A320 FMGS landing wind insertion

[Boroda]

What wind is it better to insert in PERF APPR page if ATIS gives you 270V180 degrees? RW is 180 degrees.

[Boroda]

Nobody knows? How do you fly??:)

[Cardinal]

225. It's all horseshoes and atom bombs anyway.

[Cummulo Granite]

neither, according to da book, tower wind should be inserted.

[Boroda]

May be you are right about shoes and bombs when in flight. But I have been almost fighting with my friend on ground about this horseshoes - and it is already big deal for us. When wind is strong - Vapproachtarget is strongly different during wind variations.

[Boroda]

It is tower wind 30 knots and variable in given sector
Please, just think theoretically without shoes and bombs

[aristoclis]

I would put 30kt headwind in the FMGS and compute landing distance (QRH) with zero headwind. In the worst case scenario (zero headwind at time of touch) I would have +5 knots on my Vapp (Vls+10 instead of Vls+5).

On the other hand if I put 0 headwind in the FMGC and in the worst case I had 30kt headwind at the time of touch, instead of the needed Vls+10 I would have Vapp+20kt (GSmini, which in our case is Vapp-10, plus current wind component) that would be Vls+25kt. Not true?

[OPEN DES]

If landing distance is not a factor I tend to insert the wind which results in the highest Vapp target. I.e. the wind with the lowest headwind component.

[aristoclis]

It depends. Suppose steady wind conditions at final until touch (Gs mini not affecting target speed), highest target speed i.e. Vapp would result from inserting highest headwind component (Vapp= the highest of Vls+5/Vls+one third of headwind component). Or not?

[OPEN DES]

You would still respect the Vapp=VLS+5 or VLS+1/3hw (whichever higher).

I refer to inserting the lowest possible headwind component as the TOWER WIND. (in case of variable winds, eg: in case of VRB05kt: 5 knots of tailwind)
In this way Vapp target will benefit from a higher GS MINI.

[aristoclis]

Inserting a component of less than 10kt headwind or any tailwind does not affect target speed. GSmini for these insertions is Vapp-10. So target speed at approach would be the highest of Vapp/GSmini+current wind component (headwind counting positevely).

In Boroda's extreme example inserting 270/30 would result in a Vapp=Vls+5 and if for some reason GSmini function was unavailable you would not respect the required Vapp for the case of 180/30, which is Vls+10.

GSmini function is supposed to provide a kind of protection along the final approach flying into increasing headwinds and shortly thereafter into decreasing headwinds by maintaining a minimum groundspeed. It is not supposed to substitude the increment on the Vls due to the variable wind at touchdown. Ending up potentially in Boroda's example at threshold with target speed Vls+25 is not exactly what GSmini was ment for. Was it?