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Old 15th July 2005 | 14:49
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3 Point
25 Anniversary
 
Joined: Oct 2000
Posts: 367
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From: South West UK
Mayor,

Only half right. A given power setting will result in two possible stabilised speeds (ie performances), one above Vimd and one below it. The difference however is attitude, the slower speed will require a much higher nose attitude to give a higher angle of attack (aoa) and a greater lift co-eficient (Cl) to produce sufficient lift for level flight while at the higher speed less Cl will be required to produce the lift and this will be achieved at a lower aoa ie a lower nose attitude. The total drag in both cases will be the same (ie equal to the thrust) but in the low speed case it will be made up of a greater proportion of lift induced drag and in the higher speed case there will be more zero lift drag.

So, "Attitude equals either one of two performances"
"Power equals either one of two performances"
BUT, "Attitude plus power equals just one performance"


Now for any real pedant out there I suppose it might be possible with a given power setting to produce a slow speed descending flight path with high nose attitude and high angle of attack and therefore high drag or alternatively to fly a higher speed, level or slightly climbing flight path with the same pitch attitude but less aoa and hence less lift induced drag but a rate of climb (or lower rate of descent) and more zero lift drag to counter the same thrust. That's trick flying at best though and not real world stuff!

How many of us routinely operate on the back side of the drag curve?

3 Point
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