A320 SRS During Windshear
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A320 SRS During Windshear
Does anyone know if the SRS automatically disengages (i.e. changes to CLB) when passing the acceleration altitude as set in the TO PERF page during a reactive windshear event? I am aware of some simulators doing this, but I'm looking for real-life experiences of this event particularly on newer FMGS / FAC standard A320s.
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Hi vilas,
True - provided you are out of WindShear Warning (no more warnings above 1300 ft RA anyway)
FCOM DSC-31-40: Flags and Messages Displayed on PFD / Windshear Detection Function.
True - provided you are out of WindShear Warning (no more warnings above 1300 ft RA anyway)
FCOM DSC-31-40: Flags and Messages Displayed on PFD / Windshear Detection Function.
Last edited by Goldenrivett; 20th May 2016 at 16:34. Reason: answer to xhamster below
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Golden and Xhamster
LVRCLB and change to CLB/OPCLB is triggered by what you put in the MCDU in THR RED/ACC ALT even in wind shear. The FAC will not supress it. I had asked airbus specifically this question in connection with low acceleration altitudes such as 400ft/800ft used by some airlines. There lies the danger because SRS orders are modified by FAC in wind shear to give optimum escape manoeuvre but not in CLB or OPCLB and the aircraft will pitch down to accelerate. The SIM behaviour is correct.
LVRCLB and change to CLB/OPCLB is triggered by what you put in the MCDU in THR RED/ACC ALT even in wind shear. The FAC will not supress it. I had asked airbus specifically this question in connection with low acceleration altitudes such as 400ft/800ft used by some airlines. There lies the danger because SRS orders are modified by FAC in wind shear to give optimum escape manoeuvre but not in CLB or OPCLB and the aircraft will pitch down to accelerate. The SIM behaviour is correct.
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Thanks vilas,
So it's not as clever as I thought.
If my AA was set at say 400 ft and I was still in windshear at 500 ft, then I'd have to reduce thrust to MCT then reselect TOGA in order to get SRS again.
Great!
I miss the TOGA switch which is independent of the TL position.
So it's not as clever as I thought.
If my AA was set at say 400 ft and I was still in windshear at 500 ft, then I'd have to reduce thrust to MCT then reselect TOGA in order to get SRS again.
Great!
I miss the TOGA switch which is independent of the TL position.
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Excellent points Vilas, thus reminding us we are pilots first and simply can't rely on the engineers at Airbus to save us in all cases.
Our FM stated SRS would command approximately up to 22.5 degrees pitch in windshear - this information was recently removed. (If SRS was unavailable we were to rotate to 17.5 up to alpha max if necessary still remains) Do you have any info on windshear SRS pitch guidance?
Our FM stated SRS would command approximately up to 22.5 degrees pitch in windshear - this information was recently removed. (If SRS was unavailable we were to rotate to 17.5 up to alpha max if necessary still remains) Do you have any info on windshear SRS pitch guidance?
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Mongo
That info about 22.5 is still valid but shifted to DSC-22_30-80-20 P 2/4. Airbus recommends ACC ALT of 3000ft. So in case of low acceleration altitude if only thrust levers were brought to CLB and still in SRS then take it back to TOGA and it will give optimum WS guidance till ACC ALT. But if ACC ALT is say 800ft then when SRS changes to CLB/OPCLB I feel recycling the thrust lever in active wind shear may not be the best or the only option. Instead you can disregard the FDs and follow pitch 17.5 or full back stick to prevent descent leaving the thrust in TOGA may be better.
That info about 22.5 is still valid but shifted to DSC-22_30-80-20 P 2/4. Airbus recommends ACC ALT of 3000ft. So in case of low acceleration altitude if only thrust levers were brought to CLB and still in SRS then take it back to TOGA and it will give optimum WS guidance till ACC ALT. But if ACC ALT is say 800ft then when SRS changes to CLB/OPCLB I feel recycling the thrust lever in active wind shear may not be the best or the only option. Instead you can disregard the FDs and follow pitch 17.5 or full back stick to prevent descent leaving the thrust in TOGA may be better.
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Vilas,
Thanks.
