harphunt

Visually, I have a lot of down trim on my LT-40's elevator in order to maintain straight and level flight (approx. 1/8th inch). The ailerons appear to be level. The plane is balanced. This does not seem right. Does anyone have any thoughts, input, or opinions? Thanks!

peace

dragnbye

iwould say you need to adjust your celvis start with two turns then fly adjust you radio then retrim. try to setup the plane up to useing just a few clicks of trim

Charlie P.

At what throttle setting? Flat bottom winged trainers are supposed to climb with added power. It should fly level at just over half throttle but climb with added thrust.

Missileman

Are you talking about 1/8" on your trim switch or on the elevator itself?
Down elevator is normal on a trainer with a flat bottom wing because of the high amount of lift.
As dragnbye said, adjust your clevis on your elevator until you can get near center trim on your radio.
One more question, what throttle setting are you at when setting your trim? It should be at normal cruising speed, about 1/3 to 1/2 usually.

TedMo

Don't know how much is a lot. You say something about 1/8 inch, what does that pertain to? Also at what speed high, low? We are here to help answer questions but many of you don't provide enough info for us to do so. Don't forget that is a flat bottom airfoil so speed wind direction all come into play. Will it fly inverted If so what trim for that? Should be a lot of down with that airfoil. The wing incidence may be off . You could just make trim adjustments as needed or could shim wing to modify incidence.

jetmech05

trim is adjusted to fly the aircraft straight and level, thumbs off, no wind of course......at around 1/2 throttle......You can adjust the control surface...but all you are doing is making the trim button go back to center...I am one of those that says if it aint broke don't fix it.....

harphunt

Just woke up!

The 1/8" -1/4" is the amount of down elevator physically - not on the radio. I understand that I can zero the radio trim by adjusting the elevator clevis. I don't remember having that much down elevator for level flight on my Superstar. Makes me think I need to lower both ailerons and raise the elevator. I think I'm trimmed at full throttle. I'll check at the field today. I was not aware of the "trimming at 1/2 throttle" rule. Does this rule apply to all planes? Thanks for your responses.

peace

Rodney

You might experiment a bit with changing the thrust line, increase the downthrust a bit and see what happens. It may be that you could also move the CG a bit by moving the battery forward or aft and see if there is a change.

jaka

Hi!
You always trim an airplane at full throttle!
If you fly with down elevator (how much???) at full throttle it's perfectly OK to do so. But. If you want to get ride of all the down trim you either tilt the engine down more or put a shim under the trailing edge of the wing to reduce it's angle of attack.
You should never tilt the aileron down whatever you do!!!

jetmech05

I have never trimmed an airplane at full throttle.....If you are at full throttle what are you trying to do? Climb...don't trim out the natural help you get from thrust...besides if you do trim to fly straight and level at full power, then you need back pressure on the stick when low and slow like when trying to land..if your thumb slips you're diving.......you can't even rest your thumb...

Missileman

I am sorry but no you don't always trim at full throttle.
You trim at normal cruising speed, whatever that is for your plane.
If you always fly at full throttle so be it but most people don't. If you trim most planes at full throttle you will find a tendency for the plane to want to lose altitude when you lower the throttle to your normal speed.

A. J. Clark

I trim all my planes at full throtle and I trim the elevator so the plane is always on a slight descend.
It's hard for me to control a plane that balloons or is always climbing.
I feel I have alot more control by holding the stick to control the hight.

my05monte

my instructor had me trim both ( mustang pts, sig lt40) at half throttle. He and a most of the guys at my field do trim their planes at half-throttle. The only time I'm at wot is at take-off.

DaveB

You might try Rodney's suggestion by placing washers between the firewall and the top of the engine mount. This will reduce the up thrust (increase down thrust).

DaveB