Shock cooling - and related damage. is it a myth?

Kritchlow said:
Okay... but why?? Are you trolling??
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Many whys here. Trolling by me is not one of them. I am positive that you troll. I do not grasp the “why” of your trolling but that doesn’t stop me from calling you out for it.
 
Kritchlow said:
Okay... but why?? Are you trolling??
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I seem to recall a thread a couple a weeks ago in which you were the first to post a reply. Your reply contained nothing except for a statement that the original post was too long and you weren't going to read it. You often seem like a troll to me...
 
Clark1961 said:
Many whys here. Trolling by me is not one of them. I am positive that you troll. I do not grasp the “why” of your trolling but that doesn’t stop me from calling you out for it.
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I’m positiv i I have a lot to offer this forum.
I don’t troll, but I came to this forum to offer advice if you just relax a bit you woud see I have a lot to of experience to add to the mix.

It still amazes me that all new pilots say they want to learn.......... yet two days later they don’t want advice from 20,000 hr ATP’s
 
dmspilot said:
I seem to recall a thread a couple a weeks ago in which you were the first to post a reply. Your reply contained nothing except for a statement that the original post was too long and you weren't going to read it. You often seem like a troll to me...
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Huh????!!
 
Kritchlow said:
I’m positiv i I have a lot to offer this forum.
I don’t troll, but I came to this forum to offer advice if you just relax a bit you woud see I have a lot to of experience to add to the mix.

It still amazes me that all new pilots say they want to learn.......... yet two days later they don’t want advice from 20,000 hr ATP’s
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Got it. You troll because you are a 20k hour atp. Good enough.
 
Kritchlow said:
U

Exactly. And you troll because you are a dick.
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Thank you for admitting that you troll. I do not troll because that is against forum rules. Perhaps you should adjust your approach to this forum and actually read and attempt to understand other folks’ posts. Then again maybe you think everyone is beneath you and only worthy of being trolled.
 
Clark1961 said:
Thank you for admitting that you troll. I do not troll because that is against forum rules. Perhaps you should adjust your approach to this forum and actually read and attempt to understand other folks’ posts. Then again maybe you think everyone is beneath you and only worthy of being trolled.
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Whatever. Truthfully both you and I are both considered dicks on this forum.
Beyond what others think.... you will always be the apple in my eye there big boy....

Call me.
 
Kritchlow said:
Whatever. Truthfully both you and I are both considered dicks on this forum.
Beyond what others think.... you will always be the apple in my eye there big boy....

Call me.
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I understand your position and that you mistakenly think others have the same position. It’s unfortunate but incurable. Sorry.
 
Keep it down children or we’ll be having some banhammering going on.
 
Back to the shock cooling thread.
I was taught to limit CHT cooling to 1 degree per second.
 
FORANE said:
Back to the shock cooling thread.
I was taught to limit CHT cooling to 1 degree per second.
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Although that's a good practice....from a pure science point of view....the "material limits" is what needs your focus.

500-550F seems to be the place where the Aluminum begins to yield or soften. That translates to +450 F at the point (probe location) of temperature measurement (either the plug or the bayonet location - slightly cooler than the plug).

Thermal stress cycling is another issue to consider....and limiting the max temps helps lower this stress on the s/n curve....which is why many of us limit the max CHT to 370-380F. The 370-380F lowers the thermal stress cycling. The rate of cooling does not appear to affect this stress.

The problem folks have is....that one or two times at these elevated temps (+450 F) appears to not affect anything. And it might not, but, repeated trips to those temps does raise stress in the materials and creates cracks that grow and eventually will cause a failure....if not valves to warp and burn.
 
And Sixie has the whole point. But I don’t care how anyone operates their engines. And if I’m flying someone else’s plane I’ll fly it however they want me to. Back in Navajo days it was “We’re in a hurry.” Sure thing boss.

What I don’t get is why so many care how everyone else wants to run their engines.
 
I took some notes a couple of days back about shutting down the engine and it's impact on CHT. After landing, 1 mile of taxi, then shut down, then I called the line guys, waiting 10 mins for them, then enjoyed the view of them filling up the tanks and pushing the plane back to the hangar at -10F while sitting in a warm car, then I went inside, turned on JPI to get the data dump, and saw CHTs still in 100 degree range. I would guess the CHTs were about 300 degrees or less when I landed. So yah, 100 degree per min after shutdown is definitely not true. The engine was still pretty warm.

Sent from my SM-G935V using Tapatalk
 
WannFly said:
then enjoyed the view of them filling up the tanks and pushing the plane back to the hangar at -10F while sitting in a warm car,
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That is just funny right there..!!! Did you roll the window down 1/16 of an inch and offer a dollar tip..??? :lol::lol:
 
Zeldman said:
That is just funny right there..!!! Did you roll the window down 1/16 of an inch and offer a dollar tip..???
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Naaaah.. am just too mean, I did say thank you though, not sure if they heard

Sent from my SM-G935V using Tapatalk
 
Checkout_my_Six said:
500-550F seems to be the place where the Aluminum begins to yield or soften. That translates to +450 F at the point (probe location) of temperature measurement (either the plug or the bayonet location - slightly cooler than the plug).

