CamTom12 wrote:My pmags fire at TDC during cranking. I’m pretty sure the firefly operate the same way.

Can’t get kickback that way.

Yup, this. And you can actually set them to fire just after TDC to really eliminate the possibility. Still lots of curve available for timing advance. I'm really hoping surefly will provide a get around for the battery thing. Really to bad if they can't.

CamTom12 wrote:My pmags fire at TDC during cranking. I’m pretty sure the surefly operate the same way.
Can’t get kickback that way.

Pretty sure that's what an impulse mag does too.

Yeah, that’s what the impulse mag on my O-320 used to do.

Do the big continentals not have an impulse mag? If they do, how in the world are so many people seeing kickback?

Recommended in many places to actually just start on the impulse mag instead of both if possible.

CamTom12 wrote:Yeah, that’s what the impulse mag on my O-320 used to do.

Do the big continentals not have an impulse mag? If they do, how in the world are so many people seeing kickback?

Depends on the year and/or model of cessna. All of them were equipped with either impulse mag or shower of sparks for starting.

I think these kick backs are coming for either poor technique or poorly maintained impulse couplings.

Situation is further exacerbated by this new generation of propellers with much less weight (inertia) in the blades. Heavier props can mask kickbacks to some extent.

Lyc's seem to have only one impulse (RH mag?).
Most continentals seem to have impulses in both mags.
IMHO kickbacks on the bigger 6-banger Cont's are often due to
1) weak battery or starter, won't turn the engine through the compression stroke
2) letting go of the starter button too soon
3) lightweight prop not having enough mass / inertia to go through the compression stroke

My 180 has a stock 470K, C201 Mac, energizer starter, & firewall mounted odyssey. Starts just fine.

Halestorm wrote:...Situation is further exacerbated by this new generation of propellers with much less weight (inertia) in the blades. Heavier props can mask kickbacks to some extent.

Just semantics, but heavier props prevent kickbacks is how I'd put it.

So what were the findings on this in the end?