"mike regish" wrote in message
news:37nzc.30974$2i5.23228@attbi_s52...
Could it have possibly been gusts hitting the prop? This would give the
deceleration and some changes in sound, similar to what you describe-at
least with the prop out front. Was it a gusty or thermally day?

Nope, that's not it. It was a little windy that day, but the sound was far
too regular to be any sort of response to wind gusts. Also, I've got plenty
of experience flying this airplane in a wide variety of wind conditions,
including much stronger gusts and winds than existed on this flight, and
have never experienced any sound like this as a result.

[...]
I always look for the simplest (and cheapest) explanations first.

Me too. I'm still hoping for that. But there are a number of "simplest"
explanations I can definitely rule out.

I just heard from my mechanic. He wasn't able to make it over to the
airplane today, but says he should be able to get to it tomorrow morning.
He's going to inspect the airframe and engine, do some full-power run-ups to
see if he can reproduce the sound on the ground. Hopefully I'll know
something more after that.

Anyone have any thoughts on what to do if nothing is found? I figure at
some point, a decision will need to be made as to whether to give up and
completely dismantle the engine, or to just go fly it again to see if the
problem can be reproduced. With my mechanic on board, of course, so he can
hear the noise first-hand.

As an intermediate step, it occurs to me that even though the oil was just
changed, we could change it again, and inspect the filter to see if there's
any metal. Presumably if the engine truly were on the verge of coming
apart, it'd be shedding at least some metal into the oil, right? Or wrong?
I'll be running that question past my mechanic as well, but I figure when
looking for opinions, this is a great place to ask.

Pete