Commercial Pilots who don't know about piston engines
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andrewr….yes correct but I can't get oggers to answer a few simple questions, so very basic analogy attempts were the best I could get. 
Refusal to accept that increasing pressure and dropping EGT means the correlation he observes does not equate to causation.
All Swans were white……until they found black swans.
Refusal to accept that increasing pressure and dropping EGT means the correlation he observes does not equate to causation.
All Swans were white……until they found black swans.
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I wrote:
In the case of spark advancement, heat energy from the combustion process is being created earlier relative to a retarded ignition. As a result more of that heat energy is transferred by convection and radiation to the cylinder walls and valve faces, and less of the heat energy is dissipated in the expansion of the gas, relative to a more retarded ignition.
Last edited by vh-foobar; 10th Apr 2016 at 10:07. Reason: grammar
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***
Your engine is not an air compressor.
In an air compressor, the piston is adding energy to the gas (compressing it) which heats the gas. In an engine, the piston is extracting energy from the compressed gas which actually cools the gas and lowers the EGT.
***
The exact same thing is happening in an internal combustion engine. The IAT is heated during the compression stroke.
***
You can see this in e.g. CO2 engines which run from compressed gas without combustion. They get (very) cold, not hot.
***
This is due to the fact that the air is never heated and the EXPANSION on the power stroke is cooling significantly.
***
In an IC engine the temperature creates the pressure, not the other way around.
***
The "temperature" does not create the pressure. The expansion of the burning gas that creates the pressure, the increasing pressure affects the heating. It's a small nit, but it's real.
***
The NACA report 754 alludes to this in the section on the effect of timing on valve temperature:
"The rise in valve temperature with greatly retarded spark is probably caused by the higher exhaust-gas temperature resulting from a decreased expansion after combustion"
***
They got this "probably" wrong. This is a perfect example of a correct observation leading to an incorrect assumption of causality. The later thetaPP of a retarded spark has the resultant EGT higher at a much reduced pressure. The rising valve temp in these conditions are caused by the still burning 3800dF combustion gasses going past the open valve. There was no time for the gas to expand after burning and lower the EGT. We can see this effect in very well-balanced F:A engines that are leaned beyond optimal. This is not a "normal" condition.
***
Earlier combustion = higher pressures but greater expansion after combustion (i.e. piston stroke after combustion) = more energy extracted from the gas = lower EGT but yes, probably higher CHT.
***
Correct.
Your engine is not an air compressor.
In an air compressor, the piston is adding energy to the gas (compressing it) which heats the gas. In an engine, the piston is extracting energy from the compressed gas which actually cools the gas and lowers the EGT.
***
The exact same thing is happening in an internal combustion engine. The IAT is heated during the compression stroke.
***
You can see this in e.g. CO2 engines which run from compressed gas without combustion. They get (very) cold, not hot.
***
This is due to the fact that the air is never heated and the EXPANSION on the power stroke is cooling significantly.
***
In an IC engine the temperature creates the pressure, not the other way around.
***
The "temperature" does not create the pressure. The expansion of the burning gas that creates the pressure, the increasing pressure affects the heating. It's a small nit, but it's real.
***
The NACA report 754 alludes to this in the section on the effect of timing on valve temperature:
"The rise in valve temperature with greatly retarded spark is probably caused by the higher exhaust-gas temperature resulting from a decreased expansion after combustion"
***
They got this "probably" wrong. This is a perfect example of a correct observation leading to an incorrect assumption of causality. The later thetaPP of a retarded spark has the resultant EGT higher at a much reduced pressure. The rising valve temp in these conditions are caused by the still burning 3800dF combustion gasses going past the open valve. There was no time for the gas to expand after burning and lower the EGT. We can see this effect in very well-balanced F:A engines that are leaned beyond optimal. This is not a "normal" condition.
***
Earlier combustion = higher pressures but greater expansion after combustion (i.e. piston stroke after combustion) = more energy extracted from the gas = lower EGT but yes, probably higher CHT.
***
Correct.
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***
I agree about optimizing the PP. On valve life, the flight engineer instructor says it favoured longer life, you say it doesn't. I have no way of confirming either way. It might annoy you that I don't just "believe" but that's OK.
