Shock *Heating*?

It is up to those that assert there is such a thing as damage from shock
cooling and shock heating to prove it. So far all anyone has ever offered is
a small amount of anecdotal evidence: "I knew a pilot once who did this and,
sure enough, his engine quit, although it was for some other reason."

C J Campbell wrote:

It is up to those that assert there is such a thing as damage from shock
cooling and shock heating to prove it.

With the cost of engines the way it is, I suggest that the situation is exactly
the other way 'round. Until you can prove conclusively that shock cooling does
not exist, baby the engine.

George Patterson
A diplomat is a person who can tell you to go to hell in such a way that
you look forward to the trip.

With the cost of engines the way it is, I suggest that the situation is
exactly
the other way 'round. Until you can prove conclusively that shock cooling
does
not exist, baby the engine.

That's good advice -- with any engine.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

I shock heated my engines again on Sunday... This is ~ 5,800 times on the
left engine and 6,400 times on the right engine that the metal has been
taken from ambient temperature (a balmy 28f degrees sunday) to some
1200-1300 degrees F internally in ~10 milliseconds... I watched with
incredulous eyes as neither engine had a jug fly off, nor seized up, nor
started a death rattle, nor immediately dropped compressions into the
40's...

Then upon landing I reduced the throttle and watched as the EGT took some
5,000 milliseconds to to begin to decrease and the CHT's barely dropped
until I was half way back to the hangar on the taxiway... I obviously shock
cooled it into oblivion...

denny - straight from hades...

"Jay Honeck" wrote Until you can prove
conclusively that shock cooling
does
not exist, baby the engine.

That's good advice -- with any engine.
--

denny - straight from hades...

Thanks, Denny -- I couldn't have said it better myself.

I personally don't believe in either shock cooling *or* shock heating -- but
an awful lot of mechanics do.

So, I treat my engine like it's made out of glass.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

In article eTn_b.385903$na.592869@attbi_s04,
Jay Honeck wrote:

So, I treat my engine like it's made out of glass.

Oh great, now there will be a big flamewar over whether after 100 years
of sitting your glass engine would be thicker on the bottom...

--
Ben Jackson

http://www.ben.com/

Note the top posting so it is easy to read with outhouse express and you
don't have to scroll down to read the reply:

This naturally depends on how much time you spend in inverted flight or
pulling negative g's!

Hope this helps all you morons understand thatI know whatI'm taking aboutand
that the spacebar is old from postingsomanytrolls AND YOU CAN ALL GO AND GET
STUFFED!

pETER

;)

"Ben Jackson" wrote in message
news:Nwt_b.45072$Xp.200197@attbi_s54...
In article eTn_b.385903$na.592869@attbi_s04,
Jay Honeck wrote:

So, I treat my engine like it's made out of glass.

Oh great, now there will be a big flamewar over whether after 100 years
of sitting your glass engine would be thicker on the bottom...

--
Ben Jackson

http://www.ben.com/

"Jay Honeck" wrote in message
news:eTn_b.385903$na.592869@attbi_s04...
denny - straight from hades...

Thanks, Denny -- I couldn't have said it better myself.

I personally don't believe in either shock cooling *or* shock heating --
but
an awful lot of mechanics do.

So, I treat my engine like it's made out of glass.

"Shock heating" I can understand. When you start your car on a cold morning,
you don't rev the engine to 4000 RPM, do you? Same thing when you start your
airplane's engine; you don't go immediately to full throttle.

Now, spraying cold water onto your engine as soon as you taxi in would be my
idea of "shock cooling".

Not that it's gospel but....

http://www.lycoming.textron.com/supp...enCooling.html

"And finally, power-off let downs should be avoided. This is especially
applicable to cold weather operations when shock cooling of the cylinder
heads is likely. It is recommended that cylinder head temperature change not
exceed 50oF. per minute. Plan ahead, reduce power gradually and maintain
some power throughout the descent. Also keep the fuel/air mixture leaned out
during the descent. If an exhaust gas temperature gage is installed with a
normally aspirated engine, keep it peaked to insure the greatest possible
engine heat for the power setting selected; for a turbocharged installation,
lean to peak during descent unless otherwise specified in the Pilot's
Operating Handbook, or under conditions where the limiting Turbine Inlet
Temperature would be exceeded."


And from AvWeb....

http://www.avweb.com/news/maint/182883-1.html

"My own gut tells me that shock cooling-while bound to induce dimensional
changes in the engine-is not a great contributor to cylinder cracking. We
know it induces dimensional changes, because (for example) valve sticking
has been induced in some engines by sudden power reductions. (A Lycoming
Flyer article once stated: "Engineering tests have demonstrated that valves
will stick when a large amount of very cold air is directed over an engine
which has been quickly throttled back after operating at normal running
temperatures." See 101 Ways to Extend the Life of Your Engine, page 96.) But
it's a big jump to go from that to saying you can make a cylinder head crack
just by pulling the throttle back too quickly."


Given that cylinders are 1k each, I'll keep the temps up on decent when
possible. I mean how hard is it to pull back to 2,000 RPM instead of
idle??? Yeah, it's probably a waste of gas but I'm burning the cheap stuff
anyway.


Just my $.02



"Dennis O'Connor" wrote in message
...
I shock heated my engines again on Sunday... This is ~ 5,800 times on the
left engine and 6,400 times on the right engine that the metal has been
taken from ambient temperature (a balmy 28f degrees sunday) to some
1200-1300 degrees F internally in ~10 milliseconds... I watched with
incredulous eyes as neither engine had a jug fly off, nor seized up, nor
started a death rattle, nor immediately dropped compressions into the
40's...

Then upon landing I reduced the throttle and watched as the EGT took some
5,000 milliseconds to to begin to decrease and the CHT's barely dropped
until I was half way back to the hangar on the taxiway... I obviously
shock
cooled it into oblivion...

"G.R. Patterson III" wrote in message
...


C J Campbell wrote:

It is up to those that assert there is such a thing as damage from shock
cooling and shock heating to prove it.

With the cost of engines the way it is, I suggest that the situation is
exactly
the other way 'round. Until you can prove conclusively that shock cooling
does
not exist, baby the engine.

I plead guilty. Even though I do not believe in shock cooling, I admit that
I fly as if I did believe in it.

I have my limits as to how far I will go to accommodate myth and
superstition, though. I refuse to turn my cell phone off at the gas pump
even when Fred Meyer has a big sign ordering me to do it.