A little engine trouble

[Peter Duniho]

I hesitated to even bother writing about this, since so far it seems like
pretty much a non-event. But then I figured, what the heck...hardly anyone
ever actually writes about actual flying, however mundane, in this
newsgroup, so here you go...

The plan was for me to follow a friend down to his mechanic's shop at Tacoma
Narrows (TIW) airport in Washington State. We're both based at Paine Field
(PAE) in Everett, WA, and in fact he ties his airplane down just outside my
hangar. We often trade rides, since neither of us have our airplanes
maintained at Paine Field.

The flight down was uneventful. He flew down in his airplane, while his
wife and I flew down in mine. We got to TIW, picked him up, and headed back
out. Cleared for a northbound, left downwind departure from runway 17, we
took off.

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.

I've owned the airplane ten years now, and have never heard anything like
that out of it. That was enough for me, having read plenty of the "I
Learned About Flying From That" stories in which a pilot ignored a seemingly
minor symptom that quickly turned into something major. So I got a landing
clearance back at TIW, continuing to climb until I was in a position to make
a normal power-off landing, and then of course landed. Once the power was
pulled back, I did not notice the sound again.

The whole situation is very inconvenient. My airplane is now sitting at my
friend's mechanic's shop, where his airplane *should* be sitting (waiting
for its annual inspection). I spent half the day driving back and forth, so
that we could leave his plane there as well (he flew us back to Paine, where
I picked up my car and drove back down to get him). And his airplane is
tied down in transient parking at TIW, because there wasn't a spare spot for
my airplane so I took his (we actually had expected a spot to clear before
he got back, but it didn't).

But somehow, it still seems like the right thing to have done. I haven't
had a chance to get any mechanic (mine or my friend's) to take a look at the
airplane yet. Even though this year's annual was surprisingly expensive
(and that's among some years of some pretty surprisingly expensive annuals),
I secretly hope that something serious is found wrong with the airplane so
as to justify my aborting the flight. But even if the source of the noise
turns out to be something entirely benign, I'm still comfortable in my
decision, and would do it exactly the same again.

Bottom line: another word for "inconvenience" is "adventure". And that's a
much more desirable kind of adventure than the other synonym for the word,
"engine failure". :) More importantly, I always wondered if I would have
the courage to ignore my desire to get back home and abort a flight when
things didn't seem right. Now I know that I would, and did.

Funny thing though: I've now been stranded three times with this plane over
the years (the other two times were both engine starting problems: once a
dead battery, another time a problem with the "shower-of-sparks" ignition
system). Two of those three times happened at TIW, and it's not like I
actually fly there all *that* often. Spooky...

Pete

p.s. I couldn't help think about how this situation would have affected a
renter. From past threads here, it's clear that depending on the FBO, I
could either have gotten the four-star treatment, with an FBO pilot coming
to get me, or I could have gotten the shaft, being required not only to find
my own transportation back home, but being required to recover the airplane
once it had finally been repaired. I find it odd that the latter sort of
FBO manages to stay in business.

[Dan Luke]

"Peter Duniho" wrote:

> Well, we'd only climbed a few hundred feet when something in the
airplane
> started making a very strange noise.

Sorry, Pete; you fly a ...?

> It might have been my imagination, but it seemed
> like whenever I heard the sound, there was a little
> deceleration from the airplane.

Did you happen to look at the tach or MAP during any of these events?

> But somehow, it still seems like the right thing to have done.

No question.

> But even if the source of the noise
> turns out to be something entirely benign,

Here's hoping it's not one of those intermittent, "mystery" problems and
your mechanic spots it right away. Keep us posted.
--
Dan
C172RG at BFM

[mike regish]

I was out flying the CAP's 172 yesterday when I noticed the same thing. A
growling sound. I determined that it was the soda can air vents getting hit
by the prop wash, or rather, the openings being hit and the cans amplifying
the sound.

What were you flying and could it have been the same thing?

mike regish

"Peter Duniho" > wrote in message
...

