Elevator / stab adjustment

[Austintatious]

So I have been looking back at my tail feathers in cruise and I have noticed that even with a rearward CG that my elevator is deflected UP a bit.  It would seem to me that this may be causing some extra drag.  With a movable stab, ideally they would be completely in line during cruise...  There is a trim strip along the trailing edge of the elevator.  I would like to adjust this trim strip and try to get the elevator to be in line with the stab during cruise.

 

So the question is... Which way do I bend it?   I THINK that I need to bend it UP.  This would effectively be trimming the elevator for more nose DOWN, for which I would end up trimming the stab more nose Up (leading edge down) to compensate... this should result in the two being more in line during cruise.  

Is my logic correct?

[carusoam]

See your other thread for responses...

2 hours ago, Austintatious said:

 

So the question is... Which way do I bend it?   I THINK that I need to bend it UP.  This would effectively be trimming the elevator for more nose DOWN, for which I would end up trimming the stab more nose Up (leading edge down) to compensate... this should result in the two being more in line during cruise.  

Is my logic correct?

Bending a Mooney is probably not the proper logic...

When you say... “Which way do I bend it?”

I don’t recall bending flight controls as pilot/owner maintenance...

This one makes me nervous reading about it...

So I answered in both threads...

PP thoughts only, not a mechanic... check with your mechanic before wielding any tools on your plane... 

Best regards,

-a-

[Austintatious]

Lots of aircraft have bendable trim tabs.    The one I am talking about has obviously been bent before on my aircraft... AND it was removed and re bent (to other direction ) when the elevator halfs were swapped left/right during the recent paint.

 

No need to worry

Edited November 26, 2019 by Austintatious

[thinwing]

So if you are deflecting elevator downward...you would bend tab upward....opposite...however I agree with Anthony if you haven’t adjusted flt controls before

[carusoam]

Austin,

I invited you to a rudder trim thread that came up earlier today...

Just an FYI.  You should get a note in your box for that...

Trim tabs on moving flight controls... go in the opposite direction of the change that you want the flight control to move...

• a trim tab on an elevator... if you bend the tab down, it forces the elevator to move up...
• a trim tab on a rudder... if you bend the tab left, it forces the rudder to go right...

PP thoughts only, I may have this backwards, not a mechanic...

Best regards,

-a-

[Guest]

Is the trailing edge of the elevator really meant to bent as a trim tab in the same fashion as the aileron and rudder trailing edges?  It doesn’t make sense to me.

Clarence

[thinwing]

Getting back to original question...is that trailing edge strip ment to be bent?I would question once he has tweaked his elevator ,what happens to trim of stab?His second post also raises question as he states his elevator halves have been previously bent and swapped left to right during a repaint.Maybe time to get an expert with travel boards 

[Austintatious]

On 11/26/2019 at 11:33 PM, carusoam said:

Austin,

I invited you to a rudder trim thread that came up earlier today...

Just an FYI.  You should get a note in your box for that...

Trim tabs on moving flight controls... go in the opposite direction of the change that you want the flight control to move...

• a trim tab on an elevator... if you bend the tab down, it forces the elevator to move up...
• a trim tab on a rudder... if you bend the tab left, it forces the rudder to go right...

PP thoughts only, I may have this backwards, not a mechanic...

Best regards,

-a-

no, you have it correct.... and on a fixed stab aircraft there was no doubt in my mind that was the correct way to move the tabs... However with a movable stab, I wanted to carefully think it through and get second opinions before doing anything.

I must apologize as I did not give full info in the first post.  So let me do so now.

- Shortly after purchasing the Rocket I had her painted.  The tops of the elevators had some slight hail damage so I had them flipped during paint.  This involved removing the trim strips and having them re- bent in  a device to the other direction.  FWIW, both before and after this was done, the trim strip is not straight.  If you sight down it longways, the TE waves up and down as if it has been tweaked on prior.   The end result for me is that I have no idea if it is properly set or not.   During cruise I can see the elevator counter weights sticking down below the stab by about 1 inch even with aft most CG.  On top of this I am about 10-15 knots shy of book numbers.  I do not think that the stab would cause this big of a difference, but perhaps a small part.  The real point is that I am not sure that it is CORRECT now.  Everyone seems to be in the mindset that My tab is correct now and that I will mess it up...  I am trying to find out if it is even CORRECT now!  Which is unknown!

At this point, with all the feedback, I intend to do 2 things.

1.  Get a gauge and measure the bend.  I will be looking for 7 degrees +/- 1/2 degree as per the manual.

2.  Fly the aircraft with a forwardmost CG (will be easy to do in the rocket) and note the trim required for hands off fully configured flight at 70 Kias.

