A320 target in CLB with acceleration

[Skydreamerii]

Hi.
Does enybody know what is target for FMS while it is needed to accelerate in CLB. It might be: gradient of climb, V/S, speed trend, pitch or some combination.

What would you do if after selecting conf 0 you notice negative speed trend which is going to hit increasing VLS.

[vilas]

First flaps should be retracted at correct speed and +ve trend. And climb ensures I think minimum 120ft/mt.

[FlightDetent]

What would you do if after selecting conf 0 you notice negative speed trend which is going to hit increasing VLS.When things do not go as expected, take over.

In the scenario you describe and I can pretty much visualize it, it's a tough call to give a generic answer. Sour grapes to some, the overall best is to keep the AP engaged and see how HAL manages. While keeping your instrument scan sharp and alerting the colleague to the situation, and placing your hand on the disconnect button. MCT for sure possible, TOGA - eh, please be mindful of SRS (go-around mode FD) coming if the slats have not fully retracted yet.

The speed trend arrow stretching into the yellow band itself is not a problem. It shows the expected result if the momentary deceleration would continue for 10 (? - check FCOM) seconds. However, by second #3 the AP would be doing something about it.

What I am getting at is (in19 out of 20 cases) that "the Something AP will do" will be more precise and accurate than whatever manual intervention you can realistically execute. The grim reality being, that for a simple speed drop / lazy pitch control moment, the self-rectification done by the AP is not only effortless for the pilot (hell it is) but also the most accurate.

Welcome to the reality, transport flying is being done by our eyes and minds, not the hands anymore.

How many hours (total experience on the bus) do you have? If not too many perhaps there's one thing worth watching the next time, worth pointing out.

[OPEN DES]

120 ft/min is min target in SRS only.

in CLB/OP CLB there is an energy trade-off between rate of change of kinetic (acceleration) and potential (climb rate) energy. But hard to put numbers on it. I recall something as 80/20, later revised to 60/40 or vice-versa even. Anyhow, the units of measure make for difficult one-to-one comparison. In the worst case the aircraft will fly level, any possible speed decay at that point (engine fail, windshear, temperature inversion) can always be counteracted with TOGA. (Which will give SRS with flap lever out of zero). Or cancelling the de-rate (D-CLB x)

In practical terms you could see this on the A330 with D-CLB 2 (reduced climb thrust) on a very hot day in the ME while turning. I have seen the aircraft flying level with only very little acceleration, easily solved by instantly cancelling the reduced climb thrust (a/thr disconnect).

[vilas]

Open Des
I stand corrected indeed 120ft/mt is in SRS. But I have answer for energy sharing below but it's not in FCOM
Climb : Energy sharing is applied for acceleration (70% thrust) and for altitude (30% thrust) from ACC ALT up to first climb speed. Max climb thrust is kept

[Skydreamerii]

Very good numbers, but where it from?
The reason of my question is follows: my company started a campania against short overspeeds during CONF1 retraction a couple of years ego . So now retraction at speed higher then S+10 is considered as crime even in turbulance. Thus, situation when you can hit VLS is often as S speed is lower then VLS in CLEAN (1.23 against 1.2 Vs1g). My solution always was pushing VS 0 (it is fast, reliable way with AP ON) But now new campania is sterted. At this time against using VS mode (some pilots use it not in appropriate manner, what lead to speed loss or increasing towards VMAX). Our chif pilots offer use thrust up to TOGA in this case. But when i test this technic i notice that speed trand increases for a couple of seconds, but then FD bar goes higher, what leads to increasing VS up to 50% but speed trand returns to previous. Speed rate almost the same. And it looks like in some cases this technic could be unreliable to prevent speed decay lower then VLS.
That's why i am looking for help to justify it with documents.

[vilas]

Skydream What I posted is from a very old document A319/A320/A321 Flight Deck and Systems Briefing for Pilots. All that I understood from your post is your company is having problem with short overspeed during retraction of flaps 1+F to zero. This can only happen at high takeoff weights. At 210kt the flap part auto retracts and during slat retraction a short overspeed sounds. According to Airbus that's not a problem but retraction to flap zero should not be delayed. You are adviced to read Safety First magazine control your speed during takeoff. It's a series on speed control during entire flight regime.

[pineteam]

The reason of my question is follows: my company started a campania against short overspeeds during CONF1 retraction a couple of years ego . .

Those overspeed cases happened with AP ON?

