Thread: Mini-Review F-15 Eagle Park Jet--Part 2
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Old Dec 04, 2011, 08:15 PM
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Originally Posted by aqkhana2002 View Post
my question is still same, forget about flying the plan and adjust elevator, i m concern about CG

. 1 : in video when i fly yes its go up (elevator was in normal setting )
. 2 : i did it trim up ( so from tail side it should up " force plan to move down ")
Up elevator forces the tail Down, to lift the heavy nose up. You can get the same effect by moving the battery back towards the tail and reducing the Up elevator trim.

question is that if i go to actual CG which is as per plan 2.9 (cuz my length is small)
plan already heavry from nose as you can see in video so why when i fly it its going up ? showing its tail heavy,

i can not move batter more forward cuz 2.9 cg showing alrady heavy from nose

if i pull battery back , then that mean when i will fly plan it will more heavy from tail

ahh lot of confusion.

its flying good with CG 2.1 and elevator trim up (arround 10degree or 15degree up)
A little bit of aerodynamics.
The faster you go, the elevator becomes more powerful and with the large elevator trim you have, if you dive and go faster, so the nose will come up automatically, and you have to push the nose down to stop this zooming up. If you move the batter back (a small bit at a time) you will be able to reduce the Up trim, so reducing the effect of speed variation.
There will come a point where you get the balance point too far back, and the aircraft will become very sensitive to elevator control, and become difficult to fly - your balance point is now too far back.
Many trainer aircraft are setup nose heavy because it is self stable, as the speed goes down, so the nose drops the increase the speed, and as the speed increases the nose rises to reduce the speed, which is good while you are learning to fly, but this make aerobatics difficult, and people then move the balance point backwards (a little at a time) as their skill increases. But even the best pilot in the world will fail to fly an aircraft with its balance point too far back, which is why I said move the balance point back s l o w l y.
Hope this helps
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