ORIGINAL: tomfiorentino
ORIGINAL: rmh
99% of the time - the cg location causes this to happen. the reason is that the wing is not working against gravity in knife edge - so the ''trims'' which cause a perfectly balanced hands off level flight, now become apparant.
Hey Dick listen, I know this thread was a while ago (so I hope you see this post!) but I have a quick question for you regarding a CG change and slaving elevator to rudder to fix KE flight.
I understand your quote above and have in fact experienced it with a Tiger 60 I flew the covering off of....twice!
. So when the wing is not working against gravity in KE the trims from hands off level flight become apparent. Great. Why then, are the mixes used to fix it in KE flight still relevant in level flight as well...when the wing is working against gravity?
For example, if I remove the down elevator trim through a mix with rudder input to prevent tucking in knife, why might I still need that mix to remove down elevator trim with rudder input in straight and level to prevent a dive with rudder input. The wing forces are very different relative to gravity, but the mix is the same.
Dumb question...what am I missing?
Thank you,
Tom
Great Question!
The answer is because the stab height matters....
Try a rudder input from inverted with the mix off.... try it on a down line.....
I challenge Dick to take his plane out and do the flight test maneuvers I have suggested....
particularly.... the pull to 45 degree test.....
I challenge him to pull his trimmed plane to a 45 degree line, roll to Knife Edge and let go of the sticks....
(If his plane isn't super-nose-heavy).. it should basically follow a trajectory and pull slightly to the
canopy..... now Dick... repeat and apply rudder.... guess what... it pitches! (Unless you have a model that
happens to have the stab in the correct location)
Repeat this on down lines.... on a vertical downline, most nicely trimmed models will slightly pull to canopy.....
apply rudder.... pitch to gear....
This is fairly typical and I challenge yuh'all to try this and see what happens....
(A model that has significant dihedral or a high wing like a cub may be difficult to observe some of this phenomena as there will be
significant roll coupling to the rudder)
But with a Yak, Edge, Extra, Su etc... this can be seen and repeated....