Shock Cooling a myth?

They don’t address the reason why shock cooling can be bad. And shock heating is not the same as shock cooling.
While I think shock cooling for NA engines is a myth, but turbos on the other hand...I can imagine it could be a problem. And the difficulty in knowing whether shock cooling could have caused the problem is the problem might not be discovered until many flights later.
 
MooneyDriver78 said:
They don’t address the reason why shock cooling can be bad. And shock heating is not the same as shock cooling.
While I think shock cooling for NA engines is a myth, but turbos on the other hand...I can imagine it could be a problem. And the difficulty in knowing whether shock cooling could have caused the problem is the problem might not be discovered until many flights later.
Click to expand...

I flew TSIO540VBs for a couple of years as a Cape Air captain (turbines now)

We ran those engines 2700 hours before overhaul and worked em silly hard and slam dunked em all the time. They flew in ridiculous wx hot and cold. They were just fine...

770aa92ae046bd1c97502a5ea3470b3b.jpg



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MooneyDriver78 said:
They don’t address the reason why shock cooling can be bad. And shock heating is not the same as shock cooling.
While I think shock cooling for NA engines is a myth, but turbos on the other hand...I can imagine it could be a problem. And the difficulty in knowing whether shock cooling could have caused the problem is the problem might not be discovered until many flights later.
Click to expand...
Why would a turbo be different?

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Cylinder pressures, thus heat, are greater with a turbo. When you pull the throttle(s) you are radically decreasing pressures and temps, making for much more pressure delta in a short amount of time. With no turbo, the pressures and heat is less to begin with, so when you yank the throttle the pressure and heat delta is less.
 
mwagg737 said:
Why would a turbo be different?
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Because a turbo doesn’t lose power as it climbs, and generally fly higher, in the light levels were the air is much cooler. So bigger delta between cooling air/rain and hot cylinders.
 
gsengle said:
I flew TSIO540VBs for a couple of years as a Cape Air captain (turbines now)

We ran those engines 2700 hours before overhaul and worked em silly hard and slam dunked em all the time. They flew in ridiculous wx hot and cold. They were just fine...
Click to expand...
But how often did they need to replace the cylinders?
This is only a cylinder problem.
 
MooneyDriver78 said:
But how often did they need to replace the cylinders?
This is only a cylinder problem.
Click to expand...

Very rare. Only heard of one cyl prob ever (cracked valve)... Those planes prob averaged 5 hours a flying a day 365 days a year...


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gsengle said:
Very rare. Only heard of one cyl prob ever (cracked valve)... Those planes prob averaged 5 hours a flying a day 365 days a year...
Click to expand...
In the old days, they used to assemble cylinders by hand. I wonder if this problem was confined to certain engine manufacturer or certain engines.
 
MooneyDriver78 said:
Because a turbo doesn’t lose power as it climbs, and generally fly higher, in the light levels were the air is much cooler. So bigger delta between cooling air/rain and hot cylinders.
Click to expand...
I will grant you that, but my question comes in the fact that CHT doesn't really change. Most airplanes, even with the turbo, easily sit on the 350 to 400 range.
Is it possible, even in the flight levels, to be able to cool the cylinders faster than the 50° per minute? Does it cool off faster once you shut the engine down? What about if you shut the engine down and it's negative 30 outside?
I know there are some empirical data with the TLS's and cracked cylinders, but I believe that was the IO 360 in the TLS and it had other problems.
I'm all for treating my engine well, and I do ease the power back simply because I think it's easier on a motor and mechanical things not to make rapid changes, but color me skeptical about the ability to do damage by pulling power even in cold temperatures.

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LOL. Someone posted this article on FB today too.

I’ll copy my reply there, here...

Standby. I need a minute and thirty seconds.

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mwagg737 said:
I will grant you that, but my question comes in the fact that CHT doesn't really change. Most airplanes, even with the turbo, easily sit on the 350 to 400 range.
Is it possible, even in the flight levels, to be able to cool the cylinders faster than the 50° per minute? Does it cool off faster once you shut the engine down? What about if you shut the engine down and it's negative 30 outside?
I know there are some empirical data with the TLS's and cracked cylinders, but I believe that was the IO 360 in the TLS and it had other problems.
I'm all for treating my engine well, and I do ease the power back simply because I think it's easier on a motor and mechanical things not to make rapid changes, but color me skeptical about the ability to do damage by pulling power even in cold temperatures.
Click to expand...
If descending into very cold rain, I wonder how quickly the heads can cool?
It’s not like an ice cube that cracks when dump into warm liquid, it’s more about uneven heating of the cylinders which are 2 pieces, the barrel remains hot and expands , the head cools and contracts, and if too tight may crack.
I don’t know if it’s really a problem, but I can imagine it could be and if I can avoid rapid cooling I see no reason not to, I’ll let someone else be a test pilot.
BTW, rapid heating on takeoff isn’t a problem because the cylinder is heating up evenly.
 
Shock Cooling a Myth?

If it's your engine your dealing with it's not a myth. If it's someone else's plane, then it very well might be. :)
 
gsengle said:
I flew TSIO540VBs for a couple of years as a Cape Air captain (turbines now)

We ran those engines 2700 hours before overhaul and worked em silly hard and slam dunked em all the time. They flew in ridiculous wx hot and cold. They were just fine...

770aa92ae046bd1c97502a5ea3470b3b.jpg



Sent from my iPhone using Tapatalk
Click to expand...

Likewise, when I flew the PA31 at Ameriflight, we ran the crap out of them.
 
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