Up thrust, Down thrust, What?!!!

[phippsj]

I just maidened a new 28% Wildhare Extra 300 and there appears to be some thrust corrections to be made.

The plane flew straight and level at 3/4 to full throttle with several clicks of down elevator. However, when I pulled back off the throttle, the plane pulled almost 45 deg upline. Needless to say, this made for an interesting landing.

Folks at the club field said that I need to put some up thrust into it so that when it is trimmed, it will fly straight and level on or off the throttle.

I put a lot of up thrust into it and flew it again. It still does it some, but it was too windy to really get a good feel for what was happening. Flying inverted, it wants to nose down.

Other folks say it should get down thrust instead. I'm really confused now.

The CG is good, slightly nose heavy.

[Vic3D]

If the plane goes up then you probably want downthrust. I would get an incidence meter first and check the stab alignment. That might be it.

[Tired Old Man]

If the plane pitches up when reducing throttle you have too much down thrust. With the engine carrying power the angle of the prop is pulling down to a degree. Reducing the rpm reduces the downward force applied by the propeller, causing a pitch up. This can be caused by the angle built into the firewall during construction or by using engine standoffs of unequal length. It does not take much of an angle to create this problem.

Obtain some 1/64" plywood and cut some shims that will fit under the lower engine mounts at the firewall. Install them one at a time until the problem goes away. Also check the cg again since the need for down elevator trim notes a slightly tail heavy condition. Do one thing at a time, not both at once.

[phippsj]

I used some thin aluminum washers for the shimming. I shimmed approx. 1/8" under the lower standoffs. The wing/stab incidences are OK.

I'll re-check the CG to Wildhare's specs.

[moose]

phippsij, I think the first thing you should consider before playing around with the engine thrust is to check the CG because from what you are describing, you have an extremely tail heavy plane. Don't be afraid to add weight to the nose for testing as it will in no way give you an unstable aircraft (within reason)......let us know how it goes.

Later

[crazyjoe]

I second what moose and pat said . Sorry vic your way off

[wildhare]

1/8" under the lower mounts is a HUGE change, I would cut that down to 1/16" or less. Remember those washers I gave you? 1 of them is the maximum change to do at one time.

And I agree, I'd try adding some nose weight first. I have some weight washers for a DA-50, if you want to borrow them call me.

TF

[krayzc]

keep us posted on your results

[jack01]

On your CG, trim the airplane for half throttle. Roll it inverted, and see what it does. If the nose starts to drop slightly, your CG is OK. If it starts pitching up, your tailheavy.

[Vic3D]

	Quote: Originally Posted by crazyjoe
	I second what moose and pat said . Sorry vic your way off

Sorry just trying to help!