So if SRS is active in windshear it will command up to 22.5. If SRS is not active we pitch to 17.5 or full back stick. The worst case is windshear below accel alt, pilots follows SRS pitch guidance, A/C climbs though AA, pitch guidance changes to OPN CLB or CLB but aircraft still in windshear, now pilot is to disregard FD and manually pitch to 17.5 (or full back stick) which may be higher or lower than the pitch commanded by SRS during the windshear event. That doesn't seem like a good way to go about business.
Thanks.
So if SRS is active in windshear it will command up to 22.5. If SRS is not active we pitch to 17.5 or full back stick. The worst case is windshear below accel alt, pilots follows SRS pitch guidance, A/C climbs though AA, pitch guidance changes to OPN CLB or CLB but aircraft still in windshear, now pilot is to disregard FD and manually pitch to 17.5 (or full back stick) which may be higher or lower than the pitch commanded by SRS during the windshear event. That doesn't seem like a good way to go about business.
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Isn't this all a bit hypothetical surely risk of windshear should be mitigated either by delaying takeoff or furthermore if windshear is reported and takeoff is decided TOGA becomes mandatory as stated in FCOM PRO-SUP adverse weather.
Lastly in normal law the notes in the qrh state if no SRS orders set 17.5 or increase to full back if necessary to prevent loss of altitude. The latter being key in a windshear escape. Below 1300' RA if you're in FAC detected shear the alert will be there so why on earth would you pitch down to follow an Op CLB FD order?
Lastly in normal law the notes in the qrh state if no SRS orders set 17.5 or increase to full back if necessary to prevent loss of altitude. The latter being key in a windshear escape. Below 1300' RA if you're in FAC detected shear the alert will be there so why on earth would you pitch down to follow an Op CLB FD order?
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Hi ElitePilot,
Hopefully, those of us who have followed this thread wouldn't.
But if others blindly followed the QRH Windshear procedure which says:
Thrust Levers at TOGA ... SET or Confirm
AP (if engaged).............. KEEP ON etc.
vilas has pointed out that SRS will have changed to CLB/OPCLB whilst still in windshear but above AA.
The system is not that smart.
why on earth would you pitch down to follow an Op CLB FD order?
But if others blindly followed the QRH Windshear procedure which says:
Thrust Levers at TOGA ... SET or Confirm
AP (if engaged).............. KEEP ON etc.
vilas has pointed out that SRS will have changed to CLB/OPCLB whilst still in windshear but above AA.
The system is not that smart.
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ElitePilot
Of course and obviously but this thread is not about discussing what we would do as most would do the same thing. It's more about the system logic.
If one had the AP engaged and was not expecting the SRS to revert to CLB or OP CLB?, then this is valuable energy / time lost by disengaging AP, removing FD etc.
Of course and obviously but this thread is not about discussing what we would do as most would do the same thing. It's more about the system logic.
If one had the AP engaged and was not expecting the SRS to revert to CLB or OP CLB?, then this is valuable energy / time lost by disengaging AP, removing FD etc.
Only half a speed-brake
It's slightly off the topic, let us not forget that factory standard is 1500/1500 and where required by local regulations 1500/3000.
When people start bringing up ideas such as 3000/400 they may sometimes be too smart for thier own good.
When people start bringing up ideas such as 3000/400 they may sometimes be too smart for thier own good.
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What is factory standard? Dunno, our busses are programmed for a standard 1000/1000, the value is pre-programmable though. And i would expect every airline to adjust that value to its SOP. If some airport wants NADP2 then we adjust it to 1000/3000. Therefore, 1500 is something we never use.
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ElitePilot
Every time you won't be second guy to learn from earlier guy's experience. The topic is whether in FAC detected wind shear if the THR RED/ ACC ALT is less than 1300 ft. will LVR CLB flash? Yes it will but you have to ignore it. Second while still in wind shear will SRS change to CLB/OPCLB? Yes it will. Then do you ignore the FD bars and fly the pitch or get SRS back by recycling THR levers? There is nothing hypothetical about it. It can happen if acceleration altitude is below 1300ft. If NADP is followed there is no problem.
