Question on Windshear

[Tomliner]

Please could one of you professional flyers explain what is meant by windshear being reported as + or - (x) knots during an approach and what actions are required by crews to deal with these conditions.Could windshear ever be bad enough to require a go around?Thank you EricT

[pythagoras]

Windsheer is a sudden change in wind speed or direction and can be vertical or horizontal. Windsheer of +/- 10 kts basically means that if you are flying a stable approach at say 135 kts, when you encounter the windsheer your air speed indicator will fluctuate quite rapidly between 125 & 145 kts - close to the ground if you get windsheer which de-stabalises the approach or activates the GPWS you must go around. If windsheer is reported it is often a good idea to carry a few extra knots of airspeed on the approach while also being mindful of flap limiting speeds - on some aircraft in gusty conditions at heavier weights your approach speed can be uncomfortably close to the normal landing flap limiting speed!

[GBALU53]

In certain wind directions the ground effect can come into this as well if you have a valley on the approach this can give some instability during the approach.

If the approach is over a cliff this can have an effect of wind shear.

With these sort of approach,s the U.K. air pilot could well have some thing in the remarks stating a speed loss and a rough approach when the wind is in a certain direction

[Tomliner]

Many thanks for your clear and concise replies.I had partly guessed the answer but certainly hadn't thought about flap limiting speed or the effects of valleys and cliffs.Best Wishes to you.EricT