STBYRUD
i always do this during the before takeoff check.
for example: if there is a windshear 3 miles in front of the aircraft, the crew is going to takeoff without wx radar turned on, refer to the fcom, it must be 12 seconds after the takeoff thrust set can the wx radar autoscan function provide the windshear Alerts( including the caution and warning) .
but if after that 12 second ,the speed is already passed 80 kts and the new caution alerts are inhibited, or after 12 seconds ,the speed is passed 100 kts which the new warning alerts are inhibited.
in this senerio there will be no alerts at all.
and without the alerts the crew will continue the takeoff roll and finally find that they are in or very close to the windshear area which can be avoided.
is this auto scan take too much time to work or there is some misunderstanding in there?
someone shed some more light?