Rough running primary ignition

[bvolcko38]

Flew to a pancake breakfast Sunday morning. I usually cruise on the primary ignition only. Everything nominal. Landed, had breakfast, talked told lies, talked some more, departed… took off on both ignitions as usual, got to cruise altitude ,throttled back, all good until it wasn’t. The rpm started lagging so I thought possibly the mixture was a bit rich due to higher ambient temps. No joy. Switched on secondary ignition and everything was good. Switched off secondary several times and I thought the engines would quit. Landed uneventfully. Will be pulling plugs Tuesday.

[Holmesryan]

Glad you are safe. Did you figure out the problem? Curious on the fix. Thank you

Ryan

[bvolcko38]

I changed all 8 spark plugs. The two top front plugs were sooty and possibly fouled. They run off the top magnetron. I changed out the top magnetron as well. All seems good so far. Thanks for asking.

[Raluttio]

Glad everything turned out.

Tangential question: I am new to the Aerovee. Is it common to cruise on primary only? I have seen this casually mentioned a couple of times from various sources.

[pilotyoung]

My practice has been when I get to cruise altitude or 3,000 if I am climbing higher, I turn off the secondary ignition. My landing checklist includes turning the secondary ignition back on.

[Bryan Cotton]

Is it common to cruise on primary only? I have seen this casually mentioned a couple of times from various sources.

Yep - it's a huge electrical load for our 20 A. We have enough power to run it but I'd rather put those amps into charging the battery once I'm safely away from the ground.