737NG Windshear Escape Procedures
 

Seeking confirmation that I understand the aircraft "thrust logic" for the windshear escape procedure on take-off (using reduced thrust ie derate/ATM) and on approach to land.

Take-off
Thrust is set to reduced thrust N1 and autothrottle is in "THR HLD" (throttle hold). You get a "WINDSHEAR AHEAD" warning and follow the windshear escape manoeuvre by pushing TO/GA and manually advancing thrust to the full take-off thrust rating (green N1 bugs)

Question - For a reduced thrust take-off, selecting TO/GA as part of the windshear escape manoeuvre will cancel the reduced thrust and reset the N1 bugs to the max T/O thrust N1. Correct?

Approach
On approach and you get the "GO-AROUND -WINDSHEAR AHEAD" warning. Selecting TO/GA (autothrottle in or out) will command N1 bugs to the "reduced" N1 associated with a normal go-around. As per a normal go-around you will have to hit TO/GA again to get full go-around thrust for the windshear escape manoeuvre. Correct?

As per the QRH, if terrain contact is imminent, you just push the thrust levers full forward and you have max thrust. My main query relates to getting full take-off or go-around thrust where max thrust (firewall thrust) is not yet required.

Thanks,


WW

To get full thrust on take off you manually move the thrust levers to the red line on the N1 display after they are in THR HOLD. On approach 1st push of TO/GA FMA thrust indication is GA and auto trust advances to reduced go around N1 to produce 1000-2000 fpm rate of climb. Second push of TO/GA after A/T reaches reduced go around thrust A/T advances to full go around thrust N1 limit and auto throttle FMA is N1.

Cheers

As far as the GREEN N1 bugs are concerned, they will always show you the FULL T/O Thrust (irrespective of full or reduced T/O carried out). When a Reduced Thrust T/O is carried out, on selecting TOGA... the thrust levers advance to give you reduced thrust and the N1 pointers will not travel all the way to the Green Bugs. Therefore there is no question of the N1 bugs being reset to full T/O thrust as they are always at full.
GL