Causes of TC ball being slightly off center?

[Gary0747]

My 67 F has been in good rigging but the other day I noticed my TC ball slightly off to the right in straight and level cruse, and I was wondering what the possible causes could be?

my initial thoughts include:

1. Imbalance in left/right fuel tanks?

2. Not having the Turn Coordinator centering adjustment set correctly?

3. Leak in a pneumatic rudder servo?

any thoughts or ideas?

 

[takair]

Do you have a sheetmetal rudder trim tab?  If it is just a little out, the tab can compensate.

[aaronk25]

Someone step on the right flap when de-boarding making the airplane turn left and requiring right rudder for straight flight? Either way I'd have a mooney shop with travel boards do a re-rig on it to get it flying straight.


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[gsengle]

Being solo and not sitting on the centerline.


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[aaronk25]

Na......it ain't that sensitive to seating position, probably more rotational force from the prop spinning


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[N201MKTurbo]

Busted instrument panel mounts

[N201MKTurbo]

Get a carpenters level and lay it across the seat rails. Use jacks, tire pressure or strong friends under the wings to get the plane level and confirm the instrument accuracy.

[gsengle]

Na......it ain't that sensitive to seating position, probably more rotational force from the prop spinning


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You say that but I can change the NMPG readout in my plane just by sliding the seat all the way back when solo...

If it's just slightly off, who knows.

Later birds have rudder trim.


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[aaronk25]

Really? I can get any different mpg on my J regardless of where I move CG including moving luggage to front seat rear or luggage. Yours is a O right? Maybe more nose weight so that would make sense especially with 3 blade? Just thinking out loud....


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[gsengle]

Yep, it's an Ovation (M20R), and it's def faster with a rear CoG... my guess is the tail is doing more work in the long bodies with the big engines, and thus the more noticeable inefficiency at forward CoG.

 

Um also Im not a lightweight

 

 

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[M20F]

8 hours ago, aaronk25 said:

Really? I can get any different mpg on my J regardless of where I move CG including moving luggage to front seat rear or luggage. Yours is a O right? Maybe more nose weight so that would make sense especially with 3 blade? Just thinking out loud....


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About 1kt faster in my F with seat all the way back.  

To the OP would see if the issue repeated itself a couple of times before I got to crazy.  Could be fuel, you aren't actually level, etc. 

[carusoam]

Rudder trim is definitely the answer....

The Mooneys without an adjustable rudder trim are set-up for best trim during cruise.

unfortunately that Will vary with the WnB.

With rudder trim we get to visually see how the rudder trim can be used to offset various things.  Right trim for T/O, centered during cruise, left trim for descent... always slightly different according to angle of attack.

I would bet if this came up on a recent flight, keeping the wings level with a fuel imbalance might show up as the ball being off center.

see if raising the wing using the rudders works differently then raising a wing using the airlerons...?

level the fuel load, slide the seat back and enjoy the faster mooney ride...  doing these things requires less trim related drag issues.

asside from all that technical stuff...  check the shock absorbers / panel mounts.  They age terribly.  The panel sags like an old body in uneven ways.  Your panel has probably sagged.  Get some new mounts and remove the sag...  probably less tha 0.1 amu from AS... 

Best regards,

-a-

Edited February 12, 2017 by carusoam

[kerry]

On ‎2‎/‎11‎/‎2017 at 6:17 AM, N201MKTurbo said:

Get a carpenters level and lay it across the seat rails. Use jacks, tire pressure or strong friends under the wings to get the plane level and confirm the instrument accuracy.

This is the first place I would start with.

[Gary0747]

I checked the panel and it is level with fairly new mounts. I wonder if my retractable step not fully retracting all the way could cause the ball to be off to the right?  It seems like it would cause it to be slightly left?  I plan to inspect the rubber boots on the rudder servos next.  I see nothing in the service manual about proper rigging of these servos?

[Piloto]

Speed and power can change the ball centering. Try flying at 140kts IAS, it should be center. Above 140kts the ball will drift to the left.

José

[Guitarmaster]

On 2/10/2017 at 9:26 PM, aaronk25 said:

Na......it ain't that sensitive to seating position, probably more rotational force from the prop spinning


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This along with Coriolis force and moon cycle.