PPRuNe Forums


Tech Log The very best in practical technical discussion on the web

Reply
 
Thread Tools Search this Thread
Old 5th Oct 2017, 15:54   #1 (permalink)
Thread Starter
 
Join Date: Aug 2001
Location: Above the Horizon
Posts: 80
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.
Boyington is offline   Reply With Quote
Old 5th Oct 2017, 17:17   #2 (permalink)
 
Join Date: Sep 2009
Location: Spain
Age: 33
Posts: 56
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.
fpuentegomez is offline   Reply With Quote
Old 5th Oct 2017, 17:20   #3 (permalink)
 
Join Date: Aug 2008
Location: Betwixt and between
Posts: 659
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.
Sciolistes is offline   Reply With Quote
Old 5th Oct 2017, 20:46   #4 (permalink)
 
Join Date: Jun 2014
Location: Mordor
Posts: 165
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.
Sidestick_n_Rudder is offline   Reply With Quote
Old 6th Oct 2017, 03:45   #5 (permalink)
 
Join Date: Jun 2007
Location: Wanderlust
Posts: 1,700
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
vilas is online now   Reply With Quote
Old 7th Oct 2017, 21:04   #6 (permalink)
 
Join Date: Aug 2013
Location: Middle Europe
Posts: 54
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
sierra_mike is offline   Reply With Quote
Old 8th Oct 2017, 01:24   #7 (permalink)
 
Join Date: Feb 2002
Location: Waddinxveen Netherlands
Posts: 34
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.
KingAir1978 is offline   Reply With Quote
Old 8th Oct 2017, 01:49   #8 (permalink)
Thread Starter
 
Join Date: Aug 2001
Location: Above the Horizon
Posts: 80
What exactly do you imply by manoeuvring speed? Do you mean VLS? Thanks.
Boyington is offline   Reply With Quote
Old 8th Oct 2017, 04:36   #9 (permalink)
 
Join Date: Nov 2004
Location: Stormy Peninsular
Posts: 149
F and S speeds are manoeuvring speeds.

Check out the abnormal procedure from the FCTM as it is also explained there.
Chrome is offline   Reply With Quote
Old 8th Oct 2017, 04:51   #10 (permalink)
 
Join Date: Jun 2007
Location: Wanderlust
Posts: 1,700
sierra_mike
Quote:
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
Quote:
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?
vilas is online now   Reply With Quote
Old 8th Oct 2017, 08:00   #11 (permalink)
 
Join Date: Jul 2000
Location: My views - Not my employer!
Posts: 891
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..
Cough is online now   Reply With Quote
Old 8th Oct 2017, 09:38   #12 (permalink)
 
Join Date: Aug 2013
Location: Middle Europe
Posts: 54
Quote:
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"
sierra_mike is offline   Reply With Quote
Old 8th Oct 2017, 11:07   #13 (permalink)
 
Join Date: Jun 2007
Location: Wanderlust
Posts: 1,700
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.

Last edited by vilas; 8th Oct 2017 at 14:51.
vilas is online now   Reply With Quote
Old 8th Oct 2017, 14:06   #14 (permalink)
 
Join Date: Aug 2013
Location: Middle Europe
Posts: 54
Quote:
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

Quote:
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"
sierra_mike is offline   Reply With Quote
Old 9th Oct 2017, 07:59   #15 (permalink)
 
Join Date: Mar 2012
Location: London
Age: 35
Posts: 16
Quote:
Originally Posted by Chrome View Post
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
LHRPony is offline   Reply With Quote
Old 9th Oct 2017, 11:28   #16 (permalink)
 
Join Date: Jun 2007
Location: Wanderlust
Posts: 1,700
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.

Last edited by vilas; 11th Oct 2017 at 12:02.
vilas is online now   Reply With Quote
Old 13th Oct 2017, 19:22   #17 (permalink)
 
Join Date: Nov 2004
Location: Stormy Peninsular
Posts: 149
Quote:
Originally Posted by LHRPony View Post
Chrome,
Unless our fcom's ar different, F &S are min speeds for retraction not manoeuvring. Pro sup 10
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...
Chrome is offline   Reply With Quote
Old 14th Oct 2017, 01:42   #18 (permalink)
 
Join Date: Oct 2015
Location: Millioke
Posts: 119
Quote:
Originally Posted by vilas View Post
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.
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.
CaptainMongo is offline   Reply With Quote
Old 14th Oct 2017, 10:55   #19 (permalink)
 
Join Date: Jun 2007
Location: Wanderlust
Posts: 1,700
Thanks mate!
vilas is online now   Reply With Quote
Old 14th Oct 2017, 14:31   #20 (permalink)
 
Join Date: Mar 2012
Location: London
Age: 35
Posts: 16
Quote:
Originally Posted by Chrome View Post
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...
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 is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT. The time now is 03:59.


1996-2012 The Professional Pilots Rumour Network

SEO by vBSEO 3.6.1