Windshear A320
 

Hello all, happy new year.

Question, if you experience windshear on takeoff and do a “windshear toga” escape manoeuvre, will the aircraft still go from SRS to CLB, or will the FACs keep you in SRS?


The reason why I ask is I’m aware some companies use a relatively low accel altitude,
Assuming it goes into CLB & still in windshear, you’d have to turn off FDs and pitch towards 17.5 if I’m not mistaken.
Slightly goes against the memory procedure which tells you to follow FDs?

Secondly, if the reactive windshear isn’t active till 1300ft on arrival, but PWS works from 2500-1300
If you experienced actual reactive conditions at 1600ft, would the aircraft just say “windshear ahead”? and then as PF, you have to make the decision as to whether you’re actually in it and therefore do a windshear toga, or go around flaps if you determine that you are not in the shear (based on the conditions listed in FCTM along with some common sense)
Or if >1300 and in actual windshear conditions would it just not give you any warnings?



many thanks

CLB will engage. The only condition for the SRS not to engage CLB or OPCLB at the ACC ALT is in case of OEI.
In the example you have mentioned you can either pull speed upon CLB engagement or override the FD orders and fly 17.5 watch out for level bust.

Reactive WS is either detected by the FAC or by pilot observations, ref. FCTM for the conditions in terms of speed variation, v/s, Gs deviation etc..
So you will apply the memory items even in the absence of a reactive trigger if you notice any of the above conditions.
The PWS will give you alerts cautions and warnings. It could be that the PWS does not predict any WS due to lack of Doppler feedback but the reactive system is subsequently triggered due to the aerodynamics effects of varying wing speeds and direction in the absence of any convective weather.

are you not referring to SRS GA here when it would be SRS TO?

Firsty, I deleted my reply as sonicbum noted the de-engagement from SRS to CLB at ACC ALT for all-engines operating. It was a confusing message on my behalf.

Back to FCOM for me.

no problem,


so if I set TOGA from flx/mct above accel alt AEO will it remain in CLB or go into SRS until alt*? :)
Just trying to wrap my head around it.

You were right to note SRS-TO and SRS-GA are not exactly the same.
T/O DSC-22_30-40-20-20
G/A DSC-22_30-40-90-20

What I read is the TO-SRS will engage with TL at TOGA/FLX + flaps/slats extended on the ground (with V2 inserted) or 5 sec after liftoff (no V2 inserted).
So, after you lose it through any of the disengagement conditions, you won't get it back.

However, setting TL=TOGA (from some other position) while airborne with flap lever position not in zero, will get you the GA-SRS mode.

then (FCOM)

The SRS GA mode disengages when one of the following occur:

• ‐ At the go-around acceleration altitude (GA ACC ALT), or if ALT* or ALT CST* engages (above 400 ft RA)
• ‐ If the flight crew engages another vertical mode
• ‐ If the selected target altitude is above the aircraft altitude and the flight crew selects a speed: SRS GA reverts to OP CLB
• ‐ If the AP/FD TCAS mode engages upon a RA.

Note: 1. In Engine Out conditions, the SRS GA mode does not automatically disengage at EO ACC ALT.

I understand, so to summarise based on the info from the FCOM on departure, if one was to go from FLX to TOGA above the accel alt, all engines operating, you’ll remain in CLB mode and it won’t go back to SRS as SRS TO has been disengaged by the accel alt.

is this correct?

Anytime you set TL to TOGA from somewhere else while airborne and flap lever not in zero, you will get SRS (GA).

This will automatically change to CLB at GA-ACCALT with two engines running. Funny idea right there, GA-ACCALT is derived from DEST ELEV and can be very different from TKOF ACC ALT.

If you are below GA-ACCALT a.e.o.
or above GA-ACCALT a.e.o

I think the answer to your question is YES. The SRS will remain active until ALT*, other mode or pulling the speed (OPCLB reversion). Apparently the TKOF-ACCALT does not enter the SRS-GA logic at all.
And whenever airborne you always get SRS-GA, not SRS-TO.

Cross-posted with the other reply. But I read the FCOM saying something different.

Yes, the SRS-TO is lost forever.
But you will get SRS-GA, to which tkof-ACCALT has not effect.

What do you think?

For reference of the ideas above.

I would say if you were clean it would remain in CLB mode if you set TOGA from FLX.

however if you had flaps out and were in the CLB phase (say because you hadn’t accelerated fast enough above s speed to retract) and you decided to set toga, agree that then SRS GA would engage and it would go back to SRS ga until alt* most likely? (Or until you reach the go around accel alt even though you’re on departure with SRS GA now active)


does this sound right?

Yes. And you correctly dissected the clean (no vertical mode change) / flaps out (SRS-GA) scenario.

The last finishing touch is is actually "flap lever not in zero". But for the discussed case the distinction is not relevant.

Note: the SRS-TO on the ground (or 5 sec after liftoff) apparently needs "The slats or the flaps are extended". But this may be also governed by the lever position, except the FCOM author here did not need to assume various flaps/slat locked, system / control malfunction or auto-retract scenarios.

understood, thanks for your help tonight.

Credit goes to sonicbum . Besides him make sure to keep an eye out for OPEN DES Chris Scott fdr galaxy flyer meleagertoo PJ2 Bergerie1 tdracer gums

25% of credit goes to me, the rest is all yours as I did not have access to FCOMs yesterday:8 (I am a spoiled on-leave pilot during the festive season!!) :zzz::ok: