Cracked cylinder: Typical cause?

[Peter R.]

What would be the most likely reason a cylinder in a high-time engine
would crack, old-age or poor temperature management on a descent?

--
Peter

[kage]

Neither


"Peter R." > wrote in message
...
> What would be the most likely reason a cylinder in a high-time engine
> would crack, old-age or poor temperature management on a descent?
>
> --
> Peter
>
>
>
>
>

[Peter R.]

kage ) wrote:

> Neither

Sorry for asking a close-ended question. If you could expand on your
"neither," this rather inexperienced poster could learn something.

--
Peter

[Jim Weir]

Lousy Continental engineering.

Jim

Peter R. >
shared these priceless pearls of wisdom:

->What would be the most likely reason a cylinder in a high-time engine
->would crack, old-age or poor temperature management on a descent?



Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com

[Aaron Coolidge]

Peter R. > wrote:
: What would be the most likely reason a cylinder in a high-time engine
: would crack, old-age or poor temperature management on a descent?

Pull power, full rich, shove nose over. Guy parked next to me has an
Archer, flies maybe 100 hours/year. Goes through at least one cylinder/year,
sometimes 2 or 3. That's his secret: at the top of descent he pulls power
to idle, goes to full rich, and shoves the nose over. Please note that
the full rich bit is required to properly master cylinder cracking. If you
leave the mixture alone until level-off you'll not have any trouble. Better
yet if you leave both the throttle and mixture alone.

You should have heard this guy going on at Oshkosh. He visited each cylinder
vendor that he's tried and they all suggested that he leave the mixture leaned.
He wasn't interested in their viewpoint, he just wanted to beat them up
about lousy quality.
--
Aaron Coolidge

[John_F]

The answer is primarily "metal fatigue" and design margins.

For steel if the stress is below about 15% of ultimate yield then it
does not fatigue. However the lower fatigue limit for aluminum is
ZERO. Aluminum always fatigues no matter what the stress level is.
Every time the cylinder fires the steel barrel and the aluminum head
gets a stress cycle. The stress is proportional to the peak cylinder
pressure which varies with power output of the engine. The number of
cycles to failure verses stress level is not linear. Since it is non
linear if you design a part that is subject to cyclic stress then
half the stress it will last much more than two times as long before
it cracks.

If you buy a rebuilt cylinder you do not know if it has 500 hours or
5000 hours. You also can not always tell if it has already cracked
and been welded.

In my opinion flying through a rain storm would shock cool a cylinder
MUCH faster than a sudden power reduction.

(This is my opinion and I am sticking to it until I have test data to
indicate otherwise.)
John


On Sat, 2 Oct 2004 10:35:36 -0400, Peter R. >
wrote:

>What would be the most likely reason a cylinder in a high-time engine
>would crack, old-age or poor temperature management on a descent?

[Dan Thomas]

"kage" > wrote in message >...
> Neither
>

Oh, come on. Cylinders suffer from age-related thermal damage
just like any other metal machinery that's subjected to heat.
Detonation can also be a factor in such cases.

Dan

>
> "Peter R." > wrote in message
> ...
> > What would be the most likely reason a cylinder in a high-time engine
> > would crack, old-age or poor temperature management on a descent?
> >
> > --
> > Peter
> >
> >
> >
> >
> >

[Jay Honeck]

> If you buy a rebuilt cylinder you do not know if it has 500 hours or
> 5000 hours. You also can not always tell if it has already cracked
> and been welded.

Why in the world would anyone buy a rebuilt cylinder nowadays?

The price differential between new and used is so small -- and the risks are
just too great.

Heck, I wouldn't put a rebuilt cylinder on my CAR (not that any such thing
is ever necessary on modern automobiles), let alone an airplane.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

[The Weiss Family]

> Why in the world would anyone buy a rebuilt cylinder nowadays?
>
> The price differential between new and used is so small -- and the risks
are
> just too great.
>
> Heck, I wouldn't put a rebuilt cylinder on my CAR (not that any such thing
> is ever necessary on modern automobiles), let alone an airplane.
> --
> Jay Honeck
> Iowa City, IA
> Pathfinder N56993
> www.AlexisParkInn.com
> "Your Aviation Destination"
>

On a similar note, if a cylinder compression was low, would you rebuild it,
or buy a new one?

Adam

[Michael]

Peter R. > wrote
> What would be the most likely reason a cylinder in a high-time engine
> would crack, old-age or poor temperature management on a descent?

While both are possible, neither is most likely.

When considering what causes an aviation problem, you need to consider
what aspect is most under the control of the FAA. That will be the
biggest problem.

In this case, the FAA controls design (through the awarding of a type
certificate or STC or writing the TSO) and manufacturing/quality
control (through the awarding of a production certificate or PMA) so
those are in fact the two most likely reasons for cylinder cracking -
poor design and poor QC.

Michael

[Jay Honeck]

> On a similar note, if a cylinder compression was low, would you rebuild
> it,
> or buy a new one?

It depends. Depending on the problem, and age of the cylinder, I'd probably
still buy new.

When you look at a new Millennium cylinder, and see where they have beefed
up the areas most likely to crack, it's an easy choice.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

[Newps]

Jay Honeck wrote:

>>If you buy a rebuilt cylinder you do not know if it has 500 hours or
>>5000 hours. You also can not always tell if it has already cracked
>>and been welded.
>
>
> Why in the world would anyone buy a rebuilt cylinder nowadays?
>
> The price differential between new and used is so small

Where are you shopping? A new cylinder is about $1K. Around here
overhauled cylinders, chromed are $350.


