Selected Speeds on A320

[Boyington]

Why is it that even the VApp is SELECTED in case of failures like Dual hydraulic and Slats/Flaps jammed in the A320.

[fpuentegomez]

I'm only speculating here, but it could be due to the fact of being a high workload situation for the pilot flying, in such case a fixed selected speed is less workload than following a managed target affected by GS MINI.

[Sciolistes]

To reduce speed, sometimes below maneuvering speed to avoid over speed,or to only reduce speed once the flap is extended and to ensure minimum speeds are maintained when going around or diverting.

[Sidestick_n_Rudder]

Also because the approach and maneuvering speeds with partial flaps/slats can be different than the FMS target speeds - and the FMS might not necessarily know it.

Bottom line: non standard config - non standard speeds have to be used.

[vilas]

Boyington is asking why Vapp also flown selected when it can be easily flown managed since we have corrected it in MCDU.fpuentegomez seems to have given logical answer

[sierra_mike]

i don't see any wording explicitly prohibiting the use of GS mini in mentioned cases once you're in LDG config given VAPP is amended accordingly in MCDU

[KingAir1978]

Because the autothrust system will not allow the speed to decrease below the manoeuvring speed, if you keep the speed managed.

If you have the flaps stuck at 1+f for example, you'll need flap lever position 2 for landing. (to get the slats extended in position 2) The calculated Vapp will be lower than the manoeuvring speed, so it needs to be selected.

[Boyington]

What exactly do you imply by manoeuvring speed? Do you mean VLS? Thanks.

[Chrome]

F and S speeds are manoeuvring speeds.

Check out the abnormal procedure from the FCTM as it is also explained there.

[vilas]

sierra_mike
i don't see any wording explicitly prohibiting the use of GS mini in mentioned cases once you're in LDG config given VAPP is amended accordingly in MCDU Since the QRH recommends use of select speed it takes out the GS mini out of equation. No need to expressly ban GS mini.
KingAir1978
Because the autothrust system will not allow the speed to decrease below the manoeuvring speed, if you keep the speed managed.
If you have the flaps stuck at 1+f for example, you'll need flap lever position 2 for landing. (to get the slats extended in position 2) The calculated Vapp will be lower than the manoeuvring speed, so it needs to be selected.
What you are saying is exactly opposite of what happens. S and F speeds come from flap lever position and not actual surface. So with flaps jammed at 1+F if you move the lever to position two the speed will come down to F which will be unsafe because one of the surface hasn't extended and that is why you use select speed. But the question asked is after you have configured to Vapp why can't the rest of the approach be flown in managed speed?

[Cough]

Been a while since I was on the Bus, but...

I always understood a part of the reason for using selected in these instances was due to the fact you were in direct law for landing hence had no autotrim. As GS mini oscillates the speed around the workload is going to increase for the PF as he has to retrim for each change in speed, which isn't something which is regularly practiced on the Bus... Nor is convenient if you are in manual thrust too..

[sierra_mike]

Since the QRH recommends use of select speed it takes out the GS mini out of equation. No need to expressly ban GS mini.

my current QRH only mentions to select VFE-5kt in order to configure safely. once in LDG config i don't see the procedure speaking against managed speed. purely speaking about being in LDG config, no question about the other phases.
since we use managed SPD for landing in normal daily ops i would expect airbus to explicitly tell us not to use it if they don't want us to. i.e. as they do for overweight landing procedure "SPEED AT RUNWAY THRESHOLD: VLS"

[vilas]

Cough
I think in direct law to stay in trim for a fixed Vapp speed is a very valid point. However the new QRH creates an impression that managed speed can be used at Vapp. It only says decelerate to calculated Vapp.
sierra_mike
As you correctly noted there are some changes to Landing with slats or flaps jam QRH procedure. Following notes have been deleted:
1. Use of selected speed is recommended.
2. Autopilot may be used down to 500ft AGL.
3. ATHR is recommended except B+G LO PR warning.
However in VLS greater than VFE next case is retained which can be interpreted as ATHR can be used. Below from QRH:
If VLS is greater than VFE NEXT (overweight landing case), the FLAPS lever can be set in the required next position, while the speed is reduced to follow VLS reduction as surfaces extend. The VFE warning threshold should not be triggered. In this case, disconnect the A/THR . A/THR can be re-engaged when the landing configuration is established.

[sierra_mike]

If VLS is greater than VFE NEXT (overweight landing case), the FLAPS lever can be set in the required next position

true that vilas! i have the impression that i might not have expressed myself clearly before with

since we use managed SPD for landing in normal daily ops i would expect airbus to explicitly tell us not to use it if they don't want us to.

what i meant: if airbus doesn't want us to touchdown with a managed speed target utilizing GS mini (as we normally do) they would specifically point it out as they do for example in the overweight landing procedure "SPEED AT RUNWAY THRESHOLD: VLS"

[LHRPony]

F and S speeds are manoeuvring speeds.

