Hi
It always fails on PFT9.
Thats the plan, once I find someone with a laptop and an RS232 lead I will get the diagnostics done.
Thanks
A related question on the KAP140:
We have a KAP140 in the DA40, and sometimes the AP all of a sudden turns the aircraft in an uncontrolled bank when it is in heading mode.
This is very dangerous and can only be recovered by disconnecting the AP and fly manually.
Does someone recognize this failure? What could cause this?
What is worrying is that there is no integrity check. The AP gives no warning when it happens.
turns the aircraft in an uncontrolled bank when it is in heading mode
If the bank is truly uncontrolled (say 60 degrees) then that is not a fault in the source of the heading signal (which is just a plus or minus analog voltage, representing the heading bug left/right of straight-ahead). The autopilot must limit the bank angle internally, to something like Rate 1.
If you get a roll angle well past Rate 1, it has to be a fault in the autopilot computer, or a fault in the roll reference source which tells the AP what the actual roll angle is.
I would start by checking the wiring between the AP computer and the roll reference source. If it is intermittent, it could be a real bugger…
there is no integrity check
Welcome to GA avionics 
Would it bank steeper than it would normally do? Or does it do a standard turn?
Jesse wrote:
Would it bank steeper than it would normally do? Or does it do a standard turn?
The turn starts very gentle and gets steeper over time.
The turn starts very gentle and gets steeper over time.
Seems the A/P doesn’t sense the feedback from the gyro. If the heading bug (control) part failed it would just start turning, limiting too its standard turn rate by the gyro.
