Cause of ball not being centered?

[RobertE]

I just had my engine overhauled and, also, had my annual. New engine mounts were installed.

In level cruise flight the ball is slightly off to the left. I think this is a new phenomenon. Anyone got any idea what might have caused this? Also, and this may well be unrelated, but I seem to need more nose down trim in level flight than before.

Lastly, what's the fix?

[Alan Fox]

The new mounts are changing the position of the engine , changing the thrust angle of the prop.....The "fix" is...... You guessed it more nose down trim.....As far as the ball is concerned , exit the airplane , walk around to the tail , and bend the rudder trim tab to center the ball.......That was easy!!! 

[Hank]

Old mounts let the engine sag, so the new mount will require more Down trim to balance the more-upwardly-pointing engine.

Just be very careful bending the rudder--fingers only! Don't use pliers, and don't bend the trailing edge a half inch! If you can see the bend, it's too much. Better yet, let your experienced A&P do it. My rudder doesn't have a trim tab, you have to bend the trailing edge. But then again, it's not a v-tail either, and doesn't use ruddervators. :-)

[bumper]

It's obvious none of the folks who've answered you have flown their Mooneys recently, otherwise they'd know this has happened to ALL Mooneys. Like the canary in the mine, Mooneys are sensitive and can be relied upon to sound the fist warnings. It's all due to global warming. The ice caps have melted and this has caused a shift in the earth's CG. It is now at a critical stage, the scientific name for which is "wobbulating". No one's balls are centered anymore. The end is near.

[Jerry 5TJ]

in the same vein....after an annual your wallet is thinner, and you lean a bit more to the left, causing parallax errors in reading those old round gauges.   After you have a G500 installed the parallax problem will go away.  

[Marauder]

Before you begin bending anything, make sure nothing else was changed. I recently had a "ball out of the cage" issue after some extensive work on the avionics. Turns out my TC was pulled and put back in without leveling it. For some reason I never noticed it on the ground (probably because the ball is always moving while taxiing). It was my mechanic who saw the plane after the avionics work and was able to figure it out cheaply. Since they did some work on my flight controls during the AP integration, I was assuming that it was a flight control issue.

[bumper]

in the same vein....after an annual your wallet is thinner, and you lean a bit more to the left, causing parallax errors in reading those old round gauges.   After you have a G500 installed the parallax problem will go away.  

Thin wallet leanings?? Footing the bill for the G500 install might have one totally upside down. Does the Garmin have a switch to invert that parallax free disply?

bumper

[Wistarmo]

The first thing is to make sure it is not an instrument error before assuming it is a trim error. Two causes of a ball being off-center relating to the instrument are a turn coordinator incorrectly installed or sagging instrument panel mounts. I can tell you from personal experience that the instrument panel can sag enough to put the ball out of the center lines. The way to check this is to jack and level the aircraft and then take a look to see if the ball is centered. I had to replace my instrument panel mounts and this corrected the problem. If you start trying to adjust the trim with an incorrect instrument, you will never get it right, and getting the rudder out of adjustment will lead to incorrect aileron adjustments. Been there.

[Marauder]

The first thing is to make sure it is not an instrument error before assuming it is a trim error. Two causes of a ball being off-center relating to the instrument are a turn coordinator incorrectly installed or sagging instrument panel mounts. I can tell you from personal experience that the instrument panel can sag enough to put the ball out of the center lines. The way to check this is to jack and level the aircraft and then take a look to see if the ball is centered. I had to replace my instrument panel mounts and this corrected the problem. If you start trying to adjust the trim with an incorrect instrument, you will never get it right, and getting the rudder out of adjustment will lead to incorrect aileron adjustments. Been there.

That is exactly how my mechanic determined the level issue.

[Marauder]

Thin wallet leanings?? Footing the bill for the G500 install might have one totally upside down. Does the Garmin have a switch to invert that parallax free disply?bumper

I never suspected that parallax could be an issue with the stuff sitting right in front of you. But you are right. When I got my plane back after the avionics upgrade, I found a new knob labelled "FD Parallax". My STEC FD when installed, came with this requirement. Sure enough, playing with it, I can see how parallax can impact things.

[jetdriven]

Dont forget that incorrect L-R thrust in the engine mounts or a partially open gear door can cause the incorrect yaw trim. The easiest way to bend that rudder trailing edge it to saw a 1/8" wide  (1/4" deep) groove in the edge of a foot long piece of 2x4. Use that to bend your trailing edge, but before bending metal, be absolutely sure your engine is perfectly centered in the cowling and all your doors are closing.

[Alan Fox]

Old mounts let the engine sag, so the new mount will require more Down trim to balance the more-upwardly-pointing engine.

Just be very careful bending the rudder--fingers only! Don't use pliers, and don't bend the trailing edge a half inch! If you can see the bend, it's too much. Better yet, let your experienced A&P do it. My rudder doesn't have a trim tab, you have to bend the trailing edge. But then again, it's not a v-tail either, and doesn't use ruddervators. :-)

Funny thing , the rudder in my basement from a c model , has a 6" trim tab on it..... My ruddervators have real anti servo trim tabs on them.....  

[FloridaMan]

I thought I posted on this thread...weird. My inclinometer shows my ball a little to the left too, but my butt and the D1 tells me I'm coordinated (the upset training instructor that I fly with says "man with two watches never know what time it is"). I figure the instrument is just a little bit off. My wing leveler, which usually stays turned off, seems to have a couple leaks in the system and I'm nearly certain it screws up the coordination just a little when it's on.