Shock Cooling - Myth Busted!!
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No, not really, I never had the question. However you read all sorts of threads on prune, some not in D&G which are less well informed, and folk spruik on with all manner of old wives tales, and the punters reading believe it. So facts and data are pretty good to see, and very few actually get to see it. I am fortunate, not just in what I see on my own EMS but from other sources, so it is only fair to share good facts and data when they come along.
I sent this data file complete to Mr Deakin and co as well, JD was delighted with all the other data that you just don't get from a JPI. So why not share it here. His reply started with "we're convinced
" so I figure that was good enough!
Getting onto your anecdotal story, and I do not mean that in a derogatory manner, as I believe you when you say what you saw and was told. However as remoak has pointed out already that has always been the "claim from the mechanics".
I did refer to John Deakins articles of years gone by, and while he rightly says that getting an engine REALLY Hot, and then diving at the ground, may have some negative effect, and possibly the ag ops you refer to could be less than optimal for an nine, the vast majority of flying does not involve this.
Lets look at the scenario you describe.
> Ag plane, rough and ready, but perhaps with poor baffles and maybe fuel delivery. Without proper instrumentation you would never know.
>Climb out temps, and operating temps. Again you would never know, and it is my opinion only that this is where the damage was done. It is the opinion of others as well. but again, no data to prove one way for sure.
If the cycles of shock cooling were real, why do so many flying school aircraft not suffer from it? And they are all operated sub optimal.
I think it was most likely, given the vast data and knowledge that we have today, that the genuine observations of your ag engineers of yesteryear while valid were misguided into believing the descent was to blame. Knowing what we know now, and seeing lots of good data, it is most likely what you describe was the takeoff and delivery phase.
So maybe it involves a rethink to dropping/glider ops in order to extend life.
It is a bit like the exhaust valve failures of TCM's for the last 10-15 years, all blamed on LOP operations, even when some engines never ever went LOP. It was never about mixture and all about the reaming of the valve guides and accuracy of the fit of valve to seat.
nitey nite!
Quote:
It is pretty hard to shock cool and engine that is already cool!
Do you think that perhaps you have answered your own query??
It is pretty hard to shock cool and engine that is already cool!
Do you think that perhaps you have answered your own query??
I sent this data file complete to Mr Deakin and co as well, JD was delighted with all the other data that you just don't get from a JPI. So why not share it here. His reply started with "we're convinced
" so I figure that was good enough!Getting onto your anecdotal story, and I do not mean that in a derogatory manner, as I believe you when you say what you saw and was told. However as remoak has pointed out already that has always been the "claim from the mechanics".
I did refer to John Deakins articles of years gone by, and while he rightly says that getting an engine REALLY Hot, and then diving at the ground, may have some negative effect, and possibly the ag ops you refer to could be less than optimal for an nine, the vast majority of flying does not involve this.
Lets look at the scenario you describe.
> Ag plane, rough and ready, but perhaps with poor baffles and maybe fuel delivery. Without proper instrumentation you would never know.
>Climb out temps, and operating temps. Again you would never know, and it is my opinion only that this is where the damage was done. It is the opinion of others as well. but again, no data to prove one way for sure.
If the cycles of shock cooling were real, why do so many flying school aircraft not suffer from it? And they are all operated sub optimal.
I think it was most likely, given the vast data and knowledge that we have today, that the genuine observations of your ag engineers of yesteryear while valid were misguided into believing the descent was to blame. Knowing what we know now, and seeing lots of good data, it is most likely what you describe was the takeoff and delivery phase.
So maybe it involves a rethink to dropping/glider ops in order to extend life.
It is a bit like the exhaust valve failures of TCM's for the last 10-15 years, all blamed on LOP operations, even when some engines never ever went LOP. It was never about mixture and all about the reaming of the valve guides and accuracy of the fit of valve to seat.
nitey nite!
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SHOW ME THE DATA
Wannabe biggles..... some radials have different issues, nothing to do with cooling so please do not confuse the issues
facts and data........Wannabebiggles aid about repeated data.......come on mate, John Deakin has been writing about this stuff for 10-15 years. His data has come from not just an amazing career in pitons (flat and radial) and jets but also from being involved as an unpaid test customer of GAMI/TAT and involved in the only decent pilot education program on the planet.
So this i just Jaba proving many many many years of other proven science, by those approved to test and those who do FAA approved testing. This is no way a java revelation. Just proving known facts, and those still surrounded in folklore myths (OWT's).
