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On Wed, 03 Sep 2003 19:19:13 +1000, Mike Borgelt
wrote: On Tue, 02 Sep 2003 17:34:17 +0100, Martin Gregorie wrote: On Wed, 27 Aug 2003 19:20:48 +0000, root wrote: Martin Gregorie wrote: ... Kindly draw the vector diagram before continuing. You'll see that the sinking speed velocity vector points down and the rising air vector points up. Simple vector addition says that the rising air velocity is subtracted from the sinking speed because their directions are opposite. ... But this is near like adding apples an oranges. The vector you are interested in is the relative wind vector, i.e. the velocity vector of the airmass seen from the aircraft as reference frame, for what concerns the AOA. Before entering lift, you can consider it as the sum of 2 components, a horizontal one, opposite of the horizontal speed of the glider, and a vertical one, opposite of the sinking speed. When lift is entered, a 3rd componemt is added, the lift vector. This 3rd component has the same direction as the 2nd one, i.e. both are upward. So the new relative wind clearly causes a higher AOA. Adding the sinking speed vector and the rising air vector, while mathematically possible, has no physical sense. That makes sense. Presumably the pitch down is the aircraft correcting its trimmed AOA, but where does the commonly seen airspeed increase come from? The Yates effect as the lift vector tilts forward(and increases in magnitude). Thanks -- martin@ : Martin Gregorie gregorie : Harlow, UK demon : co : Zappa fan & glider pilot uk : |
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