PPRuNe Forums - View Single Post - SRS mode during windshear - A320
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Old 25th Feb 2013, 16:21
  #19 (permalink)  
Join Date: Apr 2009
Location: Canada
Posts: 518
IIRC, 'LVR CLB' is flashing on the FMA above the acceleration alt and the FD maintains SRS till the TL's are retarded back to the CLB detent. I can be mistaken, though...
Yes this was my initial thought but we mustn't mix up ACCEL ALT with THR RED. The Situation you mention above is THR RED, not ACCEL ALT. At THR RED you will get flashing LVR CLB message but after selecting CLB you will still be in SRS mode. Once at ACCEL ALT aircraft switches to CLB mode and accelerates. (ref. DSC-22_30-80-20 p1/4 SRS Disengagement Conditions)

What villas is saying is not unreasonable, the key in the windshear situation is to use all the aircraft energy possible for a climb. Pulling speed at ACCEL ALT will maintain v2+10 or whatever SRS had commanded and will get the FG to try and give you the best climb possible with TOGA power. In windshear that's all you can hope for, if TOGA plus max nose up is not going to give you a positive climb then there's not much else left to do but start praying. In my humble opinion this will do the job. I also don't see how TOGA and 17.5degrees is wrong either, both should work, no? I think that selecting OP CLB is a better option than CLB.

The only thing left to analyse now is the difference in behavior between CLB vs. SRS, and are there some inherent differences that would render the CLB mode logic incapable of dealing with windshear (vs. SRS logic, which is obviously programmed to deal with it). SRS limits nose up to 22.5 degrees with windshear, not sure about

Last edited by Airmann; 25th Feb 2013 at 17:14.
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