> I hesitated to even bother writing about this, since so far it seems like
> pretty much a non-event. But then I figured, what the heck...hardly
anyone
> ever actually writes about actual flying, however mundane, in this
> newsgroup, so here you go...

[Peter Duniho]

"Dan Luke" > wrote in message
...
> Sorry, Pete; you fly a ...?

Lake Renegade (turbocharged model).

> Did you happen to look at the tach or MAP during any of these events?

No. Of course, in hindsight that might have provided useful information.
But even when the takeoff is going smoothly, I'm a "eyes outside" kind of
person (once the proper reading of the gauges has been confirmed during the
takeoff roll, of course).

In this particular situation, my mind was focused on where on the water
would be acceptable for a landing (though, frankly, the Tacoma Narrows are
not generally amenable to seaplane landings in any case, due to strong
currents through there), and on a possible landing back at TIW.

Maybe I could have had my front-seat passenger watch the gauges, to try to
correlate them with the noise. But I personally didn't have the attention
to spare. I would have either have had to keep my eyes on the engine gauges
until the noise occurred, or I would have had to hope to be able to shift my
attention quickly enough to evaluate the gauges in the short period during
which the sound occurred. Neither would have been practical to do, IMHO.

It's a pretty good argument for a data-recording engine monitor. :) I'll
have to think about getting one of those.

Pete

[Peter Duniho]

"mike regish" > wrote in message
news:QRXyc.95474$Ly.16002@attbi_s01...
> I was out flying the CAP's 172 yesterday when I noticed the same thing. A
> growling sound. I determined that it was the soda can air vents getting
hit
> by the prop wash, or rather, the openings being hit and the cans
amplifying
> the sound.
>
> What were you flying and could it have been the same thing?

Nope...the Renegade doesn't have those kinds of vents, and of course the
prop wash is entirely aft of cabin venting anyway.

I'm not ready to rule out some sort of aerodynamic effect -- for one, during
the annual inspection the fiberglass tips of the horizontal stabilizer were
replaced -- but it sure didn't seem like one to me at the time. My instinct
was that it was an engine issue.

Also, with ten years of experience flying the airplane, if it IS an
aerodynamic effect, it's almost certainly something new since the annual
inspection. Obviously I can't say that I've seen every single thing the
airplane could do, but I'll bet I've come pretty close over the years,
especially in what are otherwise normal situations such as this one.

Now that I think of it, another thing that's new is that I had them add a
second comm antenna. The sound happened in a climbing left turn, so I
suppose another possibility is some sort of vibration from the antenna.
I'll have to check into that.

I will, of course, post follow-ups to report what, if anything, I eventually
learn.

Pete

[Dudley Henriques]

"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.

Might be the electric hydraulic pump. It will growl if it's flooded with
hydraulic fluid.
Have it checked anyway!
Dudley Henriques
International Fighter Pilots Fellowship
Commercial Pilot/ CFI Retired
For personal email, please replace
the z's with e's.
dhenriquesATzarthlinkDOTnzt

[Marty]

"Peter Duniho" > wrote in message
...
> "Dan Luke" > wrote in message
> ...
> > Sorry, Pete; you fly a ...?
>
> Lake Renegade (turbocharged model).
>

Now I'm envious Pete.... :-)

Rest assured, it was a good call.

As a student I aborted a takeoff due to a couple of bangs on rotation and
nearly went into the grass. Turned out to be the pax seat belt hanging out
the door. The only things damaged were my ego and my rearend from the
chewing I got from my CFI.

Hope you find the culprit and the fix isn't a bank breaker.

Marty

[Dylan Smith]

In article <QRXyc.95474$Ly.16002@attbi_s01>, mike regish wrote:
> I was out flying the CAP's 172 yesterday when I noticed the same thing. A
> growling sound. I determined that it was the soda can air vents getting hit
> by the prop wash, or rather, the openings being hit and the cans amplifying
> the sound.

Sometimes odd sounds turn out to be nothing to worry about.

A week ago, I was flying my Ka-8 glider over Andreas village, which is
not far from the airfield. I had just got off a winch launch, and was in
about the first or second thermal, trying to get enough altitude to try
and get out of the area.

