73" spins right

[wingburner]

Hi Reza....I'm having problems with my 73" spinning right when I pull the elevator up fast....This happens on all 3 rates...The plane has a 3W 28 in it and weighs almost 13 pounds....I have noticed that the pushrod on the right elevator is very flexible....I am wondering if when there is enough force or a fast change in elevator movement if it is flexing enough to cause this issue.

Thanks
Jack Durgan

[Animal Jesky]

Jack,

There are two things I would check out. First get an accurate throw meter and check to make sure that both elevators are moving the same amount when moving up and down.

The second would be to check lateral balance. Take a piece of string around the crankshaft and a piece around the tail wheel hold the airplane upside down by both pieces of string and see if the airplane falls off to one side. If it does place weight in the lighter wing out at the wing time.

Andrew Jesky

[Reza]

Hi Jack,

Pushrod is certainly worth to be looked at, you don't want any flex.

Is your plane latterally balanced?
How much aileron trim do you need to fly level? If it's a lot that can cause it to snap as well.
13lbs is on the heavy side, what is your altitude? If you are in relatively high altitude and your plane weighs 13lbs that can be another reason.
Also make sure both elevators are travelling equally.

Thank you,
Reza

[wingburner]

Thanks Andrew and Reza:

I have checked the aileron trim and it looks to about 1\32" of left trim needed.

I just balanced it laterally and it needs .010 kgs which is 3-10ths of an ounce...Don't think that's enough to be the problem.

My elevation is around 2000 feet,don't think weight is the issue though I'm not exactly sure on the weight issue.

Now as far as the pushrod is concerned,if you apply pressure against the servo it starts to flex...If you apply a little more it flexes more and leaves a slight bow in the rod...I am not getting overly aggressive with the pressure..It seems that it might be possible that these rods are to long for the forces exerted on them...(this is just a thought)..

Please let me know what you think...Maybe I should build a carbon pushrod and try it.

Oops,almost forgot,I've been through the elevator geometry numerous times and really think I have that part right.

Jack

[Animal Jesky]

Jack,

Maybe a quick fix to see if the pushrod is your problem just put a piece of carbon rod over the rod there now that is flexing. This will stiffen it up.

Andrew

[wingburner]

Thanks Andrew,I think I only have small carbon for pushrods...I don't believe it'll go over the titanium pushrod.

Jack

[Reza]

Jack,

That push rod shouldn't have any flex. If you are doing a wall and one flexes more than other, it will cause the plane to snap. Eliminate the flex and see how plane behaves. If you still had the same problem, please let me know. 73" shouldn't really go over 12 lbs even at 12 lbs you are loosing performance. 13 lbs for that plane is on the high side but let's go step by step. We will help you find the problem.

Thank you,
Quique's Aircraft Support

[wingburner]

Thanks Reza,

I will try today and let you know....There is also another fellow here that has the same problem and he has a YS 140 in it...He has sold the plane so I can't check his either....I think he contacted you earlier about.

Jack

[wingburner]

Hi Reza,

Well the carbon pushrod made no difference....The only thing that kept it from wanting to spin right was to add left rudder. Aprrox. 3\4" throw at the leading edge and it wouldn't roll out on me...Don't know what that means but maybe I have a twisted stab or incidence problems of sorts....

I had the 72" and the 85" without any of these problems...They flew absolutely fantastic...This plane just doesn't seem quite right obviously.

Any more suggestions.

Thanks
Jack

[Reza]

Wow, Jack you must have a flying field in your backyard. You already fixed the rods and flew it Is there anyway you can check your stab incidence? I have the same plane, the way is set up in the manual and it flies really awesome. I wonder the same thing, do you have a warped stab? or wing? Can you get a hold of an incidence meter and check? Your stab should be 0 to+.5 not more.

Let me know,
Reza

[wingburner]

Yup...Paved airstrip at my disposal not more than one mile away

Checked the incidence on the stab..
both sides inboard 0 degrees and outboard both at-.5 degrees....Can't see that affecting to much

Checked the wing and they are with a .5 degree also...

Now I got checking the rudder and it seems to have a twist in the top half...If your behind the aircraft the twist would start at the leading edge and twist over to the left side...Perhaps that is enough,I don't know...Can't see it but I'll take a heat gun to it and see if I can straighten it.

Jack

[Reza]

Jack,

If you couldn't fix it and needed a new rudder, please PM me. Those numbers for incidence are in the range.

Thank you,
Reza