PWS on the B737 NG

[ifleeplanes]

Just trying to find out if the PWS automatically scans for windshear below 2300RA or when thrust levers are set for take off, or does the WXR switch ALSO have to have been pressed.

[JABBARA]

Hi,

Radar is not necessarily to be on. In the other cases, scan for a ws in the course of airplane automatically starts. In another word, radar starts to emmit signal similiar as it is on but there is no display of this unless a WS is detected. If a WS is detected, radar returns start to display in addition to PWS indications.

Regards

[ifleeplanes]

Thanks for the info Jabbara... cleared that up for me. :)

[BOAC]

iflleplanes - to complete the story:

-starts scanning when thrust is set for take-off
-alerts available 12 secs after above
-available below 2300'R
-Wx switch NOT required but if selected will override 12 sec delay

[The Puzzler]

Puzzle me this....

To reaffirm BOAC's comment, that is why our SOP is to have the wx radar selected on for all take offs, to override the 12 second delay. :ok:

[jetblues]

Would agree from re-reading Vol 2 that the selection of Wx Radar should delete the 12 sec delay switch over.

Keep in mind that the weather radar detects microbursts and other windshears with similar characteristics. The wx radar does not provide alerting for all types of windshear. The crew must continue to rely on traditional windshear avoidance methods.
Vol 2 15.20.14

Predictive Winshear Inhibits must be kept in mind ;

During takeoff and landing, new predictive windshear caution alerts are inhibited between 80 kts and 400 ft RA, and new warning alerts between 100 kts and 50 ft
RA. These inhibits DO NOT remove existing predictive windshear alerts. Vol 2 15.20.16

Re the Predictive Windshear Symbol (as installed), the red and black symbol will show windshear location and approximate geometric size (width and depth).

Interestingly the symbols, radials and weather radra returns automatically show when ;
* predictive windshear alert occurs
* NEITHER pilot has WXR display selected
* in expanded MAP, center MAP, VOR or APP modes

When terrain display is active, weather radar display REPLACES terrain display.
Vol 2 15.10.19