I then heard amongst the sound of the wind going past the canopy this
"Bbbbrbrbrrrrrr brrrrrrrrrrr brrbrbrbrbrbrb" sound, which
immediately made me think that it was airframe fabric vibrating in the
wind. It went quiet for a bit. Then I heard it again. Getting a bit
concerned that the glider might have hit something on the launch that
had damaged the fabric, I was thinking of levelling out for a short
while to make a decision.

Then I realised what it was. It was the sound of motorcycles
accelerating up the Sulby straight about three or four miles away...it's
amazing how well sound travels when you're above what's making the
sound.

(The nice thing about the Ka-8 is that I can hear powered aircraft in
the vicinity).

--
Dylan Smith, Castletown, Isle of Man
Flying: http://www.dylansmith.net
Frontier Elite Universe: http://www.alioth.net
"Maintain thine airspeed, lest the ground come up and smite thee"

[Bob Martin]

> As a student I aborted a takeoff due to a couple of bangs on rotation and
> nearly went into the grass. Turned out to be the pax seat belt hanging out
> the door. The only things damaged were my ego and my rearend from the
> chewing I got from my CFI.

Had something like that happen... my instructor forgot to tell me that
150's sometimes get a violent nosewheel shimmy during the takeoff
roll... well, I found that out for myself on my first solo... pushed
the power up, and a few seconds later the whole plane started
shaking... aborted the takeoff thinking it was going to come apart on
me. Course, he just tells me to keep the weight off the nose, so my
three flights were done soft-field style with the nose up as soon as
it would go.

[Larry Dighera]

On Sun, 13 Jun 2004 00:04:25 -0700, "Peter Duniho"
> wrote in Message-Id:
>:

>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.

From the description of the noise, it would be consistent with some
sort of vibratory resonance. Having actually experienced it, can you
rule that out?

>It might have been my imagination, but it seemed like
>whenever I heard the sound, there was a little deceleration from the
>airplane.

As another has suggested, the tach/MP gage should help in diagnosing
any loss of power associated with the noise.


--

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

[PaulH]

You did exactly the right thing.

I aborted a takeoff on my last BFR because "something didn't feel
right" at liftoff. Did a double-check of all systems before launching
again and everything was fine. There's only 1 engine out there, and
my home airport has no decent emergency landing sites within 5 miles.

[Peter Duniho]

"Larry Dighera" > wrote in message
...
> [...]
> From the description of the noise, it would be consistent with some
> sort of vibratory resonance. Having actually experienced it, can you
> rule that out?

Probably. Resonance can happen in a variety of ways, and can sound and feel
like a wide range of things. But my experience has been that when resonance
happens, it amplifies an existing frequency, rather than introducing a new
one. I think resonance with something is unlikely in this case.

I did forget to mention that in addition to hearing the noise, I could feel
the "rumble" in my seat. It wasn't just a noise; there was a definite
(though equally subtle) vibratory component.

> As another has suggested, the tach/MP gage should help in diagnosing
> any loss of power associated with the noise.

Yup, hindsight is 20/20. Given the conflicting priorities (diagnose or
maintain control? :) ), I'm seeing a new reason for one of those fancy
engine monitors that I never thought of. They are always touted as being
useful for diagnosing hard-to-diagnose engine problems, but I never really
thought about the problem of watching engine gauges and dealing with
potential emergencies at the same time.

Pete

[Jeremy Lew]

I once had a mysterious noise like that which turned out to be a nylon strap
from a bag which had gotten shut in the door and was hanging out of the
plane a few inches and vibrating in the airflow. I had no idea what it was
until someone who had seen me taxi away with a strap hanging out mentioned
it to me.

