New Cylinder AD's released by FAA
Join Date: Jul 2005
Location: Queensland
Posts: 686
Likes: 0
Received 0 Likes
on
0 Posts
More interesting reading by Mike Busch
- Over the past two years, ECi and various other interested parties (including me) have been on a campaign to educate pilots and aircraft owners about the critical importance of controlling CHTs, and of installing modern digital engine monitoring equipment with high-CHT alarms. It is interesting to note that there have been ZERO reported separations involving ECi cylinders in the past 18 months. A Weibull analysis calculated that there should have been a half-dozen separations during this period. This strongly suggests that the ECi separation issue is operational in nature, and that the problem is resolving itself through pilot/owner education without the need for FAA intervention.
- Head separations are very rare, and when they happen the result is generally pretty harmless. The head separates from the barrel by less than an inch, the cylinder goes to zero compression, and the engine continues to run on five cylinders and make roughly 80% power. (FAR Part 33 requires that all certificated piston engines must continue to operate safely with one cylinder shut down.) The engine runs rough, and in a single-engine airplane the pilot makes a safe precautionary landing at the nearest airport (which is exactly what happened in every instance). In a twin, the situation is even more benign—and the lion’s share of reported failures of ECi jugs occurred in Cessna 340s and 414s.
- Something rotten in the state of Texas ? My comment. RA
Join Date: Apr 2013
Location: Vail, Colorado, USA
Posts: 168
Likes: 0
Received 0 Likes
on
0 Posts
The shear strength of the threads is far less than the 20,000+ pounds of force placed upon them during the combustion event. Were it not for the interference fit--which remains quite adequate at modest CHTs--the head-barrel fit interface would fatigue and separate. When the CHTs get excessively high the interference fit is lessened. This can result in failure since the threads alone cannot sustain the load.
For this reason, the OEMs recommend controlling CHTs to around 380-400dF as a matter of routine. It's good advice.
There is a combination of proper interference fit during manufacture and controlled CHT during operation which results in success. For this reason, if the need is high power, it can better be accomplished LOP where CHTs are lower, pressures in the combustion chamber are lower and the metal is stronger.
All cylinders are not created equal where the interference fits concerned.
For this reason, the OEMs recommend controlling CHTs to around 380-400dF as a matter of routine. It's good advice.
There is a combination of proper interference fit during manufacture and controlled CHT during operation which results in success. For this reason, if the need is high power, it can better be accomplished LOP where CHTs are lower, pressures in the combustion chamber are lower and the metal is stronger.
All cylinders are not created equal where the interference fits concerned.
Join Date: Apr 2012
Location: Iraq
Age: 35
Posts: 151
Likes: 0
Received 0 Likes
on
0 Posts
Walter
Are you proposing that the head would unscrew under load without a locking device
Considering that a screw thread is a ramp.
Or is it like a main rotor grip that cracks the threads because the load has exceeded the carrying capacity
Are you proposing that the head would unscrew under load without a locking device
Considering that a screw thread is a ramp.
Or is it like a main rotor grip that cracks the threads because the load has exceeded the carrying capacity
Join Date: Apr 2007
Location: australia
Posts: 1,044
Likes: 0
Received 0 Likes
on
0 Posts
well they must put the screw thread on for a reason may be to f up post like this lol.
No lop not the main cause for head failure at the end of the screw thread age is the main reason they fail at that point. Don't see first and second life units cracking .Generally older ones that being used past there expiry date on o/h cause the owners never got any coin. I know one operator never had any problems never lop at all but he change his cylinder's after 2 lifes never had problems. Cold morning and people that don't warm there engine up before take off, we preheated oil and engine in the colder months as I said before we never had much of a problem.
No lop not the main cause for head failure at the end of the screw thread age is the main reason they fail at that point. Don't see first and second life units cracking .Generally older ones that being used past there expiry date on o/h cause the owners never got any coin. I know one operator never had any problems never lop at all but he change his cylinder's after 2 lifes never had problems. Cold morning and people that don't warm there engine up before take off, we preheated oil and engine in the colder months as I said before we never had much of a problem.
