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KFC225 autopilot question

Hi,
my aircraft have KFC225 autopilot. When i turn on the autopilot with the AP button the autopilot switch on in Roll pitch mode. As i know in this mode the aircraft must flying straight forward, but my aircraft turning ca. 3 degrees left. In this mode i can draw a big cicrle to the sky :) , not a line. In headning mode work it perfect. Is it normal? If not, what can i do to work the AP normal?
Thank you!
Zoltan

Greece


Greece

What bank angles do you get in left and right turns in HDG mode?
It sounds like the roll null is incorrectly adjusted. This is quite easy to correct.

Avionics geek.
Somewhere remote in Devon, UK.

Gosh that panel looks just like mine did before it got upgraded with the 2x Sandel SN3500 some years ago.

The KI256 / KFC225 roll null – if that’s what the problem is – is a bugger to adjust for the average person because you need the KC225 bus extender. I bought one of these, 50/50 with another KFC225 owner, some years ago. It came as a kit and cost us about $2000. Search here for “bus extender”. As it turned out it was never used because all the KI256s we had were the Mod 11 ones which have a buffered output and have a negligible zero error (supposedly). We bought it because there are almost no avionics shops in Europe which can do this work.

I reckon this behaviour would not be noticed by most people because almost nobody knows what the ROL mode does, so they fly only with HDG or NAV

Administrator
Shoreham EGKA, United Kingdom

The in-flight roll null is simple and done without the extender. The ‘Pot’ is accessed through the front panel above the UP button.

Avionics geek.
Somewhere remote in Devon, UK.

Aha yes I now remember doing this in flight, some years ago.

It is quite easy to do but you need the right size screwdriver to turn that pot, otherwise it gets damaged and then you have a duff KC225; I believe they cost best part of $10k.

From vague memory, the “pot” looks like this

and it needs a screwdriver blade width around 2-3mm. When turning it there is no feedback and it is easy to break it. An incredibly stupid system, when King already have a software (laptop) config, and a means of storing values in an EEPROM. They could have used a couple of buttons to do the up/down function.

Administrator
Shoreham EGKA, United Kingdom

Thank you so much!
I will try it , after i’ll report what happened.
Zoltan

Greece
7 Posts
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