New Cylinder AD's released by FAA
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If the engine is run as per the book you generally don't have problems.
On the other hand, if you set up the SAME HP, LOP, the engine will run 30℉ COOLER, enjoy much lower PEAK combustion pressure, and use about 3 GPH LESS fuel. You can prove this in any twin, with engine monitors.
That's pretty close to paying for a new engine at TBO at US prices.
The engine is designed around the px in the chambers.
The bearings will fail before the head.
Rapid cooling is something else which is hard on an engine. Flight schools and meat bomb aircraft suffer the worst cracking.
Now, if you want to run the CHTs up to redline, and then chop the power, THAT may be "Shock Cooling," but I just call it "abuse."
So which will crack first. If you have an aircraft that is px to a max diff of 8.5 psi and you fly it un pressurized will it crack more at max diff or with no px in the cabin.
John Deakin
jdeakin // at // advancedpilot.com
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So, let’s assume we have two identical model piston aero engines that were manufactured at the same time, are fitted to the same aircraft type and have exactly the same number of cycles and exactly the same time in service with the same operator.
However, let’s also assume that one engine is always run in the cruise at a mixture setting that produces internal cylinder pressures of around 600 PSI, and the other is always run in the cruise at a mixture setting that produces internal cylinder pressures of around 1100 PSI.
Which of those two engines is more likely to have a cylinder failure first? (Fingers crossed and breath bated for a potential breakthrough…. )
However, let’s also assume that one engine is always run in the cruise at a mixture setting that produces internal cylinder pressures of around 600 PSI, and the other is always run in the cruise at a mixture setting that produces internal cylinder pressures of around 1100 PSI.
Which of those two engines is more likely to have a cylinder failure first? (Fingers crossed and breath bated for a potential breakthrough…. )
(But you forgot to specify "at the same power.")
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I've only seen lock wire work once.
John Deakin
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Flight schools and meat bomb aircraft suffer the worst cracking.
Fact is, here in AU, with flying school engines running under AD/ENG/4, an 0-200 with 3500+ hours and still going strong, with nothing more but routine maintenance, is common.
Under the old (when CAA/CASA had some engine expertise) life extension programs , used by the small Regionals, regularly had TSIO-540 making 28/2900 hours, and again, having to change a cylinder was a rare thing, and usually a manufacturing defect. In the UK, I have had IO 540 over 3000h, running always low RPM/high boost.
Those of us who know what we are doing have replicated exactly what Walter Atkinson and John Deakin are talking about, long ago.Anybody with at least half a brain can see they are right.
I think the big problem with the cylinder AD is that FAA is now showing the same loss of technical expertise in management that happened in AU CAA, even before AU CASA was "invented", after yet another inquiry.
Remember, given the choice between a conspiracy and a cockup, go for the cockup every time, you won't often be wrong. A couple of FAA bureaucrats have backed themselves into a corner, and don't want to lose face.
Tootle pip!!
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Let us consider another demonstration of the false idea of "Shock Cooling."
Bob Hoover, and his Shrike Commander.
I have personally discussed this with him.
He'll come screaming down, past the redline speed, and simply yank both prop levers to full feather (leaving throttles full open, and mixtures full rich).
After a manuever or three with both engines stopped, he'll simply push both prop levers to full forward, and the unfeathering accumulators do their thing, the props start turning, the engines start, and return to max power.
Prop levers to feather, fly, prop levers to full. Over and over again, several times per show, usually multiple shows a day.
His engines routinely go to TBO and beyond.
Shock cooling is a myth, except for what Walter is about to tell you.
Bob Hoover, and his Shrike Commander.
I have personally discussed this with him.
He'll come screaming down, past the redline speed, and simply yank both prop levers to full feather (leaving throttles full open, and mixtures full rich).
After a manuever or three with both engines stopped, he'll simply push both prop levers to full forward, and the unfeathering accumulators do their thing, the props start turning, the engines start, and return to max power.
Prop levers to feather, fly, prop levers to full. Over and over again, several times per show, usually multiple shows a day.
His engines routinely go to TBO and beyond.
Shock cooling is a myth, except for what Walter is about to tell you.
On lockwiring:
In a previous life, I was an Avionics Technician working on RAAF Mirage Fighter jets. One of their least reliable bits of equipment was the AN/APN 153(v) Navigation Doppler radar that rarely provided the pilots with Drift Angle and Ground Speed. The black box that provided all this data had a Mean Time Between Failure (MTBF) of about 30 minutes by my assessment. But we still had to lockwire the damned thing in there. And the 47 screws of the cover plate just to get access to the bloody thing.