Every time you won't be second guy to learn from earlier guy's experience. The topic is whether in FAC detected wind shear if the THR RED/ ACC ALT is less than 1300 ft. will LVR CLB flash? Yes it will but you have to ignore it. Second while still in wind shear will SRS change to CLB/OPCLB? Yes it will. Then do you ignore the FD bars and fly the pitch or get SRS back by recycling THR levers? There is nothing hypothetical about it. It can happen if acceleration altitude is below 1300ft. If NADP is followed there is no problem.
Only half a speed-brake
Denti: Unbox a freshly delivered A/C, power up and all the 6 altitudes are set 1500. What you say is true but that's the next step.
Alternatively, you train at Airbus Training Centre in TLS, and all the sims are like that (2005 experience).
reference:
A320 Flight Management System Pilot’s Guide, Honeywell, 1993
- Figure 3.2-51 TAKEOFF Page
Airbus A319/320/321 Pegasus Flight Management System Pilot's Guide, Honeywell, 2002
- PERF TAKEOFF Page Figure 4--61
"These altitudes are displayed in blue and default to departure field elevation plus 1500 ft AGL (or as defined in the AMI database). They can only be changed in the PREFLIGHT phase."
New FM rev1 Pilot's Guide A32s, Smiths & THALES, 2004
- FLIGHT PHASES: PREFLIGHT - Complete PERF page (p96)
SA - Honeywell Release 1A FMS Standard, Airbus SAS Ref. X22PR0816632, 2010
- TAKE OFF PERF page, slide 28
- noteworthy: "THR RED can now be higher than ACC"
Alternatively, you train at Airbus Training Centre in TLS, and all the sims are like that (2005 experience).
reference:
A320 Flight Management System Pilot’s Guide, Honeywell, 1993
- Figure 3.2-51 TAKEOFF Page
Airbus A319/320/321 Pegasus Flight Management System Pilot's Guide, Honeywell, 2002
- PERF TAKEOFF Page Figure 4--61
"These altitudes are displayed in blue and default to departure field elevation plus 1500 ft AGL (or as defined in the AMI database). They can only be changed in the PREFLIGHT phase."
New FM rev1 Pilot's Guide A32s, Smiths & THALES, 2004
- FLIGHT PHASES: PREFLIGHT - Complete PERF page (p96)
SA - Honeywell Release 1A FMS Standard, Airbus SAS Ref. X22PR0816632, 2010
- TAKE OFF PERF page, slide 28
- noteworthy: "THR RED can now be higher than ACC"
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Predictive windshear operates below 2300' RA. Reactive windshear operates from takeoff and anytime below 1300' RA with flaps min of Conf 1.
Our company has recommended procedures (take off and landing) to implement in case of potential windshear where avoidance is not required. IE, take off - use longest runway which avoids suspect windshear, flaps 2, TOGA, increase Vr, etc.
It would seem to me one additional procedure would be to set accel alt to a minimum of 1500' to avoid the whole SRS to OPN CLB/CLB problem. Anybody have any Airbus literature on what Airbus recommends to set accel alt to in case of suspected windshear?
Our company has recommended procedures (take off and landing) to implement in case of potential windshear where avoidance is not required. IE, take off - use longest runway which avoids suspect windshear, flaps 2, TOGA, increase Vr, etc.
It would seem to me one additional procedure would be to set accel alt to a minimum of 1500' to avoid the whole SRS to OPN CLB/CLB problem. Anybody have any Airbus literature on what Airbus recommends to set accel alt to in case of suspected windshear?
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Mongo
This is part of the Airbus reply on the subject.
To avoid LVR CLB message (at THR RED ALT) and CLB (OP CLB) engagement (at ACC ALT) while in windshear conditions, reduction of THR RED / ACC ALT should be avoided when windshear conditions are expected (note: it is already recommended to disregard NADP procedures in case of suspected windshear).
This is part of the Airbus reply on the subject.
To avoid LVR CLB message (at THR RED ALT) and CLB (OP CLB) engagement (at ACC ALT) while in windshear conditions, reduction of THR RED / ACC ALT should be avoided when windshear conditions are expected (note: it is already recommended to disregard NADP procedures in case of suspected windshear).