Nasa Icing courses

There is also the fact that the oil pump is at one end of
the engine and the cam shaft lobe that fails is probably at
the other [a guess] and the oil takes some time to reach the
journal and establish a full oil bearing.

Add a little sludge, maybe some cold oil and an over-revved
engine, and you get cam lobe /journal failure or the lifter.

Pilot error due to poor operation.


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

--
The people think the Constitution protects their rights;
But government sees it as an obstacle to be overcome.
some support
http://www.usdoj.gov/olc/secondamendment2.htm
See http://www.fija.org/ more about your rights and duties.


"George Patterson" wrote in message
news:J11wf.517$sa4.41@trnddc07...
| Jay Honeck wrote:
|
| Does anyone *really* know what causes a camshaft to fail
like this? I read
| about it happening with alarming regularity, and it's
never attributed to
| anything in particular.
|
| In the absence of some catastrophe, such as a bent
pushrod, this is generally
| caused by not flying enough. The layer of hardened steel
on a camshaft is fairly
| thin. Let the plane sit long enough, and rust will form.
When the engine starts
| again, the rust is worn away, making the thin layer of
hardened steel thinner.
| The worst wear points, of course, are the tips of the
lobes. Once the hardened
| steel wears through, the softer steel underneath goes
pretty rapidly.
|
| "So why not build the shaft entirely of hardened steel?",
I hear you cry. That's
| because the harder steel is, the more brittle it becomes.
The best strength
| comes from this sort of lamination of hard and soft
steels.
|
| George Patterson
| Coffee is only a way of stealing time that should by
rights belong to
| your slightly older self.

Add a little sludge, maybe some cold oil and an over-revved
engine, and you get cam lobe /journal failure or the lifter.

Can you expand on that a bit, Jim? What, exactly, is an "over-revved
engine"?
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

Start with the throttle 1/2 open, zero rpm to 1800 with no
oil pressure. Etc.


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

--
The people think the Constitution protects their rights;
But government sees it as an obstacle to be overcome.
some support
http://www.usdoj.gov/olc/secondamendment2.htm
See http://www.fija.org/ more about your rights and duties.


"Jay Honeck" wrote in message
newsb1wf.471788$084.269539@attbi_s22...
| Add a little sludge, maybe some cold oil and an
over-revved
| engine, and you get cam lobe /journal failure or the
lifter.
|
| Can you expand on that a bit, Jim? What, exactly, is an
"over-revved
| engine"?
| --
| Jay Honeck
| Iowa City, IA
| Pathfinder N56993
| www.AlexisParkInn.com
| "Your Aviation Destination"
|
|

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.

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

--
The people think the Constitution protects their rights;
But government sees it as an obstacle to be overcome.
some support
http://www.usdoj.gov/olc/secondamendment2.htm
See http://www.fija.org/ more about your rights and duties.


"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.

Start with the throttle 1/2 open, zero rpm to 1800 with no
oil pressure. Etc.

I aim to keep RPMs at 1000 (or less) from start-up to run-up. (My A&P
showed me that 1000 RPM is too low to kick up stones, so being patient and
taxiing slowly really saves your prop.)

What do you think causes a problem like Ray's, Jim? It just seems to, I
don't know -- random.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

Low rpm does save the prop, it also keeps the load on the
bearings a little less, throttle jockeying is worst, cold
oil doesn't flow quickly in response to throttle changes.
Also, if you have a constant speed prop, the governor uses
engine oil, so avoid taxing the oil pressure with rpm and /
or prop changes until the oil has had a chance to warm up a
little.

It also came to mind, that a sticking valve will cause more
wear on that cam/lifter assembly, so that can be a problem
to check.

Most engines have the oil pump at one end and oil pressure
is measured from a point on the other end, probably a cam
shaft gallery so that you can tell that oil passages are not
blocked. That is one reason for the "shutdown in 30
seconds" if you don't have oil pressure on starting note.

