Shock Cooling - Myth Busted!!
Thread Starter
Join Date: Jul 2007
Location: in the classroom of life
Age: 55
Posts: 6,864
Likes: 0
Received 1 Like
on
1 Post
Trent, you are getting confused.
I was not trying to prove the myth is busted. I was trying to be a smart arse with BN APP who was trying to be a smart arse with me.
I was trying alright, I was trying to descnd a fast as I could possibly go, believe me, VNE for TAS and VNE once TAS was not an issue and the out of the yellow arc over the hills and bumps.
I WAS TRYING but it was not about a shock cooling effort, I never gave that a thought as I knew it was a myth. Driving home talking to Chimbu Chuckles he or I made the comment about how that busts the myth on shock cooling so I went back and downloaded the data a few days later.
You got that
How does the quote fit in with my BMP.....exactly, I don't fit in with it. The Lycoming quote is laughable. my BMP is the reason for the 32dF delta T.
Am I not making sense, or are you trying to wind me up?
Trouble with debating you smart blokes, even when you are off track its hard to keep up 
Maybe I am fatigued. Should impliment a pprune fatigue management plan! 
I was not trying to prove the myth is busted. I was trying to be a smart arse with BN APP who was trying to be a smart arse with me.
I was trying alright, I was trying to descnd a fast as I could possibly go, believe me, VNE for TAS and VNE once TAS was not an issue and the out of the yellow arc over the hills and bumps.
I WAS TRYING but it was not about a shock cooling effort, I never gave that a thought as I knew it was a myth. Driving home talking to Chimbu Chuckles he or I made the comment about how that busts the myth on shock cooling so I went back and downloaded the data a few days later.
You got that
Sorry Jaba, I missed your and T28's last post while I was typing.
What was that in your quote box in previous post.... Ah yes
Quote:
......slowly lean the mixture from full rich to maximum power
How does that fit in with your BMP (Big Mixture Pull)?
What was that in your quote box in previous post.... Ah yes
Quote:
......slowly lean the mixture from full rich to maximum power
How does that fit in with your BMP (Big Mixture Pull)?
How does the quote fit in with my BMP.....exactly, I don't fit in with it. The Lycoming quote is laughable. my BMP is the reason for the 32dF delta T.
Am I not making sense, or are you trying to wind me up?
Trouble with debating you smart blokes, even when you are off track its hard to keep up Maybe I am fatigued. Should impliment a pprune fatigue management plan!
Thread Starter
Join Date: Jul 2007
Location: in the classroom of life
Age: 55
Posts: 6,864
Likes: 0
Received 1 Like
on
1 Post
Who wrote this rubbish Trent. What garbage!!
This is fact, bank it. The scope for engine damage as defined by the area under the curve is considerably greater on the Rich side of Peak.
I will repeat that slower, the area under the curve where there is a greater chance of both detonation (especially in a turbo at high MP) and from general high CHT and ICP, is biased heavily on the ROP side of the curve.
The LOP side of the curve is so much better, considerably so, that there is less scope LOP to do long term (hundreds of hours) damage that the statement you quote is scientifically and factually false.
Have you ever watched the detonation index on a fully instrumented dyne with a high HP turbocharged piston engine, while you do all manner of things to it? It really is an education.
Some folk might find it like drinking from a firehose, but it seriously is very educational. The myths and rubbish stories like the one you just posted soon become nothing but laughing stock.
PA46 hey, the TSIO520E where the engine manufacturer actually states how to set up the max cruise HP setting of 75% and 235HP; Set RPM for desired cruise setting (note nothing specific, the smart ones have already worked out why this matters not), and then shock horror, lean to .....no surely not.....OMG LOP!!!!
Not sure why they then go on to say 235HP is at 31" and 2400RPM and a 25-50F LOP setting, because when LOP the rpm does not matter but anyway old habits die hard.
So there ya go! Funny hey!
The burned valves were all Factory Fitted Options, the result was the same despite what the pilot did.
And in the PA46 case all the accelerated failures, forgetting the valve guide issues, the ones with major problems were from pilots who read this manual, and just as their old CFI or hangar buddies said, a bit richer would be better. So they went from a perfectly happy 50LOP to around typically 25-50 ROP against the manuals advice.
Where do you think the highest CHT/ICP and valve temps live?
So these guys blame LOP ops when they were in fact ROP.
I am glad you brought up the PA46 because this actually supports my previous post about where the risky side of the curve lives.
Now back to my Quizz
This is fact, bank it. The scope for engine damage as defined by the area under the curve is considerably greater on the Rich side of Peak.
