Sender: <marv@lancaironline.net> (Marvin Kaye)
To: lml
Date: Wed, 15 Jan 2003 15:41:44 -0500
Message-ID: <redirect-1984107@logan.com>
Reply-To: "Dan Schaefer" <dfs155@earthlink.net>
From: "Dan Schaefer" <dfs155@earthlink.net>
Subject: Re: Wing Loading mysteries
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Scott wrote:

"....All I know is that the faster I go, the more I must trim nose down, not
nose up."

Makes sense, Scott. The airplane weight doesn't change due to going faster
(ignoring the slight decrease due to fuel burn) so the lift generated by the
wing needs to stay nearly the same to keep you at a constant altitude (also
ignoring some second order effects such as the engine's alignment, etc.).
Since lift is some function of airspeed and AOA, as you increase speed, AOA
must be reduced by trimming nose-down to compensate.

Interestingly, the elevator will still be producing about the same amount of
down-force because, at the higher speed, it takes less deflection to
generate the same (negative) lift. Interestingly, if you could arrange to
fly with zero up or down elevator force in all cruise regimes (not
recommended without a computer controlled stability augmentation system)
your aircraft's efficiency, e.g., speed and range and/or endurance per fuel
burn, would be maximized.

Cheers,

Dan Schaefer