Check out the abnormal procedure from the FCTM as it is also explained there.

Chrome,
Unless our fcom's ar different, F &S are min speeds for retraction not manoeuvring. Pro sup 10

VLS is however a manoeuvre speed. 1.13 vs after take off, 30 degree bank turn stall speed increase is approx 1.08,
1.23 vs after retraction of 1 stage, 1.28 vs clean
Stall speed increase for 45 degree bank is 1.19, so you've got at least 30 bank avail + 15 over bank at VLS

[vilas]

I stand corrected. According to Airbus they are manoeuvre speeds but not limitations. It is safe to fly between VLS and Vmax (VMO, VLE, VFE). The required aerodynamic margin is properly ensured. Also in Slat/flap jam Autopliot use upto 500ft. is relocated and not removed.

[Chrome]

Hi LHRPony,

Taken from the FCTM that I have;
Abnormal Flaps/Slats Configuration
Failure During The Approach
... With A/THR operative, the managed speed target will become the next manoeuvring characteristic speed e.g. S speed when selecting flap lever to 1...

[CaptainMongo]

vilas

My motto is, "I wish I knew what I wish I knew."

I am a huge fan of this forum. It is one of the very few places on the sewer of the internet where fresh water is available.

Vilas, as a 319/320 pilot, Captain, and Line Check Airman, I always have put great value into your input into this forum. Your correction only adds to that value.

[vilas]

Thanks mate!

[LHRPony]

Cheers Chrome,
So we have fcom defining they are retraction speeds, fctm saying they are man speeds.
Genuine question, what manoeuvre margin exists at the f and S? it's defined for VLS,but I haven't come across any definition for manoeuvre margin for f and s.
And not wishing to get into a tit for tat, it does also say if their is a discrepancy between fcom and fctm then fcom takes precedence.
But as always happy to be corrected.
Thanks for your input, always good to rattle these things around and see where we end up.

[vilas]

LHRPony
Genuine question, what manoeuvre margin exists at the f and S? it's defined for VLS,but I haven't come across any definition for manoeuvre margin for f and s.
17th Performance and Operations Conference in Dubai explains this topic in detail. Extract below:
Maneuvering capability
• At V2, one engine out:
• Stabilized turn at 30° bank before alpha max
• At V2 + 10, all engines operative:
• Stabilized turn at 40° before alpha floor
• At Green Dot:
• Stabilized turn at 45° bank before alpha prot
• At Vls (final takeoff up to landing) :
• Stabilized turn at 40° bank before alpha floor
With AP on you won't use these bank angles nor for that matter in manual flight.

[LHRPony]

That's great, many thanks Vilas.

[Chrome]

Cheers Chrome,
So we have fcom defining they are retraction speeds, fctm saying they are man speeds.

Affirm LHRPony, on takeoff they are retraction speeds. The same part of the FCOM also defines F and S speeds are target speeds for the approach.

And thanks too vilas for sharing.

[CMpilot1]

Vilas,
This is regarding S and F speed mentioned in your post. As far as my understanding goes, the VFE next and VFE that are displayed on the PFD is based on the the FLAPS lever position. I couldn't locate the information that S and F are also displayed according to the flap lever position. I have referred to the old blue bulletin "Characteristic and protection speeds" as well. Could you please clarify. Thanks in advance

[sonicbum]

Hi,

check FCTM - PRO - ABN - F/CTL - Abnormal flaps/slats configuration - Failure during approach.
It’s the main reason we must pull speed selected to avoid further deceleration.

[CMpilot1]

https://cimg6.ibsrv.net/gimg/pprune.org-vbulletin/856x552/aeb4d4c2_a937_4bd6_9100_a46e724fb4de_1820e2e32484c4c53af8b4c 15c95d87e7409a823.jpeg
https://cimg8.ibsrv.net/gimg/pprune.org-vbulletin/991x1114/b6bd00e0_5627_49f6_a81f_c83ff417d72c_d00a5068e9ec06e51ae8009 ad716c834c84d1094.jpeg
Hi sonic,
have a look at the above attachments. The QRH clearly states that the vfe and vfe next are displayed according to the lever position. Also, have a look at the blue bulletin( airbus has stopped publishing these). The F,S,O speeds are computed according to the aircraft configuration and not according to the lever position

[sonicbum]

I am not sure I got Your point…
Once You select flaps 1 in approach you will get S speed displayed, computed by the FAC based on aerodynamic or FMGC data. This depends on MSNs as “newer” ones (and NEOs) will display FMGC speeds based on weight data for consistency purposes, so you don’t have different characteristic speeds between the PFD and the MCDU values.
If you get slats locked the S speed will not change, hence pull the speed in order to avoid decelerating to a speed not suitable for that configuration.