***
We can confirm this if we understand the difference between the higher EGT very late in the cycle as I explained in the post above and the engineer's reasoning being correct and a higher EGT in a normal combustion cycle which is what I have been talking about. We are not in disagreement, just talking about two very different conditions--one normal, the other abnormal. The standard takeoff timing was so late during cruise operation as to have the valve opening while the gas was still burning. That is not good and is bad for valve life, as the engineer correctly surmised. That's not what I was talking about in the normal combustion event. They advanced the timing to allow the valve to be closed during combustion event and not have the extremely hot gasses flow by the valve face. We show these different conditions on leaning traces in the APS class.
***
But if you advance the timing to keep the same theta PP, you (obviously) start burning earlier BTDC and will burn more of the mixture before top dead centre (i.e. timing 20 degrees BTDC you have 36 degrees of rotation before the theta PP, 30 BTDC gives 46 degrees. At 20 degrees you are half way there at 4 degrees BTDC, 30 degrees half way is 9 degrees BTDC.
***
By measurement, half of the F:A mixture is consumed at the thetaPP. If the thetaPP is the same the same amount of gas has been burned regardless of the spark event timing. The reason this works is two-fold. The flame front is organized slower and the burn is slower. SO, the amount of increased pressure on the up-stroke is not significantly different.
***
Does this not increase ICP? Not that I think increased ICP is a problem, within design parameters, but you seem to be aiming to reduce it?
***
See explanation above. The ICP is "increased" from a very low number, very late in the cycle to the designed ICP at the right place in the stroke. These ICPs are still much lower than those seen at 50dF ROP, hence the desire to lower them to this level.
***
In particular, I believe that the statement that operating according to engine manufacturer recommendations will result in a decreased service life deserves better data than service information from radial engines 50 years ago.
***
The physics are everywhere the same. Sir Isaac Newton.
There are more similarities than differences in radials and flat engines. They had 400 MILLION flight hours of data. We have more than 4 million flight hours of data on the flat engines and it is all in a agreement. (Thank you to Sir Isaac!)
***
Is it not possible that Lycoming has incorporated some of the information that was discovered to improve their engines and eliminate many of the causes of failure?
***
One would hope so.
I agree about optimizing the PP. On valve life, the flight engineer instructor says it favoured longer life, you say it doesn't. I have no way of confirming either way. It might annoy you that I don't just "believe" but that's OK.
***
We can confirm this if we understand the difference between the higher EGT very late in the cycle as I explained in the post above and the engineer's reasoning being correct and a higher EGT in a normal combustion cycle which is what I have been talking about. We are not in disagreement, just talking about two very different conditions--one normal, the other abnormal. The standard takeoff timing was so late during cruise operation as to have the valve opening while the gas was still burning. That is not good and is bad for valve life, as the engineer correctly surmised. That's not what I was talking about in the normal combustion event. They advanced the timing to allow the valve to be closed during combustion event and not have the extremely hot gasses flow by the valve face. We show these different conditions on leaning traces in the APS class.
***
But if you advance the timing to keep the same theta PP, you (obviously) start burning earlier BTDC and will burn more of the mixture before top dead centre (i.e. timing 20 degrees BTDC you have 36 degrees of rotation before the theta PP, 30 BTDC gives 46 degrees. At 20 degrees you are half way there at 4 degrees BTDC, 30 degrees half way is 9 degrees BTDC.
***
By measurement, half of the F:A mixture is consumed at the thetaPP. If the thetaPP is the same the same amount of gas has been burned regardless of the spark event timing. The reason this works is two-fold. The flame front is organized slower and the burn is slower. SO, the amount of increased pressure on the up-stroke is not significantly different.
***
Does this not increase ICP? Not that I think increased ICP is a problem, within design parameters, but you seem to be aiming to reduce it?
***
See explanation above. The ICP is "increased" from a very low number, very late in the cycle to the designed ICP at the right place in the stroke. These ICPs are still much lower than those seen at 50dF ROP, hence the desire to lower them to this level.
***
In particular, I believe that the statement that operating according to engine manufacturer recommendations will result in a decreased service life deserves better data than service information from radial engines 50 years ago.
***
The physics are everywhere the same. Sir Isaac Newton.