"Peter Duniho" > wrote in message
...
> "Larry Dighera" > wrote in message
> ...
> > [...]
> > From the description of the noise, it would be consistent with some
> > sort of vibratory resonance. Having actually experienced it, can you
> > rule that out?
>
> Probably. Resonance can happen in a variety of ways, and can sound and
feel
> like a wide range of things. But my experience has been that when
resonance
> happens, it amplifies an existing frequency, rather than introducing a new
> one. I think resonance with something is unlikely in this case.
>
> I did forget to mention that in addition to hearing the noise, I could
feel
> the "rumble" in my seat. It wasn't just a noise; there was a definite
> (though equally subtle) vibratory component.
>
> > As another has suggested, the tach/MP gage should help in diagnosing
> > any loss of power associated with the noise.
>
> Yup, hindsight is 20/20. Given the conflicting priorities (diagnose or
> maintain control? :) ), I'm seeing a new reason for one of those fancy
> engine monitors that I never thought of. They are always touted as being
> useful for diagnosing hard-to-diagnose engine problems, but I never really
> thought about the problem of watching engine gauges and dealing with
> potential emergencies at the same time.
>
> Pete
>
>

[mike regish]

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.

[Kyle Boatright]

"Peter Duniho" > wrote in message
...
> "Dan Luke" > wrote in message
> ...
> > Sorry, Pete; you fly a ...?
>
> Lake Renegade (turbocharged model).
>
> > Did you happen to look at the tach or MAP during any of these events?
>
> No. Of course, in hindsight that might have provided useful information.
> But even when the takeoff is going smoothly, I'm a "eyes outside" kind of
> person (once the proper reading of the gauges has been confirmed during
the
> takeoff roll, of course).
>
> In this particular situation, my mind was focused on where on the water
> would be acceptable for a landing (though, frankly, the Tacoma Narrows are
> not generally amenable to seaplane landings in any case, due to strong
> currents through there), and on a possible landing back at TIW.
>
> Maybe I could have had my front-seat passenger watch the gauges, to try to
> correlate them with the noise. But I personally didn't have the attention
> to spare. I would have either have had to keep my eyes on the engine
gauges
> until the noise occurred, or I would have had to hope to be able to shift
my
> attention quickly enough to evaluate the gauges in the short period during
> which the sound occurred. Neither would have been practical to do, IMHO.
>
> It's a pretty good argument for a data-recording engine monitor. :) I'll
> have to think about getting one of those.
>
> Pete

Any idea of what your passengers were doing at the time. In my airplane (an
RV-6) there is a noticable change in the tone and volume of cockpit noise
(and vibration) either the pilot or passenger shifts his/her feet on the
floor. I know when I move my feet, so it doesn't surprise me, but when I've
got a "shifty" passenger, s/he will put me on edge for a few seconds here
and there.

Getting back to your situation, is it possible that a passenger found a neat
way to rest a hand/arm/foot/etc. that created an unusual resonance? I
realize this wouldn't have caused a power loss.

One other thing to consider is a stuck valve. Your description sounds
similar to my understanding of the symptoms of a stuck valve.

KB

[Peter Duniho]

"Kyle Boatright" > wrote in message
...
> Any idea of what your passengers were doing at the time. In my airplane
(an
> RV-6) there is a noticable change in the tone and volume of cockpit noise
> (and vibration) either the pilot or passenger shifts his/her feet on the
> floor.

No, no idea. But I've never experienced anything like that before, and I
have often flown with passengers over the years.

The one "passenger-induced emergency" in my airplane I'm aware of is that
the front seat passenger can actually push on the yoke lever with their
feet. Oddly enough, the one passenger to show this to me (unintentionally,
of course) was the same one that a few years earlier kept messing with my
elevator trim on a nighttime flight, by repeatedly alternating the position
of his seat back (it was a clear night, he was in the back seat in a 182RG,
and he kept lowering the seat back so that he could look at the stars, and
then raising it again to look out the side and front).

> One other thing to consider is a stuck valve. Your description sounds
> similar to my understanding of the symptoms of a stuck valve.

Unfortunately, that's the best conclusion I've been able to come to as well.
I've never experienced a stuck valve with this engine, so I don't know what
sort of power loss to expect. I'd *think* it'd be more significant than
what I noticed, but I don't really know.

The engine just got all new exhaust valves and guides a few years ago, so if
it's an exhaust valve problem, I'll be sorely disappointed. I suppose it
could be an intake valve problem, even though they don't get the kind of
wear and tear the exhaust valves do.

