737 MAX Flight Crew Operations Manual
Flight Management, Navigation -
Navigation Systems Description
MN-FLT-OH-201
11.20.21
On descent, below 2300 ft the weather scan switches from a 180 degree scan to a
120 degree scan, which indicates the windshear detection system is activated. The
smaller scan sector allows faster updates and also allows weather and windshear
events to be shown simultaneously during the entire windshear event. Windshear
detection is always activated when the aircraft is below 2300 ft in the takeoff and
landing environment even when the radar is turned off. Warnings and Cautions are
enabled from the time the aircraft passes 1200 ft until 400 ft. From 400 ft until 50
ft, only Warnings are enabled. From 50 ft until touchdown (0 ft), all new alerts are
disabled.
Windshear detection is activated during both manual and automatic radar
operation.
If the radar is on in the MAP or TEST mode and the system detects a windshear
event, the system display automatically changes to the WX+T mode to show the
weather and windshear icons. The selected range does not change automatically.
A windshear WARNING is generated whenever a detected windshear event
occurs within ± 0.25 NM of the longitudinal axis of the aircraft and within ± 30
degrees of the aircraft heading. When the aircraft is on the ground (takeoff roll),
the windshear WARNING occurs for windshear events within 3 NM.
A windshear CAUTION is generated whenever a detected windshear event occurs
outside the windshear warning region and within ± 30 degrees of the aircraft
heading and less than 3 NM from the aircraft.
March 1, 2021