Hey ranga
DOGIES!!!!!!!!! \\\\ ////
Anecdotal evidence...but from a reliable source
This was from the USA, and in response to my data, just saying......
SHOW ME THE DATA
Wannabe biggles..... some radials have different issues, nothing to do with cooling so please do not confuse the issues
facts and data........Wannabebiggles aid about repeated data.......come on mate, John Deakin has been writing about this stuff for 10-15 years. His data has come from not just an amazing career in pitons (flat and radial) and jets but also from being involved as an unpaid test customer of GAMI/TAT and involved in the only decent pilot education program on the planet.
So this i just Jaba proving many many many years of other proven science, by those approved to test and those who do FAA approved testing. This is no way a java revelation. Just proving known facts, and those still surrounded in folklore myths (OWT's).
Hey ranga
DOGIES!!!!!!!!! \\\\ ////
Anecdotal evidence...but from a reliable source
I was chief pilot of a busy skydiving operation with 3 Cessna 185s which have TCM 520s. I was involved with the operation in various capacities for 25 years.
We would climb at gross mostly on hot days, always at Vy, to 11,500. Descend empty as fast as we could for the next load.
Always had good experience with cylinders, mostly because we flew alot.
Shock cooling is obviously a myth.
We would climb at gross mostly on hot days, always at Vy, to 11,500. Descend empty as fast as we could for the next load.
Always had good experience with cylinders, mostly because we flew alot.
Shock cooling is obviously a myth.
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big cracks, engineers put it down to shock cooling.
LAME's and their ilk may know how to tear down and build up engines and fix things but the majority do not conduct further in-depth reading once they have their licence. Therefore to say "engineers put it down to shock cooling" means nothing since they are personal opinions and not hard measured data.
While I listen what an LAME has to say, I also treat his opinion on engine handling with great reservations knowing it is a personal opinion only.
Jabawocky, could it not also be that in that Quote you posted, its as I was saying, its hard to do if you're taking care of the engine and doing the right things?
Obviously I think everyone can agree that Shock Cooling is a real possibility, but it seems (Keep in mind this is based on my own relatively low experience and the data from your graph) that it would mostly be caused by poorly managed engines and perhaps those with higher T/Os and LDGs cycles operated in hotter climates?
I've always wondered somewhat about the relationship between Dropships going up to say 10,000ft or more and the positives that the cooler air up there have on the engine in respect to Shock Cooling. Wouldn't it be fair to say that as you get higher that the cooler temperatures can help the engine from getting as hot as one operated lower and then, when on Jump Run, as the power is brought back, with the cowls open and the nose brought down the effects of being nice and high would allow the engine to cool somewhat before you even begin your descent?
I always remembered the worst part of any hot day was the first 5,000ft or so with the aircraft at gross and watching all the temps get waaayy waaaayyyy waaaaaayyyyyy up the dials, after that though you were usually free and clear!
Obviously I think everyone can agree that Shock Cooling is a real possibility, but it seems (Keep in mind this is based on my own relatively low experience and the data from your graph) that it would mostly be caused by poorly managed engines and perhaps those with higher T/Os and LDGs cycles operated in hotter climates?
I've always wondered somewhat about the relationship between Dropships going up to say 10,000ft or more and the positives that the cooler air up there have on the engine in respect to Shock Cooling. Wouldn't it be fair to say that as you get higher that the cooler temperatures can help the engine from getting as hot as one operated lower and then, when on Jump Run, as the power is brought back, with the cowls open and the nose brought down the effects of being nice and high would allow the engine to cool somewhat before you even begin your descent?
I always remembered the worst part of any hot day was the first 5,000ft or so with the aircraft at gross and watching all the temps get waaayy waaaayyyy waaaaaayyyyyy up the dials, after that though you were usually free and clear!
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I think its operation type dependant. Having a a gliding background, i've seen plenty of cracked cylinders.
Tug ops would have to be the worst environment. its full noise to TOC (normally 2000') normally at 60 knots. then power off and nose down for a stuka descent.
Looking at jaba's data and thinking about the other ops, most of them have a period where they are running at a lower power level.
Even meatbombers run for a period that full power is not being used. Looking at Jaba's data, the run into the drop appears to be enough time to drop the CHT's back to cruise levels.
