Technical data

Product Specification
HIF-2121/R5 CAGE CODE: 97896 SCALE: NONE SIZE: A DWG NO: 965-1176-601 REV: D SHEET 85
2
4
WINDSHEAR CAUTION
DECREASING
HEADWIND
(KNOTS/SEC)
TAKEOFF
APPROACH
0
2
1000
2000
0
1000
2000
4
Typical Alert Envelope for Airspeed = 150 Knots
Mode 7-Windshear
WINDSHEAR WARNING
UPDRAFT
(FEET/MIN)
INCREASING
HEADWIND
(KNOTS/SEC)
DOWNDRAFT
(FEET/MIN)
FIGURE 6.5.1-3: TYPICAL WINDSHEAR ALERT THRESHOLDS
Logic is provided to distinguish between the takeoff and approach phases of flight. Slightly different enable logic and gain
curves are used for detection in each of these phases of flight as shown in figure 6.5.1-3. The threshold value is also
increased by 0.01 g’s for the takeoff phase of flight reflecting the lower performance of the aircraft during this phase.
Mode 7 also provides a windshear caution (sometimes referred to as windshear prealert) which can be disabled via a program
pin option. This alert is triggered for headwind and updraft conditions that typically exist on the leading edge of a microburst
windshear. The same total shear signal is used for the caution as is used for the warning. The threshold magnitude is the same
as that used for the windshear detection warning logic, only the polarity is inverted. Threshold modulation as a function of
temperature, flight path angle, and lift is not used for the caution.
The windshear caution condition is maintained for a period of at least 8 seconds in order to prevent multiple alerts for a given
event due to turbulence. This alert output is disabled when windshear warning conditions prevail. A separate discrete output
is activated for this condition. For the basic caution function no voice output is given. However, a program pin option exists
to allow for a “Caution Windshear” voice to be given.