Vilas please correct me if I'm wrong but from memory, with the Auto Thrust active and AP ON the aircraft will automatically pitch up until the flaps are fully retracted to prevent an overspeed in climb or will spool down if Auto Thrust is in speed mode to avoid going above Vmax until the flaps are fully retracted.

[FlightDetent]

This happens in level flight, the AP cannot overrule ALT (green). Some departures from LGW may, but many Russian airports certainly do have a low hard limit climb altitude (900m / 600 m). If the frequency is busy or they just need you there, you stay level. And ALT* comes very early. Then,

210 flaps auto retract
You move the flaplever to 0 at S speed.
Red barber pole disappears
But before slats physically retract (not that fast, 5 seconds), you zoom over 230 kts.

FDM event is triggered and the chief pilots table starts to fill. And that is when good managers start to create procedures beyond FCOM.

Hint: Any procedure that ever was been better compared to what FCOM suggested then have been already embedded. These days, going beyond the book will cause some trouble somewhere some day.
​​

[vilas]

Those overspeed cases happened with AP ON?

Vilas please correct me if I'm wrong but from memory, with the Auto Thrust active and AP ON the aircraft will automatically pitch up until the flaps are fully retracted to prevent an overspeed in climb or will spool down if Auto Thrust is in speed mode to avoid going above Vmax until the flaps are fully retracted.
Airbus training DVD showed that during GA FMGS will restrict the speed to Vmax, Vfe, Vle, Vmo by pitch up even with ATHR left in TOGA. But ALT* overrules that. I have confirmed this in the sim. I think with ATHR in CLB it should protect but some excursion occurs. The following SAFETY FIRST discusses the situation after take off. https://safetyfirst.airbus.com/control-your-speed-during-climb/

[pineteam]

I'm pretty sure I have seen the engines spooling down to avoid overspeeding the flaps maximum speed when levelling off but I guess the flaps lever was not yet set at zero. From what I understand, Let's assume you level off at 2000 feet, aircraft reach ALT* and speed target is 250kt but you don't retract the flaps. In that case the Auto thrust will automatically limit the speed to 230 kt ( VFE flaps 1 on A320) and no overspeed should occur. But in the case you retract the flaps, no more protection at VFE and if the aircraft accelerate too fast and exceed 230 kt before the flaps are at zero then you will overspeed. Am I correct?

[vilas]

Yes I think you are correct. The GA example was a case where ATHR was left in TOGA so ATHR was not active and the protection came from FMGS. If thrust levers are brought to CLB then ATHR is active and as you say thrust will come back to prevent exceedance. Also as you say when flap 0 is selected protection shifts VMO (beyond 230kt) and if flaps(slats actually) are still retracting ATHR will not take part at 230kts and a fleeting exceedance occurs.

[FlightDetent]

@pinteam sounds rational but we all know that when airbus truly bites logical reasoning is no defence.

I'd like to ask @vilas a bit later about how some of the discussed behaviour is replicated on the FTDs, yet before placing the question let's establish what the aircraft do or does not, as well whether or not the FCOMs tells us so (it normally does but not 100%).

For that, if you could kindly help, do you have a moment to rephrase the query from #11 with more precision, differentiating CF = 1 for take-off is 1+F (S=1 and F=1) where
- Vfe 1+F is 215
- F auto retract from 1 to 0 at 210
- S don't auto-retract, Vfe is 230
- the baber pole moves first when commanded by the auto-retract at 210 kt (F=0 blue on ECAM) from 215 to 230
- the barber pole disappears when commanded by lever movement S 1 -> 0
- the actual overspeed and its warning (clacker + red ECAM) is not tied to the barber pole display but to the real position (=until completely retracted) and limiting 230 kt
- the overspeed protection by A/THR is tied to the barber limit (?) / Vmo (?) / FCS (?) overspeed threshold - green tick (could be three separate values)

Appreciated. While I understand perfectly what you said, going deeper we need to avoid saying "retract the flaps" while we mean commanding slats to 0 at a moment when the flaps themselves are already closed. Again, not the situation you described but may be coming soon. :-)

[vilas]

I am just trying to find some logic. Airbus has some specialities like flap lever has straight forward five postions but actual slat/flap surface combinations are different. So perhaps in unusual situations may be the warning also act different. Like the GPWS too low flap only comes from flap, the slat plays no part. So if flap cannot go to three we are asked to switch off the mode itself. In this ATHR overspeed protection in normal situation flap lever(barber pole) is not the factor to trigger ATHR overspeed protection. But the flap auto retract may be making the difference or the system doesn't have time to trigger ATHR during the short duration of retracting slat. By the time it retards thrust the situation is over but warning is triggered.