Someone mentioned training aircraft doing laps. Same would apply as PJ ops. The run on downwind at less than full power, is enough to lower the temps to an acceptable range. And if you think about it truly, in a warrior, turning base you drop the power to 1700 rpm, which means you are still generating power/heat. Rethinking it a lil, it might not be as critical as PJ ops, as the climb is shorter so the chance of reaching max CHT lowers.
I relate this whole thread back to the one we had about turbo charger cool down.
In this case, for most operation types, it's an old OWT, however in an operation like glider tugging, it is a very real threat, and one that needs carefull management.
Tug ops would have to be the worst environment. its full noise to TOC (normally 2000') normally at 60 knots. then power off and nose down for a stuka descent.
Looking at jaba's data and thinking about the other ops, most of them have a period where they are running at a lower power level.
Even meatbombers run for a period that full power is not being used. Looking at Jaba's data, the run into the drop appears to be enough time to drop the CHT's back to cruise levels.
Someone mentioned training aircraft doing laps. Same would apply as PJ ops. The run on downwind at less than full power, is enough to lower the temps to an acceptable range. And if you think about it truly, in a warrior, turning base you drop the power to 1700 rpm, which means you are still generating power/heat. Rethinking it a lil, it might not be as critical as PJ ops, as the climb is shorter so the chance of reaching max CHT lowers.
I relate this whole thread back to the one we had about turbo charger cool down.
In this case, for most operation types, it's an old OWT, however in an operation like glider tugging, it is a very real threat, and one that needs carefull management.
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I've always wondered somewhat about the relationship between Dropships going up to say 10,000ft or more and the positives that the cooler air up there have on the engine in respect to Shock Cooling. Wouldn't it be fair to say that as you get higher that the cooler temperatures can help the engine from getting as hot as one operated lower and then, when on Jump Run, as the power is brought back, with the cowls open and the nose brought down the effects of being nice and high would allow the engine to cool somewhat before you even begin your descent?
And this next bit taken as a whole only applies to naturally aspirated,
The thing to remember, is that the by product of power production, is heat. So as you climb past Full throttle height, the amount of heat you are capable of generating lessens. Then you add in the fact you pointed out the air is cooler. So heading towards the top of climb, things are working in your favour (except climb rate). Even the best jump pilots will have 30-60 seconds of run into the drop at a reduced power level. Yes its cooling, but not at a prodigous rate, as 1. the engine is still producing power, slowing the cooling rate, and 2, still at a slow airspeed, so cold air is not being rammed through the baffles. Using jaba's graph as a guide, i wouldn't expect a jump engine to be much hotter than normal cruise once he points the nose at the ground, and CLOSES the cowl flaps to keep the heat in.
I always remembered the worst part of any hot day was the first 5,000ft or so with the aircraft at gross and watching all the temps get waaayy waaaayyyy waaaaaayyyyyy up the dials, after that though you were usually free and clear!
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IXILY and Jaz
I think if you mean getting an engine up to 475F or something stupid, and then doing a dive, it may be possible. However I doubt from basic engineering understanding that the Delta T can still exceed something reasonable. I have not tried it, but I can assure you a few of the known "guru" folk do not see it being reasonable. You will have to trust me on that one.
If you dive at twice the rate, say 4-5K FPM will you double the cooling rate? how about square the rate? It is still bugger all. It is still less than the heat up rate, or the after shut down rate.
It is like the turbo cooling debate, everyone with an pinion has never stuck multiple thermocouples to a turbo and done it. The one group who have have a bunch of data that proves the old myths are full of BS. Unless you have data to prove the other data wrong, well its just an opinion.
Meat bombers do have a period of transition, even they can't do engine suicide, otherwise the grass darts would not get out!
I think if you mean getting an engine up to 475F or something stupid, and then doing a dive, it may be possible. However I doubt from basic engineering understanding that the Delta T can still exceed something reasonable. I have not tried it, but I can assure you a few of the known "guru" folk do not see it being reasonable. You will have to trust me on that one.
If you dive at twice the rate, say 4-5K FPM will you double the cooling rate? how about square the rate? It is still bugger all. It is still less than the heat up rate, or the after shut down rate.
It is like the turbo cooling debate, everyone with an pinion has never stuck multiple thermocouples to a turbo and done it. The one group who have have a bunch of data that proves the old myths are full of BS. Unless you have data to prove the other data wrong, well its just an opinion.
