Trim position on take-off in a short body?

[Prior owner]

Disregarding the trim position indicator in the cockpit, if you look over your shoulder, what is the position of the elevator (with hands off the yoke) when you set your takeoff trim?

[Bryan]

In the C and F that I have flown, the position of the trim does not change the elevator position - which makes since since the you are triming the entire horizonal and vertical stablizer.

[Skates97]

2 minutes ago, Bryan said:

In the C and F that I have flown, the position of the trim does not change the elevator position - which makes since since the you are triming the entire horizonal and vertical stablizer.

Are you sure? The whole thing does move, but the yokes move forward/aft and the elevator does move up and down some as you trim.

I will have to take a look and see where it is on mine when it is set for takeoff trim. I honestly have not paid that close attention to its position.

[Bryan]

No, not sure - I have been flying a M20K (electric trip) for the last two years.  I still don't remember the elevator chaning position on trimming on the C and F.  We have one at the airport that I fly occasionally and will look next time.  I remember at rest, it seems to be elevator high all the time when no forces applied to it.

[MIm20c]

I have mine set for 1 inch low with full tanks and two in the front. However, my plane is on the forward edge of the CG envelope in this configuration. 

[PT20J]

Mooney's up through the J's have trim assist bungees that bias the elevator as the tailplane angle changes with the trim. That's why the yokes move. On airplanes with trim tabs, the proper takeoff trim setting generally results in the trim tab being aligned with the elevator. On the J (and I would think this would apply to the C, D, E, F, but I haven't verified that) the proper takeoff trim setting results in the elevator being aligned with the stabilizer. It varies slightly with CG location, of course.

Skip

Edited May 22, 2019 by PT20J

[Prior owner]

5 minutes ago, PT20J said:

Mooney's up through the J's have trim assist bungees that bias the elevator as the tailplane angle changes with the trim. That's why the yokes move. On airplanes with trim tabs, the proper takeoff trim setting generally results in the trim tab being aligned with the elevator. On the J (and I would think this would apply to the C, D, E, F, but I haven't verified that) the proper takeoff trim setting results in the elevator being aligned with the stabilizer. It varies slightly with CG location, of course.

Skip

Yes, I should have stated that I have bungees in my vintage D and that the elevator certainly does move a great deal on the ground as trim is moved along with the entire tail moving forward and aft. Thank you

[takair]

Mine is slightly trailing edge up, slightly more than my normal cruise position, which also tends to be slightly trailing edge up.  I would guess that cruise is about 3-5 deg up and takeoff is 5-10.  This does not seem to be consistent among like models, some tend to be trailing edge down in cruise....could be rigging tolerances and wt and balance.

Found this picture of my trim in take-off position.

[PT20J]

Interesting. As near as I can tell, most M20C-E tend to cruise with the elevator nearly in alignment and the M20F-J cruise with the trailing edge down, so it makes some sense that the takeoff trim position might be opposite. It doesn't really matter. The drag contribution would be small from such a minor elevator deflection. Most of trim drag comes from the induced drag of the tail generating a tail down force and the incremental induced drag of the wing caused by the additional lift necessary to offset the tail down force.

Skip

[Shadrach]

The elevator on my F moves considerably with trim on the ground.  Nose down will put that yokes almost against the panel.  I know this because I put them in this position when working on the underside of the panel (hose and filter replacement) to give extra room to move about the front seats.  I spilled a drink and some maintenance paperwork that I left on the elevator the last time I did it.  The deflection is not insignificant.  I have not really checked in flight at different positions, but I will.  The elevator rigging specs are different for the short and medium bodies but the effect should be the same.

[PT20J]

6 hours ago, Shadrach said:

Nose down will put that yokes almost against the panel.  I know this because I put them in this position when working on the underside of the panel (hose and filter replacement) to give extra room to move about the front seats

Great idea. Wish I’d have thought of that last time I extricated myself from under there

[vorlon1]

On 5/22/2019 at 4:03 PM, PilotCoyote said:

Disregarding the trim position indicator in the cockpit...

Why would you do that?

[Prior owner]

2 hours ago, vorlon1 said:

Why would you do that?

Well, Because I haven’t flown the plane yet and I’m curious about whether my trim Indicator in the cockpit is pointing anywhere near the “takeoff” marking... plenty of things have required adjusting thus far, and I’m betting this will require some attention as well. I appreciate all the responses- thank you!

Edited May 23, 2019 by PilotCoyote

[Shadrach]

On 5/23/2019 at 7:36 PM, PilotCoyote said:

Well, Because I haven’t flown the plane yet and I’m curious about whether my trim Indicator in the cockpit is pointing anywhere near the “takeoff” marking... plenty of things have required adjusting thus far, and I’m betting this will require some attention as well. I appreciate all the responses- thank you!

I use the trim indicator on every take off. The take off position is about perfect. If you want to test to see if the indication is accurate, run full nose down trim and see where the indicator is.  Then run full nose up trim and see where the indicator is .  If full nose up/down correspond with the positions on the indicator then it should be accurate for the take off position.

It should take at least three minutes to determine whether or not it’s correct...

Edited May 26, 2019 by Shadrach

[Prior owner]

14 hours ago, Shadrach said:

I use the trim indicator on every take off. The take off position is about perfect. If you want to test to see if the indication is accurate, run full nose down trim and see where the indicator is.  Then run full nose up trim and see where the indicator is .  If full nose up/downbcorrespond with the positions on the indicator then it should be accurate for the take off position.