[CMpilot1]

please refer to my post #24. My question was with reference to a statement by VILAS that Fand S speeds are calculated in accordance to the lever position. I am of the opinion that only VFE and VFE next are calculated according to the lever position. The screen shots were attached as an exhibit for my source of information.

[vilas]

CM pilot 1
It's sure confusing. One way to make out if it's real time speed is it will move gradually as the surface extends. VFE changes instantly and even if the surface doesn't extend but VLS changes gradually. If S or F speeds don't change with a jam then they are predetermined. VLS remains correct with proper flap/slat configuration or even with one or both surfaces jammed. Also if S and F speeds are correct then there's no need to select speed but procedure demands it.

[vilas]

https://cimg8.ibsrv.net/gimg/pprune.org-vbulletin/1080x1151/screenshot_20210730_105141_2_f2fc45dfdf960f8b9dcb1c5c5a0ba0e 8056ee974.png
This is in the Airbus training document and we always taught this.

[CMpilot1]

Vilas,
Thanks for sharing the slide. However, would you be having any other document to corroborate the information provided on this slide. The QRH and blue bulletin doesn't substantiate the information provided in the slide. Thanks

[vilas]

I had the training DVD for FFS but a few years ago there was a problem between Adobe and some other agency involved after that it stopped working. But I remember it was always taught that way at least for more than a decade.

[CMpilot1]

Just thinking loud. Could this info be as outdated as the term "PNF" denoted on top of the slide

[vilas]

The last training DVD made by Airbus was in 2016/17. That also gives the same info. After that it's available to only their trainees on line.

[CMpilot1]

Thanks Vilas.
How can I access these videos?

[vilas]

As I said before there was some issue with the app and it doesn't work anymore.

[Rocket3837]

Hi all,
There is no harm in reverting to managed spd after setting the flaps lever to landing confg and ensuring that Vapp is correctly programmed in Fmgc....
Even if the spd is left selected for landing, it will change to managed if GA is initiated... And again, you have to go from managed to selected spd during GA....

[Nick 1]

You can find all in this channel , but be careful is not updated...

https://youtu.be/RUXQPsgBSC0

[vilas]

Rocket3837

As discussed before in managed speed you will activate GSmini. If you happen to be in direct law the shifting speed target will make flying difficult. Direct law unlike conventional speed stable aircraft doesn't have any feel and is sensitive. Also depending on the position of the jam speed addition could be high you wouldn't want any addition to that for any reason.
In case of GA the SRS will engage in managed speed. You need select speed only during acceleration phase and by then you are back in alternate law. It's not a good idea to fly the approach in managed speed.

[sonicbum]

Rocket3837

Hi,

As per FCTM, use of selected speed is a must during abnormals involving slats/flaps. Although something may seem like a smart move, don’t go against manufacturer’s/operators documentation as you might end up with big arguments during sim sessions or worst in real life occurrences.

[CaptainMongo]

The earth is littered with broken airplanes and broken bodies flown by pilots who thought they were smarter than the aircraft manufacturer, regulatory authority and their own training department.

[OPEN DES]

vilas

Hello there,

(For Direct Law Airbus recommends use of manual thrust.)

The technical reasons for using Selected speed for VAPP with LDG with S/F jammed are the following:
1. The selected LDG CONF on the MCDU may not correspond with the actual Flaps lever position for landing. This could limit your Managed Speed target to F, which could be above your abnormal VAPP. (i.e. no deceleration to Vapp tgt)
2. VFE exceedance, due GSmini, whenever the actual CONF (due jam) is higher than the Flaps lever position for landing. (i.e. the actual VFE is lower than the one displayed on the PFD speed tape)

It is true that high-energy during last stage of final approach can be avoided by not having GSmini, although for the A330, A320neo and A350 with k-factors significantly reduced this is much less of an issue than with the A320ceo.

Indeed, in the case of a G/A with S/F jammed, selected VAPP will become managed upon SRS engagement. Speed will have to be Pulled upon reaching Acceleration Altitude. (Top-tip: Speed can be inserted as a SPD constraint in the missed app, as a reminder)

[vilas]

OP DES
Except that the FCTM says selected speed must be flown there's no reason given as to why. So if you have any document it would be nice to have. As far as Direct Law is concerned except B+G where STATUS tells you to switch off ATHR I haven't seen anything regarding G+Y or any other. Rather explaining abnormals it says even with loss of AP, the ATHR may be available. Although I can see some merit in manual thrust. The GS mini activation as a cause we are offcourse logically guessing. But strange as it may sound the ATHR has nothing to do with GSmini function. GSmini requires only APP phase and Managed speed. So, even if you switch off the ATHR your Vapp will shift but it will not be flown since thrust won't respond to it, unless you move it manually. When under pressure of abnormalities flying 15 or 20 kts below Vapp will make anyone very uncomfortable. Only Select Speed will freeze the Vapp target. Good to have any other information.