Thermal stress cycling is another issue to consider....and limiting the max temps helps lower this stress on the s/n curve....which is why many of us limit the max CHT to 370-380F. The 370-380F lowers the thermal stress cycling. The rate of cooling does not appear to affect this stress.

The problem folks have is....that one or two times at these elevated temps (+450 F) appears to not affect anything. And it might not, but, repeated trips to those temps does raise stress in the materials and creates cracks that grow and eventually will cause a failure....if not valves to warp and burn.
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The same guy who taught me the 1 degree per second also taught me to never exceed 400 CHT saying that aluminum began to soften above 400 (even though lycoming has redline of 500). He also taught that once below 300 CHT that rate of cooling wasn't a concern. That instructor was the Lancair instructor (one of very few approved by Lancair at the time) who was former airline pilot, former USAF IP, former corporate pilot, gold seal instructor, etc...
 
Why is there any debate at all? Telling others how I do things doesn't mean I'm right and they're wrong. It's just how I do things. If we don't share experience and what we've learned from it there's little point to these forums other than for some guys to wag their johnsons at each other.
 
The engine stopped running at 1,000 ft and about 300ish yards from the end of the runway, and no parts fell off. After I stopped rolling, I restarted it and taxied back.
I didn't close the door on the Cub while taxiing.
I think some of my parts fell off.
Here endeth the PIREP.
 
Checkout_my_Six said:
Although that's a good practice....from a pure science point of view....the "material limits" is what needs your focus.

500-550F seems to be the place where the Aluminum begins to yield or soften. That translates to +450 F at the point (probe location) of temperature measurement (either the plug or the bayonet location - slightly cooler than the plug).

Thermal stress cycling is another issue to consider....and limiting the max temps helps lower this stress on the s/n curve....which is why many of us limit the max CHT to 370-380F. The 370-380F lowers the thermal stress cycling. The rate of cooling does not appear to affect this stress.

The problem folks have is....that one or two times at these elevated temps (+450 F) appears to not affect anything. And it might not, but, repeated trips to those temps does raise stress in the materials and creates cracks that grow and eventually will cause a failure....if not valves to warp and burn.
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I didn’t think it had to do with absolute temperatures, but the super cooled head shrinks, the hot cylinder has expanded and the result is a cracked head.
 
Kritchlow said:
Huh????!!
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You were arguing about what happened in the "JetBlue Pilot Assists Cirrus Pilot" thread. When the JetBlue Pilot himself posted, you replied:

"Likely good info, but too long to read."
 
teejayevans said:
I didn’t think it had to do with absolute temperatures, but the super cooled head shrinks, the hot cylinder has expanded and the result is a cracked head.
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I've not heard anything scientific that supports that concept....maybe if you tried to super cool it...and shock it with liquid nitrogen, used in MilSPec thermal shock tests....but, it would take more than just cold air.
 
Timbeck2 said:
Seems to me that those of you with CHT and MP monitors, worry the most about shock cooling. Myself, I have neither so I don't worry about it. ;)
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You joke about that, but you just described my operating experience and philosophy over three engines (Conti O-200,Lyco O-320, angled Lyco IO-360) and whatever many hours. They all liked WOT, none had internal temp gauges of either kind. They all hummed along, haven't exploded into 13 pieces inflight yet. Hell, no oil samples either.

I dunno, maybe my work airplane has me desensitized about what others view as life-threatening operating practices. :D Joking aside, I know my lane and I know myself. I have no business flying a turbo piston installation. That's too much babying and tinkering for my recreational taste. Case and point, Seneca II cockpit picture:

upload_2018-1-15_14-30-35.png

I keed I keed. :D
 
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hindsight2020 said:
You joke about that, but you just described my operating experience and philosophy over three engines (Conti O-200,Lyco O-320, angled Lyco IO-360) and whatever many hours. They all liked WOT, none had internal temp gauges of either kind. They all hummed along, haven't exploded into 13 pieces inflight yet. Hell, no oil samples either.

I dunno, maybe my work airplane has me desensitized about what others view as life-threatening operating practices. :D Joking aside, I know my lane and I know myself. I have no business flying a turbo piston installation. That's too much babying and tinkering for my recreational taste. Case and point, Seneca II cockpit picture:

View attachment 59310

I keed I keed. :D[/QUOte

Must be an MEI: he looks comfortable in the right seat.
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Checkout_my_Six said:
I've not heard anything scientific that supports that concept....maybe if you tried to super cool it...and shock it with liquid nitrogen, used in MilSPec thermal shock tests....but, it would take more than just cold air.
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Well that’s how they are manufactured, doing the opposite by freezing the cylinder, heating the head in an oven so when they equalize it’s a permanent fit. So I can at least imagine it happening but yes, maybe adding some super cooled precipitation might do it.
We need data on cracked cylinder heads, I’m betting they show up on turbocharged planes flown high.
 
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