Trim question

[MarcR]

Hey Folks!

I've got a question on the trim control. My trip to New Holstein this year was my first really long x-c in 197T, and I noticed a slight problem. I was constantly creeping up in altitude. Finally, on the way back to MKC, I noticed that over time, the trim was rotating back towards nose up trim. I'd guess about a quarter turn in 15-20 minutes, then it seemed to stabilze. Not really sure,but I never noticed it going any farther.

So, the question. Is this just something that happens, or is it a potential problem I should look into?

Marc R.

 

[sj]

Marc,

197T never did that to me, but I have had other planes do it. I used to be able to fly that plane hands off for 3 hours without touching anything. I'll keep and eye on it tomorrow when I am in it.

sj

 

[Fortysix12]

Nothing a bungee cord couldn't fix. Seriously, If the entire trim mechanism is the same as a later model I can only apply a probable cause to your problem. Excessive wear combined with tail flutter created by the prop and airstream. The cure short of overhauling the jackscrew assemble would be to creat some friction. Maybe some fiber or nylon washers at the trim crank pulley. Only speculation of coarse. No airplane should trim itself in flight. So you need to remedy to the problem. Ever look at your tail during take off. They take a lot of prop wash and look like there going to shake loose.

 

[Bill Rusk]

Sounds like the plane is seeking some sort of equilibrium. Wonder how changing the thrustline would affect it. Have you noticed this at other CG positions? Were you loaded aft with lots of gear for NH that you don't normally have in the plane? Interesting.

Bill

 

[behindpropellers]

Sure the trim handle is actually moving? Did you think about fuel burn making the plane lighter and causing the plane to climb??

just a thought.

Tim

 

[MarcR]

Tim,
Yep, I'm sure. I checked it several times, and the trim handle did rotate. For level flight it was at about 9 o'clock. 15-20 minutes later I would check and find it a 6 o'clock.

Bill,
I haven't noticed it in other CG configs, but then this was the first long x-c I've done in the airplane. I mostly have been just playing around in the local area, landing practise, manuvering, etc., so constantly adjusting trim isn't a surprise. Although, now that you mention it, I don't remember the problem when I was flying from Ohio to New Holstein with Jim in the back seat.

I'll see what Steve finds after he flys it tomorrow. I think he's got a couple of folks that are working on tailwheel endorsements( or building enough TW time to satisfy the insurance requirements )

Marc R.

 

[Jerry Burr]

Surprise.

Ok Steve. You can tell him about the auto pilot you had installed now. Jerry.

 

[sj]

Jerry, well, it was under very smooth conditions... :roll:

sj

 

[85Mike]

One of the differences in 180's and 185's is in the trim wheel detents. the 180 has 1 and the 185 has 2. They are the same spring and ball detents that are used in the air vents in the wing roots!! When the spring in 1 detent in the trim wheel breaks or gets weak, my 185 trims itself up a lot and is very frustrating!! But I know where the spares are!!!!

Mike

 

[Crash]

Trim

From what we heard about the strong margueritas at New Holstein I don't think there's anything wrong with your plane. Wait a few days and go fly it again. Crash

 

[MarcR]

But I didn't have any margueritas! I swear!

 

[behindpropellers]

Marc-

Where are you from in ohio?

 

[MarcR]

I'm not actually from Ohio. I had gone there to pick up my son-in-law, who went with me to Nolstein. He lives in Apple Creek, and we flew out of Wadsworth( 3G3 ).

Marc R.

 

[Anne]

What's the correct tension for the tailbrace wires? And how do you check it?

Anne.

 

[Cajun Joe]

proper tension check for annestoi

The proper tension is a G flat

 

[Steve Pierce]

The tail brace wires should deflect 1/2" by with a 12-15 lb. pull. I use a fish scale and a long ruler.

 

[bob turner]

Speaking of trim - why is it that some cubs can be flown without much attention to trim, and others simply cannot be flown without one hand on the trim handle? I have a friend with a 160 hp Cub that can be flown in the pattern full flap to zero flap without touching the trim; another with a 150 hp. that cannot be flown under the same condition without adjusting trim. Still looking for a nice PA-18-95 - bob

 

[T.J.]

delete

 

[MarcR]

Thanks for all the suggestions. I'll try to check them out this weekend, and report back.

Marc R.

 

[idscub]

Speaking of trim - why is it that some cubs can be flown without much attention to trim, and others simply cannot be flown without one hand on the trim handle? I have a friend with a 160 hp Cub that can be flown in the pattern full flap to zero flap without touching the trim; another with a 150 hp. that cannot be flown under the same condition without adjusting trim.

Has to do with the rigging of your stick. If you cub is rigged with the stick more aft in the neutral position you are past the leverage point, therefor making it harder to use and requiring more trim.

 

[jimpattensc]

trim changes

I had exactly this problem in my previous Cub when I bought it. After much detective work, it turned out that the problem was a worn out jack screw assembly. Replacement fixed the problem cold. I flew that plane to Alaska right after the fix, nearly 10,000 miles in less than 3 weeks, some 17 hr tach time days, with no trim problems. The worn out jack screw issue was caused by flying in Arizona, around Yuma, and the very abrasive dust. My guess is that there is lots of play in your jack screw assembly...easy to check, but be sure that everything is clean first.