A320 Flex temperature tailwind

[Speedwinner]

Hello folks,

What influence has a 5 kts tailwind on the performance calculation. Any rule of thumbs like without tailwind 55 and with a tailwind of 5kt then 45. I want to know in case of short notice of the tailwind and we can take a formula to do a quick change.

Thanks!

Sw

[vodmor]

There is no rule of thumb. Takeoff performance can be limited by any of several factors: TODA, ASDA, second segment climb performance, obstacle and so on... You really can`t use any rule of thumb to predict how the 5kt tailwind will influence the takeoff performance in any given case.

[J.L.Seagull]

Use TOGA!?!? LOL!

Why not just write down the corrections on a piece a paper (from your OFP TLR) and keep it handy. If the tower informs you of a tailwind, just make the corrections on the PERF page. Shouldn't take more than 10 seconds...

[vodmor]

What if your headwind decreased by 5kts? What if wind changed direction by 20-30 degrees? What if wind changes during the takeoff run? You can`t really take into account any wind variation. What is a chance that actual wind during takeoff will be exactly the same as given in ATIS?

[Goldenrivett]

What is a chance that actual wind during takeoff will be exactly the same as given in ATIS?

That's why the performance calculation uses 50% the head wind or 150% of the tailwind in the maths.

Worst case is a calm wind in the maths, then you pick up a tailwind during the take off.

[PENKO]

If conditions vary that much (variable winds on the ATIS, thunderstorms in the area etc), then surely, as an experienced pilot you would have calculated the takeoff with a tailwind!

[Escape Path]

If you're operating out of an airport with a long runway, sea level, no obstacles and so on, your 5 kt tailwind might not do too much for you. But if you're about to takeoff from a short runway, or a high elevation airport, or terrain is a concern, you either have a set of calculations previously done handy or you advise ATC you're not ready to depart and run a new calculation. It takes 30 secs on the FlySmart thingy.

Don't modify the performance numbers so arbitrarily, especially on a high performance aircraft. Too many factors contribute to a takeoff to "just add/subtract 5 kts for this or that"

[tubby linton]

I have just looked at our paper performance charts for Birmingham. At low weights flex stays the same, at medium weights 5kt tail reduces flex by 2 or 3 degrees and towards the upper end it reduces by 6 degrees until it becomes a performance limit. There is no rule though and you should compute performance from a chart or the flysmart app.

[energysaver]

As Penko rightly says apply the KISS principle and, if variable conditions, just use a tailwind in the initial calcs.

If conditions change dramatically then stop and re do the calcs, it doesn't take that long even without the flysmart software.