 

Once I have made those two observations I will know better were I sit and will then decide what to do.  I appreciate everyone's feedback, however there is no reason for anyone to worry about my safety.  I have a fair bit of experience when it comes to aerodynamics and aviation in general and I take a cautious approach to anything I do regarding aircraft.  I seek out other opinions before doing anything and then make small incremental changes.

Edited November 28, 2019 by Austintatious

[Yetti]

Don't do it.   Between the moveable tail and different loading conditions and trim.   You would be bending things alot depending on fuel load, people and where other things are.   I was noticing just yesterday that my flap adjustment bolt still has factory paint on it.  That made me happy.

Edited November 28, 2019 by Yetti

[Austintatious]

Yetti, what makes you think I intend to adjust it for every condition?    I am intending to first Find out if it is even properly deflected now... I dont know this.... Everyone has been reading my post as assuming it is correct now and that I will be changing it to something else...  It may be excessively bent downwards now. 

You cannot approach an issue with assumptions.... Dump your presumption that my trim tab is in the correct position and then go read the thread again.

[Guest]

1 hour ago, Austintatious said:

Yetti, what makes you think I intend to adjust it for every condition?    I am intending to first Find out if it is even properly deflected now... I dont know this.... Everyone has been reading my post as assuming it is correct now and that I will be changing it to something else...  It may be excessively bent downwards now. 

You cannot approach an issue with assumptions.... Dump your presumption that my trim tab is in the correct position and then go read the thread again.

This might help, from the K model maintenance manual.

Clarence

[Austintatious]

3 hours ago, M20Doc said:

This might help, from the K model maintenance manual.

Clarence

Yes, I have seen that.  I do not know if my tab falls into that tolerance or not.  That will be the first thing I check

[Guest]

46 minutes ago, Austintatious said:

Yes, I have seen that.  I do not know if my tab falls into that tolerance or not.  That will be the first thing I check

I don’t know what the starting point or Zero point is to begin measuring.

Clarence

[Austintatious]

5 minutes ago, M20Doc said:

I don’t know what the starting point or Zero point is to begin measuring.

Clarence

yea, neither do I... I would assume that they mean a 7 degree deflection from a flat piece of sheet metal

[Guest]

7 minutes ago, Austintatious said:

yea, neither do I... I would assume that they mean a 7 degree deflection from a flat piece of sheet metal

Or from the theoretical center line of the elevator.  Unfortunately the manual doesn’t give this detail.

Clarence

[PT20J]

2 hours ago, M20Doc said:

Or from the theoretical center line of the elevator.  Unfortunately the manual doesn’t give this detail.

Clarence

Given that the aileron and rudder adjustments are relative to  the centerline, I’d go with that. I’d make a template accounting for the slope of the elevator skin. I think Mooney didn’t provide details because it’s supposed to be set at the factory and not adjusted further. OP’s is in question because apparently a paint shop mixed up the elevators and then instead of correcting their mistake, bent the trailing edge tab to compensate. 

Skip

[Guest]

53 minutes ago, PT20J said:

Given that the aileron and rudder adjustments are relative to  the centerline, I’d go with that. I’d make a template accounting for the slope of the elevator skin. I think Mooney didn’t provide details because it’s supposed to be set at the factory and not adjusted further. OP’s is in question because apparently a paint shop mixed up the elevators and then instead of correcting their mistake, bent the trailing edge tab to compensate. 

Skip

It would be easy to measure the angle of the upper and lower skins and divide it in half to find the center line, them measure from there.  But it might be easier to switch the elevators back to the correct positions than to try re bend the trailing edge.

Clarence

[Bob Weber]

It would be easy to measure the angle of the upper and lower skins and divide it in half to find the center line, them measure from there.  But it might be easier to switch the elevators back to the correct positions than to try re bend the trailing edge.

 

 

Bingo, been waiting to hear this..

We used to say you were becoming a test pilot when swapping parts like that on an aircraft.

Edited November 29, 2019 by Bob Weber

[PT20J]

39 minutes ago, Bob Weber said:

Bingo, been waiting to hear this..

We used to say you were becoming a test pilot when swapping parts like that on an aircraft.

Problem is, the OP said in a parallel thread on Modern Mooney Discussion that the paint shop bent the tabs rather than correct their installation mistake.So, apparently it’s not clear to him that they meet spec. now. 

