Question Centering the ball

[Neal]

Sometimes I have to lift my feet off the pedals as I tend to push harder on one side and obviously the lightweight cub responds to these little pressures. I lift my feet to check the ball and the tracking of the plane. I don't know how accurate "the ball" is but it seems to have a slight bias to the left of center which drives my OCD'ness crazy. I've been bending, or at least I think I am, the trim tab on the rudder to the right to help it kick left rudder. Yesterday I had to maintain constant pressure on the left rudder to move the ball right to center.

What are others seeing as far as ball centering with feet off the pedals? Is RPM a factor? Also check how your plane tracks by picking a point in the distance and see if the plane tracks straight or not.

 

[Cactus Charlie]

There was a disagreement between the slip balls of my G5, which I installed, and the PFD. It was slight but it bugged me. After I replaced the GSU 25 and performed the required alignment the disagreement was gone.

The slip ball will have an error if the GSU 25 calibration was not performed with the aircraft at exactly zero roll angle. I adjusted the roll attitude with small changes in tire pressure.

Feet off and stick free my FX-3 flies wings level with zero slip. I have not noticed any change with power but I have probably only flown stick free and feet off at normal cruise speed.

 

[Neal]

Had an ahaaah moment yesterday as to why the ball is slightly left (right yaw). I have a GoPro out on the right wing just below the tie down. I'm sure that drag is the cause. No plan to remove the camera. Wish the rudder trim tab had enough to counter it, need to explore various speeds as most of my flying has been around 24/24 of late to burn off water, etc. from infrequent flying.

 

[Cactus Charlie]

If I needed to adjust the rudder trim tab I would remove it and put in a vice with improvised large radius jaw pads.

I might consider making a temporary unpainted tab to find out what offset was required. That temporary tab could perhaps be made of softer, easier to bend, material. I expect the original tab is 6061-T6 and that won't take repeated bending without being annealed first.

 

[Neal]

If I needed to adjust the rudder trim tab I would remove it and put in a vice with improvised large radius jaw pads.

Agreed. Those small screws are not going to do well against any force to bend it.

 

[ve6yeq]

Ever since I took delivery, the “ball” has always been slightly to the left when trimmed out in cruise requiring a constant slight left rudder input. The "ball" on the G3X Touch PFD matches the G5 BFD (although over time the altitude between the two has drifted to now about 20 ft).

After a couple hours, my left foot gets tired but I am starting to get used to it. Initially, I thought that it might be the aileron rigging as the ailerons do not perfectly line up with the wing tips but at the first annual we checked the rigging angles and cable tensions and everything is setup correctly, it just must be that the wing tips are not perfectly aligned.

I have thought about trying to adjust the rudder trim tab but in practice I really have to keep my feet on the rudders constantly due to turbulence and trying to add the correct rudder input to keep up with the autopilot.

 

[Cactus Charlie]

(although over time the altitude between the two has drifted to now about 20 ft)

You are either doing well or you don't many hours on it yet.

My G5/GSU altitude split increased slowly to about 60 ft at which point I decided it was intolerable.

I launched on a project to build a prototype air data test set. When it was mature enough I brought the G5 home and calibrated it from 0 to 30,000 ft. That brought the difference down to 10 ft which is tolerable.

 

[ve6yeq]

Feet off and stick free my FX-3 flies wings level with zero slip. I have not noticed any change with power but I have probably only flown stick free and feet off at normal cruise speed.

Can you please send some of that smooth air down here? It is very rare that I ever find smooth enough air to fly completely hands off…

 

[ve6yeq]

You are either doing well or you don't many hours on it yet.

I have about 160 hours in the last 2 years, and I will be due next month for the required 24-month calibrations, which should zero out the altitude difference between the G3X Touch PFD and G5 BFD again.

 

[Cactus Charlie]

A typical altimeter test will check the altimeters and encoder are within limits but not adjust anything. It's typically a pass/fail test.

Perhaps you have an arrangement to do more than that required test. Maybe the requirements are different for Canada.

 

[ve6yeq]

A typical altimeter test will check the altimeters and encoder are within limits but not adjust anything. It's typically a pass/fail test.

I have never done this before as the plane is just coming up on 24 months...

Perhaps you have an arrangement to do more than the required test. Maybe the requirements are different for Canada.

The Transport Canada Maintenance requirements explicitly mention "shall be calibrated" not just "tested":

13. Altimetry Devices
(a) Altimeters and other Altimetry devices installed in aircraft operating under Instrument Flight Rules, or under visual flight rules in Class B and C Airspace or Class C and D Airspace that is designated as "Transponder Airspace" shall be calibrated at intervals not exceeding 24 months, to the parameters and tolerances outlined in Appendix B of Standard 571, or to equivalent standards acceptable to the Minister.
(b) For the purpose of this section, the term "altimetry devices" includes any air data computer, or other barometric device, providing a flight crew station, or an auto pilot, or automatic pressure altitude reporting system, or altitude alerting system with altitude data derived from static pressure.

So to me, this is more than just a pass/fail check, especially as the tolerance at sea level is listed as 20 ft, so either or both of the GSU-25 and G5 will need adjustment.

 

[Cactus Charlie]

Ok, the TC rule is different from FAA rule.

The FAA equivalent is 14 CFR 91.411 which includes -

"Within the preceding 24 calendar months, each static pressure system, each altimeter instrument, and each automatic pressure altitude reporting system has been tested and inspected and found to comply with appendices E and F of part 43 of this chapter;"

There is no requirement in USA to perform the IFR altimeter check to operate in Class B airspace. Although my FX-3 is IFR capable I have not performed the 14 CFR 91.411 altimeter check in the last 5 years so I cannot legally operate IFR.

The USA VFR requirement is a transponder check every 2 years. That does not require any altimeter accuracy check but, typically, there is a spot check of pressure altitude indication at field elevation.

FAA allows up to 75 ft altimeter error at field elevation so a G5 and GSU 25, at their allowed extremes of error, could be 150 ft different and legal for VFR operation.