Pete

[Peter Duniho]

"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

[Kyle Boatright]

"Peter Duniho" > wrote in message
...
>
<<<much snipped>>>

> The one "passenger-induced emergency" in my airplane I'm aware of is that
> the front seat passenger can actually push on the yoke lever with their
> feet. Oddly enough, the one passenger to show this to me
(unintentionally,
> of course) was the same one that a few years earlier kept messing with my
> elevator trim on a nighttime flight, by repeatedly alternating the
position
> of his seat back (it was a clear night, he was in the back seat in a
182RG,
> and he kept lowering the seat back so that he could look at the stars, and
> then raising it again to look out the side and front).
>
> Pete

Hijacking the thread here, but...

We had a fatal accident in an Ercoupe in the local area last year that
possibly/probably involved accidental control manipulation by the passenger.
Apparently, the aircraft ran out of fuel and the pilot had lined up for a
landing in a field. Most likely survivable, possibly even a field he could
have flown out of after adding fuel. However, the airplane went in almost
vertical at the "approach end" of the field. Speculation is/was that the
passenger used his feet to brace himself for the off-field landing and
unknowingly used the elevator control linkages in the footwell as a place to
brace. The harder he braced, the more the airplane pitched nose down...
Right into the ground. Two fatalities in an accident that shouldn't have
even resulted in injuries.

KB

[Larry Dighera]

On Mon, 14 Jun 2004 16:39:51 -0700, "Peter Duniho"
> wrote in Message-Id:
>:

>I've never experienced a stuck valve with this engine, so I don't know what
>sort of power loss to expect.

It's not only a specific engine that characterizes the nature of a
stuck valve. The magnitude of the effect of a stuck valve can vary
depending the position in which the valve sticks. If it sticks wide
open, it could contact the piston possibly with catastrophic results.
If it just sticks open a smidgen occasionally, it would obviously be
less severe.


--

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

[Larry Dighera]

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,

[G.R. Patterson III]

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.

[Happy Dog]

"Peter Duniho" >

> I've owned the airplane ten years now, and have never heard anything like
> that out of it. That was enough for me, having read plenty of the "I
> Learned About Flying From That" stories in which a pilot ignored a
seemingly
> minor symptom that quickly turned into something major. So I got a
landing
> clearance back at TIW, continuing to climb until I was in a position to
make
> a normal power-off landing, and then of course landed. Once the power was
> pulled back, I did not notice the sound again.

Can't think of a better choice.

I was flying a short hop across Toronto at about 2000' Asl (1200 ' AGL).
There was a sudden, but only slight, hesitation. It steadily deterioted
until I had just enough power to get about 300FPM climb. I was near a
soccer field and a few miles away from a private airport (DeHaviland
Factory). I asked for, and received a clearance to climb to 7000' in CYYZ
Terminal Airspace which would give me an easy glide into the airport. But I
stayed close to the soccer field JIC. My first guess was fuel. No luck
there. I isolated the problem to one magneto. Timing slipped, I assumed as
all cylinders were showing roughly the same EGT (JPI EDM-800). Feeling
confident that the problem was isolated to one half of the ignition system,
I requested the same altitude to within a copule miles of my destination
airport. The problem doesn't seem to be timing though. Plug and plug
hardware look more likely. But why a few of them all at once is still a
mystery.

le moo

www.aerobatics.ca

[mike regish]

Stuck valve or maybe a floating valve?

mike regish

"Kyle Boatright" > wrote in message
...
>
> One other thing to consider is a stuck valve. Your description sounds
> similar to my understanding of the symptoms of a stuck valve.
>
> KB
>
>

[Peter Duniho]

Well, as promised, here's my follow-up...

Went down to TIW today, after picking up Ron my mechanic first. Yesterday,
one of his employees went over to check the airplane out, full-power run-up,
inspection, etc. He found no sign of anything wrong.

I did my usual thorough preflight, while Ron double-checked some stuff. We
did find a loose rivet on the fixed trim tab on the elevator, but nothing
that would make a noise you'd be able to hear in the cabin.

