Performance Vref Question
Join Date: Jun 2006
Location: Europe
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With regards to the crosswind at 90 degrees to the runway; bear in mind the following:
--the wind direction may vary up to but (but not including??) 60 degrees without this being reportable in a metar. A left direct crosswind of 10G20 could veer up to 30 degrees, which would yield a HWC of 5G10, legally without any mention of this in the metar. It could also back bu the same amount, yielding a max TWC of 5G10. Ie total shear in headwind could be .... 10G20!
-- when crabbing on final in a direct crosswind (compared to the runway), the wind is not directly across compared to you, i.e. the gust would have a headwind component.
-- gusts tend to veer compared to the mean wind direction in the northern hemisphere
-- gusts that are the result of showers or mechanical turbulence may just as likely change direction as intensity.
--the wind direction may vary up to but (but not including??) 60 degrees without this being reportable in a metar. A left direct crosswind of 10G20 could veer up to 30 degrees, which would yield a HWC of 5G10, legally without any mention of this in the metar. It could also back bu the same amount, yielding a max TWC of 5G10. Ie total shear in headwind could be .... 10G20!
-- when crabbing on final in a direct crosswind (compared to the runway), the wind is not directly across compared to you, i.e. the gust would have a headwind component.
-- gusts tend to veer compared to the mean wind direction in the northern hemisphere
-- gusts that are the result of showers or mechanical turbulence may just as likely change direction as intensity.
