Nasa Icing courses

The intake cam lobe for the #3 and #4 cylinders failed and is worn down
considerably, hence the engine coming off and waiting for the crate.

I've been following your engine woes with great interest, Ray, and not a
small bit of horror. To say you are living one of my worst nightmares is
not far from the truth, and I feel your pain.

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. It's always treated like an act of God, or like a
weather phenomenon, rather than like the mechanical failure it is.

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

("Peter Duniho" wrote)
[snip]
It seems to me that airframe icing is primarily an IFR issue, possibly of
interest to people reading r.a.piloting, and hardly applicable to people
involved in their primary training (the main audience in r.a.student).


Jim (OP) has experience with people involved in their primary training.

Weather is taught to VFR primary students, why not icing?

"Clouds ......recognize and avoid!"
"T-storms ...recognize and avoid!"
"Icing ..........recognize and avoid!"


Montblack

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.

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"

"George Patterson" wrote

In the absence of some catastrophe, such as a bent pushrod, this is
generally caused by not flying enough.

Whenever I see less than 200 hours on an engine in a year, it seems like
there are tales of destruction of an engine to follow.

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

Whenever I see less than 200 hours on an engine in a year, it seems like
there are tales of destruction of an engine to follow.

???

That describes almost every privately owned aircraft at our airport. Only
trainers routinely put on more than 200 hours per year.

Mary and I fly more than anyone at the airport, and we just barely put 200
hours on last year.
--
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"
|
|

Whenever I see less than 200 hours on an engine in a year, it seems like
there are tales of destruction of an engine to follow.

???

That describes almost every privately owned aircraft at our airport. Only
trainers routinely put on more than 200 hours per year.

Mary and I fly more than anyone at the airport, and we just barely put 200
hours on last year.

Really? I would have thought you put far more than that on, per year.

OK, then perhaps it is the frequency of being well warmed up that is the
more important factor. I have always read that the moisture that is the
killer, and when engines sit for more than a couple weeks, frequently, that
the rust begins killing the internals.

I wonder what the minimum time per year, and maximum frequency of running is
necessary to keep rust at bay?

Still, I think that only rollers touching the cams would be beneficial. I
wonder how many kits have been designed to retrofit popular lycosaruses?
--
Jim in NC

"Montblack" wrote in message
...
Jim (OP) has experience with people involved in their primary training.

Weather is taught to VFR primary students, why not icing?

Because they have enough to learn already?

Seriously though, a primary student's knowledge of icing need not extend
much further than "don't fly when freezing rain is forecast". For extra
credit, a short discussion of what causes freezing rain might be called for.

Most icing occurs inside a cloud, and VFR pilots should not have to worry
about that, or anything else that might happen inside a cloud.

But more importantly (and more to the point) the r.a.student newsgroup is
more about the process of learning to fly, and especially as it applies to
primary students, than it is about any random topic a pilot might be
educated on. Here's the charter:

It's been said that every good pilot is a student pilot -- for
life. This group is dedicated to learning experiences and questions,
particularly (but not exclusively) by and for those who haven't
yet attained the private pilot certificate. Written exams, solo
flights, learning to land, maneuvers, flight tests, instructors
and instructional techniques, etc.

Pete