There are more similarities than differences in radials and flat engines. They had 400 MILLION flight hours of data. We have more than 4 million flight hours of data on the flat engines and it is all in a agreement. (Thank you to Sir Isaac!)
***
Is it not possible that Lycoming has incorporated some of the information that was discovered to improve their engines and eliminate many of the causes of failure?
***
One would hope so.
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***
The NACA report 754 alludes to this in the section on the effect of timing on valve temperature:
"The rise in valve temperature with greatly retarded spark is probably caused by the higher exhaust-gas temperature resulting from a decreased expansion after combustion"
***
They got this "probably" wrong. This is a perfect example of a correct observation leading to an incorrect assumption of causality. The later thetaPP of a retarded spark has the resultant EGT higher at a much reduced pressure. The rising valve temp in these conditions are caused by the still burning 3800dF combustion gasses going past the open valve. There was no time for the gas to expand after burning and lower the EGT. We can see this effect in very well-balanced F:A engines that are leaned beyond optimal. This is not a "normal" condition.
Correct.
The NACA report 754 alludes to this in the section on the effect of timing on valve temperature:
"The rise in valve temperature with greatly retarded spark is probably caused by the higher exhaust-gas temperature resulting from a decreased expansion after combustion"
***
They got this "probably" wrong. This is a perfect example of a correct observation leading to an incorrect assumption of causality. The later thetaPP of a retarded spark has the resultant EGT higher at a much reduced pressure. The rising valve temp in these conditions are caused by the still burning 3800dF combustion gasses going past the open valve. There was no time for the gas to expand after burning and lower the EGT. We can see this effect in very well-balanced F:A engines that are leaned beyond optimal. This is not a "normal" condition.
Correct.
Last edited by vh-foobar; 10th Apr 2016 at 23:28. Reason: grammar
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Lead Balloon
Well, I don't speak for Eddie Dean, but that quote most definitely doesn't mention 30ROP being the best place to run an engine for longevity, which is an argument you seem strangely keen for someone, anyone, to take up!
0ggers went on to say:
Gosh. You haven't been paying much attention to the detail of the 'debate' Downunda, have you. For example, Eddie Dean said at post 242 of this very thread:
I'm not aware that anyone has ever argued 30 ROP is the best place to run an engine for longevity.
I have worked with several operators and Chief Engineers over recent years, all of them are against the APS LOP theory and have warned their pilots of such.
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i think the problem with these guys, is they "think" they are LOP, one or 2 cylinders might be, but the others could well be right in the danger zone about 50 ROP. to run reliably at LOP, you need good monitoring, and a conforming engine. without that, you see the results, damage caused by those that think, but arnt running all cylinders LOP.
That's why it's very important not to confuse trying to run LOP, or believing an 'engine' is LOP, for each cylinder being LOP.
Otherwise you also have to exclude engines from the non-LOP camp too: those who don't lean, those who lean but not in accordance with manufacturer's instructions, any engines that have suffered overheating, engines with bad baffling...
If you start excluding those who fail to follow instructions correctly, pretty soon reliability data is meaningless.
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***
Your engine is not an air compressor.
In an air compressor, the piston is adding energy to the gas (compressing it) which heats the gas. In an engine, the piston is extracting energy from the compressed gas which actually cools the gas and lowers the EGT.
***
The exact same thing is happening in an internal combustion engine. The IAT is heated during the compression stroke.
Your engine is not an air compressor.
In an air compressor, the piston is adding energy to the gas (compressing it) which heats the gas. In an engine, the piston is extracting energy from the compressed gas which actually cools the gas and lowers the EGT.
***
The exact same thing is happening in an internal combustion engine. The IAT is heated during the compression stroke.
The "temperature" does not create the pressure. The expansion of the burning gas that creates the pressure, the increasing pressure affects the heating. It's a small nit, but it's real.
***
The NACA report 754 alludes to this in the section on the effect of timing on valve temperature:
"The rise in valve temperature with greatly retarded spark is probably caused by the higher exhaust-gas temperature resulting from a decreased expansion after combustion"
***
They got this "probably" wrong. This is a perfect example of a correct observation leading to an incorrect assumption of causality. The later thetaPP of a retarded spark has the resultant EGT higher at a much reduced pressure. The rising valve temp in these conditions are caused by the still burning 3800dF combustion gasses going past the open valve. There was no time for the gas to expand after burning and lower the EGT.