With nothing left to do but fly, we taxied out, with the plan that we'd
climb over the airport and then depart to the east (back to my mechanic's
airport) if everything looked good. Well, we got to the runway end, where I
did my run-up, and the right mag was *really* rough.

Ron was pretty sure that we were just looking at a fouled plug(s), so we
pushed the power up to burn the crud off. It took a while, and pretty high
power settings, but we actually managed to clear the plug(s).

Oddly enough, his employee found no plug fouling the yesterday. This was
apparently some new accumulation.

Anyway, once we got a normal runup, with both mags running nice and smooth,
we were ready to go. Took off, did our climb (and discovered that TIW has
one of those pesky Letters of Agreement with Seattle Approach where they
abdicate ownership of their airspace above 1700' AGL), and everything
sounded and felt fine, so we headed back to his airport.

The whole flight went just dandy. Ron's current theory is that there was
some small chunk of carbon floating around in the cylinder, that
intermittently was affecting the plug. He says he's seen that before, and
generally the debris makes its way out of the cylinder through the exhaust
before too long. If it got really stuck, it would explain the rough mag
we'd found on the run-up as well.

Without anything to fix and the airplane apparently running fine, I took it
back home to PAE.

Was Ron right about my problem? I have no idea. I'm a bit skeptical, just
because the problem didn't seem like the sort of thing that was affecting
just one plug on one cylinder, but it's hard to say. I one time lost an
entire mag shortly after takeoff, and the only sign that there was a problem
was that my fuel burn was a little higher for the same power setting. The
engine ran nice and smoothly, and I didn't even find out the mag wasn't
working until I did my run-up for my next flight. But I suppose in that
case, all of the cylinders were being affected identically and that if just
one or two was being affected, that might show up as some roughness.

On my way back to PAE, I was reminded about another effect that I'd
forgotten about. Due to the way the sound waves propagate within the cabin,
there are "hot spots" of noise. If I move my head to a particular spot, a
noise that is otherwise inaudible becomes apparent. I was unable to find
such a spot at which I heard a noise identical to what I heard last
Saturday, but I didn't remember this until I was in cruise flight. If I
remember, I'll try moving my head around during my next takeoff and see if I
can come up with the same noise I heard before. Maybe it WAS just the
result of a particular kind of resonance after all, as Larry suggested.

Anyway, that's all I know for now. I realize this thread belongs as much in
r.a.owning as it does here, but I haven't been following that newsgroup, and
it seems on-topic here too, so here it is. Thanks for those who showed
interest...I hope it wasn't too much of a letdown to not find out exactly
what the problem was after all. I guess a theory is better than nothing.
:)

Pete

[Bela P. Havasreti]

On Wed, 16 Jun 2004 18:09:46 -0700, "Peter Duniho"
> wrote:

I had a plug that would fire intermittent in the air (tested
fine on the ground with a pressurized tester). Lesson learned:
No ground-based pressure tester can replicate the heat/pressure the
plugs are subjected to at cruise (or high) power settings....

With a 6-cyl Continental, when one plug goes of line, the thing still
runs smooth, it just drops 25 or so rpm and "sounds different".

After putting new plugs in ($300 or so bucks), she runs like an old
Singer sewing machine.

Also, maybe forgive me for saying so, but I'm of the opinion that high
power ground runs in an attempt to clear fouled plugs is (obviously)
way harder on the engine than simply pulling & cleaning them (such is
our fate running 100LL in these older engines these days)..