Join Date: Nov 2004
Location: Perth - Western Australia
Age: 75
Posts: 1,805
Likes: 0
Received 0 Likes
on
0 Posts
Train wheels don't fall off because both components, the hub and the steel tyre, are made of the same metal.
Expansion rates are identical with both components, so the interference fit is virtually unaffected by temperature extremes.
The problem with these engine cylinders and heads, is that the basic head/cylinder design is faulty from the word go - because the expansion rate of aluminium when heated is considerably more than steel. Thus the basic design is setting up the owners/users for a fail.
A good cylinder and head design would have the interference fit zone and thread area, remaining the same interference fit, at all temperature extremes encountered - or even tightening at higher operating temperatures.
The entire cylinder/head design needs to be seriously reworked to eliminate the major reduction in clamping force in the interference fit zone, when operating at high cylinder head temperatures.
Expansion rates are identical with both components, so the interference fit is virtually unaffected by temperature extremes.
The problem with these engine cylinders and heads, is that the basic head/cylinder design is faulty from the word go - because the expansion rate of aluminium when heated is considerably more than steel. Thus the basic design is setting up the owners/users for a fail.
A good cylinder and head design would have the interference fit zone and thread area, remaining the same interference fit, at all temperature extremes encountered - or even tightening at higher operating temperatures.
The entire cylinder/head design needs to be seriously reworked to eliminate the major reduction in clamping force in the interference fit zone, when operating at high cylinder head temperatures.
yr right wrote: "Cold morning and some people that don't warm there [sic] engine up before takeoff,"
Over thirty years, this has sadly been an all too often observation for me. But I'm talking about other pilots. And that's quite often followed by a downwind takeoff. Why would you want to do that? Saving fuel?
So perhaps warm the engine correctly, take off into wind and lean to LOP in the cruise...
(My apology for the thread drift.)
Over thirty years, this has sadly been an all too often observation for me. But I'm talking about other pilots. And that's quite often followed by a downwind takeoff. Why would you want to do that? Saving fuel?
So perhaps warm the engine correctly, take off into wind and lean to LOP in the cruise...
(My apology for the thread drift.)
Join Date: Jul 2005
Location: Queensland
Posts: 686
Likes: 0
Received 0 Likes
on
0 Posts
The entire cylinder/head design needs to be seriously reworked to eliminate the major reduction in clamping force in the interference fit zone, when operating at high cylinder head temperatures.
Join Date: Apr 2007
Location: australia
Posts: 1,044
Likes: 0
Received 0 Likes
on
0 Posts
Mike Busch has over 4,800 hours on 9 of his 12 cylinders
That depending is 3 to 4 lives this from here on in is in the danger zone from my experience. Hi heat is not the only thing that is going on. The metal is changing taking on what has been burnt in the combustion process as well fatigue is the biggest killer of cylinder's that also needs to be addressed.
They don't last forever.
Also there is a lot of difference between a train wheel and a removable cylinder on an aircraft wheel, And occasionally they also do let go as I recall Germanys worst train accident was caused by a wheel failure.
Cheers
That depending is 3 to 4 lives this from here on in is in the danger zone from my experience. Hi heat is not the only thing that is going on. The metal is changing taking on what has been burnt in the combustion process as well fatigue is the biggest killer of cylinder's that also needs to be addressed.
They don't last forever.
Also there is a lot of difference between a train wheel and a removable cylinder on an aircraft wheel, And occasionally they also do let go as I recall Germanys worst train accident was caused by a wheel failure.
Cheers
Join Date: Jul 2005
Location: Queensland
Posts: 686
Likes: 0
Received 0 Likes
on
0 Posts
I recall Germanys worst train accident was caused by a wheel failure.
Due to the appalling safety record of 1 every 10 million miles all train wheels must now be replaced before the train leaves the next station.
Join Date: Jan 2008
Location: lancs.UK
Age: 77
Posts: 1,191
Likes: 0
Received 0 Likes
on
0 Posts
NOSTALGIA ALERT!