I will repeat that slower, the area under the curve where there is a greater chance of both detonation (especially in a turbo at high MP) and from general high CHT and ICP, is biased heavily on the ROP side of the curve.
The LOP side of the curve is so much better, considerably so, that there is less scope LOP to do long term (hundreds of hours) damage that the statement you quote is scientifically and factually false.
Have you ever watched the detonation index on a fully instrumented dyne with a high HP turbocharged piston engine, while you do all manner of things to it? It really is an education.
Some folk might find it like drinking from a firehose, but it seriously is very educational. The myths and rubbish stories like the one you just posted soon become nothing but laughing stock.
PA46 hey, the TSIO520E where the engine manufacturer actually states how to set up the max cruise HP setting of 75% and 235HP; Set RPM for desired cruise setting (note nothing specific, the smart ones have already worked out why this matters not), and then shock horror, lean to .....no surely not.....OMG LOP!!!!
Not sure why they then go on to say 235HP is at 31" and 2400RPM and a 25-50F LOP setting, because when LOP the rpm does not matter but anyway old habits die hard.
So there ya go! Funny hey!
The burned valves were all Factory Fitted Options, the result was the same despite what the pilot did.
And in the PA46 case all the accelerated failures, forgetting the valve guide issues, the ones with major problems were from pilots who read this manual, and just as their old CFI or hangar buddies said, a bit richer would be better. So they went from a perfectly happy 50LOP to around typically 25-50 ROP against the manuals advice.Where do you think the highest CHT/ICP and valve temps live?
So these guys blame LOP ops when they were in fact ROP.
I am glad you brought up the PA46 because this actually supports my previous post about where the risky side of the curve lives.
Now back to my Quizz
Join Date: May 2009
Location: Australia, maybe
Posts: 559
Likes: 0
Received 0 Likes
on
0 Posts
Who wrote this rubbish Trent. What garbage!!
Not sure about the cruise power settings you quote for the TIO-540 AE2A Jaba, my book says
Lycoming recommends that a cruise setting of 65% power be used for typical flight profiles. This power setting corresponds to 2400 RPM, 29 in. Hg. manifold pressure. Recommended TIT is 1650°F or 100 degrees richer than peak TIT whichever is less.
When I go to my night job I get to play with 4 very big round things from Derby UK and I operate them exactly as per the OEM manual, because IF and WHEN they go BANG, I won't have to pay them off over the next thousand years. If I were to say to the boss "I found a better way on the internet to operate the engine" and it went BANG, I think I would be ringing up TruckMasters looking for a job.
Last edited by Trent 972; 7th Sep 2012 at 13:25. Reason: typo
Thread Starter
Join Date: Jul 2007
Location: in the classroom of life
Age: 55
Posts: 6,864
Likes: 0
Received 1 Like
on
1 Post
Quote:
Who wrote this rubbish Trent. What garbage!!
The Manufacturer!
Who wrote this rubbish Trent. What garbage!!
The Manufacturer!
When I go to my night job I get to play with 4 very big round things from Derby UK and I operate them exactly as per the OEM manual, because IF and WHEN they go BANG, I won't have to pay them off over the next thousand years. If I were to say to the boss "I found a better way on the internet to operate the engine" and it went BANG, I think I would be ringing up TruckMasters looking for a job.
Do they say things contradictory to other similar manuals?
Do they say things that contradict themselves in their own publications?
Do they have contradictions in the same very manual?
Most likely not. If they do, and any of it contradicts known science, why would you not go see the boss and get him to investigate it with your help and get a change made to the SOP.
I am privilleged to be reading a Curtis Wright troubleshooting manual "Troubleshooting for Optimum Performance" at the moment, very good stuff. Printed in 1957. Why was it these guys back in the 50's had it nailed? Wot Went Wong in the last 40 years? (rhetorical question)
Join Date: May 2009
Location: Australia, maybe
Posts: 559
Likes: 0
Received 0 Likes
on
0 Posts
I am privilleged to be reading a Curtis Wright troubleshooting manual "Troubleshooting for Optimum Performance" at the moment, very good stuff. Printed in 1957. Why was it these guys back in the 50's had it nailed? Wot Went Wong in the last 40 years? (rhetorical question)
Wot Went Wong in the last 40 years?
Join Date: May 2009
Location: Australia, maybe
Posts: 559
Likes: 0
Received 0 Likes
on
0 Posts
Morning Clinton, I hope you're well.