Bela P. Havasreti

>Well, as promised, here's my follow-up...
>
>Went down to TIW today, after picking up Ron my mechanic first. Yesterday,
>one of his employees went over to check the airplane out, full-power run-up,
>inspection, etc. He found no sign of anything wrong.
>
>I did my usual thorough preflight, while Ron double-checked some stuff. We
>did find a loose rivet on the fixed trim tab on the elevator, but nothing
>that would make a noise you'd be able to hear in the cabin.
>
>With nothing left to do but fly, we taxied out, with the plan that we'd
>climb over the airport and then depart to the east (back to my mechanic's
>airport) if everything looked good. Well, we got to the runway end, where I
>did my run-up, and the right mag was *really* rough.
>
>Ron was pretty sure that we were just looking at a fouled plug(s), so we
>pushed the power up to burn the crud off. It took a while, and pretty high
>power settings, but we actually managed to clear the plug(s).
>
>Oddly enough, his employee found no plug fouling the yesterday. This was
>apparently some new accumulation.
>
>Anyway, once we got a normal runup, with both mags running nice and smooth,
>we were ready to go. Took off, did our climb (and discovered that TIW has
>one of those pesky Letters of Agreement with Seattle Approach where they
>abdicate ownership of their airspace above 1700' AGL), and everything
>sounded and felt fine, so we headed back to his airport.
>
>The whole flight went just dandy. Ron's current theory is that there was
>some small chunk of carbon floating around in the cylinder, that
>intermittently was affecting the plug. He says he's seen that before, and
>generally the debris makes its way out of the cylinder through the exhaust
>before too long. If it got really stuck, it would explain the rough mag
>we'd found on the run-up as well.
>
>Without anything to fix and the airplane apparently running fine, I took it
>back home to PAE.
>
>Was Ron right about my problem? I have no idea. I'm a bit skeptical, just
>because the problem didn't seem like the sort of thing that was affecting
>just one plug on one cylinder, but it's hard to say. I one time lost an
>entire mag shortly after takeoff, and the only sign that there was a problem
>was that my fuel burn was a little higher for the same power setting. The
>engine ran nice and smoothly, and I didn't even find out the mag wasn't
>working until I did my run-up for my next flight. But I suppose in that
>case, all of the cylinders were being affected identically and that if just
>one or two was being affected, that might show up as some roughness.
>
>On my way back to PAE, I was reminded about another effect that I'd
>forgotten about. Due to the way the sound waves propagate within the cabin,
>there are "hot spots" of noise. If I move my head to a particular spot, a
>noise that is otherwise inaudible becomes apparent. I was unable to find
>such a spot at which I heard a noise identical to what I heard last
>Saturday, but I didn't remember this until I was in cruise flight. If I
>remember, I'll try moving my head around during my next takeoff and see if I
>can come up with the same noise I heard before. Maybe it WAS just the
>result of a particular kind of resonance after all, as Larry suggested.
>
>Anyway, that's all I know for now. I realize this thread belongs as much in
>r.a.owning as it does here, but I haven't been following that newsgroup, and
>it seems on-topic here too, so here it is. Thanks for those who showed
>interest...I hope it wasn't too much of a letdown to not find out exactly
>what the problem was after all. I guess a theory is better than nothing.
>:)
>
>Pete
>

[Paul Sengupta]

"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]

"Peter Duniho" > wrote in message
...
> Thanks for those who showed
> interest...I hope it wasn't too much of a letdown to not find out exactly
> what the problem was after all. I guess a theory is better than nothing.
> :)

Well, anything which turns out to not be a problem, or is cheap to
fix is worth knowing for the rest of us in case we experience it!

Paul

[Peter Duniho]

"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]

"Paul Sengupta" > wrote in message
...
> Well, anything which turns out to not be a problem, or is cheap to
> fix is worth knowing for the rest of us in case we experience it!

I'm just sorry I don't have anything more specific. Granted, that's not
entirely unheard of. Transient problems do sometimes remain simply that:
transient, never to appear again. And of course there's always the "happens
every now and then, but not with enough regularity to diagnose" kinds of
problems.

Even so, I'm always a little more comfortable when I can point to something
and say for sure, "that was the problem". Seems so much more settled that
way. :)

And frankly, I wouldn't want this particular experience to encourage other
pilots to ignore their "gut reaction" to anomalies. Even after all of this,
with all of the added hassle involved in the follow-up to my aborting the
flight (my rough guess is about 16 man-hours of wasted time, most my own),
I'm happy with my decision, and would do it again if I ever had that feeling
again.

Pete

[Paul Sengupta]

"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