UL912 Intermiddent engine failure

Hi Mirek

Thank you for  sharing your experience with me. We will evaluate and see if we have the same experience. I'll let know you know.

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I am having a similar problem. So far seems to run OK at full throttle, but at cruise RPM occasionally dips by up to a couple hundred RPM then picks back up. I have rebuilt the carbs, balanced them and replaced the sparkplugs. I have also done a leakdown test and it was good. 

I went for a test flight today and had the same symptoms. I had previously noticed that negative G's seemed to trigger the problem, so I tried that again. It was like switching the ignition off. RPM dropped a lot and almost as soon as I saw negative G's. 

The only place the two ignition systems have common connections are the ground (which seems tight - haven't checked it for corrosion though) and at the ignition switch. Wiggling the wires doesn't do anything, but I suppose it is possible that it is the switch. 

David, if you can instigate the problem with some negative G then that sounds more like a fuel problem than an electrical one. I would be thinking more of float/float valve/diaphragm/main needle slider (piston) problems.

Thank you for advice, we will replace the mechanical driven fuel pump as part of the troubleshooting .

B.Rgds

Peter