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Variable Winds And Impact On Take Offs/Landings

Posted: Tue Jul 20, 2010 2:03 am
by rotation18L
I'm an aviation enthusiast, not a pilot .......... yet.   

I have a question regarding the impact of headwinds v crosswinds/tailwinds on take-off and landing. Is a direct headwind the most optimal, and if so, is it because it makes the wings more efficient; i.e., more lift with shorter runway to use on T/O? What is the benefit for landings v a tailwind? Does a tailwind make the aircraft more unstable?

Also, what impact do dramatically variable winds have on landings? For instance, say you receive vectors to final with a planned touchdown on 18L at any given airport. If you are on the downwind or base leg, or even on short final, and the fairly gusty winds (say, 30k or higher) suddenly shift from 174 degrees, for example, to 345 degrees.

In those situations, are you required to cancel the landing on the planned rwy so that you can take advantage of the winds blowing in the opposite direction, more or less, or is it ultimately up to the PIC right up to DH as to whether the aircraft should land on 36R after vectors have been received? (Or does ATC simply call for a 'go-around' at that point?)

Thanks in advance for your responses!

Rotation18L

RE: Variable Winds And Impact On Take Offs/Landings

Posted: Tue Jul 20, 2010 10:07 am
by tdscanuck
Quoting rotation18L (Thread starter):
Is a direct headwind the most optimal

Yes.

Quoting rotation18L (Thread starter):
is it because it makes the wings more efficient; i.e., more lift with shorter runway to use on T/O?

The wings aren't any more efficient, but with a headwind you need less groundspeed for a given airspeed (and wings care about airspeed).

Quoting rotation18L (Thread starter):
What is the benefit for landings v a tailwind?

Landing in a tailwind is to be avoided if possible.

Quoting rotation18L (Thread starter):
Does a tailwind make the aircraft more unstable?

No, but it raises your groundspeed for approach, and brakes care about groundspeed.

Quoting rotation18L (Thread starter):
Also, what impact do dramatically variable winds have on landings?

They make them harder, and raise your approach speed to make sure a gust doesn't accidentally drop you below safe approach airspeed.

Tom.

RE: Variable Winds And Impact On Take Offs/Landings

Posted: Mon Jul 26, 2010 6:28 am
by swiftski
Quoting rotation18L (Thread starter):
What is the benefit for landings v a tailwind?

On my aircraft type for every 2kts of tailwind the calculated landing roll is increased by 10%.