A320 SRS During Windshear

[xhamster]

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.

[vilas]

Yes. LVRCLB will also flash at thrust reduction and at ACCALT SRS will change to CLB/OPCLB. This is confirmed from airbus.

[xhamster]

Thankyou. Any details of this confirmation from Airbus?

[Goldenrivett]

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.

[xhamster]

DSC-31-40 then what?

[vilas]

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.

[Goldenrivett]

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.

[CaptainMongo]

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?

[vilas]

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.

[CaptainMongo]

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.

[ElitePilot]

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?

[Goldenrivett]

Hi ElitePilot,
why on earth would you pitch down to follow an Op CLB FD order?
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.

[xhamster]

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.

[FlightDetent]

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.

[Denti]

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.

[xhamster]

You use 1000/3000 for NADP2?

[vilas]

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.

[FlightDetent]

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)
http://s32.postimg.org/nq3t0zpo1/thales_TO_PERF.jpg (http://postimg.org/image/nq3t0zpo1/)

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"

[CaptainMongo]

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?

[vilas]

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).

[CaptainMongo]

Vilas,

"reduction of THR RED / ACC ALT should be avoided"

Reduction from what? From Airbus recommend THR RED / ACC ALT's ? What are Airbus recommended THR RED / ACC ALT's?

This is a hole in our manual (company generated) which needs to be filled.

[vilas]

Airbus clarification in wind shear conditions recommended THRRED/ACC ALT of at least 1500ft and TOGA take off.

[safelife]

If a windshear is suspected, put 9999 in as acceleration altitude, and push (or pull) CLB when you're at your desired acceleration altitude, and still no shear.
Failing (forgetting) that, pull speed when CLB engages.

[ElitePilot]

Vilas: Absolutely agree with what you're saying but the key is to minimize height loss as stressed in the note in the qrh and fctm.
So if SRS is there follow it, if it reverts to Op Clb/Clb pitch accordingly to keep climbing (full back if necessary)... basics.

[vilas]

ElitePilot
It is not that basic unless a thought is given to it. In WS when you are battling to centre the FDs you are not likely to notice the FMA change. Every one knows what to do when FDs are not there but to ignore the FDs because change in SRS to CLB requires preplanning.

[CaptainMongo]

Vilas,

Exactly.

We train pilots to follow the FD religiously. In only rare instances do we teach them to disregard FD commands. When sheite hits the fan, you get into a full blown windshear event, the FD in SRS is giving you good info - you follow it. When you reach ACC ALT as programmed in the box, it now gives you bad info - now you are to disregard it - that is asking a lot if a normal line pilot to absorb and respond correctly to in an incredibly stressful and dangerous environment.

Vilas, do you have an Airbus publication reference for setting 1500' ACC ALT as a precautionary windshear procedure? TIA

[vilas]

Mongo and xhamster
As mentioned by me earlier this was stated in the answer by airbus to me by name so I am not sure if I should post it in public but you can write an email to me.
xhamster
There is minimum 120ft ROC protection in CLB but the result of the battle between pitch and ROC may be uncertain.

[MD83FO]

Hello guys, is there any development in this regard?
Has any airbus publication updated this procedure?
in suspected windshear increase AA or be mindful to reset TOGA in case of FMA change during wind shear

[vilas]

Procedure remains same. If thrust is reduced before the shear then offcourse must select TOGA. PM has a important role. Mostly I have seen PM calling only winds speed and head or tail. I think key to survival is climb He must call climbing or descending as the case may be. Because if the aircraft is descending PF will require full back stick if he is not doing then it will serve as a reminder to do so. Also if aircraft speed is rapidly increasing it should be called so PF can fly above the FD to reverse the trend and then get back to FD. If speed is dropping should not be called because intuitively he will push forward which may be dangerous. In airbus AoA protection will look after low speed.

[alexschmalex]

the 120ft ROC protection is only in SRS but not in CLB or Open CLB.
If I would have a W/S during acceleration and wouldn´t pull Speed, the AC would accelerate to 250kts and for that would also descend.
At least I couldn´t find any other info in the manuals

[vilas]

the 120ft ROC protection is only in SRS but not in CLB or Open CLB.
If I would have a W/S during acceleration and wouldn´t pull Speed, the AC would accelerate to 250kts and for that would also descend.
At least I couldn´t find any other info in the manuals
Sorry! But it's the other way around. 120ft ROC is only in CLB or OPCLB and not in SRS. SRS is not an acceleration mode but a fixed speed climb mode. In SRS the FAC modified FD range to give upto 22.5° pitch instead of normal 17.5°. That doesn't happen in CLB/OPCLB.