Meat bombers do have a period of transition, even they can't do engine suicide, otherwise the grass darts would not get out!
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i'm with you jaba,
was on the turbo debate also.........
Of i was to put my position down, i'd say in short.
1) in general operations, operating within the manufacturers guidlines, shock cooling is pretty much impossible.
2) operations like glider towing do present a risk of shock cooling. No manufacturer offers guidlines on engine management for this type of operation, so everything done, is based on OWT's, and the very real and frequent cylinder cracking that occurs.
was on the turbo debate also.........
Of i was to put my position down, i'd say in short.
1) in general operations, operating within the manufacturers guidlines, shock cooling is pretty much impossible.
2) operations like glider towing do present a risk of shock cooling. No manufacturer offers guidlines on engine management for this type of operation, so everything done, is based on OWT's, and the very real and frequent cylinder cracking that occurs.
I always used 380 dgrs as a top limit in the climb and did not usually lean below around 5000ft depending on the day. Regardless until level on jump run it was not below 18 gph at 12000 ft, I would lean it more before descent, close cowl flaps etc temps now in low 300s dgrs.
Also at WOT and full rich at the start of the climb I liked the fuel flow on the red line, to me this was minimum, not maximum. The only trouble I ever had with cylinders was sometimes having to relap exhaust valves. I always had factory remans rather than rebuilds, mainly to save time.
I did use LOP on any cruise flights, going to maintenance etc, and it worked very well, just as advertised.
Also at WOT and full rich at the start of the climb I liked the fuel flow on the red line, to me this was minimum, not maximum. The only trouble I ever had with cylinders was sometimes having to relap exhaust valves. I always had factory remans rather than rebuilds, mainly to save time.
I did use LOP on any cruise flights, going to maintenance etc, and it worked very well, just as advertised.
You guys all seem to believe the wives tale that your fancy gauges have their probes in exactly the right position for all enviroments and that cylinders have equal temps across them.
With a bit of intelligent operation shock cooling should not happen, but nothing is fool-proof.
With a bit of intelligent operation shock cooling should not happen, but nothing is fool-proof.
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SHOW ME THE DATA
On the hourly rate the farmer was often cracking the whip for the fastest job, on the ton mile rate the Company kept a very close eye on times, so the power off high speed descent was an easy way to save a few minutes, but was hard on cylinders.
As has been stated by Glider tug and parachute operators the problem was much alleviated when a trickle of power was left on for the descent.
Perhaps if the problem of cracking cylinders in these type operations was referred to as thermal cycling rather than shock cooling it would be more accurate.
A good example would be the Lycoming IO720 when used in the agricultural role had a TBO of around 1,500 hrs.
The same engine used in a Queenair regularly flying 2:30 legs we got the TBO up to 2,400 hrs.
Last edited by prospector; 26th Aug 2012 at 22:54.
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Perhaps if the problem of cracking cylinders in these type operations was referred to as thermal cycling rather than shock cooling it would be more accurate.
Some years ago I spent some time with a technical representative from Teledyne Continental in respect to a court case that involved cracked cylinders on a couple of TSIO-520s. The matter involved a dispute where one party was arguing the cylinder cracking was caused by the operator and the other party was arguing the cracking was caused by fatigue (despite the engines only having about 300 hours time since new).
The cylinders are made up of a number of different metals with different expansion rates, (aluminium alloy heads, steel barrels, steel valves, steel spark plugs, steel studs & inserts, bronze valve guides and stainless or inconel exhausts etc).... these all expand and contract at different rates as a result experience considerable stress during rapid temperature changes.
If you rapidly apply full power to a cold engine or cut the power to hot engine and allow it to rapidly cool as would occur after TOD before a high speed descent the amount of stress over a period of time will cause the cylinders to crack.
On the IO-520 and TSIO-520s one of the weakest points is between the upper spark plug insert and the fuel injector port. If repeated rapid engine cooling occurs, the alloy cylinder head will cool much quicker as a result of the cylinder cooling fins dissipating the heat much more quickly than other parts of the head such as the steel spark plugs... as a result the hotter plug causes considerable stress on the now cooler (and shrinking) plug hole... over time the stress is released by cracking from the plug hole (often towards the injector)
A similar thing occurs on the 360 Lycomings where you will get cracking in the exhaust port emanating from stress around the valve guide and seat.
