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Old Feb 17, 2005, 10:22 AM
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FREDERICK, MD
Joined Jul 2003
197 Posts
Why does a nose heavy plane climb during a dive test?

This seems counter-intuitive; I would expect a tail heavy plane to want to nose-up when the stick is released. I posed this question to two of my flying friends, (what would a tail heavy plane do in a dive test), and both quickly answered the question wrong! Can anyone enlighten us on this?
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Old Feb 17, 2005, 10:51 AM
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Andy W's Avatar
Marietta, GA
Joined Jun 1999
43,312 Posts
Because if it's nose heavy, you have 'up' trimmed into the elevator to compensate. When you put it in a dive, this trim causes the model to 'recover'..

You can also perform this test inverted (if you have the skill!) to ensure it's accurate..
..a
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Old Feb 17, 2005, 11:38 AM
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FREDERICK, MD
Joined Jul 2003
197 Posts
Thanks! That was the only reason I could think of, at least I haven't totally lost my mind yet!
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Old Feb 17, 2005, 02:07 PM
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BMatthews's Avatar
The 'Wack, BC, Canada
Joined Oct 2002
11,616 Posts
If it helps remember that weight distribution (nose or tail heavy) is constant but the trim needed to compensate is sensitive to speed. So the nose heavy model pitches up when it goes faster.
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Old Aug 06, 2005, 06:54 AM
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Viktoria, British Kolumbia, Kanada
Joined Feb 2005
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I like the way Andy put it. Most of us would understand it best that way, I think.
Also, I think it's mostly due to the relationship between cg and cl and how cg has less effect in a dive because of the change of angle (gravity is acting, in a 90-degree dive, totally differently than in "normal" flight).
Still, with respect to inertia, not gravity, the dive angle would make no difference. Wow, this stuff is compllicated.
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