A Ignition Spark Plugs

[bobg56]

Does anyone happen to know which spark plugs the A ignition fires? When I turn off B it seems to run a bit rougher and has about 150 rpm drop than when B is off...B drop is around 100-120 drop. I know the drop is well within limits but the roughness is noticable.

 

[sailvi767]

Is a cylinder going cold at that point? Sounds like you may only be on 1 plug. If so you should also see a elevated EGT on that cylinder with both ignitions on.

 

[Piper J3]

Are you checking at 4000 RPM and with engine at operating temp?

 

[Bob Y]

Does anyone happen to know which spark plugs the A ignition fires?

You don’t say if you’ve got a ULS or iS, so here are the relevant sections from each Rotax Heavy Maintenance Manual.

 

[bobg56]

Yes I do it @ 4000

 

[Piper J3]

Yes I do it @ 4000

I check ignitions in-flight almost every time I fly. Maybe 50 RPM drop at 5400 cruise RPM - barely perceptible. Engine runs equally smooth on either ignition when in cruise flight. I consider this a good check for determining ignition heath...

 

[bobg56]

I found the info I needed A does 1T 2T 3B 4B...also saw a Lockwood video that says to pull the choke out slowly, if engine runs smoother it's a carb issue, if it gets worse then ignition...thanks for the suggestions everyone!