For any Technicians that ever had to remove and refit the Doppler R/T baseplate, there should be a Commonwealth Award just for that!
And also for the pilots that managed to fly them safely IFR..
In a previous life, I was an Avionics Technician working on RAAF Mirage Fighter jets. One of their least reliable bits of equipment was the AN/APN 153(v) Navigation Doppler radar that rarely provided the pilots with Drift Angle and Ground Speed. The black box that provided all this data had a Mean Time Between Failure (MTBF) of about 30 minutes by my assessment. But we still had to lockwire the damned thing in there. And the 47 screws of the cover plate just to get access to the bloody thing.
For any Technicians that ever had to remove and refit the Doppler R/T baseplate, there should be a Commonwealth Award just for that!
And also for the pilots that managed to fly them safely IFR..
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***Shock cooling is a myth, except for what Walter is about to tell you. ***
OK, here goes.
No one had ever heard of shock cooling until the pressurized, turbocharged twin Cessnas came along in the 1970s. There are no maintenance reports of the hard to manage supercharged radials ever having shock cooling problems. We had 65+ years of aviation with no reports of shock cooling.
So where did this come from?
In the 70s, these new turbo twins began flying at much higher altitudes than their NA brethren. So what, you might ask? Well, the fuel in the wings at altitude was becoming super-cooled, cold-soaked to very low temps. No one routinely had flown that high before. Since they were pressurized, and rapid depressurization was not a problem for passengers, the pilots were descending rapidly from altitude to land and, guess what they did next? They followed the POH's recommendations to go full rich in the pattern before landing. This shoved a large amount of very COLD fuel onto the intake walls of the warm cylinder. This resulted in cracks forming--in the INTAKE area, NOT in the cylinders. In any case, this required cylinder replacement.
Pilots who ignored the POH recommendation to go full rich, and left the mixture leaned, or added mixture very slowly when approaching the pattern, did not suffer these cracks.
Soooo, LAMEs and A&Ps made the CORRECT OBSERVATION that these cracks followed rapid descents, but then assigned the WRONG cause as to the phenomenon, resulting in pilots doing something really silly----reducing power 1" per minute or some such insanity and starting their descents more than 100 miles out. It did nothing to address the problem where the cylinder was concerned since there was no problem with the cylinder in the first place, but did allow the fuel to warm up a bit before it was thrown agains the intake walls.
You can descend as rapidly as you want, with the power as low as you want, with CHTs plummeting and as long as you do not throw super-cooled fuel rapidly against the intake walls, you will not have "shock cooling" problems.
This is a perfect example of pilots, LAMEs and A&Ps making a valid observation, yet assigning improper causality and creating another aviation Old Wives Tale.
If the rapid change in CHT was the problem and inconsistent heating or cooling, there would be frequent cylinder failures as we fly into cold rain (of which there is no record) and parachute droppers would never make TBO (which they regularly do) or we would suffer shock heating on every takeoff (which we don't).
OK, all of that said, there are those who are convinced (without data) that shock cooling is real and will continue to recommend unnecessary actions or take unnecessary actions like the above to avoid a problem that simply has never existed.
My flame suit is on in preparation to receive incoming from those with no data.
OK, here goes.
No one had ever heard of shock cooling until the pressurized, turbocharged twin Cessnas came along in the 1970s. There are no maintenance reports of the hard to manage supercharged radials ever having shock cooling problems. We had 65+ years of aviation with no reports of shock cooling.
So where did this come from?
In the 70s, these new turbo twins began flying at much higher altitudes than their NA brethren. So what, you might ask? Well, the fuel in the wings at altitude was becoming super-cooled, cold-soaked to very low temps. No one routinely had flown that high before. Since they were pressurized, and rapid depressurization was not a problem for passengers, the pilots were descending rapidly from altitude to land and, guess what they did next? They followed the POH's recommendations to go full rich in the pattern before landing. This shoved a large amount of very COLD fuel onto the intake walls of the warm cylinder. This resulted in cracks forming--in the INTAKE area, NOT in the cylinders. In any case, this required cylinder replacement.
Pilots who ignored the POH recommendation to go full rich, and left the mixture leaned, or added mixture very slowly when approaching the pattern, did not suffer these cracks.
Soooo, LAMEs and A&Ps made the CORRECT OBSERVATION that these cracks followed rapid descents, but then assigned the WRONG cause as to the phenomenon, resulting in pilots doing something really silly----reducing power 1" per minute or some such insanity and starting their descents more than 100 miles out. It did nothing to address the problem where the cylinder was concerned since there was no problem with the cylinder in the first place, but did allow the fuel to warm up a bit before it was thrown agains the intake walls.