If you wish to take the time to check back on any of my previous posts you will see that I have not posted personal opinion, rather I have referenced links from OEM's. If one were to continually discount OEM recommendations as what you say as
It would be silly of me to continue.
As Benjamin Franklin said
I am quite comfortable with my own knowledge on this subject, however I do fear for some who may try some of this 'home brew', without the benefit of previous experience.
Caveat Emptor.
If you wish to take the time to check back on any of my previous posts you will see that I have not posted personal opinion, rather I have referenced links from OEM's. If one were to continually discount OEM recommendations as what you say as
...inconsistent and demonstrably unscientific assertions of some manufacturers
As Benjamin Franklin said
The definition of insanity is doing the same thing over and over and expecting different results.
Caveat Emptor.
Hi Trent,
Please post that link you have! I am learning a lot from this thread and the guys who are posting real data are doing a lot for my education. I'd really appreciate it!
Please post that link you have! I am learning a lot from this thread and the guys who are posting real data are doing a lot for my education. I'd really appreciate it!
Join Date: May 2009
Location: Australia, maybe
Posts: 559
Likes: 0
Received 0 Likes
on
0 Posts
Clinton, therein lies our difference.
I am not prepared to discount the wisdom of the people who built the engine.
I am not prepared to tell you to do other than whatever you wish with your own engine.
I am prepared to say it is wrong to suggest to other people to ignore the wisdom of the people who designed and built the engine.
On Benjamin Franklin's advice I shall retire, because I'm still trying to get to grips with Jaba's statement
Detonation caused by ROP?
Low Octane and Lean Mixtures Advanced Spark and high inlet air temperatures causes detonation. Show me where that is wrong and I'll keep my ear/mind open.
Apologies McGrath, I missed your post while typing. Anything I have posted here is easily found by a google search. ATM I now have to prepare for my next MS flight Sim session. I'll be back in about 16 hours.
I am not prepared to discount the wisdom of the people who built the engine.
I am not prepared to tell you to do other than whatever you wish with your own engine.
I am prepared to say it is wrong to suggest to other people to ignore the wisdom of the people who designed and built the engine.
On Benjamin Franklin's advice I shall retire, because I'm still trying to get to grips with Jaba's statement
I will repeat that slower, the area under the curve where there is a greater chance of both detonation (especially in a turbo at high MP) and from general high CHT and ICP, is biased heavily on the ROP side of the curve.
Low Octane and Lean Mixtures Advanced Spark and high inlet air temperatures causes detonation. Show me where that is wrong and I'll keep my ear/mind open.
Apologies McGrath, I missed your post while typing. Anything I have posted here is easily found by a google search. ATM I now have to prepare for my next MS flight Sim session. I'll be back in about 16 hours.
Last edited by Trent 972; 8th Sep 2012 at 01:21. Reason: response to McGrath
Join Date: Jan 2008
Location: Australia
Posts: 768
Likes: 0
Received 0 Likes
on
0 Posts
the area under the curve where there is a greater chance of both detonation (especially in a turbo at high MP)
And that folks is why on blown engines the compression ratio is lower than normall aspirated engines.
And that folks is why on blown engines the compression ratio is lower than normall aspirated engines.
Interestingly, the factory manual for the 1980 PA31-325 that I operate offers 50 deg LOP as an alternative to ROP. It even goes so far as to give instructions to get to LOP if the EGT limit is reached before obtaining LOP.
Ok, all very interesting and a great thread BUT:
There is precious little information about best practice. I have a long involvement with a company operating 200 series and 185 Cessna's with O520 and policy has always been: Full power for take off, 25/25 for the climb and 2400/23 for the cruise. Lean to top of green on pressure gauge in climb and to 2 divisions ROP in cruise. Engines have always made TBO + extension, a top is generally done around 1200. This policy works well, but what would work better? The 185's are on floats and despite 1500 odd metre 3 minute takeoffs and 20' sectors the engines still make TBO + 100 with few problems. You guys hint that these are poor practices but offer no alternative suggestions other than to fit multi point digital thingies and LOP
In my Scout (O360 + CSU) my policy is about the same although I sometimes I leave the throttle wide open in the climb and simply reduce RPM to 2500. Leaning to a couple or three divs rich of peak at 2400/23" gives a burn of 30 per taco hour. How can I improve this? I do note with this engine that shock cooling seems impossible, CHT is very stable in all stages of flight at around 330 - 365F regardless of power setting, only have single probes though.
Sadly I am unable to make NATFLY where I think some of you are doing presentations.
