Engine Thrust Offset?
 

I have an old Pilot Models Christen Eagle .60 bipe. Any time I change the throttle setting the trim changes drastically which makes it really difficult to fly. I am going to assume its too much down thrust on the engine. What would be the best way to set this up accurately? Also..what is the best general settings? I have heard 2% down and 2% right. Any help would be appreciated.

Thanks

Engine Thrust Offset?
 

Your problem may not be an engine thrust issue. It could be a stab incidence problem, a wing incidence problem, or a engine thrust problem. Without knowing what the wing and stab incidence is, you will just be guessing.

Vince

Engine Thrust Offset?
 

Vince,

I will check that as well..I know its +1 top and 0 bottom.

Thanks,

MM

Engine Thrust Offset?
 

Also, make sure the incidence is in reference to the stab - I had a bipe once, that I checked, re-checked, and checked again, the wing incidence was perfect!!! Was ready to throw it in the trash, before I checked the stab incidence, and found that the wing was +3 and +4 off the stab, even though it was +1 and 0 to each other...corrected that, and it flew like a champ!!

Sometimes the simple things elude us!!

Engine Thrust Offset?
 

Roger,

I think I am checking the incidence in reference to the stab when im doing it but im not sure.

I put a small level on the stab and jack up the tail until its level..then take the Robart meter and take incidence readings. Is that the correct way to do it?

Thanks

MM...
 

That's the basics of it, but trim and incidences can be very touchy. By leveling the stab, and checking wing against it, you are setting those together. But the stab should also be set with reference to the centerline of the model, as well, which is "built in" as the model is built, and rather diffiicult to change, once it is built. That's why a lot of Pattern Plane designs incorporate stab incidence adjusters during building. You can get quite involved, making minute adjustments on wing, stab, and motor thrust lines, to make the "perfect" flying airplane to your flying style. It just depends how much work you want to do...

Then, there's the engine thrust, which can be sometimes tricky to get just right - only crashed my Gentle Lady, with an OS .10 about 6 times, before I ended up with about 7 degrees of downthrust, so it wouldn't crash every time I landed!

There are several Trim Charts on the following websites, that can give you some pointers. They have basically step-by-step instructions, and they can give you a big insight into why your plane flies the way it does...and they cover everything from incidences, to engine thrust, to aileron differential, on and on. I use them all the time, especially with a new bird.

Click here: RCFaq Website

It's near the top, under "trimmming your plane"...check out all the charts, print out a couple, and go fly! Have someone with you, that can tell you the next step, and take notes of what you see your plane do...it's easy to forget on the ride from the field to home - don't ask how I know this!! :rolleyes:

Good luck, let us know what you find out!!