Magnetron and Ignition Coils

[Aldo]

Hello Everybody,

The Sonex literature has great info on installing the magnetron and coils, but not much info on how these actually work and what they do. I have only flown traditional certified aircraft until now. So, I am used to two mags, mag checks, etc.

The Sonex I have has one mag toggle switch and one coil toggle switch. Should I be doing some sort of preflight check on these items? Do both need to be working correctly for the engine to operate? It would seem the coils may not be necessary once the engine is running. As always, any help understanding these systems is appreciated.

Aldo

[ScottM-Sonex1629]

I'm sure others will chime in, but here's what I know.

The AeroVee heads have been modified for a secondary spark plug, which is run by the ignition coils (and become your secondary electrical ignition). The Magnatron ignition system on the AeroVee is run off the flywheel by a magnetic trigger. Both are independent and both use a wasted spark firing mode. The top mag fires two plugs (left and right bank of cylinders) and the bottom mag does the same with the remaining two cylinders. I believe the left and right coils operate similarly.

So when both ignition systems are "timed" correctly your engine runs stronger and has a more full ignition sequence. You can run the engine on either system (in case one fails).

During the run up you should be checking for rpm drop between the primary (mag) ignition and secondary (coil) ignition.

Hope this helps.

[Sonerai13]

As Scott has suggested, a traditional "run-up" is appropriate before flight. If the secondary ignition is timed correctly, you will only have a very slight change in engine operation with either ignition switched off. You'll notice a slight difference in sound, a slight difference in vibration, and possibly a slight reduction in RPM (although sometimes you won't notice an RPM drop on some instruments).