Those of a certain age, may have memories of an entertainment programme called "wheel tappers and shunters club"
Railways employed men with a hammer to "ding" a railway-wheel...the sound would alert to any that were unsound.
I suspect the screw-thread on the head is primarily to overcome the differential-expansion problem, while the engine temperature stabilises. Not enough attention is given to proper warming and heat-soak.
Those of a certain age, may have memories of an entertainment programme called "wheel tappers and shunters club"
Railways employed men with a hammer to "ding" a railway-wheel...the sound would alert to any that were unsound.
I suspect the screw-thread on the head is primarily to overcome the differential-expansion problem, while the engine temperature stabilises. Not enough attention is given to proper warming and heat-soak.
Peterma,
Creampuff is being entirely candid when he claims to have entered an engineering apprenticeship at age 15.
I was rather fortunate to be a little bit older "Adult Trainee" at the same institution that he was within. I was 17 in 1975 there.
Creampuff may have taken advantage of further education since then, though....
Years 11 and 12 maybe? Or perhaps a law degree with First Class Honours?
But as yr right may say: " What would I know.."
Creampuff is being entirely candid when he claims to have entered an engineering apprenticeship at age 15.
I was rather fortunate to be a little bit older "Adult Trainee" at the same institution that he was within. I was 17 in 1975 there.
Creampuff may have taken advantage of further education since then, though....
Years 11 and 12 maybe? Or perhaps a law degree with First Class Honours?
But as yr right may say: " What would I know.."
The maximum combustion pressure I can find for cyl is under 2000 psi.
Where did the 20000 psi come from?
Where did the 20000 psi come from?
The above is from the testing of a 1910 engine used by the Wright Bros, I think it was around 20 to 30 HP.
I think you'll find Mr Atkinson did not say the pressure in the cylinder was that high. I think you'll find Mr Atkinson was talking about the pressure on the threads.
I'm guessing that the pressure on the threads has something to do with the surface area of the threads, but I'll leave it to the experts to explain.
I'm guessing that the pressure on the threads has something to do with the surface area of the threads, but I'll leave it to the experts to explain.
Join Date: Apr 2007
Location: australia
Posts: 1,044
Likes: 0
Received 0 Likes
on
0 Posts
Point is and know has yet said at what life are the new cly failing. I have never seen up to a to a 3 life OEM cly fail. If these cly are failing when new there is a problem. Where is the DATA not on failure rates but when.
BTW an academic dose not mean he is a good engineer.
BTW an academic dose not mean he is a good engineer.
Join Date: Apr 2007
Location: australia
Posts: 1,044
Likes: 0
Received 0 Likes
on
0 Posts
As an LAME im not allowed to interrupt the law, even though I have to pass AA to get a lic im still not allowed to, even though every day I have to work within it and make decisions on it im still not allowed. I am how ever allowed to have an understanding of it.
Now a lawyer is just a word smith. They know zero about engineering. They look at words they allowed to interrupt the law but they have zero understanding of engineering.
Now Jaba ask me how I beat the dark side in court. Well it all depends on the solicitor on the dark side. But if you know the law and engineering and you know they lying as they do and you know how they trying to trick you up its not hard.
And yes Jaba I smashed them.
How ever I have also help them if its required.
The said thing is that every CASA awi dose not work the same as the person beside them, or in another office even though they may work from the same book its all different.
So even though im a dyslexic F^&K I still know my **** because im not an academic who cares I see the result I may learn in a different way to most but I can still have a say.
Cheers
Off to do more science.
Now a lawyer is just a word smith. They know zero about engineering. They look at words they allowed to interrupt the law but they have zero understanding of engineering.
Now Jaba ask me how I beat the dark side in court. Well it all depends on the solicitor on the dark side. But if you know the law and engineering and you know they lying as they do and you know how they trying to trick you up its not hard.
And yes Jaba I smashed them.
How ever I have also help them if its required.
The said thing is that every CASA awi dose not work the same as the person beside them, or in another office even though they may work from the same book its all different.
So even though im a dyslexic F^&K I still know my **** because im not an academic who cares I see the result I may learn in a different way to most but I can still have a say.
Cheers
Off to do more science.