And Jabba, I look forward to your answers, unfortunately I don't know
There is precious little information about best practice. I have a long involvement with a company operating 200 series and 185 Cessna's with O520 and policy has always been: Full power for take off, 25/25 for the climb and 2400/23 for the cruise. Lean to top of green on pressure gauge in climb and to 2 divisions ROP in cruise. Engines have always made TBO + extension, a top is generally done around 1200. This policy works well, but what would work better? The 185's are on floats and despite 1500 odd metre 3 minute takeoffs and 20' sectors the engines still make TBO + 100 with few problems. You guys hint that these are poor practices but offer no alternative suggestions other than to fit multi point digital thingies and LOP
In my Scout (O360 + CSU) my policy is about the same although I sometimes I leave the throttle wide open in the climb and simply reduce RPM to 2500. Leaning to a couple or three divs rich of peak at 2400/23" gives a burn of 30 per taco hour. How can I improve this? I do note with this engine that shock cooling seems impossible, CHT is very stable in all stages of flight at around 330 - 365F regardless of power setting, only have single probes though.
Sadly I am unable to make NATFLY where I think some of you are doing presentations.
And Jabba, I look forward to your answers, unfortunately I don't know
Leaning to a couple or three divs rich of peak at 2400/23"
)
I have a few hours sitting behind IO520/550s - so here, for what its worth, is my take on this!
1) If you are paying the maintenance bills on the engine - do whatever you like!
2) If you are not paying the maintenance bills - then do what you are told to do by the person who is!
3) If in doubt - do what the POH says!
Dr
1) If you are paying the maintenance bills on the engine - do whatever you like!
2) If you are not paying the maintenance bills - then do what you are told to do by the person who is!
3) If in doubt - do what the POH says!
Dr
Thread Starter
Join Date: Jul 2007
Location: in the classroom of life
Age: 55
Posts: 6,864
Likes: 0
Received 1 Like
on
1 Post
Ok Trent,
You have just shot yourself in the butt here, there is nothing home cooked about the data and advice given by at least some of us. It is well researched, and documented, going back 60 years. The home brew stuff is mostly what the flying schools dish out as a one size fits all, and they get it wrong.
Fuel and and O2 do not know the difference between your IO550 or the Brigs and stratten mower engine. All air cooled fixed spark 4 stroke petrol engines share 99% of things in common.
No they had pilots and a flight engineer, and good data logs, not the JPI type, more the paper and pencil type, but effective non the less.
Ok this is not going to be easy here, this sort of stuff is part of a multi day professional training course, and is impossible to easily replicate that on prune, and I am not about to try. However here is a snapshot of the answer.
Detonation potential exists in far greater amounts on the ROP side of the curve, the region on the leans side is fairly narrow even at full MP, so lets say in simple terms 30" up the beach at 500-1000' once on the LOP side of the curve the detonation region is from peak to maybe 20FLOP and the risk is eliminated at anything past 40LOP, the best place to be running here is 60-90LOP. And this is a fairly small movement of the mixture knob.
On the Rich side of the curve, the region is far greater, from peak through 75ROP which is best power and through to maybe 125-150 ROP and once out to a region of 200ROP the problem goes away again.
So tell me ......which side of the curve, has the most potential? And understanding that you do need high HP high temps and high IAT to get it going. And on a Turbo this is much easier to do!
Courtesy of Advanced Pilot Seminars
So when you say a Lean mixture is what causes detonation, what you really mean is a Rich mixture that is not Rich enough. I am sure I have said this before, technically all mixtures on the curve above to the left of peak EGT are RICH and all the graph to right of peak is a lean mixture.
By definition TOO LEAN would have to be from the RHS and to be too lean over there, the engine stops.
To be TOO RICH, you would be way out the left and drowning the engine, but if you lean the flow and get to a bad zone that would be correctly described as NOT RICH ENOUGH.
Tinstaafl, yes indeed.....they just do not do many manuals, and probably yours any justice with a thorough explanation so hence the reason the pilots who fly them get a wird mix of the manual Vs the CFI..... and that is where the trouble starts.
I have to go to a School function, so Aussie Bob and McGrath, when I get home I will pay particular attention to your questions.
J
And Forkie......that post is the worst of yours I have ever seen
Wait till Chuckles gets a hold of you
I am quite comfortable with my own knowledge on this subject, however I do fear for some who may try some of this 'home brew', without the benefit of previous experience.
Fuel and and O2 do not know the difference between your IO550 or the Brigs and stratten mower engine. All air cooled fixed spark 4 stroke petrol engines share 99% of things in common.