[Yetti]

On 11/28/2019 at 10:10 AM, Austintatious said:

Yetti, what makes you think I intend to adjust it for every condition?    I am intending to first Find out if it is even properly deflected now... I dont know this.... Everyone has been reading my post as assuming it is correct now and that I will be changing it to something else...  It may be excessively bent downwards now. 

You cannot approach an issue with assumptions.... Dump your presumption that my trim tab is in the correct position and then go read the thread again.

So based on the missing paint on my elevator counterbalance weight no assumptions were made. I think it is normal for the elevator to be down a bit.  Best thing would be to find a similar plane that has been unmolested and take measurements off that plane to compare to your plane.

[Andy95W]

Then again, there are loads of Mooneys around that fly crooked because their owners, in the greatest CB traditions, insist that they know better than the engineers and the MSCs how to make their airplanes fly "right".  

It provides job security for MSCs when the next owner buys the airplane.

[Austintatious]

On 11/28/2019 at 7:15 PM, PT20J said:

Given that the aileron and rudder adjustments are relative to  the centerline, I’d go with that. I’d make a template accounting for the slope of the elevator skin. I think Mooney didn’t provide details because it’s supposed to be set at the factory and not adjusted further. OP’s is in question because apparently a paint shop mixed up the elevators and then instead of correcting their mistake, bent the trailing edge tab to compensate. 

Skip

You guys really need to stop inserting your own assumptions into the mix.  It has made this thread (and the other) very frustrating.   many of the responses have been based on assumptions that are not accurate to the situation. 

- many of you assume that the trim piece in question is currently set correctly... that is unknown at this time.

-some of you seem  think I'm going to kill myself if I slightly tweak the tab...  This is hyperbole and serves no purpose

- some of you thought I was going to bend this for every flight.. I have no idea how that was concocted and that was never my intent.

- some of you thought that my elevators have been bent....   no, they were not... the TRIM piece at the TE is a bit wavy as if someone has tweaked on it before. (not a lot though)

-It has been insinuated that I think I "know better" than the engineers...  I stated pretty clearly that I intend to measure the deflection and stay within tolerance.

-and now the assumption that a mistake was made in paint.... a harmless assumption but an assumption none-the-less.  The paint shop did not get the two elevators mixed up and cover up their mistake.  They were deliberately swapped from left to right so that some minor hail damage was relocated to the bottom where it cannot be seen.  The trim tab was removed and bent OFF the aircraft on a machine which was necessary to have it deflected the proper direction, I would HOPE to the correct number of degrees, but at this point I do not know.

 

So based on the missing paint on my elevator counterbalance weight no assumptions were made. I think it is normal for the elevator to be down a bit.  Best thing would be to find a similar plane that has been unmolested and take measurements off that plane to compare to your plane.

I don't know what your elevator has to do with My elevator... You say it is normal for the elevator to be down a bit... Well, mine is UP.  Still think you have not made any assumptions?

As far as taking measurements off another aircraft, luckily, I will be taking delivery of a second Rocket in the next 2 weeks which will be awesome for comparison purposes.

 

Anyhow, to wrap up on this thread... I will be taking measurements, checking them twice... then also taking comparison measurements and flight observations off the second aircraft I have inbound and then I will make a determination.   Then and ONLY Then, when I am 100% certain the tab needs to be bent and 100% on which direction it needs to be bent... I will bend it to within the specified tolerances.

Thank you to those that posted relevant data and input.

Edited November 30, 2019 by Austintatious

[carusoam]

This is an interesting thread regarding how accurate the English language is or isn’t...

It doesn’t seem accurate enough to describe what Austin is doing.

It sounded to me, Austin, you looked out the window and saw the elevator trimmed properly, but it isn’t aligned with the horizontal tail...

... then you wanted to bend things to make it align...

 

Maybe, this helps you understand how somebody in the NE understood your posts...

 

Now...

Your getting a second Rocket?

His and hers?

That would be cool.
 

Best regards,

-a-

[Austintatious]

Not a his and hers.. that would be cool...   I will own half of each plane with the same partner. 

[EricJ]

10 hours ago, Austintatious said:

- some of you thought that my elevators have been bent....   no, they were not... the TRIM piece at the TE is a bit wavy as if someone has tweaked on it before. (not a lot though)

What "trim" piece are you talking about?   There really isn't a trim piece, just the elevator.   The methodology from the service manual for both the rudder and the elevator is to bend the edge of the elevator.   The same on the rudder.  Since aluminum work hardens every time it is bent, I think this is why some express concern here.   I wouldn't fault folks for trying to help, on the internet that takes many forms and points of view.   Most can be learned from, either if they're a bit off the mark.