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Old Sep 12, 2010, 06:35 AM
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The effect of wind on the aircraft in flight

http://www.bmfa.org/publications/fil...02FullBook.zip


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BRIEFING 3 - THE EFFECT OF WIND ON THE AIRCRAFT IN FLIGHT

There is probably more nonsense talked and written on this subject than any other connected with the practical side of flying! In reality, the matter is very simple - it is just that so many people find it hard to accept.

Provided that your flying area is clear of vertical obstructions (houses, trees, hedges, hangers etc.) the wind will blow fairly steadily from a constant direction once the aircraft is above about 50ft. Below this height, and depending on the surface of your flying site and the proximity of obstructions, there will be some turbulence both vertical and lateral.

Once you understand this principle you will see that a turn from an into wind heading to crosswind will appear to be a fairly sharp turn when seen from the ground and a turn from downwind to crosswind will appear to be slow and elongated. You must accept these visual effects for what they are and remember at all times that if you have not altered your throttle setting and the aircraft is at constant height then your airspeed is constant and the aircraft is in no danger of stalling.

Once the aircraft has climbed out of this turbulent level it is, in effect, flying in a steadily-moving block of air. Thus, with a windspeed of 10 mph the block of air in which your aircraft is flying is moving downwind at a speed of 10 mph. So, your aircraft which flies at a speed of, say 20 mph will appear to be doing only 10 mph when flying into the wind (flying speed less windspeed) and 30 mph when flying downwind (flying speed plus windspeed). In point of fact your aircraft knows nothing about the windspeed at all and is flying at a steady 20 mph all the time!

You will often hear people say that their aircraft tends to climb when turning into wind and dive when turning downwind. What is really happening, of course, is that they are subconsciously trying to compensate for the apparent variation in speed and themselves causing the aircraft to climb and dive.

One major point to remember - donít try to keep your apparent speed constant or you will find that you will have your aircraft at full throttle when going into wind and stalling when it goes downwind.

If you find all this difficult to visualise, try to imagine yourself piloting a model boat from the bank of a fast-flowing river. In this situation you will find that you can understand the problems outlined above.

When flying in a wind of any strength you will find that your model can be carried away from you very quickly when it is travelling downwind. It is essential not to let it go too far. If you do, not only do you stand a good chance of losing control because you just canít see the aircraft properly, but it is a long and slow slog back to your position against the full strength of the wind. There is another major factor - if your engine stops it will be difficult or impossible to glide the aircraft back to your position if it is too far downwind.

So always try to keep your aircraft upwind of your position as much as possible. By doing so you will save yourself from falling into some very difficult situations.
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Old Sep 12, 2010, 03:25 PM
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That was very helpful, but couldn't locate the document / .zip file, if you can provide the full link again I'd appreciate it.
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Old Oct 12, 2010, 01:15 AM
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Originally Posted by tobermei View Post
That was very helpful, but couldn't locate the document / .zip file, if you can provide the full link again I'd appreciate it.
http://www.bmfa.org/publications/files/EUA.pdf
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Old Oct 12, 2010, 03:18 AM
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Thanks
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Old Mar 18, 2011, 01:29 AM
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+1. Very useful information to keep in mind.
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