Rhetorical answer. My first guess would be that they had 'flying spanners' to look after the engines.
because I'm still trying to get to grips with Jaba's statement
Quote:
I will repeat that slower, the area under the curve where there is a greater chance of both detonation (especially in a turbo at high MP) and from general high CHT and ICP, is biased heavily on the ROP side of the curve.
Detonation caused by ROP?
Low Octane and Lean Mixtures Advanced Spark and high inlet air temperatures causes detonation. Show me where that is wrong and I'll keep my ear/mind open.
Apologies McGrath, I missed your post while typing. Anything I have posted here is easily found by a google search. ATM I now have to prepare for my next MS flight Sim session. I'll be back in about 16 hours.
Quote:
I will repeat that slower, the area under the curve where there is a greater chance of both detonation (especially in a turbo at high MP) and from general high CHT and ICP, is biased heavily on the ROP side of the curve.
Detonation caused by ROP?
Low Octane and Lean Mixtures Advanced Spark and high inlet air temperatures causes detonation. Show me where that is wrong and I'll keep my ear/mind open.
Apologies McGrath, I missed your post while typing. Anything I have posted here is easily found by a google search. ATM I now have to prepare for my next MS flight Sim session. I'll be back in about 16 hours.
Detonation potential exists in far greater amounts on the ROP side of the curve, the region on the leans side is fairly narrow even at full MP, so lets say in simple terms 30" up the beach at 500-1000' once on the LOP side of the curve the detonation region is from peak to maybe 20FLOP and the risk is eliminated at anything past 40LOP, the best place to be running here is 60-90LOP. And this is a fairly small movement of the mixture knob.
On the Rich side of the curve, the region is far greater, from peak through 75ROP which is best power and through to maybe 125-150 ROP and once out to a region of 200ROP the problem goes away again.
So tell me ......which side of the curve, has the most potential? And understanding that you do need high HP high temps and high IAT to get it going. And on a Turbo this is much easier to do!
So when you say a Lean mixture is what causes detonation, what you really mean is a Rich mixture that is not Rich enough. I am sure I have said this before, technically all mixtures on the curve above to the left of peak EGT are RICH and all the graph to right of peak is a lean mixture.
By definition TOO LEAN would have to be from the RHS and to be too lean over there, the engine stops.
To be TOO RICH, you would be way out the left and drowning the engine, but if you lean the flow and get to a bad zone that would be correctly described as NOT RICH ENOUGH.
Tinstaafl, yes indeed.....they just do not do many manuals, and probably yours any justice with a thorough explanation so hence the reason the pilots who fly them get a wird mix of the manual Vs the CFI..... and that is where the trouble starts.
I have to go to a School function, so Aussie Bob and McGrath, when I get home I will pay particular attention to your questions.
J
And Forkie......that post is the worst of yours I have ever seen
Wait till Chuckles gets a hold of you
Last edited by Jabawocky; 9th Sep 2012 at 00:25.
Join Date: May 2009
Location: Australia, maybe
Posts: 559
Likes: 0
Received 0 Likes
on
0 Posts
EXPERTS ARE EVERYWHERE TO HELP YOU
THE “NEW” OLD LEANING TECHNIQUE (smallish pdf)
caution it is another Lycoming link...
(OEM keeps getting it wrong.... or do they?)
THE “NEW” OLD LEANING TECHNIQUE (smallish pdf)
caution it is another Lycoming link...
(OEM keeps getting it wrong.... or do they?)
Thread Starter
Join Date: Jul 2007
Location: in the classroom of life
Age: 55
Posts: 6,864
Likes: 0
Received 1 Like
on
1 Post
Ahh time to kill while waiting!
Aussie Bob,
You are quite correct, there is little written about best practise by the manufacturers, and it is quite surprising, when back in the radial days it was quite the opposite. The last 40 years has been different, Lycoming have been known to print that they think the process I use every flight, and thousands of others do every day, is too hard for the average pilot to cope with. They said different words, but thats what they meant.
Full power for take off
25/2500 for the climb
This is not nice to engines. Unless there is a limitation in the LIMITATIONS section, you should be climbing WOT/2700RPM and using a target EGT that you had at 1000 AMSL lean back every couple of thousand to that same EGT number. This works even with a single point probe.
Last week I did a batch of takeoff and climb tests with all the data being logged. The 4 flights were the same place the same route the same as I could make them and at the same IAS 120knots. I did this after I mentioned it to George Braly and his reply was
The data files are quite huge and video massive, and has been given to John for processing to see if there is any useful classroom stuff in it, so I wont try to post it all here, however here is my email to George Walter and John.
