It’s quite easy to check the KS271C servos, with a very simple wire harness. I think I posted the wiring here previously. 28V power, a switch to supply 28V to the clutch, and you open the black plastic case and waggle the motor+gearbox assembly while measuring the -3V to +3V torque output.
Very often the strain gauge assembly is broken. The is a design defect in that they allow too much bending (too much strain) on the steel cantilever, and this causes the strain gauges to become unglued. One can glue them back on – it’s only epoxy.
If anyone has burnt out servos of this type, I am very interested. I collected a few in the past, all declared “beyond economic repair”. The servo assembly can be transplated out of those, in a few minutes. No calibration of the gauge amplifier is likely to be required.
New datas…
During steady climbs (and descents), constant heading and turns (L and R), it appeared that:
When I have the time, I will post some video.
On the previous one, I think that the VS oscillation was to be linked with updraughts at low level with some terrain not far…
My actual conclusion is that ACC calibration mainly solved the problem.
However, i may send the pitch servo to a solid workshop for bench test during next annual. It can’t do arm, and will allow to check the trim sensor in it.
Once again, Peter is right 
Alternate air will actually apply to the AP static source.
This test may be significant in my case.
182 STATIC LINE MAP
KAP 140 STATIC LINE CONNECTION (please refer to color code)
EDIT: reading again the post and my problem, unstable VS during TURN, I wonder if my main problem is not around imbalanced static input. I guess this is where I should start, and ALTERNATE STATIC will obviously help…
Alt static will apply to it, I am sure.
Water is common, as are bugs (live and dead).
Also pipes pinched by stuff, even by control linkages I know one owner who collected his plane from a famous German company with a pinched static line, and I collected my plane from a famous UK company with control linkages cutting into a cable harness… so anything is possible.
Yes… the hangar where one can work Lack of these is what keeps the maintenance business in business, at many places. And a heated hangar is absolute luxury.
So it’s own port but not its own source/line.
I must check if alternate static also applies to it. Don’t know how it works.
Water is weird… but why not.
Maybe there is somewhere with my static line to sort out.
Loads of possibility then….
If only I had the possibility to perform those inspections with the help of a mechanic, by myself, in a heated hangar :-)
In the above diagram you see hose #13 which connects into the static pipework of the aircraft.
Also this is in the IM
One weird possibility is that there is water in the pipes which shifts around when you turn.
I thought it was using its own.
Straubing made it confused to me.
And the IPC too (above), where it seems to connect to the static line.
Will check the POH.
Nice to see how technical data meets exploitation considerations :-)
PetitCessnaVoyageur wrote:
Does the KAP140 use its proper static source, or the static source line of the aircraft ??? In that case, it could explain some thing….
On the 172 it uses its own static port. But surely that information is in the POH for your aircraft!?
The ball is…. hey showing I kept applying right rudder while the plane had leveled… I am not a champion here :-)
The question of static, I am not sure.
Does the KAP140 use its proper static source, or the static source line of the aircraft ??? In that case, it could explain some thing….
As well, I could try the alternate static to see how it goes
In that case I agree it won’t likely be the servos.
Has it always behaved like this?
What is the ball doing? One possibility is that, especially in a non coordinated turn, something goes wrong with the static air system and the autopilot is seeing the wrong altitude and thus derives the wrong VS from it.