Another example was on the TSIO-520s, in aircraft like the C402, where repeated rapidly applying full power on take off without warming up the engines properly would likely manifest itself by the alloy cylinder head separating from the steel cylinder barrel. This is because the alloy head and combustion chamber heat up far more quickly that the barrel... the end result is cracking and eventual separation between the head and barrel.
Good engine warm up, smooth application of power, smooth reduction of power and good temperature management will result in far fewer engine problems including cracked cylinders and wear, particularly older manufactured engines where the manufacturing process resulted in metal that is not quite a strong.
As for parachute & glider ops, we worked out years ago by slowly pulling of the power prior to drop or release, and carrying some power on descent until slowed up on final approach, exerted far less stress on the engines.
I wish I still had the Continental report from the court case, but it was a beautifully written technical document that said the operator was a hamfisted mug!!
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i have heated quite complex aluminium/steel/titanium aircraft fittings/casting and forgings to well over 500degC for quite a few hrs, then dunked them in room temperature water..
never had one crack.. (shock cooling in manufacture tends to create a part thats more resistant to cracking)
is it possible that cylinder cracking might be caused by incorrect torque down procedures? ill fitting/re-used gaskets?.
never had one crack.. (shock cooling in manufacture tends to create a part thats more resistant to cracking)
is it possible that cylinder cracking might be caused by incorrect torque down procedures? ill fitting/re-used gaskets?.
Uniform heating shouldn't introduce unwanted internal stresses in a properly designed component.
The thermal gradient (and number of cycles) within the cylinder itself are the primary causes of thermal fatigue problems, at least as I was taught.
Using reworked cylinders seems to set one up for these sort of problems.
The thermal gradient (and number of cycles) within the cylinder itself are the primary causes of thermal fatigue problems, at least as I was taught.
Using reworked cylinders seems to set one up for these sort of problems.
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Jaba, really interesting data in the graphs. Thank you for posting. Probably the most interesting stuff I've seen on here for ages.
Just a couple of questions if I may be so bold.
In accordance with your statement
Can you confirm that
One minute after TOD as you passed 11,000 ft with a MAP of 15.3 inches and a Fuel Flow of 32 Litres/Hour the throttle was at Idle?
The MAP increases to 16.4 inches over the next 3 minutes as you approach 9,000 ft at which time the MAP drops to 13.6 inches.
The MAP then increases once again to 14.2 inches over the next minute as you pass through 8,000 ft and it seems that an idle MAP (MAP drops to 8.5 inches) is indicated as you passed 6,400 ft @14.37 (MAP drops to 8.5 inches) until you reach 2,800ft at 14.39, indicating that twice or (perhaps only once with the RPM increase) that the throttle was reduced again.
The delta T from 13k down to 6,400 ft on cylinder #1 was a modest 26 Degree F. However the Delta T from 6,400ft to 2,800ft on that cylinder was 39 degrees F. coinciding with the 8.5 inch MAP.
It seems to me that the data shows (by the step increases in MAP as air density increases on descent, that the engine wasn't fully at idle until passing 6,400ft).
I'm just a poor layman trying to interpret that awesome data graph.
I find the info you provided fascinating. Well done.
Just a couple of questions if I may be so bold.
In accordance with your statement
Throttle was pulled right back
One minute after TOD as you passed 11,000 ft with a MAP of 15.3 inches and a Fuel Flow of 32 Litres/Hour the throttle was at Idle?
The MAP increases to 16.4 inches over the next 3 minutes as you approach 9,000 ft at which time the MAP drops to 13.6 inches.
The MAP then increases once again to 14.2 inches over the next minute as you pass through 8,000 ft and it seems that an idle MAP (MAP drops to 8.5 inches) is indicated as you passed 6,400 ft @14.37 (MAP drops to 8.5 inches) until you reach 2,800ft at 14.39, indicating that twice or (perhaps only once with the RPM increase) that the throttle was reduced again.
The delta T from 13k down to 6,400 ft on cylinder #1 was a modest 26 Degree F. However the Delta T from 6,400ft to 2,800ft on that cylinder was 39 degrees F. coinciding with the 8.5 inch MAP.
It seems to me that the data shows (by the step increases in MAP as air density increases on descent, that the engine wasn't fully at idle until passing 6,400ft).
I'm just a poor layman trying to interpret that awesome data graph.
I find the info you provided fascinating. Well done.
