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hawk37
29th Oct 2015, 12:40
I've never heard this is an approved procedure, is it ever done?

Certainly take off distance is affected by headwind, however the few jets I've flown did not use a different v1 based on wind. My thoughts are that increasing V1, where a headwind exits, would provide a shorter balanced field length than a V1 not adjusted for headwind, and thus allow a higher take off weight for a balanced field situation

Does this make any sense?

Hawk

B737900er
29th Oct 2015, 13:34
Wind component is taken into consideration when determining Vspeeds

hawk37
29th Oct 2015, 14:47
Wind component is taken into consideration when determining Vspeeds

Thanks B737900er. By Vspeeds I presume you are not referring to Vr and V2, or are these 2 somehow wind component affected?

V1 is already adjusted for wind component, ok thanks. On the learjet I fly it isn't, however that must be a manufacturer's choice not to I presume

Hawk

lomapaseo
29th Oct 2015, 14:52
Isn't this akin to the conveyor belt discussion?

Intruder
30th Oct 2015, 01:57
In our takeoff performance from Aerodata for the 744, headwind is only taken into account if the runway length is marginal, and the headwind is required for a legal takeoff. A note shows up when that happens.

KingAir1978
30th Oct 2015, 14:03
Some EFB have the option to use 'improved climb analysis'. If a runway is very long (not limiting) the V speeds are increased, as to delay rotation. This will benefit the climb gradient later on (far out obstacle).

john_tullamarine
30th Oct 2015, 23:08
'improved climb analysis'. If a runway is very long (not limiting) the V speeds are increased, as to delay rotation. This will benefit the climb gradient later on (far out obstacle)

Or, more particularly,

(a) the aim is to get a higher V2

(b) in the main, V2 will determine VR

(c) V1 generally will be pushed high to minimise TOD, subject to ASDA comfort

(d) the climb benefit starts straight away

(e) obstacle clearance will be degraded until the intersection of the standard and overspeed flight paths. Just where this will occur depends on the numbers

parabellum
30th Oct 2015, 23:12
"Improved climb" is a misnomer! Airlines I've worked for used it for improved payload! ;)

B737900er
30th Oct 2015, 23:29
Or and increased Assumed temperature derate if you don't take the extra payload.

john_tullamarine
1st Nov 2015, 04:45
"Improved climb" is a misnomer! Airlines I've worked for used it for improved payload! ;)

Indeed, good sir. All depends on the tint of one's glasses on the day.

Came past you last night on the way home .. however, didn't drop in to say hi ... figured 0100 might have been a tad late ...

falconer171
1st Nov 2015, 08:59
More tailwind requires a lower V1 because it hurts the stopping capability in case of a rejected takeoff. Consequently more headwind allows a higher V1. Wind has no effect on VR and V2.

hhassan
22nd Apr 2019, 15:56
More tailwind requires a lower V1 because it hurts the stopping capability in case of a rejected takeoff. Consequently more headwind allows a higher V1. Wind has no effect on VR and V2.
Ok Tailwind will reduce V1 for ASDR understood, but why would a headwind increase V1 , dont get it ?

FZRA
22nd Apr 2019, 16:08
Ok Tailwind will reduce V1 for ASDR understood, but why would a headwind increase V1 , dont get it ?

Presumably because with a headwind your groundspeed is less; therefore V1 can be increased to take in to account the less stopping distance required if aborting from a lower groundspeed.

FE Hoppy
22nd Apr 2019, 20:21
Ok Tailwind will reduce V1 for ASDR understood, but why would a headwind increase V1 , dont get it ?


Think about this.

I can stop from 100kts groundspeed in 500meters.

Zero wind 100kts GS =100 KIAS

50 head 100GS = 150KIAS

Same stopping distance.

The higher V1 gives a higher potential RW limited TOW, by moving the crossover point where Vstop = Vgo. Just like upslope would do. And the opposite to downslope or degraded braking (wet or ice).

Here is a simplified idea of optimised V1 and headwind moves the stop line to the right.

https://cimg9.ibsrv.net/gimg/pprune.org-vbulletin/640x480/v1_001_jpg_jpeg_1bb99ffa03c87fba76d95c26800940766b7a6040.jpg

AerocatS2A
23rd Apr 2019, 00:40
Presumably because with a headwind your groundspeed is less; therefore V1 can be increased to take in to account the less stopping distance required if aborting from a lower groundspeed.
The key here is whether your airline has chosen to be go minded or stop minded or somewhere in between. If the preference is to stop then the V1 will be as fast as it can be so a headwind will result in a faster V1 provided itís not limited by something else. On the other hand, if the preference is to go then there is no reason to increase V1 with a headwind.