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I've heard about this formula and have my doubts. I just compare the ATIS winds to what the FMS is telling me, and compare them. Here at IAH the winds are usually 150 at 4-5, but over the marker the FMS may read 200 at 040, so somewhere along the line I expect windshear. I keep the engines spooled up and carry a few extra knots, knowing once I am through the shear everything wil stabilize.
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You'll find that probably 90% of the time the winds are 90 degrees different and 15-30 knots stronger at 2000 AGL than at 300 AGL. 300-500 AGL is the "breaking point" where you get to the surface winds. That's why I usually keep my speed at around Vapp + 15 on the ILS, and it will normally (depending on wind direction of course) ease itself down to Vapp by the time I reach 500 feet, without any major power adjustment.
I see a lot of people who try and stabilize at like 2000 AGL, when in reality at 500 AGL the winds might be totally different. Particularly in areas with ground interference, whether it be buildings, hills, mountains, whatever.
The worst I've ever seen is when the winds at 2000 were something like 150 at 68, then tower reported was 180 at 10 gusting to 30. Twas a bit bumpy on approach. I was upset I didn't bring my chocolate milk that day.