-- and the risks are
> just too great.


>
> Heck, I wouldn't put a rebuilt cylinder on my CAR (not that any such thing
> is ever necessary on modern automobiles), let alone an airplane.

I have 6 chromed first run cylinders on my 182, can't see why you
wouldn't go that way.

[PaulH]

"Jay Honeck" > wrote in message news:<8Q38d.171959$D%.3931@attbi_s51>...
> > If you buy a rebuilt cylinder you do not know if it has 500 hours or
> > 5000 hours. You also can not always tell if it has already cracked
> > and been welded.
>
> Why in the world would anyone buy a rebuilt cylinder nowadays?
>

There does seem to be a general opinion that new Continental cylinders
are not a good buy. Both L&C seem to have lost their best
metallurgical engineers.

[TripFarmer]

But don't buy them from J & J Air parts in Texas.


Trip


In article <jic8d.168563$MQ5.108036@attbi_s52>, says...
>
>> On a similar note, if a cylinder compression was low, would you rebuild
>> it,
>> or buy a new one?
>
>It depends. Depending on the problem, and age of the cylinder, I'd probably
>still buy new.
>
>When you look at a new Millennium cylinder, and see where they have beefed
>up the areas most likely to crack, it's an easy choice.
>--
>Jay Honeck
>Iowa City, IA
>Pathfinder N56993
>www.AlexisParkInn.com
>"Your Aviation Destination"
>
>

[The Weiss Family]

"Jay Honeck" > wrote

> It depends. Depending on the problem, and age of the cylinder, I'd
probably
> still buy new.
>
> When you look at a new Millennium cylinder, and see where they have beefed
> up the areas most likely to crack, it's an easy choice.
> --
> Jay Honeck
> Iowa City, IA
> Pathfinder N56993
> www.AlexisParkInn.com
> "Your Aviation Destination"

The reason I was asking is that the plane I'm buying needed a cylinder
rebuilt, and the owner elected to have it rebuilt rather than buy a new one.
I'm sure it will be OK...but for how long?
All I can say is that the owner has been extremely agreeable.
We had that agreement that he may or may not fix anything above $500.
So far, the annual has been about $4K, and he has been more than happy to
fix everything (including the cylinder rebuild).

[Jay Honeck]

> We had that agreement that he may or may not fix anything above $500.
> So far, the annual has been about $4K, and he has been more than happy to
> fix everything (including the cylinder rebuild).

Good to hear you found a good seller.

More often we hear about the shysters...
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

[Kai Glaesner]

Adam,

> On a similar note, if a cylinder compression was low, would you rebuild
it,
> or buy a new one?

If it's low e.g. because an exhaust valve is leaking rebuilding would make
sense, would'nt it?

Regards

Kai

[Newps]

> Adam,
>
>
>>On a similar note, if a cylinder compression was low, would you rebuild
>
> it,
>
>>or buy a new one?

If you have a bad valve there's no rebuilding to do. You put in a new
valve and go flying.

[Doug]

With everyone criticizing Lycoming and Continental, I will point out a
couple of items. I have Lycoming 1996 0-360 in my Husky. Since NEW, it
has 2200 tach time (about 2600 Hobbs). No oil usage, no metal in the
filter, oil analysis is good and makes above 70 on the compression.
Goes as fast and climbs as well as when new. Engine has never had any
engine components serviced. (accessories like alternator, yes).

I know of a certain government aircraft (two actually), Cessna 185's
that have AWAYS made TBO. They automatically replace the engine at TBO
with Continental factory rebuilt. They have gone through 6 engines
over the years, and EVERY engine has made TBO without cylinder
replacments. The 185 engines are notorious for cracked cylinders.

Then I hear of rebuilt engines from whoever, cracked cylinders,
rebuilt cylinders etc. But the above are factory Lycoming and factory
Continental. All stock factory components. And they did just fine.

[Newps]

Doug wrote:

> With everyone criticizing Lycoming and Continental, I will point out a
> couple of items. I have Lycoming 1996 0-360 in my Husky. Since NEW, it
> has 2200 tach time (about 2600 Hobbs). No oil usage, no metal in the
> filter, oil analysis is good and makes above 70 on the compression.
> Goes as fast and climbs as well as when new. Engine has never had any
> engine components serviced. (accessories like alternator, yes).

Lyc's last a long time. But look at the prices of new ones from the
factory, they are more than two and a half times the cost of a similar
Continental. This is because Lyc is recouping the cost of their
crankshaft debacle of a couple years ago. The cost of a new Cessna 206
could be reduced by 80 Grand if they simply switched back to a Continental.


>
> I know of a certain government aircraft (two actually), Cessna 185's
> that have AWAYS made TBO. They automatically replace the engine at TBO
> with Continental factory rebuilt. They have gone through 6 engines
> over the years, and EVERY engine has made TBO without cylinder
> replacments. The 185 engines are notorious for cracked cylinders.
>
> Then I hear of rebuilt engines from whoever, cracked cylinders,
> rebuilt cylinders etc. But the above are factory Lycoming and factory
> Continental. All stock factory components. And they did just fine.

Buddy of mine has a PA-12 with 6500 SMOH and 3500 since the last top.