So a climb of 4500 feet and the time to TOC was in order of run, 3.5min, 4.0min, 4.5min, 3.5min.
The temps CHT was 15F hotter by 2500 and they started that run about 10-15 cooler.
Here is a photo I snapped with my iphone of the trusty G296.The inner most arc is the first run and the turn being done is the 4th run at the same place, same as the initial control run.
Once in the cruise, either an appropriate ROP setting or an appropriate LOP setting is the go.
Now I would really have to question why you think the engine life you are seeing in these engines is normal and acceptable
Why is it acceptable to have engines that are run all the time in commercial ops (the best kind) to have tops at 1200 hours? That is not what I would call optimal. Operators in the USA who changed their training and better understood their engines soon find that their engines are reaching TBO with no or very little work, especially if fitted with cylinders that were built right to begin with. So your observation while you think it is good and normal, is exactly the opposite, but only because you have never known otherwise. TBO of those big cranky difficult radials (Wright & P&W) engines was around 3600, and run LOP!
mcgrath,
You would be correct, that would depending on the scale, be 75ROP which is best power. If it was 50 ROP or near enough some will be either side, but roughly that is near the high point of ICP and CHT, at around 30-40ROP.
This is not ideal, there are better places to be, but getting to the bottom of that in this one post is not possible. Bob's 2400/23" is at a power where there is not any real danger, it is not optimal, but it is not deadly.
If you guys want to talk about this some time get in contact with me, happy to help, but there is no simple post, no simple 30 minute phone call and definately no cookbook recipe that can be given. This is what the TCM and LYC manuals give you, a couple of samples recipe's they do not teach you about the engine. It really takes a 2-3 day APS course that is extremely well constructed, in a step by step building block approach. I have never heard anyone say they wanted their money back. Thats testimony in itself.
Unfortunately Ada Ok is a long way away, but I reckon there may be some classes in Oz in 2013, so hang in there, read the John Deakin articles until then. When I get a whisper I will make sure you gus are the first to know
Aussie Bob,
You are quite correct, there is little written about best practise by the manufacturers, and it is quite surprising, when back in the radial days it was quite the opposite. The last 40 years has been different, Lycoming have been known to print that they think the process I use every flight, and thousands of others do every day, is too hard for the average pilot to cope with. They said different words, but thats what they meant.
Full power for take off
25/2500 for the climb
This is not nice to engines. Unless there is a limitation in the LIMITATIONS section, you should be climbing WOT/2700RPM and using a target EGT that you had at 1000 AMSL lean back every couple of thousand to that same EGT number. This works even with a single point probe.Last week I did a batch of takeoff and climb tests with all the data being logged. The 4 flights were the same place the same route the same as I could make them and at the same IAS 120knots. I did this after I mentioned it to George Braly and his reply was
Actually - - that would be pretty nice. So, yes. Please!
1st run = Data 15901 – 16184 Trial run done as a normal lean in the climb WOT/2650/Target EGT
2nd run = Data 16515 – 16820 WOT/2650/full rich all the way to 5500
3rd run = Data 17100 – 17452 WOT full bore till 500 AGL then @1300’ (1000AGL) back to 25/25 and full rich.
4th run = Data 17783 - 18000 a proper WOT/2650/Target EGT
Things I noted already without reviewing the data, just the video.
Noting the RMI as I fly down RWY12 at about 700AGL and the RMI pointer says I have passed the ARP, the power is on and away we go, in both video 3 & 4. So my start is consistent, yet going through 2500’ which is only 1500 of climb, the 25/25 is already almost 15F hotter. The time to 5500’ is 4.5min Vs 3.5 minutes.
I reckon if I climbed slower, apart from a pitch attitude more common to Jay Apt, the temps would have been more noticeable, but just a guess.
2nd run = Data 16515 – 16820 WOT/2650/full rich all the way to 5500
3rd run = Data 17100 – 17452 WOT full bore till 500 AGL then @1300’ (1000AGL) back to 25/25 and full rich.
4th run = Data 17783 - 18000 a proper WOT/2650/Target EGT
Things I noted already without reviewing the data, just the video.
Noting the RMI as I fly down RWY12 at about 700AGL and the RMI pointer says I have passed the ARP, the power is on and away we go, in both video 3 & 4. So my start is consistent, yet going through 2500’ which is only 1500 of climb, the 25/25 is already almost 15F hotter. The time to 5500’ is 4.5min Vs 3.5 minutes.
