Why does a nose heavy plane climb during a dive test?

EABiker · Feb 17, 2005, 09:22 AM

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?

Andy W · Feb 17, 2005, 09:51 AM

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

EABiker · Feb 17, 2005, 10:38 AM

Thanks! That was the only reason I could think of, at least I haven't totally lost my mind yet!

BMatthews · Feb 17, 2005, 01:07 PM

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.

jay flay tway · Aug 06, 2005, 05:54 AM

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.

Feb 17, 2005, 09:22 AM	#1
EABiker Registered User 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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Feb 17, 2005, 09:51 AM	#2
Andy W RIP Ric Marietta, GA Joined Jun 1999 43,272 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

Feb 17, 2005, 10:38 AM	#3
EABiker Registered User 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!

Feb 17, 2005, 01:07 PM	#4
BMatthews B for Bruce The 'Wack, BC, Canada Joined Oct 2002 9,448 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.

Aug 06, 2005, 05:54 AM	#5
jay flay tway Tryin 2 get in2 slot cars Viktoria, British Kolumbia, Kanada Joined Feb 2005 410 Posts	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.