Technical data

Product Specification
HIF-2121/R5 CAGE CODE: 97896 SCALE: NONE SIZE: A DWG NO: 965-1176-601 REV: D SHEET 44
6.0.3 MKVIII EGPWS Windshear Takeoff/Approach Mode
Separate logic is utilized to control the takeoff/approach mode switching for mode 7 windshear detection. The takeoff state
actually reflects takeoff or go-around. The approach state reflects final approach. The state of this latch is maintained in
nonvolatile memory in order to prevent inadvertent mode switching as a result of power loss.
6.0.4 Mode 2 Takeoff
A Mode 2 Takeoff Latch is provided to enable Mode 2B for the first 60 seconds following a takeoff. This latching function is
not power saved and a system reset will force it false.
This feature addresses certain false “TERRAIN” warnings that occur just after takeoff caused by false radio altimeter
excursions between 1000 and 1500 ft AGL. These typically are a sharp increase, followed by a sharp decrease in radio
altitude. This problem is solved by activating Mode 2B for the first 60 seconds after takeoff. Limiting the Mode 2 closure
rate to +3000 fpm effectively prevents the “TERRAIN” warnings in the same manner as is used on approach.
6.0.5 Simulator Reposition
When the EGPWC is installed on an aircraft simulator, special consideration must be taken when the simulation is
repositioned for different flight scenarios. The normal logic of the EGPWC assumes actual flight phase transitions; the abrupt
repositioning of a simulation can cause false warnings or cause the normal EGPWC logic to “lock up” awaiting a valid
transition.
For the MKVI/MKVIII EGPWS the simulator reposition is provided via a keyboard monitor command. When instructed
(RS232 command over the J3 (test) connector) the EGPWS will remain in a reposition setup mode for approximately 3
seconds after the command to “normal” has been received.
6.0.6 Terrain Awareness Alerting Guard
Terrain Awareness caution and warning voice alerts, lights and threat display are inhibited below 30 feet of radio altitude
within 1 mile of the runway, or below 60 knots groundspeed.