I like to idle an engine for a minute (4-5 minutes with
turbocharged engine) to allow it to cool before shutdown
while still having oil cooling. This would be at
1,000-1,200 rpm so the prop would be blowing some air
through the cowl. I then think it is a good idea to
throttle back to minimum rpm, to see that the idle is smooth
at 500-700 rpm range and I do a mag grounding check at that
point and then pull the mixture to shut it down. That
should show a slight 25-50 rpm increase just as it shuts
down since idle should be a little rich.

I start the engine at minimum throttle and using as little
priming as possible [wait after priming a few seconds to a
minute in cold weather to allow the fuel to vaporize, liquid
doesn't burn and it washes the oil off the cylinder walls]
then after it starts, advance the throttle smoothly to 1000
rpm to get some prop wash cooling and generator output.

Change to oil often, it is a lot cheaper to change the oil
than to tear down the engine. Use the best oil you can find
and the multi-weight oils do start working/ pumping faster.
Oil changes can be done by the pilot/owner as preventative
maintenance. A logbook entry is required and you must
follow the service manual procedures. Be sure to check for
leaks after the change and be sure to safety any drain
plugs. A quick drain system makes it a lot easier to do,
and an extension hose on the drain will keep the cowl clean.
Filters may not need to be changed every time if the oil
change is due to calendar time and condensation draining.
The oil filter does work on engine time in service since it
only functions when the oil is flowing and being filtered.
But follow the manual, if it says change the filter with
every oil change, you should do so.


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

--
The people think the Constitution protects their rights;
But government sees it as an obstacle to be overcome.
some support
http://www.usdoj.gov/olc/secondamendment2.htm
See http://www.fija.org/ more about your rights and duties.


"Jay Honeck" wrote in message
news:_J8wf.714011$xm3.343650@attbi_s21...
| Start with the throttle 1/2 open, zero rpm to 1800 with
no
| oil pressure. Etc.
|
| I aim to keep RPMs at 1000 (or less) from start-up to
run-up. (My A&P
| showed me that 1000 RPM is too low to kick up stones, so
being patient and
| taxiing slowly really saves your prop.)
|
| What do you think causes a problem like Ray's, Jim? It
just seems to, I
| don't know -- random.
| --
| Jay Honeck
| Iowa City, IA
| Pathfinder N56993
| www.AlexisParkInn.com
| "Your Aviation Destination"
|
|

"Jim Macklin" wrote in message
news:Wgcwf.40975$QW2.5751@dukeread08...
point and then pull the mixture to shut it down. That
should show a slight 25-50 rpm increase just as it shuts
down since idle should be a little rich.


For my TIO540-S1AD, Lycoming says five rpm, not more than ten.

Stan

I'll buy that, always best to use specific data rather than
a generic answer. It takes a pretty good eye and tach to
see 5 rpm.


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

--
The people think the Constitution protects their rights;
But government sees it as an obstacle to be overcome.
some support
http://www.usdoj.gov/olc/secondamendment2.htm
See http://www.fija.org/ more about your rights and duties.


"Stan Prevost" wrote in message
...
|
| "Jim Macklin" wrote
in message
| news:Wgcwf.40975$QW2.5751@dukeread08...
| point and then pull the mixture to shut it down. That
| should show a slight 25-50 rpm increase just as it shuts
| down since idle should be a little rich.
|
|
| For my TIO540-S1AD, Lycoming says five rpm, not more than
ten.
|
| Stan
|
|

Stan Prevost wrote:
"Jim Macklin" wrote in message
news:Wgcwf.40975$QW2.5751@dukeread08...

point and then pull the mixture to shut it down. That
should show a slight 25-50 rpm increase just as it shuts
down since idle should be a little rich.

For my TIO540-S1AD, Lycoming says five rpm, not more than ten.

The mixture on injected engines typically is not as rich at idle as carburetted
engines, so the rpm increase should not be as great.

George Patterson
Coffee is only a way of stealing time that should by rights belong to
your slightly older self.