I reckon if I climbed slower, apart from a pitch attitude more common to Jay Apt, the temps would have been more noticeable, but just a guess.
The temps CHT was 15F hotter by 2500 and they started that run about 10-15 cooler.
Here is a photo I snapped with my iphone of the trusty G296.The inner most arc is the first run and the turn being done is the 4th run at the same place, same as the initial control run.
Once in the cruise, either an appropriate ROP setting or an appropriate LOP setting is the go.
Now I would really have to question why you think the engine life you are seeing in these engines is normal and acceptable
Why is it acceptable to have engines that are run all the time in commercial ops (the best kind) to have tops at 1200 hours? That is not what I would call optimal. Operators in the USA who changed their training and better understood their engines soon find that their engines are reaching TBO with no or very little work, especially if fitted with cylinders that were built right to begin with. So your observation while you think it is good and normal, is exactly the opposite, but only because you have never known otherwise. TBO of those big cranky difficult radials (Wright & P&W) engines was around 3600, and run LOP!mcgrath,
You would be correct, that would depending on the scale, be 75ROP which is best power. If it was 50 ROP or near enough some will be either side, but roughly that is near the high point of ICP and CHT, at around 30-40ROP.
This is not ideal, there are better places to be, but getting to the bottom of that in this one post is not possible. Bob's 2400/23" is at a power where there is not any real danger, it is not optimal, but it is not deadly.
If you guys want to talk about this some time get in contact with me, happy to help, but there is no simple post, no simple 30 minute phone call and definately no cookbook recipe that can be given. This is what the TCM and LYC manuals give you, a couple of samples recipe's they do not teach you about the engine. It really takes a 2-3 day APS course that is extremely well constructed, in a step by step building block approach. I have never heard anyone say they wanted their money back. Thats testimony in itself.
Unfortunately Ada Ok is a long way away, but I reckon there may be some classes in Oz in 2013, so hang in there, read the John Deakin articles until then. When I get a whisper I will make sure you gus are the first to know
Thread Starter
Join Date: Jul 2007
Location: in the classroom of life
Age: 55
Posts: 6,864
Likes: 0
Received 1 Like
on
1 Post
Trent
Yes you found one of Lycomings real Gems.
I dare you, pick up the phone and call George Braly and ask him what he thinks of that cracker.I know what he thinks, and why they wrote it too. i would love to see what you write back with.
You obviously will not believe me and all you are doing is ruining a constructive sequence of posts.
But at the same time, for the rest of the readers read that publication with a careful and critical eye.
They own graphs, their own comments, and their own contradictions. This is also the one where they say 98% of pilots are too dumb to do it safely.
And you wonder why I and many others are so critical of the TCM and Lycoming publications.
Keep throwing them up, you are helpng my cause, especially for the astute reader.
Yes you found one of Lycomings real Gems.
I dare you, pick up the phone and call George Braly and ask him what he thinks of that cracker.I know what he thinks, and why they wrote it too. i would love to see what you write back with.
You obviously will not believe me and all you are doing is ruining a constructive sequence of posts.
But at the same time, for the rest of the readers read that publication with a careful and critical eye.
They own graphs, their own comments, and their own contradictions. This is also the one where they say 98% of pilots are too dumb to do it safely.
And you wonder why I and many others are so critical of the TCM and Lycoming publications.
Keep throwing them up, you are helpng my cause, especially for the astute reader.
Join Date: May 2009
Location: Australia, maybe
Posts: 559
Likes: 0
Received 0 Likes
on
0 Posts
Jaba, I'm sorry that you think I am "ruining a constructive sequence of posts". All I have offered to the readers of this thread is links to Lycoming's position.
You and I both know who Lycoming targeted with the previous link I put up.
As he could, he had his own shot back.
I'd like you to offer your thoughts on whether 'Detonation' can be heard in the typical GA engine in flight. I'm sure that, like me, you know that it is a much deeper sound and unless you know exactly what to listen for, it is almost impossible to hear. (unlike a car engine).
For those who didn't bother to read the link, here is the important bit
I have no doubt that you and your friends fit the first sentence, but the vast majority fit the last sentence. I wish you all the luck in educating the pilot fraternity, and hope that you have better success than Lycoming, who after years of preaching the same, gave up and now recommend the conservative alternative.
You and I both know who Lycoming targeted with the previous link I put up.
As he could, he had his own shot back.
