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First, the background. I own an aircraft which is powered by a 912iS Sport engine, the propeller is a Woodcomp electrically controlled constant speed unit, the instrumentation is via Dynon Skyview HDX.

On Saturday I was flying when the instrumentation suddenly indicated information concerning Lane A voltage and fuel flow was missing - see attached picture. Worse, the propeller went full fine and the engine suddenly accelerated - I reacted and pulled the throttle back before it exceeded 6100rpm. At no time were any Lane faults showing, I cycled the Lanes to see if this would help (it didn't).

I switched the propeller controller into manual mode and was able to set the pitch and increase throttle back to a level to allow me to fly "normally" - with the exception of no Eco mode, so this showed that the controller was able to adjust the pitch of the propeller.

A few seconds after landing, the issue resolved itself - the information came back; I flew again 3 times and the problem didn't reappear but it was unnerving to have the engine suddenly go overspeed.

I checked the data from the Skyview - sure enough, the CAN data for the Lane A volts was missing when the issue appeared, as was the Fuel flow. But the RPM data was correct as were other data supplied via the CAN such as MAP, Oil Pressure, Oil temperature which I believe can rule out an issue with the CAN Bus..

As indicated, the Lane A voltage didn't drop to zero, it was just "missing", as if the system had switched off, before initialisation for engine start.

So my question: What can cause this data to go missing; worse, why would the lack of that data suddenly cause the propeller control unit command full fine pitch?

Any ideas?

10889_1_missing data.jpg (You do not have access to download this file.)
  • Re: CAN Bus data / Issue with Lane A Voltage

    by » 16 hours ago


    Does the prop controller monitor engine speed via CAN to set its pitch, or does it have its own sensor on/near the gearbox? My Airmaster has its own, but if yours gets engine speed via CAN, and CAN went "goofy," it wouldn't surprise me if its failure mode is Full Fine.

     


  • Re: CAN Bus data / Issue with Lane A Voltage

    by » 16 hours ago


    The propeller monitors the RPM of the engine via the CAN bus but as said, the CAN RPM signal was, at all times, correct, only the Lane A voltage and Fuel fuel indications dropped out temporarily. I've written to the manufacturer of the controller to see if a dodgy Lane A voltage could cause an issue. 


  • Re: CAN Bus data / Issue with Lane A Voltage

    by » 6 hours ago


    Oil pressure and temperature come from the Lane B CAN only.  Tachometer comes from both. However, EGT and Coolant temp come from Lane A only and these were not interrupted, so I agree the lane and CAN buss remained active during this event.  Possibly this is the result of data errors on the buss.  I don’t know about the Dynon system, but the Garmin system keeps track of data buss errors on the system information page so I would think Dynon does also. On my system I never see any errors, so I think with a properly working network there are very few.  Fortunately CAN data transmission is quite resilient to data errors, but it’s something you might want to look into. You can investigate the cable shield grounding and also check connections and that the resistance between CAN Lo and CAN Hi is nominally 60 ohms when all cables are terminated.  


  • Re: CAN Bus data / Issue with Lane A Voltage

    by » 3 hours ago


    Steve:

    Check the cable and connection good health from the Rotax CAN Fadec BUS and the propeller controller. I would do that before checking anything on the ECUs themselves.

     


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