CofG and induced drag
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Originally Posted by airfoilmod
Do I miss your point
- you seem to be the only person posting from the point of an extremely aft COGI can't argue with what you say - all perfectly correct as far as I understand, but also perfectly irrelevant to a legally loaded civil aircraft of 'conventional' disposition.. where there's going to be a nose down couple, opposed by the tail feathers.
As to the original question, why a fwd COG increases induced drag, I think it's been answered many times over. So long as you start with the reasonable assumption that the COG is ahead of the neutral point.
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Right. fwd cg difficult to raise the nose; aft cg difficult to lower it, all related to the distance of the cg from the tail. The key is the discrepancy in up or down authority, as the cg moves in relation to the control surface necessary to rotate the mass. The tail is necessary to balance the airframe. Disregard the cg. Think of the Lever. The cg is the fulcrum. Nose and tail are either end, move the fulcrum and gain an "advantage". The warning to everyone is this: when the force necessary to move the nose up or down differs by more than a little bit, you are having cg issues.
AF
Mark - The difference in cg isn't so important as the Physics when it changes. I'm the only one?
AF
Mark - The difference in cg isn't so important as the Physics when it changes. I'm the only one?
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OK, at least now I understand where we're misunderstanding each other....
The CG is NOT the fulcrum. The neutral point is. It's possibly just a frame of reference thing, but..
The CG is NOT the fulcrum. The neutral point is. It's possibly just a frame of reference thing, but..
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I'm not entering into the discussion other than to give some references by which anyone interested may gain some insight.
http://www.flightlab.net/pdf/5_Longi...cStability.pdf
http://www.flightlab.net/pdf/6_Longi...gStability.pdf
http://www.flightlab.net/pdf/7_Longi...cStability.pdf
To sum for those who have little interest in going further,
Conventional handling qualities require that the aircraft c.g. lie ahead of the stick-free static neutral point. If c.g. lies on the neutral point stick forces are zero. If c.g. moves behind the neutral point, control forces reverse. A pull force becomes necessary to hold the aircraft in a dive; a push force becomes necessary in a climb.
http://www.flightlab.net/pdf/5_Longi...cStability.pdf
http://www.flightlab.net/pdf/6_Longi...gStability.pdf
http://www.flightlab.net/pdf/7_Longi...cStability.pdf
To sum for those who have little interest in going further,
Conventional handling qualities require that the aircraft c.g. lie ahead of the stick-free static neutral point. If c.g. lies on the neutral point stick forces are zero. If c.g. moves behind the neutral point, control forces reverse. A pull force becomes necessary to hold the aircraft in a dive; a push force becomes necessary in a climb.
