Nasa Icing courses

"Morgans" wrote in message ...

snip

All of this would not be nearly as likely (it seems to me) if aircraft engines were equipped with rollers on the cams.
--
Jim in NC


Yes, the 'new' roller cams finally address this issue...

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"
|
|

George Patterson writes:


"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.

Saw a show w/ a Japanese craftsman making a sword. Two layers of
different steels. Pounded it thin; folded it over; pounded...
Many layers later, that was the sword...

--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

"Jay Honeck" wrote in message news:
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?)

I've gone through a couple on one engine and they had those exact symptoms.
One AME suggested that the front lobes wear more quickly since the cam is
slightly elevated at the front so the oil drains off more quickly. There
are as many theories as worn cams, it sometimes seems.

moo

"Jay Honeck" wrote in message
news:jN8wf.472265$084.362812@attbi_s22...
....
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.

The oil film, when all goes well, prevents actual metal to metal contact.
Just like the plain bearings on the crankshaft.

Google the word "tribology": WEB RESULTS 1 - 10 of about 48,500

--
Geoff
the sea hawk at wow way d0t com
remove spaces and make the obvious substitutions to reply by mail
Spell checking is left as an excercise for the reader.

The oil film, when all goes well, prevents actual metal to metal contact.
Just like the plain bearings on the crankshaft.


I had to have my engine (Lycoming O-235) overhauled last year at less than
1/2 TBO, partially for cam pitting. Prior to my owning it, it hadn't flown
too much for the past few years.

Now, I'm flying every 2 weeks, at least, if weather permits, and am using
Avblend. This additive is supposed to better impregnate the metal, and
prevent some of this corrosion.

I now have the plane in a hanger, instead of outside in the cold and added
moisture.


The few things I've heard about causing the problems a

Flying too infrequently, with oil seeping off the cam and moisture eating at
the exposed surfaces.

When flying happens, not getting the oil completely hot, so as to eliminate
the moisture from it.

Running the engine too slow at startup. Apparently, the cams in some
engines get lubrication mainly from the oil splashing around inside the
case. In some engines, 1000 RPM may not be sufficient for full lubrication
after startup. My A&P suggested 1100 - 1200 RPM.


I'm certainly hoping that the steps I'm taking will keep the engine in good
shape. I can't afford another overhaul anytime soon.

Paul Missman

"Paul Missman" wrote in message
...

....
The few things I've heard about causing the problems a

Flying too infrequently, with oil seeping off the cam and moisture eating
at the exposed surfaces.

When flying happens, not getting the oil completely hot, so as to
eliminate the moisture from it.

That's one thing that could be changed on aircraft engines that would give a
LOT of bang for the buck - positive crankcase ventilation. Huge reduction in
unburned hydrocarbons (you may or may not care about that), and a lot less
moisture in the crankcase - engines last a lot longer.

The straight up auto style PCV valve probably wouldn't be the way to go,
though. It won't get you much at higher altitudes where you have the
throttle wide open.

Running the engine too slow at startup. Apparently, the cams in some
engines get lubrication mainly from the oil splashing around inside the
case. In some engines, 1000 RPM may not be sufficient for full
lubrication after startup. My A&P suggested 1100 - 1200 RPM.

Anything's possible.


--
Geoff
the sea hawk at wow way d0t com
remove spaces and make the obvious substitutions to reply by mail
Spell checking is left as an excercise for the reader.

David Lesher wrote:

Saw a show w/ a Japanese craftsman making a sword. Two layers of
different steels. Pounded it thin; folded it over; pounded...
Many layers later, that was the sword...

Yep, that's a very old technique. Westerners call it "Damascus steel."

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

Jay Honeck wrote:

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

Why?

Once again. When the layer of hardened steel wears through, the rest of the lobe
wears *very quickly*.

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

George Patterson wrote:
David Lesher wrote:
Saw a show w/ a Japanese craftsman making a sword. Two layers of
different steels. Pounded it thin; folded it over; pounded...
Many layers later, that was the sword...

Yep, that's a very old technique. Westerners call it "Damascus steel."

Got a knife made using that technique. Beautiful grain, sort of like a
nice gun stock made with multiple layers of different wood, beautiful
when carved.

The Monk