It should take at least three minutes to determine whether or not it’s correct...

Actually, that was the very reason that I suspected something wasn’t right- the Indicator doesn’t go to full up to full down... We’re going to check the rigging of the indicating system and the trim system itself.

[Shadrach]

On 5/24/2019 at 10:00 AM, PilotCoyote said:

Actually, that was the very reason that I suspected something wasn’t right- the Indicator doesn’t go to full up to full down... We’re going to check the rigging of the indicating system and the trim system itself.

The indicator mechanism is dirt simple. It’s a threaded block (16) on a jackscrew with the cable attached that runs to the display (42) in the cockpit. Perhaps the cable is stuck. Barring that, someone would’ve had to physically remove the block and then reinsert it on the Jack screw with the trim in the wrong position. I’m not sure but your trim travel could be inhibited in one direction or the other if he block is positioned incorrectly.

Edited May 26, 2019 by Shadrach

[carusoam]

Often crusty grease gets in the way of the jack screw mechanism of the tail’s trim system...

A pilot would want to know that the tail is going through the entire range first...

There is a gearbox in there that has a load of old grease.   The screw itself has the ability to have rocks of old grease stuck on it...

All things worthy of inspection if you haven’t done so as a new owner....

PP thoughts only, not a mechanic...

Best regards,

-a-

[MB65E]

I have simple trim indications on the tail. One set for landing and one for T/O. During preflight I make sure that I re-trimmed nose down for T/O. 

-Matt

[S.C.]

I use a ton of nose up trim for landing.  The pilot  I bought the plane from, said he was using landing trim for take off trim.    (Yes, I embarrassed to admit It’s a conscious effort for me to crank the trim back down prior to take off and it took me few attempts before I figured it out.) .  What I have observed is if  the indicator is a little above take off I’m usually in good shape.  Each of these birds has some subtle differences and while usually well maintained, there are some things that you’ll just have to get the feel for, and will learn by familiarity.  

[carusoam]

SC,

That is some quirky advice to have received...

Some M20C Pilots were given the advice..... you can never get enough up trim in a Mooney... as there is plenty of up trim used when landing flaps are used...

And again plenty of up trim used when the back seats are empty....

But... T/O with the same up trim as landing... that will most likely have the plane’s nose pointing towards the sky under full power...

 

Was your experience anything like this?

PP thoughts only, not a CFI...

Best regards,

-a-

 

[Shadrach]

34 minutes ago, S.C. said:

I use a ton of nose up trim for landing.  The pilot  I bought the plane from, said he was using landing trim for take off trim.    (Yes, I embarrassed to admit It’s a conscious effort for me to crank the trim back down prior to take off and it took me few attempts before I figured it out.) .  What I have observed is if  the indicator is a little above take off I’m usually in good shape.  Each of these birds has some subtle differences and while usually well maintained, there are some things that you’ll just have to get the feel for, and will learn by familiarity.  

When light with a forward CG, I use all of my nose up trim by short final

[Prior owner]

Yes, it appears I have my work cut out for me... we’re going to go through the entire system and I will post my results here. It’s going to be a few weeks before that happens, though.  

The trim indicator panel was removed for painting and carpet replacement, and prior to re-installing it the trim indicator travel was checked (inside the cockpit only)-  the indicator wire moved along with the trim wheel in both directions without any apparent binding, but it would not travel far enough to indicate at both ends of the scale. And that was with the indicator wire placed in the first hole on the arrow (closest to the pivot for the greatest amount of travel). The indicator travel was not checked prior to disassembly, however, it was assembled in exactly the same manner that it was disassembled per our before and after pics. So the problems likely existed prior to us messing with it.

I was able to adjust the cable clamp to have it indicate full nose up or full nose down, but not both. So there is definitely a problem here, and it could be any of those listed above. The position of the block was not checked yet- hopefully it’s as simple as that.

[Hank]

6 hours ago, PilotCoyote said:

Yes, it appears I have my work cut out for me... we’re going to go through the entire system and I will post my results here. It’s going to be a few weeks before that happens, though.  

The trim indicator panel was removed for painting and carpet replacement, and prior to re-installing it the trim indicator travel was checked (inside the cockpit only)-  the indicator wire moved along with the trim wheel in both directions without any apparent binding, but it would not travel far enough to indicate at both ends of the scale. And that was with the indicator wire placed in the first hole on the arrow (closest to the pivot for the greatest amount of travel). The indicator travel was not checked prior to disassembly, however, it was assembled in exactly the same manner that it was disassembled per our before and after pics. So the problems likely existed prior to us messing with it.

I was able to adjust the cable clamp to have it indicate full nose up or full nose down, but not both. So there is definitely a problem here, and it could be any of those listed above. The position of the block was not checked yet- hopefully it’s as simple as that.

Your jack screw under the rear belly panel may need to have old, hard grease removed. I'd suspect that before trouble with the cabin indicator. 

[Hank]

7 hours ago, Shadrach said:

When light with a forward CG, I use all of my nose up trim by short final

When I land my C solo, the trim is often very near the Takeoff mark. Forgot to take pictures today, but I have posted them here before. 

[Prior owner]

I will surely let you know what we find when I get back to the hangar in a few weeks