A little engine trouble

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? A little
thermal turbulence will hit the prop from all kinds of angles changing its
sound.

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

mike regish

"Peter Duniho" wrote in message
...

Well, we'd only climbed a few hundred feet when something in the airplane
started making a very strange noise. My friend's wife heard it too. It
was
sort of a rapid "growling" sound, lasting a second or two at a time, with
maybe five or ten seconds between. It seemed most likely to be coming
from
the engine, but it was subtle enough I couldn't rule out some sort of
airframe flutter. It might have been my imagination, but it seemed like
whenever I heard the sound, there was a little deceleration from the
airplane.

"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

On Mon, 14 Jun 2004 16:49:49 -0700, "Peter Duniho"
wrote in Message-Id:
:

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.

I would suggest that you attend his inspection, and take a mechanic's
stethoscope with you. That way you'll know what he did and did not
check, and can delve a little deeper into the issue. Someone with a
personal interest and a keen sense of concern can often suggest
relevant procedures beyond those of an average A&P. At least you'll
be able to watch the gages while he runs it up.

I have had experienced mechanics completely overlook subtle nuances of
anomalous behavior that only the owner, who regularly experiences the
machine in its nominal state, can readily discern.


--

Irrational beliefs ultimately lead to irrational acts.
-- Larry Dighera,

Peter Duniho wrote:

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?

Probably not. While there are a few problems that will shed metal particles into the
oil (a disintegrating bearing, for example), most will not. For example, a valve
that's beginning to stick will not.

George Patterson
None of us is as dumb as all of us.

"Peter Duniho" wrote in message
...
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.
Anyone have any thoughts on what to do if nothing is found?
As an intermediate step, it occurs to me that even though the oil was just
changed,

Did the plane just have an inspection? Was the fuel filter/gascolator
inspected/cleaned? Whenever my plane just comes out of an annual
I have to run it for a bit to get the air out of the fuel lines. Can also be
bubbles when it's hot but I guess you know that. Usually disappears
by the time I complete the run-up, but if I were quick I guess I could
take it into the air.

Paul

"Paul Sengupta" wrote in message
...
Did the plane just have an inspection? [...]

Define "just". It did recently come out of its annual inspection. However,
it'd had four flights already since the inspection and before the flight on
which this happened. Also, this is the eleventh annual inspection since I
purchased the airplane, so if air in the fuel lines were a normal
post-annual-inspection thing, I'd think that I'd have seen that before.

I can't rule out fuel contamination, just as I can't rule out many other
things. But the one time I had water (not air) in the fuel, the power loss
I experienced was greater than, and rougher than, what I experienced this
time. So I'm inclined to think it wasn't that.

Pete

"Peter Duniho" wrote in message
...
"Paul Sengupta" wrote in message
...
Did the plane just have an inspection? [...]

Define "just". It did recently come out of its annual inspection.
However,
it'd had four flights already since the inspection and before the flight
on
which this happened.

Ah, then I guess not. It's just the first time I start the engine after the
annual that it happens on my plane.

Just an idea.

Paul