Selected Speeds on A320
Why is it that even the VApp is SELECTED in case of failures like Dual hydraulic and Slats/Flaps jammed in the A320.
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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.
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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.
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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. |
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
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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
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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 exactly do you imply by manoeuvring speed? Do you mean VLS? Thanks.
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F and S speeds are manoeuvring speeds.
Check out the abnormal procedure from the FCTM as it is also explained there. |
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. |
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.. |
Since the QRH recommends use of select speed it takes out the GS mini out of equation. No need to expressly ban GS mini. 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" |
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. |
If VLS is greater than VFE NEXT (overweight landing case), the FLAPS lever can be set in the required next position 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. |
Originally Posted by Chrome
(Post 9917935)
F and S speeds are manoeuvring speeds.
Check out the abnormal procedure from the FCTM as it is also explained there. 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 |
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.
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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... |
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. |
Thanks mate!
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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. |
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. 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. |
That's great, many thanks Vilas.
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Originally Posted by LHRPony
(Post 9924957)
Cheers Chrome,
So we have fcom defining they are retraction speeds, fctm saying they are man speeds. And thanks too vilas for sharing. |
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 |
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. |
https://cimg6.ibsrv.net/gimg/pprune....e7409a823.jpeg
https://cimg8.ibsrv.net/gimg/pprune....4c84d1094.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 |
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. |
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.
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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. |
https://cimg8.ibsrv.net/gimg/pprune....e8056ee974.png
This is in the Airbus training document and we always taught this. |
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 |
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.
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Just thinking loud. Could this info be as outdated as the term "PNF" denoted on top of the slide
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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.
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Thanks Vilas.
How can I access these videos? |
As I said before there was some issue with the app and it doesn't work anymore.
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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.... |
You can find all in this channel , but be careful is not updated...
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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. |
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. |
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