The NACA report 754 alludes to this in the section on the effect of timing on valve temperature:
"The rise in valve temperature with greatly retarded spark is probably caused by the higher exhaust-gas temperature resulting from a decreased expansion after combustion"
***
They got this "probably" wrong. This is a perfect example of a correct observation leading to an incorrect assumption of causality. The later thetaPP of a retarded spark has the resultant EGT higher at a much reduced pressure. The rising valve temp in these conditions are caused by the still burning 3800dF combustion gasses going past the open valve. There was no time for the gas to expand after burning and lower the EGT.
A flame is just hot gas anyway. The 3800F heat doesn't just disappear once the burn is complete. The gas remains at that temperature until it loses the energy to something else.
There are basically 5 places that energy can go:
1) Turning the propeller by expanding against the piston - this is obviously where we want the energy to go
2) Out the exhaust (EGT)
3) Into the cylinder head/valves
4) Into the piston
5) Into the cylinder barrel.
That's it. All that 3800F heat has to go down one of those paths.
The earlier you burn the more the gas can expand against the piston and the more energy goes down the useful path - and the sum of all the other energies must be less (even if e.g. CHT is higher).
If the burn finishes late much more energy (heat) remains in the gas or is transferred to other engine parts. EGT is higher and as you say this will heat the valves. CHT may be lower because the heat is spread through a larger volume in the cylinder, but I would be very interested to see measurements of cylinder barrel temperatures in particular. I would expect them to rise as the CHT decreases with leaner mixtures. You can look at the fins to see which part is intended to receive most heat.
All the explanations need to follow the principles of chemistry and conservation of energy. If they don't e.g. some energy just disappears there is something missing from the explanation.
I see, oggers. When Eddie referred to all those operators and Chief Engineers who've "rejected the APS LOP theory and have warned their pilots of such", he meant (of course) that those operators and Chief Engineers were warning against operating engines 30 degrees F rich of peak.
I picked 30. I could have picked 40. Or 47.397. Or 27.3333. The number matters not (except, perhaps, for the purposes of whatever it is you're arguing) until all cylinders are far enough ROP.
Andrewr: You are in my view absolutely correct. The 'data' derived from multi-cylinder engines with a single EGT probe and a single CHT probe and no way of calculating accurate % power measurements are absolutely meaningless for the purposes of deciding whether ROP is "better" than LOP for a multi-cylinder engine. That's one of the reasons why opinions about the causes of the unreliability of and damage to a piston engine with a single EGT probe and single EGT probe are also absolutely meaningless.
I picked 30. I could have picked 40. Or 47.397. Or 27.3333. The number matters not (except, perhaps, for the purposes of whatever it is you're arguing) until all cylinders are far enough ROP.
Andrewr: You are in my view absolutely correct. The 'data' derived from multi-cylinder engines with a single EGT probe and a single CHT probe and no way of calculating accurate % power measurements are absolutely meaningless for the purposes of deciding whether ROP is "better" than LOP for a multi-cylinder engine. That's one of the reasons why opinions about the causes of the unreliability of and damage to a piston engine with a single EGT probe and single EGT probe are also absolutely meaningless.
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Walter Atkinson,
Andrewr posted
...you posted
No Walter you are not right about this at all. In a heat engine there is this thing called a 'heat addition process' - ie when combustion happens. It is not called a 'pressure addition process'. Heat and temperature are not the same thing but andrewr is absolutely correct that "the temperature creates the pressure not the other way around". The pressure rises because the heat of combustion raises the temperature of the gas and the pressure therefore has to go up and/or expansion occur.
The "expansion of the burning gas" does not "create the pressure". The expansion of the gas reduces the pressure. You cannot argue with that, it is the gas law. That is not to say that pressure cannot rise while expansion takes place, but that is different and not what you claim.
It would be fair to say the burning of the gas is creating the pressure, or causing the expansion. In neither case is the "expansion of the burning gas creating the pressure".
Sorry Walter but this is not a small nit it is thermodynamics 101 and you have it wrong.
