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A320 QNH Correction to V2

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A320 QNH Correction to V2

Old 18th May 2019, 11:24
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A320 QNH Correction to V2


Can someone please throw some light on this, thanks.
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Old 21st May 2019, 19:25
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It must be a printing error - you can't have V2 below VR.
If you look at the corrections published for -10 Kts and +10 Kts, they show only -1 Kt correction which makes the results sensible.
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Old 21st May 2019, 20:32
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Maybe for flat earth only
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Old 22nd May 2019, 00:16
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Originally Posted by Haroon View Post

Can someone please throw some light on this, thanks.
To have the proper answer you must check the Maximum Permissible Take Off Weight for the airport and runway in use. After that compare the speeds . Remember that no correction on speeds is required if applying bleed and qnh correction to flex take off. Refers to PER-TOF-TOC-20–10 P 5/14 “Correction produced on the RTOW chart” para 2 last sentence.
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Old 22nd May 2019, 11:54
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Originally Posted by Goldenrivett View Post
It must be a printing error - you can't have V2 below VR.
If you look at the corrections published for -10 Kts and +10 Kts, they show only -1 Kt correction which makes the results sensible.
I have seen it on some other charts too and not only on this one.


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Old 22nd May 2019, 11:58
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Originally Posted by joe falchetto 64 View Post
To have the proper answer you must check the Maximum Permissible Take Off Weight for the airport and runway in use. After that compare the speeds . Remember that no correction on speeds is required if applying bleed and qnh correction to flex take off. Refers to PER-TOF-TOC-20–10 P 5/14 “Correction produced on the RTOW chart” para 2 last sentence.
Correct! But lets assume its not a flex case e.g. OAT is 44, QNH is 1003 and actual TOW is 70.5 tons. The speed correction will be applicable in this case right?
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Old 22nd May 2019, 15:53
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Hi,

the reference is in PER-TOF-TOC-12-10 P 5/14 (TEMPERATURE ENTRY).

(...)Check that the resulting speeds are higher than the minimum speeds displayed on the RTOW
chart and that V2 is higher than the VMU limited speed (Refer to PER-TOF-TOD-25-20 MINIMUM
V2 LIMITED BY VMU/VMCA (KT IAS)).

(...)
If OAT is higher than TVMC (line 3) or if the above speed check is not fulfilled, apply ΔW correction
from line 3 and ΔV1/ΔVR/ΔV2 corrections from line 4. No speed check is required.

Your speed are 149/150/151.
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Old 22nd May 2019, 16:30
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Hi
Originally Posted by sonicbum View Post
Hi,

the reference is in PER-TOF-TOC-12-10 P 5/14 (TEMPERATURE ENTRY).

(...)Check that the resulting speeds are higher than the minimum speeds displayed on the RTOW
chart and that V2 is higher than the VMU limited speed (Refer to PER-TOF-TOD-25-20 MINIMUM
V2 LIMITED BY VMU/VMCA (KT IAS)).
(...)
If OAT is higher than TVMC (line 3) or if the above speed check is not fulfilled, apply ΔW correction
from line 3 and ΔV1/ΔVR/ΔV2 corrections from line 4. No speed check is required.
The Note on the same page say: "No speed check is required for the first correction".

In any case the min V speeds on that chart are:

which are way below.

Your speed are 149/150/151.
How did you determine that? You've only reduced V1 whereas the correction applies to all.
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Old 23rd May 2019, 01:49
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Haroon, you need to check with your Flight Operations Engineering department, and they probably with Airbus.

It makes no sense, and I think the explanations provided so far are valid for something else than you asked about.

To reiterate my understanding of your original question:
In case you needed to apply the speed corrections for low QNH, the resulting V2 is invalid. How come?


​​​​​

Last edited by FlightDetent; 23rd May 2019 at 15:54. Reason: undone auto-correct
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Old 23rd May 2019, 08:10
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Originally Posted by FlightDetent View Post
Harpoon, you need to check with your Flight Operations Engineering department, and they probably with Airbus.​​​​​
Thanks, I guess so.

In case you needed to apply the speed corrections for low QNH, the resulting V2 is invalid. How come?
That's correct.

I would be grateful if some A320 pilots could have a quick glance in their books to see if they could find similar sort of stuff. Thanks.



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Old 23rd May 2019, 08:37
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Originally Posted by Haroon View Post
Thanks, I guess so.



That's correct.

I would be grateful if some A320 pilots could have a quick glance in their books to see if they could find similar sort of stuff. Thanks.
Haroon, I haven't seen initially the minimum speed You have published, hence my answer does not apply to Your question. Best thing as suggested is to mail Your perf dept. and check with them.
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Old 23rd May 2019, 08:56
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Thank you. Query already sent, lets see what do they have to say.
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Old 23rd May 2019, 09:26
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Originally Posted by Haroon View Post
Thank you. Query already sent, lets see what do they have to say.
Cheers. Let us know the answer. For some reasons (not sure which) I believe it will end up by applying the corrections from line 3 and 4 so that V2 is not lower than Vr.
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Old 23rd May 2019, 14:01
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Originally Posted by sonicbum View Post
Cheers. Let us know the answer.
I am quite curious too.
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Old 23rd May 2019, 14:46
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Will share with all
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Old 8th Jul 2019, 20:23
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The reply was:
"Software is designed to calculate Charts including speeds and corrections separately. After applying corrections if V2 decreases from VR then apply the basic performance rules and take V2 equal to VR."
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