Tuesday, March 6, 2012
Ten Things The Textbooks Don’t Tell You
9 Ground-Level Venturi Effects "Whoa! What was that?" We've all felt it on either landing or takeoff. Everything will be going just great, when we're hit with something from the side that feels as if we've gone through a jet-engine blast. Usually, it's a narrow steam of wind caused by a crosswind flowing between two obstacles (buildings, trees, etc.). The venturi formed by those obstacles causes the wind to narrow and accelerate, creating the jet-blast effect. These are quite often formed only during specific wind conditions, e.g. for a given airport, it may be a wind from 030 that happens to line up with a venturi-like gap between a building and a billboard, or something similar.
10 The "Character" Of The Wind Is As Important As Direction Or Velocity It's not unusual to find ourselves working our butts off in a little 12-knot wind when we know that we've handled 25-knot winds with far less work. All winds aren't created equal, and it's the character of the wind that makes up much of the difference. Is it quirky with some sort of weirdly changing direction, or it's three knots, gusting to 12 knots and the changes are instantaneous, so you often get left hanging? The personality types of wind are almost limitless. The good news is that by studying the wind sock and the local environment, you can get a rough idea of the general character of the wind you'll be fighting.
The winds you actually experience when landing may be different from those that were reported. Factors such as topography and venturi effects will all come into play.
Pay special attention to everything around the airport and the runway that can indicate wind. This includes flags, hanging decorations on businesses, tethered balloons, etc. If you see a flag that's off-airport that indicates a wind that's quite a bit different than the sock, you know something exciting is happening in between. If the grass next to the runway is laying flat, you know it's one of those "nasties" that retains its velocity right down to the surface. Watch out!
A runway is nothing more than a long string of micro climates, little bubbles of wind, temperature, humidity, etc. that change as we travel down the runway from bubble to bubble. Knowing that arms us with one very important fact: Regardless of what the tower or wind sock tells us, we should be prepared to deal with whatever we're seeing around the airplane at any given moment. The old adage, "Fly the airplane," applies here. If something is making it do something you don't want it to do, we don't really care what's causing it. We just do our pilot thing and put the airplane where we want it.
Incidentally, there's no takeoff that absolutely has to be made. If the wind is too far out of your comfort zone, don't fly. And we should never allow a fuel situation to develop that forces us into making a landing in a wind condition we think is over our heads. Always be prepared to go looking for an alternate airport with friendlier winds.
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Labels: Features, Flying Skills, Pilot Skills, Safety, Takeoffs and Landings, Weather, Weather Flying, Weather Skills, Winds