You can descend as rapidly as you want, with the power as low as you want, with CHTs plummeting and as long as you do not throw super-cooled fuel rapidly against the intake walls, you will not have "shock cooling" problems.
This is a perfect example of pilots, LAMEs and A&Ps making a valid observation, yet assigning improper causality and creating another aviation Old Wives Tale.
If the rapid change in CHT was the problem and inconsistent heating or cooling, there would be frequent cylinder failures as we fly into cold rain (of which there is no record) and parachute droppers would never make TBO (which they regularly do) or we would suffer shock heating on every takeoff (which we don't).
OK, all of that said, there are those who are convinced (without data) that shock cooling is real and will continue to recommend unnecessary actions or take unnecessary actions like the above to avoid a problem that simply has never existed.
My flame suit is on in preparation to receive incoming from those with no data.
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Anyone remember this thread a few years ago....I collected the data....the cooldown rate was impressive for its lack of anything. 
http://www.pprune.org/pacific-genera...th-busted.html
http://www.pprune.org/pacific-genera...th-busted.html
Here is a little story I thought I would share with you.
One of the great Old Wives Tales, Shock Cooling!
Well I am not sure how easy it would be to do this, apart from spear into a lake, that would do it for sure, but even in an extreme descent with 2000FPM plus ROD I can't seem to do it.
So here is the story, last Saturday returning from St George Qld to Caboolture (Brisbane) I climbed to FL130 and was enjoying 45 knots on the tail, so a GS of 210 knots. As I was about 20 minutes out, I advised BNE CEN that my TOD point was 46 miles from YCAB and that was 13 minutes, to allow for a 12000' descent to circuit area altitude. I do this so it helps them with all the crossing traffic I have going against the flow. My tracks are often a pain I am sure.
Anyway 13 minutes comes and goes, and I think any second now........10 minutes, hmmm I wonder if my mate is on BNE APP this afternoon. Anyway they are busy with jet traffic and RFDS etc into YBBN, so I figure I can fit in with whatever keeps everyone happy. At 6.5 minutes to run, 22NM to destination.....the following occurs;
BNE CEN: Lima November Lima, Descend 6000 and contact BNE APP on 124.7 , I do the read back and over I go to 124.7,
LNL: Brisbane Approach, Lima November Lima FL130 cleared 6000 and Visual.
BNE APP: Lima November Lima, cleared to leave on descent, Brisbane QNH 1014, good afternoon Brownie!
LNL: Cleared to leave on descent, 1014 LNL....and gooday to you NP and did you have something to do with the late descent?
BNE APP: I have NO Idea what you are talking about <laughing>
LNL: WATHCH THIS <laughing>
Now 6 minutes and 20 miles
Now not exceeding VNE (by TAS), and then as the bumpy bits over the mountains (ok hills) staying out of the yellow arc and not wanting to lose the game, I had a job to do. At times the ROD was around and over 2000 FPM, and I watched happily the CHT's very slowly decline. The Throttle was pulled right back and the RPM about half way down was increased to 2550 to help the cause. Pitch went from +1 in cruise to -8.5 at times and mostly -5 to -7 and this was a very different view of the Brisbane region.
So I have downloaded the data, and done a Delta T on CHT and the graph shows a flat line. The cumulative Delta T shows a greater ramp for the taxi and take off than at any point in the descent. Unfortunately the Delta T will not upload to the SAVVY site, however you can see the slope on the curves.
I have uploaded the file to the Savvy site, you can click on the extra displayed data to show Vert Speed or other things.
https://my.savvyanalysis.com/public/...1-b50788c2095a
No doubt some flat earthers will tell me that the cylinders will fall apart due cracks in a few hundred hours.
It is pretty hard to shock cool and engine that is already cool!
Shock Cooling - BUSTED!
One of the great Old Wives Tales, Shock Cooling!
Well I am not sure how easy it would be to do this, apart from spear into a lake, that would do it for sure, but even in an extreme descent with 2000FPM plus ROD I can't seem to do it.
So here is the story, last Saturday returning from St George Qld to Caboolture (Brisbane) I climbed to FL130 and was enjoying 45 knots on the tail, so a GS of 210 knots. As I was about 20 minutes out, I advised BNE CEN that my TOD point was 46 miles from YCAB and that was 13 minutes, to allow for a 12000' descent to circuit area altitude. I do this so it helps them with all the crossing traffic I have going against the flow. My tracks are often a pain I am sure.
