Nasa Icing courses

And mechanical failures should have simple explanations, no? WHY did
one of the cam lobes fail? Why didn't ALL of the cam lobes fail?

Timeless issue. www.aviationconsumer.com has hours of reading on the
subject. The common factor is infrequent flying.

I suppose the *real* issue should be: Why do camshafts work at all? When
you sit down and rationally analyze what is happening inside your engine,
the danged thing should just throw itself to pieces in the first ten minutes
of operation.

Yet, most of them don't.

Some, however, like Ray's engine, do -- and in very peculiar ways. (Just
ONE cam lobe went bad?)

Why?
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

I wonder if there is any statistical evidence on this issue regarding
incidences per region?

Are planes out here in the desert SW less prone to this?

Just wondering out loud...

That would be an interesting study. It might tell how much of a factor
condensation is.
--
Jim in NC

"Jay Honeck" wrote

Some, however, like Ray's engine, do -- and in very peculiar ways. (Just
ONE cam lobe went bad?)

Why?

Could it be a bad part? Nah!!! Lycosarus never makes a bad part! Not!
--
Jim in NC

On Sun, 08 Jan 2006 13:45:12 GMT, Jay Honeck wrote:

Or, put another way, it's four 1-hour hamburger flights per week, every
week, all year long...

Is this slightly low Jay? 1/2 hour each way? My hamburger runs are
minimum 1 hour each way, which would reduce it to 2 hamburger flights per
week.

You are right, 200 hours a year is an awful lot of flying. You had me
curious for me, how much in a year I fly, and it was as follows:

2001 11.7
2002 49.5
2003 142.2
2004 192.9
2005 126.4
2006 4.0

I try to fly once a week at minimum myself and no less then one hour air
time when I fly.

I was told ground runs is one of the worst things you can do to an airplane
engine, as it was designed for sustained high RPM operations, not ground
run RPMS.

Allen

I was told ground runs is one of the worst things you can do to an airplane
engine, as it was designed for sustained high RPM operations, not ground
run RPMS.

You know, I've heard that since Day One of ownership, too, but ya just
gotta wonder if it's not yet another "old wive's tale", like so many of
these "tried and true" things. How does the engine know the
difference between ground runs at, say 2000 RPM (run-up speed on our
plane) and an extended descent? Is *that* "bad" for the engine, too?

Doesn't running it for 30 minutes on the ground circulate the oil, and
prevent corrosion? Can't you get oil temps up to 150 or better (I
know, 180 is optimal, but...) with a ground run? Isn't that better
than letting it sit and rot till spring?

I fly too often for this to really matter, but I always wonder if it's
a real issue or not? Kinda like "shock cooling" and "pulling the prop
through" before starting on a cold day... And Marvel Mystery oil,
while we're at it...

:-)
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

On 1/8/2006 5:51 AM, Jay Honeck wrote:

And mechanical failures should have simple explanations, no? WHY did
one of the cam lobes fail? Why didn't ALL of the cam lobes fail?

Timeless issue. www.aviationconsumer.com has hours of reading on the
subject. The common factor is infrequent flying.

I suppose the *real* issue should be: Why do camshafts work at all? When
you sit down and rationally analyze what is happening inside your engine,
the danged thing should just throw itself to pieces in the first ten minutes
of operation.

Yet, most of them don't.

Some, however, like Ray's engine, do -- and in very peculiar ways. (Just
ONE cam lobe went bad?)

Why?

I wonder if this was the first cam lobe to actually fail. Have they all
been measured and determined to be within spec?

--
Mark Hansen, PP-ASEL, Instrument Airplane
Sacramento, CA

Strictly my opinion -

Your bad lobe is one of the cam lobes that operates two lifters, so it,
or its companion will be the first to go in a marginal lubrication
situation. The lobes depend on oil thrown from the crankshaft cheeks -
some thing that I don't think happens for a couple of minutes after a
cool start - especially with a cold engine.

It isn't a question of how quickly does the oil pump get oil get to the
cam bearings as journal bearings will retain enough oil to allow them
to be starved for a minute or two and oil gets there in a few seconds
anyway.

More critical though is how quickly does the crankcase develop that
general fog/spray of oil to finally lubricate all the miscellaneous
(and expensive) surfaces such as cam lobes and cylinder bores. The cam
is at the top of the engine & the lobes are the last thing to get lube.
Possibly if the crank is turning too slow, gravity is such that thrown
blobs of oil can't even make it to the lobes until the oil; gets really
thin. Remember that a new engine will inherently have considerably
less oil leakage from the bearings.