Last edited by Trent 972; 27th Aug 2012 at 01:14. Reason: remove the 'Z' from the times because arriving Cab at 1439Z doesn't make sense.
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Do note this is a Lycoming, and not a Cuntinental who seem to have much bigger issues with this.
Anyone like to comment on using TAS not IAS for VNE ?
In cruise, roughly what % power you using? Something like 65%
I noticed 18.5 MP / 2450 RPM in cruise. Why use climb RPM? just curious, not saying it is bad, just trying to learn other reasoning?
What is "Pitch" on the graph?
Fantastic graph by the way.
Anyone like to comment on using TAS not IAS for VNE ?
In cruise, roughly what % power you using? Something like 65%
I noticed 18.5 MP / 2450 RPM in cruise. Why use climb RPM? just curious, not saying it is bad, just trying to learn other reasoning?
What is "Pitch" on the graph?
Fantastic graph by the way.
Last edited by diddly squat; 27th Aug 2012 at 02:00.
It seems that they build engines better these days. I have long suspected that many of the failures of the past have been down to the fact that while the basic design was right, the manufacturing of the engine was so poor.
From FLYING APR 2012
Improvements in modern reciprocating engine production all start with the switch-over to more modern machining, which can cut metal to incredibly close tolerances. This means that a Continental, Lycoming or Rotax engine built today is a physically better aircraft engine than has ever been mass-produced. You might recall that Continental at one point offered a Platinum-series engine that cost more to buy but had tighter tolerances and therefore a longer warranty. With improvements in machining — including a change to automated manufacturing processes — all the engines Continental builds today meet or exceed the Platinum specifications, and so the special line has been discontinued.
From FLYING APR 2012
Improvements in modern reciprocating engine production all start with the switch-over to more modern machining, which can cut metal to incredibly close tolerances. This means that a Continental, Lycoming or Rotax engine built today is a physically better aircraft engine than has ever been mass-produced. You might recall that Continental at one point offered a Platinum-series engine that cost more to buy but had tighter tolerances and therefore a longer warranty. With improvements in machining — including a change to automated manufacturing processes — all the engines Continental builds today meet or exceed the Platinum specifications, and so the special line has been discontinued.
The shock cooling debate has been a fixture of operating piston engines for a good long time. I think care has to be taken in out and out rubbishing "old wives" tales. Many reflect opinions that are reflective of a lot of practical experience as well as the innate conservatism of an endeavor where the penalty for getting it wrong can be unforgiving.
That been said my 02 cents are as follows
1) Understanding the effect the mixture has on engine temps is IMO generally rather poor for GA operations. In particular I just cringe when I see the mixture jammed full rich prior to the start of the descent, particularly on cool days.
2) Flying the airplane comes first. Ya do what Ya gotta do. If that means a rapid power reduction because you got held up close and high well then that is what you do.
3) Despite point 2 in general my feeling is that piston engines have a lot of hot parts moving at high speed. It would seem to me that "gentle" handling of the engine, that is slow and smooth power changes and in particular a slow reduction in power as the airplane descends will make life easier for the engine
4) I think care must be taken in interpreting EMS data. The only temperature that is measured is that at the probe. I am not sure you can automatically assume you have the entire picture of what is happening at every part of the cylinder. That been said EMS data is still extremely useful particularly in diagnosing engine faults earlier enough to prevent damage.
That been said my 02 cents are as follows
1) Understanding the effect the mixture has on engine temps is IMO generally rather poor for GA operations. In particular I just cringe when I see the mixture jammed full rich prior to the start of the descent, particularly on cool days.
2) Flying the airplane comes first. Ya do what Ya gotta do. If that means a rapid power reduction because you got held up close and high well then that is what you do.
3) Despite point 2 in general my feeling is that piston engines have a lot of hot parts moving at high speed. It would seem to me that "gentle" handling of the engine, that is slow and smooth power changes and in particular a slow reduction in power as the airplane descends will make life easier for the engine
4) I think care must be taken in interpreting EMS data. The only temperature that is measured is that at the probe. I am not sure you can automatically assume you have the entire picture of what is happening at every part of the cylinder. That been said EMS data is still extremely useful particularly in diagnosing engine faults earlier enough to prevent damage.
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Well, one thing is for sure... this thread is a very good reason why the ancient design of most common aircraft engines should be dumped in favour of a good, reliable turbine! Try shock-cooling that sucker... it will just laugh in your face and carry on regardless...