Another Teddy Ruxpin silly question - Windshear...
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Another Teddy Ruxpin silly question - Windshear...
This is a sudden, unpredictable (unless pre-warned by a leading a/c) phenomona, right?
So - would one feel Windshear from the ground; while walking for example; if you were underneath it, however unlikely that may be?
regards all
TR
So - would one feel Windshear from the ground; while walking for example; if you were underneath it, however unlikely that may be?
regards all
TR
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In general, I don't think you would. As you walked along into a stiff easterly breeze, would you know that a hundred feet above you there was a stiff westerly breeze? I bet we have all been in that situation many times and not realised it.
But someone in a light aircraft descending at approach airspeed through that velocity shear would have an interesting experience: if he was heading west, the airspeed would disappear like the dew in the morn as he got into the easterly flow. And if he was heading east (likely, because that's what a windsock on the ground would be telling him to do), his airspeed would suddenly increase near the ground and it would be float, float, float time as heaps of runway went past. Remember that the aircraft tries to maintain its inertial speed over the ground; if the wind changes the airspeed changes until you do something about it.
You cannot hear windshear because the differential air velocities are too small. But you can hear shear when the differential velocity is high: listen at an airshow to the whistle as a wingtip-vortex from a recent high-'g' pass reaches the ground. It's quite distinctive. Fast jet operators are very used to the sound.
But someone in a light aircraft descending at approach airspeed through that velocity shear would have an interesting experience: if he was heading west, the airspeed would disappear like the dew in the morn as he got into the easterly flow. And if he was heading east (likely, because that's what a windsock on the ground would be telling him to do), his airspeed would suddenly increase near the ground and it would be float, float, float time as heaps of runway went past. Remember that the aircraft tries to maintain its inertial speed over the ground; if the wind changes the airspeed changes until you do something about it.
You cannot hear windshear because the differential air velocities are too small. But you can hear shear when the differential velocity is high: listen at an airshow to the whistle as a wingtip-vortex from a recent high-'g' pass reaches the ground. It's quite distinctive. Fast jet operators are very used to the sound.
Last edited by D120A; 26th Feb 2009 at 06:45. Reason: Removed post.
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Windshear takes place at all levels of the atmosphere, all over the world, all the time. Windshear is nothing more than a change in direction or velocity of airflow, somewhere in the atmosphere. It can take place close to the ground, horizontally, vertically, or high in the atmosphere.
Of course you can feel windshear, if it occurs where you are. Downdrafts, gusts of wind, changes in wind direction, etc, are all shear effects.
How windshear affects an aircraft depend very much on the conditions at the time, including the airspeed and configuration of the aircraft, the magnitude of the change in velocity (speed or direction), etc.
Windshear is frequently encountered in flight, often with little or no obvious effects. Windshear in the form of a strong microburst, which a sudden flow of wind from a thunderstorm, can create unusual reactions, including significant airspeed loss, altitude loss, etc, during an approach to land. Most of the time, however, when an aircraft encounters windshear, hardly anybody on board is any the wiser.
Of course you can feel windshear, if it occurs where you are. Downdrafts, gusts of wind, changes in wind direction, etc, are all shear effects.
How windshear affects an aircraft depend very much on the conditions at the time, including the airspeed and configuration of the aircraft, the magnitude of the change in velocity (speed or direction), etc.
Windshear is frequently encountered in flight, often with little or no obvious effects. Windshear in the form of a strong microburst, which a sudden flow of wind from a thunderstorm, can create unusual reactions, including significant airspeed loss, altitude loss, etc, during an approach to land. Most of the time, however, when an aircraft encounters windshear, hardly anybody on board is any the wiser.