That's why preheat is so important to a Lycoming engine. It isn't as
though it is someting that should be done (usually). It is something
that must be done religiously every time (especially with summer weight
oil) as once cam surfaces are scratched, failure isn't far away. The
longer an engine has been sitting, the more the need for preheat. The
newer the engine, the more the need for preheat too. When and how
much? Who knows.

Also - thick oil reduces the flow demand of the engine, and more of it
will simply blow over the relief valve. Oil that is bypassed this way
has no access to the heat of the engine. Oil warmup will be slow even
if the CHT is getting into an operating range.

My guess is that there was a cold start or summer oil combination
somewhere in its history although you indicated you always preheated.
Or maybe the cam which is supposed to be case hardened isn't as hard as
it should be. You might check the cam hardness with a new file on
another lobe. It should not be able to bite into it. If it does, get
a hardness test done on it.

Strictly my opinion -

Your bad lobe is one of the cam lobes that operates two lifters, so it,
or its companion will be the first to go in a marginal lubrication
situation. The lobes depend on oil thrown from the crankshaft cheeks -
some thing that I don't think happens for a couple of minutes after a
cool start - and especially with a cold engine.

It isn't a question of how quickly does the oil pump get oil get to the
cam bearings as journal bearings will retain enough oil to allow them
to be starved for a minute or two and oil gets there in a few seconds
anyway.

More critical though is how quickly does the crankcase develop that
general fog/spray of oil to finally lubricate all the miscellaneous
(and expensive) surfaces such as cam lobes and cylinder bores. The cam
is at the top of the engine & the lobes are the last thing to get lube.
Possibly if the crank is turning too slow, gravity is such that thrown
blobs of oil can't even make it to the lobes until the oil; gets really
thin. Remember that a new engine will inherently have considerably
less oil leakage from the bearings.

That's why preheat is so important to a Lycoming engine. It isn't as
though it is someting that should be done (usually). It is something
that must be done religiously every time (especially with summer weight
oil) as once cam surfaces are scratched, failure isn't far away. The
longer an engine has been sitting, the more the need for preheat. The
newer the engine, the more the need for preheat too. When and how
much? Who knows.

Also - thick oil reduces the flow demand of the engine, and more of it
will simply blow over the relief valve. Oil that is bypassed this way
has no access to the heat of the engine. Oil warmup will be slow even
if the CHT is getting into an operating range.

My guess is that there was a cold start or cool start with summer oil
combination somewhere in its history although you indicated you always
preheated. Or maybe the cam which is supposed to be case hardened
isn't as hard as it should be. You might check the cam hardness with a
new file on another lobe. It should not be able to bite into it. If
it does, get a hardness test done on it.

wrote:
On 7-Jan-2006, Ray Andraka wrote:


The engine is 26 months and 178 hours out of a new limits Penn Yan
overhaul with new ECI titan stud assemblies, new cam, new accessory
gears, new oil pump, all new accessories, etc. About all that wasn't new
was the crank and case, and those were reworked during the overhaul.



So, is Penn Yan providing the new engine at no cost, or pro-rated? Are they
picking up any of the removal/reinstallation and shipping expenses?


Well, I don't know the full story yet. It will at least be pro-rated
because I am still in the pro-rate part of the warranty period. They
cover it full for 2 years then after that it is pro-rated 40 hours/month.

Even a 1000 rpm could be a little higher than ideal. It is
hard to say what causes problems sometimes. There are
manufacturing defects, there is a possibility that an oil
passage is partially plugged. Sometimes the mechanic who
assembled the engine can have missed getting assembly lube
on the cam or journal. If it is on a cam and or lifter,
even valve spring tension will effect the load on the wear
surfaces.

Best you can do is follow the engine manufacturer's
recommendations about starting and shutdown, oil changes,
etc and save money for the unexpected work.


--
James H. Macklin
ATP,CFI,A&P

--
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But government sees it as an obstacle to be overcome.
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"Ray Andraka" wrote in message
news:mQ2wf.41528$Mi5.36676@dukeread07...
| Jim Macklin wrote:
|
| Start with the throttle 1/2 open, zero rpm to 1800 with
no
| oil pressure. Etc.
|
|
|
| No, I don't start mine like that. On shut down, I set the
throttle for
| 1000 RPM and lock it. The throttle doesn't move again
until the engine
| is warmed up. I preheat religiously below 30F, and I
don't leave the
| preheater plugged in.
|
| Also, if it were corrosion that got mine, why only one cam
lobe?? My
| mechanic tells me there have been a rash of problems with
newer cams
| with flaws in the case hardening. I haven't seen evidence
to prove it
| though.