[alexschmalex]

I found now the reference in the fcom: 1.22.30 P47.
Can you confitm it´s also 120ft/min in CLB or OPCLB?
I couldn't find anything.
Fortunately I'm in the simulator tonight and will check it there.

[Goldenrivett]

Sorry! But it's the other way around. 120ft ROC is only in CLB or OPCLB and not in SRS.
Hi Vila’s, DSC 22-30-80-20

“GUIDANCEIn SRS mode, the aircraft maintains a speed target equal to V2+10 kt in normal engine configuration. When the FMGS detects an engine failure, the speed target becomes the highest of V2 or current speed, limited by V2+15 kt.

The SRS guidance law also includes:

Attitude protection to reduce aircraft nose-up effect during takeoff (18 ° or 22.5 ° maximum in case of windshear)

Flight path angle protection that ensures a minimum vertical speed of 120 ft/min

A speed protection limiting the target speed to V2+15 kt.”

[alexschmalex]

I found now the reference in the fcom: 1.22.30 P47.
Can you confitm it´s also 120ft/min in CLB or OPCLB?
I couldn't find anything.
Fortunately I'm in the simulator tonight and will check it there.
I just came back from the simulator and we checked it there. In CLB or OPCLB the AC goes into a descend in order to hold the Speed during a Windshear.

[FlightDetent]

I just came back from the simulator and we checked it there. In CLB or OPCLB the AC goes into a descend in order to hold the Speed during a Windshear. Same, well reversed, as OP DES during the driftdown, there used to be a picture showing the residual climb the PERF section.

Indeed, 'always positive' ROC is a key design target behind SRS.

The only confusing thing is why and how vilas got confused, having been correct as ever on the first occasion. :E

​​​​

[vilas]

Alex, golden and FD my apology. I had erroneously mentioned in post 27 that CLB instead of SRS gives 120ft/mt protection. I just repeated that error in the previous post. Indeed it's in SRS and not CLB or OP CLB. As it happens in CLB/OPCLB the mode priority seems to be speed and not climb. So in WS it may even descend. All the more reason to reselect TOGA in windshear to get SRS and more energy, also prevent descent by flying whatever pitch it takes SRS or no SRS.

[CMpilot1]

Airbus clarification in wind shear conditions recommended THRRED/ACC ALT of at least 1500ft and TOGA take off.
Hi Vilas,
If you don't mind could you please post the Airbus reply here. Our company has a procedure to modify thrust reduction to 500ft. If windshear is expected the thrust reduction has to be set to 1000ft AAL. Going by your thread, I think even 1000ft AAL won't be a good idea. You could edit out the personal details for maintaining anonymity and then post the reply.

[Sergei.a320]

Hello everyone! It’s very strange how Vilas started his explanation in the correct way and made this error in his later posts. I respect him and FlightDetent and in most cases I agree with their posts. By the way :
1.Could someone provide me concrete reference from FCOM/FCTM for TOGA thrust use recommendation/precaution in suspected W/S.
2. There was SB from Airbus about W/S Det. Function and it also covers SRS logic and it states:
”In fact, FMGC orders the SRS mode engagement when:
* At least one of thrust levers is set to TOGA detention and,
-the slats are extended
-main landing gears are not compressed

OR
*At least one thrust of thrust levers is set to MCT/FLX or TOGA and,
- FLEX temp. Inserted in MCDU
-V2 inserted
-slats extended
-the aircraft has been on ground for 30 sec at least

When SRS mode is engaged and if shear conditions stress aircraft’s capability, FMGC progressively adapts pitch orders to the following survival strategy:
1. First, it controls speed to maintain speed target
2. If speed cannot be maintained,it targets +120 ft/min of vertical speed,
3. If vertical speed cannot be maintained,it increases pitch up to 22,5 deg.

Hope it helps:)

[vilas]

sergie
The answer to your para1is in FCTMGENERAL GUIDELINES

Predictive windshear@ warning (“WINDSHEAR AHEAD" and "GO AROUND WINDSHEAR AHEAD" aural alerts, associated with the W/S AHEAD that appears on the PFDs), reactive windshear warning ("WINDSHEAR WINDSHEAR WINDSHEAR" aural alert, associated with the WINDSHEAR that appears on the PFDs) and windshear detected by the flight crew, request immediate actions.

The following recommendations apply for takeoff after V1 and when airbone (including approach and go around phases):


The flight crew must set TOGA thrust and should follow SRS orders (if necessary pull the sidestick fully back).