I'd like you to offer your thoughts on whether 'Detonation' can be heard in the typical GA engine in flight. I'm sure that, like me, you know that it is a much deeper sound and unless you know exactly what to listen for, it is almost impossible to hear. (unlike a car engine).
For those who didn't bother to read the link, here is the important bit
Lycoming is in complete agreement that it is possible to
operate an engine on the lean side of peak TIT. It is done on
engines in our well-instrumented Experimental Test laboratory
every day. There is nothing detrimental in operating an engine in
this manner. However, we can attest to the fact that things that
work well in the test laboratory have not always proven
successful in service. In the sales literature provided for this
“new” technique, it is stated that Lycoming recommended this
operational procedure in an owner’s manual that dates back to the
late ‘60’s. No mention is made why it is no longer recommended
on our present engines. The fact is that the technique of operating
lean of peak and power recovery was discontinued due to the
resulting increase in service issues.
operate an engine on the lean side of peak TIT. It is done on
engines in our well-instrumented Experimental Test laboratory
every day. There is nothing detrimental in operating an engine in
this manner. However, we can attest to the fact that things that
work well in the test laboratory have not always proven
successful in service. In the sales literature provided for this
“new” technique, it is stated that Lycoming recommended this
operational procedure in an owner’s manual that dates back to the
late ‘60’s. No mention is made why it is no longer recommended
on our present engines. The fact is that the technique of operating
lean of peak and power recovery was discontinued due to the
resulting increase in service issues.
Somewhere in one of the Baron series POH's there is a statement that goes something like this;
When operating the engine at between 65% to 75% do not set mixtures between 25c LOP and 25c ROP.
This is a fairly broad range and I am certain that it is broad so as to accommodate the scatter of peak points on a standard engine. It moves you away from the narrow area of margin for detonation.
Trent
I doubt very much that when you read the POH you are reading the wisdom of those that built the engine. But the wording of the marketing/legal team. Many of the Lycoming Flyer articles are a great resource but the Flyer responding to LOP operations was little more than a hurt response from a company being exposed for not doing enough to accurately tune their engines. Humans are fairly predictable.
About a year or so ago I was speaking to one of Lycomings senior tech reps, he fully acknowledged the short comings of the old 50F ROP recommendation and much preferred running at peak. LOP was not on the menu as it was unlikely that smooth running could be achieved. Solve the smooth running issue and no problems.
Shock cooling is and is not a myth in much the same way as shock heating is and is not a myth.
If the cylinders are old, + 3000 hours they are reasonably fatigued if you subject an old cylinder to rapid cooling, say greater than 50F/minute and you commence this process from a high temperature were the tensile yield values are low you will probably enhance the risk of cracking in areas around steel components, such as valve seat inserts, the cylinder barrel itself and the spark plugs.
Those who have spent some time flying the small PW series radials (985/1340) will know all too well that the cylinders could have been in service since the mid 50's. They fail all the time, cracking ears and around the cylinder barrel, this happens regardless of how the engine is managed but those that boost them hard seem to have more failures than those that don't, (observation only).
I don't hear anywhere near as much carry on these days about shock cooling as was around 25 years ago. I think most have grasped the subject.
When operating the engine at between 65% to 75% do not set mixtures between 25c LOP and 25c ROP.
This is a fairly broad range and I am certain that it is broad so as to accommodate the scatter of peak points on a standard engine. It moves you away from the narrow area of margin for detonation.
Trent
I am not prepared to discount the wisdom of the people who built the engine.
About a year or so ago I was speaking to one of Lycomings senior tech reps, he fully acknowledged the short comings of the old 50F ROP recommendation and much preferred running at peak. LOP was not on the menu as it was unlikely that smooth running could be achieved. Solve the smooth running issue and no problems.
Shock cooling is and is not a myth in much the same way as shock heating is and is not a myth.
If the cylinders are old, + 3000 hours they are reasonably fatigued if you subject an old cylinder to rapid cooling, say greater than 50F/minute and you commence this process from a high temperature were the tensile yield values are low you will probably enhance the risk of cracking in areas around steel components, such as valve seat inserts, the cylinder barrel itself and the spark plugs.
Those who have spent some time flying the small PW series radials (985/1340) will know all too well that the cylinders could have been in service since the mid 50's. They fail all the time, cracking ears and around the cylinder barrel, this happens regardless of how the engine is managed but those that boost them hard seem to have more failures than those that don't, (observation only).
I don't hear anywhere near as much carry on these days about shock cooling as was around 25 years ago. I think most have grasped the subject.
Last edited by Obidiah; 8th Sep 2012 at 09:45.