If you thought the O300 on a stock 170B was underpowered before, try running on 5 cylinders. This came apart in flight at ~1500AGL. Lost a few hundred RPM, but it kept running to a field. No oil loss, and no metal anywhere else in the engine. A cylinder change and back in action.

A good outcome, but it get's your attention with wife and daughter on board.

That's quite an elegant failure.

I am sure it was very stressful, what did it sound like?

Wow. Any postmortem analysis?

Rocker arms look unscathed. Those cast rocker shaft journals always give me the creeps though. Looks like it's not unfounded.

The best comparison would be that it felt a little worse than a stuck valve. Same sort of total engine response. It went way out of balance, rattling like crazy, and dropped RPM.

If you look at the pictures, you can see two different colors - it must have originally cracked at some point in the past, and then finally gave away. We had been at cruise power for 20 minutes, and had not touched the throttle for a bit.

Asking two different guys how you would prevent this, the response was, you probably couldn't. Maybe a die penetrant test, but why would you think to do that here on the cylinder? Maybe always go with new cylinders instead of overhauled to avoid unknown, unknown metal fatigue?

Just spitballing. I don't really know. Just be constantly prepared to put it down.

Oooo Weeee! That was close! Altitude is your friend!

Kurt

Mine happened at night with passengers. Piston pin plug let go and absolutely zero compression in #4 as a result.

I just throttled up a little more and immediately landed after about a 8 min flight on 5 cylinders.

My passengers had no idea.

The O-300 on 5 cylinders is still smoother than a Lycoming O-360 running on all 4. [emoji23]

I would say shutup but you are right.. lol...


To OP, glad it all worked out and you got it on the ground safely!

Yeah, that'll happen I've changed out a number of cylinders with that issue over the years. Each one made it back to the field. I figured it could be caused by valves sticking. Didn't seem to be an issue with the engines running on mogas