If the FD bars are not displayed, the flight crew should move toward an initial pitch attitude of 17.5 °. Then, if necessary, to prevent a loss in altitude, increase the pitch attitude.

If the AP is engaged, the flight crew should keep it engaged. The AP disengages if the angle of attack value goes above αPROT

The flight crew should monitor the flight path, the speed and the speed trend.


Suspected windshear (upon ATC or traffic notification or flight crew observation) and predictive windshear@ caution (“MONITOR RADAR DISPLAY" aural alert, associated with W/S AHEAD that appears on the PFDs) request anticipation of the flight crew to be prepared for a possible windshear

[sonicbum]

Hello everyone! It’s very strange how Vilas started his explanation in the correct way and made this error in his later posts. I respect him and FlightDetent and in most cases I agree with their posts. By the way :
1.Could someone provide me concrete reference from FCOM/FCTM for TOGA thrust use recommendation/precaution in suspected W/S.
2. There was SB from Airbus about W/S Det. Function and it also covers SRS logic and it states:
”In fact, FMGC orders the SRS mode engagement when:
* At least one of thrust levers is set to TOGA detention and,
-the slats are extended
-main landing gears are not compressed

OR
*At least one thrust of thrust levers is set to MCT/FLX or TOGA and,
- FLEX temp. Inserted in MCDU
-V2 inserted
-slats extended
-the aircraft has been on ground for 30 sec at least

When SRS mode is engaged and if shear conditions stress aircraft’s capability, FMGC progressively adapts pitch orders to the following survival strategy:
1. First, it controls speed to maintain speed target
2. If speed cannot be maintained,it targets +120 ft/min of vertical speed,
3. If vertical speed cannot be maintained,it increases pitch up to 22,5 deg.

Hope it helps:)

Hi Sergei,

Are You referring to the fact that when the predictive windshear procedure migrated from the FCOM to the FCTM the wording and format changed?
In the "old" FCOM PRO-SUP-91 Adverse Weather the use of TOGA as a precaution was specifically mentioned. In the FCTM the use of TOGA is related to the crew and/or PWS detection of the windshear.
Is that what You were thinking about?

Cheers.

[Sergei.a320]

sergie
The answer to your para1is in FCTMGENERAL GUIDELINES

Predictive windshear@ warning (“WINDSHEAR AHEAD" and "GO AROUND WINDSHEAR AHEAD" aural alerts, associated with the W/S AHEAD that appears on the PFDs), reactive windshear warning ("WINDSHEAR WINDSHEAR WINDSHEAR" aural alert, associated with the WINDSHEAR that appears on the PFDs) and windshear detected by the flight crew, request immediate actions.

The following recommendations apply for takeoff after V1 and when airbone (including approach and go around phases):

The flight crew must set TOGA thrust and should follow SRS orders (if necessary pull the sidestick fully back).

If the FD bars are not displayed, the flight crew should move toward an initial pitch attitude of 17.5 °. Then, if necessary, to prevent a loss in altitude, increase the pitch attitude.

If the AP is engaged, the flight crew should keep it engaged. The AP disengages if the angle of attack value goes above αPROT

The flight crew should monitor the flight path, the speed and the speed trend.


Suspected windshear (upon ATC or traffic notification or flight crew observation) and predictive windshear@ caution (“MONITOR RADAR DISPLAY" aural alert, associated with W/S AHEAD that appears on the PFDs) request anticipation of the flight crew to be prepared for a possible windshear



It's about actions just in case of....
So it seems that FLEX T/O is permitted in case of suspected w/s , and if suspect is confirmed by crew or alert - use TOGA ,otherwise use flex...
There is a list in FCTM that gives precautionary measures for appch with suspected w/s. I thought that there is something similar for T/O in manuals. Thanx.

[Sergei.a320]

Hi Sergei,

Are You referring to the fact that when the predictive windshear procedure migrated from the FCOM to the FCTM the wording and format changed?
In the "old" FCOM PRO-SUP-91 Adverse Weather the use of TOGA as a precaution was specifically mentioned. In the FCTM the use of TOGA is related to the crew and/or PWS detection of the windshear.
Is that what You were thinking about?

Cheers.
YES! Because I checked SUP for Adverse Wx especially W/s and found nothing :)
I just wanted to highlight the priorities of SRS. FCOM doesn't specify this.

[vstar]

Hi Sergei.a320 Would you be able to share with me the SB that covers the SRS logic. Cheers