Andrewr posted
In an IC engine the temperature creates the pressure, not the other way around.
The "temperature" does not create the pressure. The expansion of the burning gas that creates the pressure, the increasing pressure affects the heating. It's a small nit, but it's real.
The "expansion of the burning gas" does not "create the pressure". The expansion of the gas reduces the pressure. You cannot argue with that, it is the gas law. That is not to say that pressure cannot rise while expansion takes place, but that is different and not what you claim.
It would be fair to say the burning of the gas is creating the pressure, or causing the expansion. In neither case is the "expansion of the burning gas creating the pressure".
It's a small nit, but it's real
Last edited by oggers; 11th Apr 2016 at 14:32. Reason: grammar
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Lead balloon
as I posted:
I see, oggers. When Eddie referred to all those operators and Chief Engineers who've "rejected the APS LOP theory and have warned their pilots of such", he meant (of course) that those operators and Chief Engineers were warning against operating engines 30 degrees F rich of peak.
I picked 30. I could have picked 40. Or 47.397. Or 27.3333. The number matters not (except, perhaps, for the purposes of whatever it is you're arguing) until all cylinders are far enough ROP
I picked 30. I could have picked 40. Or 47.397. Or 27.3333. The number matters not (except, perhaps, for the purposes of whatever it is you're arguing) until all cylinders are far enough ROP
Lead Balloon
Well, I don't speak for Eddie Dean, but that quote most definitely doesn't mention 30ROP being the best place to run an engine for longevity, which is an argument you seem strangely keen for someone, anyone, to take up!
0ggers went on to say:
I'm not aware that anyone has ever argued 30 ROP is the best place to run an engine for longevity.
Gosh. You haven't been paying much attention to the detail of the 'debate' Downunda, have you. For example, Eddie Dean said at post 242 of this very thread:
I have worked with several operators and Chief Engineers over recent years, all of them are against the APS LOP theory and have warned their pilots of such.
Last edited by oggers; 11th Apr 2016 at 14:08.
I suspect that 'Lead Balloon' may be a rather junior aeromodeller, perhaps flying his first Enya 15 powered model aircraft?
So he'd have no idea of how an IO520 engine in a family owned Bonanza would operate? Things like how to run the engine at its most efficient leisure. And how to keep his life and that of his pax safe?
Clearly, he doesn't have a clue..
So he'd have no idea of how an IO520 engine in a family owned Bonanza would operate? Things like how to run the engine at its most efficient leisure. And how to keep his life and that of his pax safe?
Clearly, he doesn't have a clue..
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So he'd have no idea of how an IO520 engine in a family owned Bonanza would operate? Things like how to run the engine at its most efficient leisure. And how to keep his life and that of his pax safe?
Clearly, he doesn't have a clue..
Clearly, he doesn't have a clue..
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Walter Atkinson:
That claim about TBO is unverified and therefore suspect. When I do a search to verify that claim, the only links I get are ones to you making the same claim on other forums without any evidence.
Who say:
redskyventures.org EGT Procedures ALCOR pdf
So the "innovators" at Alcor have identified a correlation between EGT and exhaust valve temp.
Figure 9:
When running the TC-18 engines ROP, the TBO was 600 hours. When operating LOP, the TBO was 3600 hours. Why? Lower ICPs and CHTs resulted in greater longevity and fewer maintenance issues at the same power output. THAT was easier on the exhaust valves. They could not measure EGT on the engines as installed. That awaited the innovations of Alcor.
They could not measure EGT on the engines as installed. That awaited the innovations of Alcor.
"The exhaust valve is usually the most critical with respect to excessive temperatures.
When the mixture is enriched at powers above 65% to maintain constant exhaust valve temperature, the EGT versus power curve is as shown in Figure 9. As illustrated, the EGT at 100% power needs to be 100°F lower than peak EGT at 65% if the exhaust valve is to be maintained at the same temperature as it is at peak EGT for 65% power."
When the mixture is enriched at powers above 65% to maintain constant exhaust valve temperature, the EGT versus power curve is as shown in Figure 9. As illustrated, the EGT at 100% power needs to be 100°F lower than peak EGT at 65% if the exhaust valve is to be maintained at the same temperature as it is at peak EGT for 65% power."