Anyway 13 minutes comes and goes, and I think any second now........10 minutes, hmmm I wonder if my mate is on BNE APP this afternoon. Anyway they are busy with jet traffic and RFDS etc into YBBN, so I figure I can fit in with whatever keeps everyone happy. At 6.5 minutes to run, 22NM to destination.....the following occurs;
BNE CEN: Lima November Lima, Descend 6000 and contact BNE APP on 124.7 , I do the read back and over I go to 124.7,
LNL: Brisbane Approach, Lima November Lima FL130 cleared 6000 and Visual.
BNE APP: Lima November Lima, cleared to leave on descent, Brisbane QNH 1014, good afternoon Brownie!
LNL: Cleared to leave on descent, 1014 LNL....and gooday to you NP and did you have something to do with the late descent?
BNE APP: I have NO Idea what you are talking about <laughing>
LNL: WATHCH THIS <laughing>
Now 6 minutes and 20 miles
Now not exceeding VNE (by TAS), and then as the bumpy bits over the mountains (ok hills) staying out of the yellow arc and not wanting to lose the game, I had a job to do. At times the ROD was around and over 2000 FPM, and I watched happily the CHT's very slowly decline. The Throttle was pulled right back and the RPM about half way down was increased to 2550 to help the cause. Pitch went from +1 in cruise to -8.5 at times and mostly -5 to -7 and this was a very different view of the Brisbane region.
So I have downloaded the data, and done a Delta T on CHT and the graph shows a flat line. The cumulative Delta T shows a greater ramp for the taxi and take off than at any point in the descent. Unfortunately the Delta T will not upload to the SAVVY site, however you can see the slope on the curves.
I have uploaded the file to the Savvy site, you can click on the extra displayed data to show Vert Speed or other things.
https://my.savvyanalysis.com/public/...1-b50788c2095a
No doubt some flat earthers will tell me that the cylinders will fall apart due cracks in a few hundred hours.
It is pretty hard to shock cool and engine that is already cool!
Shock Cooling - BUSTED!
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To summarise:
Cylinder damage/cracking is caused by manufacturer or the LAME/A&P.
Anecdotal stories from some posters is data/acceptable evidence
CMI and Lycoming are conspiring with FAA/CASA to shut down a PMA organization
Cylinder damage/cracking is caused by manufacturer or the LAME/A&P.
Anecdotal stories from some posters is data/acceptable evidence
CMI and Lycoming are conspiring with FAA/CASA to shut down a PMA organization
Unless you are being deliberately disingenuous, NH, you too have a substantial learning difficulty.
I had thought that was implied in the assumptions of my question, but evidently not. Thank you, Sir.
And my apologies to AndrewR if that was the point you were trying to make.
(But you forgot to specify "at the same power.")
And my apologies to AndrewR if that was the point you were trying to make.
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No Hoper, I think you are distorting the truth a little.
To summarise:
Cylinder damage/cracking is caused by manufacturer or the LAME/A&P. Most likely they are of manufacture or from excessive heating issues and often unlogged as nobody would know. I doubt very much the LAME is the cause, who said they were anyway? Or are you fishing for a debate?
Anecdotal stories from some posters is data/acceptable evidence Anecdotal only to those who have not seen the data. Remember some on here have access to far more data and knowledge than the rest put together. For them it is not anecdotal at all.
CMI and Lycoming are conspiring with FAA/CASA to shut down a PMA organization
That is plausible, but who will ever know?
Cylinder damage/cracking is caused by manufacturer or the LAME/A&P. Most likely they are of manufacture or from excessive heating issues and often unlogged as nobody would know. I doubt very much the LAME is the cause, who said they were anyway? Or are you fishing for a debate?
Anecdotal stories from some posters is data/acceptable evidence Anecdotal only to those who have not seen the data. Remember some on here have access to far more data and knowledge than the rest put together. For them it is not anecdotal at all.
CMI and Lycoming are conspiring with FAA/CASA to shut down a PMA organization
That is plausible, but who will ever know?
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Glider tugs which are abused by reducing power too much, too quickly will crack heads. If you do not call that shock cooling fair enough!
They often add very efficient cowl flaps to reduce airflow through cowlings to reduce this. If it is not the quick cooling during the descent after a hot climb then what causes it!
We have even gone to Chevies to try to find a solution.
They often add very efficient cowl flaps to reduce airflow through cowlings to reduce this. If it is not the quick cooling during the descent after a hot climb then what causes it!