[OPEN DES]

Hi vilas

Thanks for your reply.
Two reasons I gave I cannot give you a reference for, sorry. But let’s say that it is pretty reliable.

Indeed, only G+B SYS LO PR mandates A/THR OFF due to reduced pitch authority to counteract pitch-power couple.

A/THR off for Direct Law is recommended though as per L2 note in FCOM-PRO-ABN-F/CTL-DIRECT LAW. :ok:

Well aware of GSmini not being related to A/THR.

[vilas]

OP DES
Thanks found it. It's other way round, use of manual Thrust is recommended. But it doesn't appear in STATUS for failures.

[OPEN DES]

Yes, A/THR off = Man Thr

[Check Airman]

Well aware of GSmini not being related to A/THR.

Unrelated, but I’ve flown with one or two people who did not know that.

[vilas]

OP DES
It's strange that actual failures (except HYD G+B) which put the aircraft in Direct Law does not mention anything about use of manual thrust in the STATUS of the failures. And except dual RA failure no one reads the FCOM for Direct Law. So a question arises, is Airbus really serious about manual thrust in Direct Law?

[OPEN DES]

Hi Vilas,
As you know the Summary is a tool to manage the workload during a complex failure when time is critical.
The Summaries contain the minimum information to get the aircraft on the ground safely. In fact some procedures embedded in the Summary have been greatly reduced of information given the context of an already high workload vs time-criticality.
A ‘blanket’ recommendation to use manual thrust when in Direct Law does not fit in the philosophy of a Summary, after all it is not prohibited: hence safe enough and not worthy of mention in the Summary.
If remembered and applied by the crew as a technique, it’s a bonus.

Sorry, just read you were talking about the STS page. Same applies there to a certain extent, STS does not mention recommendations.

G+B is a special case due handling degradation in addition to the obvious F/CTL law degradation.

[Goldenrivett]

OP DES
So a question arises, is Airbus really serious about manual thrust in Direct Law?

Good question vilas. In 2013 the recommendation was in the manuals - see prune Fcom Direct Law (https://www.pprune.org/tech-log/520854-a320-fcom-direct-law-thr-where.html)
but I can’t find any reference today.

[OPEN DES]

The recommendation is still there. Check L2 note inside FCOM-PRO-ABN-F/CTL-DIRECT LAW.

[Goldenrivett]

Thanks Open DES.
I missed the note 2 times during my searches.

[vilas]

Golden rivette
The reference for Direct Law is given by OP DES. The problem is aircraft just doesn't transit by itself to Direct Law but it's the result of other multiple failures. There is no point giving the information in Direct Law which no one reads. The STATUS of the failure should ask you to switch off the ATHR. Unless it's a personal choice as is in the case of OEI. The reason for recommendation of manual thrust is understandable. In Direct Law the aircraft switches from flight path stable to conventional speed stability. So it's liable to pitch up with thrust changes like B 737, A310, A300 so if AP off, then ATHR OFF.

[OPEN DES]

It’s a recommendation only, so it will never become an action-line. (Except for G+B) Not in the Summary nor on the STS page. There are cases where you’d want to keep the A/THR on against the general recommendation.
Airbus will never explicitly ask you to switch off a system that is still available and certified for use.

[champair79]

As mentioned, ATHR is not ‘failed’ in direct law. It’s only a technique to manage the pitch/power couple. Have you tried flying with the autothrust engaged in the sim when in direct law? It’s harder than it looks! For a start, you’re having to predict what the autothrust is going to do and you have to keep scanning the engine instruments to anticipate the pitch/power couple, then make the pitch correction, then trim. If it’s a gusty day, the autothrust will start hunting the speed and it will destabilise you potentially even causing PIO.

It is far, far, far easier to set a datum with the thrust levers, disconnect the autothrust and be in total control of the aeroplane. Making as few thrust changes as possible is the key to flying a stabilised approach in direct law.

[vilas]

I agree and said the same thing but an important recommendation should also be in the STATUS as "Consider Manual Thrust" or discussed in FCTM. Hardly any pilot if at all gets the experience of Direct Law in real life so it remains a simulator exercise but many Pilots who are exposed to G+Y fail in recurrent don't use manual thrust.

[CMpilot1]

True. Even though the FCOM direct law procedure recommends A/THR off. However, one can always say that its only recommended and not compulsory.