So the "innovators" at Alcor have identified a correlation between EGT and exhaust valve temp.
Figure 9:
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Oggers said:-
What you and others seem unable to get your heads around is that BEFORE top dead centre (TDC) the size (volume) of of the container holding the gas is decreasing. Even without igniting the gas the pressure and temperature increase. You know-same number of molecules squeezed into a smaller space.
How much anti-work pressure ( pressure trying to make the engine go backwards) depends on where you light the fire. Remember all the way up the upstroke the volume of the part of the cylinder containing the gas is decreasing. So if you light the fire early the pressure increases sooner. The worst / hardest you can be on your engine is to burn all the fuel/air mixture before TDC . At that point your combustion chamber is the smallest it's going to get and you've added ALL the the energy from combustion plus the normal heat from compressing the intake gas to 12% of it's original volume.
This gives a very high temperature and internal cylinder pressure (ICP) but because of the geometry of the piston / con rod / crankshaft at that point no work is being done. The piston is pushing straight down on top of the crankshaft (trying to push it through the bottom of the sump) but giving NO rotational force.
Once past TDC the pressure starts to do some useful work. Unfortunately the greatest mechanical advantage occurs when the con rod is at right angles to the crank web (BTW Not 90* after TDC ) This is no use as by the time the crank reaches that angle the combustion chamber is many times larger and the pressure many times smaller and not worth using.
So the trick is to have peak ICP occur where there some mechanical advantage but the volume of the combustion chamber hasn't grown big enough to adversely effect the pressure to an unacceptable extent.
This "sweet spot" occurs when the fuel/air mixture finishes burning at 12* to 15* after TOD. As a fair bit of the combustion and hence energy increase takes place after TDC where the combustion chamber is starting to increase in volume it is obvious the ICP and temperature wont be as high as it would be if that energy had been added at or before TDC.
Anyone trying to get their head around piston engines must keep in mind the constantly changing volume of the combustion chamber and also the speed of the combustion event along with the factors affecting it.
Here's a good pub quizz to win a couple of beers.
After fuel ignites in an internal combustion engine what is it's average burn speed?
A 60 k/h
B 100 k/h
C 500 k/h
D 950 k/h
E Almost instantaneous. Can't be measured.
The expansion of the gas reduces the pressure.
How much anti-work pressure ( pressure trying to make the engine go backwards) depends on where you light the fire. Remember all the way up the upstroke the volume of the part of the cylinder containing the gas is decreasing. So if you light the fire early the pressure increases sooner. The worst / hardest you can be on your engine is to burn all the fuel/air mixture before TDC . At that point your combustion chamber is the smallest it's going to get and you've added ALL the the energy from combustion plus the normal heat from compressing the intake gas to 12% of it's original volume.
This gives a very high temperature and internal cylinder pressure (ICP) but because of the geometry of the piston / con rod / crankshaft at that point no work is being done. The piston is pushing straight down on top of the crankshaft (trying to push it through the bottom of the sump) but giving NO rotational force.
Once past TDC the pressure starts to do some useful work. Unfortunately the greatest mechanical advantage occurs when the con rod is at right angles to the crank web (BTW Not 90* after TDC ) This is no use as by the time the crank reaches that angle the combustion chamber is many times larger and the pressure many times smaller and not worth using.
So the trick is to have peak ICP occur where there some mechanical advantage but the volume of the combustion chamber hasn't grown big enough to adversely effect the pressure to an unacceptable extent.
This "sweet spot" occurs when the fuel/air mixture finishes burning at 12* to 15* after TOD. As a fair bit of the combustion and hence energy increase takes place after TDC where the combustion chamber is starting to increase in volume it is obvious the ICP and temperature wont be as high as it would be if that energy had been added at or before TDC.
Anyone trying to get their head around piston engines must keep in mind the constantly changing volume of the combustion chamber and also the speed of the combustion event along with the factors affecting it.
Here's a good pub quizz to win a couple of beers.
After fuel ignites in an internal combustion engine what is it's average burn speed?
A 60 k/h
B 100 k/h
C 500 k/h
D 950 k/h
E Almost instantaneous. Can't be measured.