We have even gone to Chevies to try to find a solution.
In geared 375 hp continentals, rapid power reduction = death. Gear boxes will not tolerate being driven backwards and engines need to be ROP with easy power reductions due to marked inability to match fuel flow to air cooling flow (despite lots of aftermarket injector money spent).
Stark contrast to c340/335 which will run sub 300 cht at all times lop at about 13 gph w/o much shock cooling regardless of experience of pilots with GAMIs.
But by all means, at about $75k for a frem of a GTSIO 520, do what you want. (Not that I have any personal checkbook damage In this regard...)
Stark contrast to c340/335 which will run sub 300 cht at all times lop at about 13 gph w/o much shock cooling regardless of experience of pilots with GAMIs.
But by all means, at about $75k for a frem of a GTSIO 520, do what you want. (Not that I have any personal checkbook damage In this regard...)
Last edited by 421dog; 24th Apr 2014 at 23:00.
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Good post. Lest we forget.
My last one was after the Dawn Service at the Australian War Memorial, after Breaky, just been back fro the Anzac Day Parade, great day indeed. FA18's to boot
Some good reading here from Mike Busch How Do Piston Aircraft Engines Fail? « Opinion Leaders
John or Walter....Mike was a three time APS student was he not?
My last one was after the Dawn Service at the Australian War Memorial, after Breaky, just been back fro the Anzac Day Parade, great day indeed. FA18's to boot
Some good reading here from Mike Busch How Do Piston Aircraft Engines Fail? « Opinion Leaders
John or Walter....Mike was a three time APS student was he not?
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!!!OLD WIVES TALE ALERT!!!
***In geared 375 hp continentals, rapid power reduction = death. Gear boxes will not tolerate being driven backwards...***
It's the gear slap that is the problem and that observation holds a lot of truth.
***and engines need to be ROP with easy power reductions due to marked inability to match fuel flow to air cooling flow (despite lots of aftermarket injector money spent).***
Confucius say, "Do not tell man something impossible when he already do it!"
I've run C-421s at 35"/1800 and 50-60dF LOP with no problems whatsoever. (Yes, the top of the green arc on MP is 32.5", but that's set in the event one runs it ROP. When LOP, the MP can be higher with less stress on the engine. The f:A ratios were well balanced with GAMIjectors and a LOT of fixing induction leaks for which these engines are known---and the engines ran beautifully--to TBO. Those power setting result in the same TAS as the normally used ROP MP and RPM, BUT with lower CHTs, and on 17 gph rather than 21 GPH per engine.
The GTSIO-520 was developed under the watchful eye of Carl Goulet who was at the time the VP of engineering at TCM. I recall flying those engines as described above with an FAA DER on board who said, "This is how God and Carl Goulet INTENDED these engines to be run."
Be careful in assigning causality to a valid observation.
***In geared 375 hp continentals, rapid power reduction = death. Gear boxes will not tolerate being driven backwards...***
It's the gear slap that is the problem and that observation holds a lot of truth.
***and engines need to be ROP with easy power reductions due to marked inability to match fuel flow to air cooling flow (despite lots of aftermarket injector money spent).***
Confucius say, "Do not tell man something impossible when he already do it!"
I've run C-421s at 35"/1800 and 50-60dF LOP with no problems whatsoever. (Yes, the top of the green arc on MP is 32.5", but that's set in the event one runs it ROP. When LOP, the MP can be higher with less stress on the engine. The f:A ratios were well balanced with GAMIjectors and a LOT of fixing induction leaks for which these engines are known---and the engines ran beautifully--to TBO. Those power setting result in the same TAS as the normally used ROP MP and RPM, BUT with lower CHTs, and on 17 gph rather than 21 GPH per engine.
The GTSIO-520 was developed under the watchful eye of Carl Goulet who was at the time the VP of engineering at TCM. I recall flying those engines as described above with an FAA DER on board who said, "This is how God and Carl Goulet INTENDED these engines to be run."
Be careful in assigning causality to a valid observation.
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***Mike was a three time APS student was he not?***
A lot of folks appreciate Mike as a knowledgeable pilot and mechanic and follow his thoughts closely. He has been a friend for a long time and we agree on most, but not all, issues regarding engine management. We should agree; as you reported, he took the APS class three times and then became an expert on engine management!
A lot of folks appreciate Mike as a knowledgeable pilot and mechanic and follow his thoughts closely. He has been a friend for a long time and we agree on most, but not all, issues regarding engine management. We should agree; as you reported, he took the APS class three times and then became an expert on engine management!