I have a 912ULS and have a problem with the SMD Electronic Modules when I try to start. I know that I must change both but my question is about the real function of these modules. I want to know if they are only to star the engine or if have any other function during flight. Obviously, I am worried about the possibility that the engite stoped during flight because these modules but I don't know if this is possible or not as I don't know it they are only to start the engine. Please, If there is anybody who can explain me the real function of this modules or if could stop the engine during flight, I would be very grateful.
I have ordered them but they will delay a bit and I would like if I can flight meanwhile without risks,
Thank you
  • Re: SMD-ELECTRONIC MODULE problem

    by » 11 months ago


    Yes, you need those modules for the engine to start and run and shut down. They are the electronic interface between the coils that provide the energy for the spark and the pulse coils that sense for spark timing. I have flown on aircraft were you have to start to engine after cooling the modules with a bag of ice first, but would have preferred it to be repaired properly. By installing new modules your engine will have the benefit of built in soft start to delay the spark after start for 4 seconds to avoid kickback and they seem to be much more reliable as far as the start issue is concerned.

  • Re: SMD-ELECTRONIC MODULE problem

    by » 11 months ago


    Thank you for your answer. So, I understand that the possibility that the engine could stop during a flight exist if these modules are not working well, ins't it?

  • Re: SMD-ELECTRONIC MODULE problem

    by » 11 months ago


    Thats why there are 2 modules, in case one fails in flight. I doubt they would both quit at the same time and failing while running is not in there history, it is just a starting issue.

  • Re: SMD-ELECTRONIC MODULE problem

    by » 11 months ago


    It is not likely that both modules will fail in flight at the same time. Just make sure that both ignition systems are operational during your power checks and before shut-down at the end of the flight.

  • Re: SMD-ELECTRONIC MODULE problem

    by » 11 months ago


    The electronic ignition modules have two modes: START and RUN. The older modules have a known, documented problem with the START mode failing intermittently. As far as I know, no one has reported such problems with the RUN mode. The engine will start if the START mode is working on just one module. Only if both come up in the intermittent fail mode will the engine refuse to start. Both my modules developed the intermittent START problem a couple of years ago. Now and then the engine would not start, but if I let it sit for some period of time the problem would go away temporarily. I replaced one module and have had no problems since. I'm sure my old original module comes up in the fail-to-start mode now and then but this is transparent to the operator; my engine starts reliably on the new module regardless of what the old one is doing. Once in the RUN mode (ie, starter disengaged) both modules work fine. NOTE: the ignition modules are a safety-of-flight item and I do NOT suggest anyone fly with any known ignition problem. BTW, the way the ignition modules are clamped together on top of the engine where they get good and hot is nuts. Heat is the enemy of solid-state electronics. The least they could have done is mount the modules separated from each other. Clamping them together significantly reduces the area for heat rejection out of the modules. Also a heat sink would have been a good idea.

    Thank you said by: RotaxOwner Admin

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