So oggers, because I'm a dumb pilot with no other qualifications, please tell me which of one the alternative EGT settings will all those wise "engineers and test pilots of the manufacturers combined" say is the best setting for the longevity of the engines on which my life relies:
- 30 ROP
Or
- 30 LOP.
(Or if you like:
- 40 ROP
Or
- 40 LOP
Or if you would prefer:
- 47.397 ROP
Or
- 47.397 LOP
Or perhaps instead:
- 27.3333 ROP
Or
- 27.333 LOP.)
What is a dumb pilot to do when the wise manufacturer's recommendations are contrary to what the data prove?
- 30 ROP
Or
- 30 LOP.
(Or if you like:
- 40 ROP
Or
- 40 LOP
Or if you would prefer:
- 47.397 ROP
Or
- 47.397 LOP
Or perhaps instead:
- 27.3333 ROP
Or
- 27.333 LOP.)
What is a dumb pilot to do when the wise manufacturer's recommendations are contrary to what the data prove?
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oggers
You are reduced to publishing alcor's material now as gospel.
The game is up. You will not take the advice of Walter, yet you will stand on the old Alcor advertisement material …….
As for the TBO….perhaps Walter might just have done a lot of work with and has a lot of papers from the guys that flew them. I have in my office an excellent publication from Curtis Wright which is not easily found where they talked heavily about what we know today to be true. Some folk from the DC-7 and Connie days could help you fill in the blanks. APS are just lucky to have one such gentleman, his name is John Deakin.
American Airlines would be an excellent source. Give them a call.
You are reduced to publishing alcor's material now as gospel.
The game is up. You will not take the advice of Walter, yet you will stand on the old Alcor advertisement material …….
As for the TBO….perhaps Walter might just have done a lot of work with and has a lot of papers from the guys that flew them. I have in my office an excellent publication from Curtis Wright which is not easily found where they talked heavily about what we know today to be true. Some folk from the DC-7 and Connie days could help you fill in the blanks. APS are just lucky to have one such gentleman, his name is John Deakin.
American Airlines would be an excellent source. Give them a call.
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Re pub quizz
Oops
None are correct so pick the one nearest.
Note to self. If you're going to celebrate the removal of a much hated Airport Manager by drinking heavily don't post on Pprune.
Oops
None are correct so pick the one nearest.
Note to self. If you're going to celebrate the removal of a much hated Airport Manager by drinking heavily don't post on Pprune.
Join Date: Nov 2005
Location: Zulu Time Zone
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Rutan around:
Sure, I would assume everyone gets that. It is obvious but it is beside the point. Walter Atkinson wrote - as a rebuttal to andrewr -
which is a misunderstanding of how an engine works thermodynamically and an equally incorrect understanding of the gas laws. That is the point.
Jabawocky
I have not claimed that Alcor document is gospel. Walter said "Alcor are innovative" so I simply reproduced some of their material. Somehow I didn't think you would like it. "Gospel" is your word - I wouldn't use it. If there is a part of that document you wish to rebut then feel free; I may or may not agree with your opinion.
Ok, so the calim by APS is "TC18 engines only made 600hrs TBO when run ROP, and they made 3600hrs when run LOP". If you have the documents from Wright where they verify this you will be able to post it here.
What you and others seem unable to get your heads around is that BEFORE top dead centre (TDC) the size (volume) of of the container holding the gas is decreasing. Even without igniting the gas the pressure and temperature increase. You know-same number of molecules squeezed into a smaller space.
The expansion of the burning gas creates the pressure
Jabawocky
oggers
You are reduced to publishing alcor's material now as gospel.
The game is up. You will not take the advice of Walter, yet you will stand on the old Alcor advertisement material …….
You are reduced to publishing alcor's material now as gospel.
The game is up. You will not take the advice of Walter, yet you will stand on the old Alcor advertisement material …….
"Gospel" is your word - I wouldn't use it. If there is a part of that document you wish to rebut then feel free; I may or may not agree with your opinion.
As for the TBO….perhaps Walter might just have done a lot of work with and has a lot of papers from the guys that flew them. I have in my office an excellent publication from Curtis Wright which is not easily found where they talked heavily about what we know today to be true.
Last edited by oggers; 12th Apr 2016 at 10:56.