector sum of inertial vs. airmass accelerations along the flight path and perpendicular to the flight
path. These shears result from vertical winds and rapidly changing horizontal winds.
Windshear warning alerts are given for decreasing head wind (or increasing tail wind) and severe vertical down drafts.
Windshear caution alerts are given for increasing head wind (or decreasing tail wind) and severe up drafts. The windshear
microburst phenomenon and windshear caution and warning levels are illustrated in figure 1.2.3-1.
3000
2000
1000
0
1000
2000
3000
02 4642 6
UPDRAFT (FEET PER MIN)
DOWNDRAFT (FEET PER MIN)
DECREASING
HEADWIND
(KTS PER SEC)
INCREASING
HEADWIND
(KTS PER SEC)
CAUTION
WINDSHEAR
WINDSHEAR
WARNING
MICROBURST
WINDSHEAR
CAUTION
LAMP
WINDSHEAR"
WINDSHEAR
"WINDSHEAR
RUNWAY
MODE 7
EXCESSIVE
WINDSHEAR
DETECTION
AREA
AREA
FIGURE 1.3.1.9-1: TYPICAL MICROBURST ENCOUNTER