New Cylinder AD's released by FAA [Archive]

cockney steve

21st Apr 2014, 09:45

^^^^^^ And before that, many a Wells-Fargo stagecoach completed it's journey on wooden wheels, with shrunk-on steel tyres.!

Wooden barrells also rely on the steel hoops to hold the staves tightly -enough together , that the barrell is fluid-tight.

There's nowt much new in engineering,just the knowledge falls into disuse when an alternative technology becomes more suitable for purpose, for a while.

As an aside, underfloor Central -heating is now the "in" high-efficiency heating-method........WELL! fancy that! the Romans had it a few THOUSAND YEARS AGO.

A great piece of research, nevertheless....about time the US Pilots started a class action against the legislators, for dereliction of duty, unfitness for purpose and Commercial bias against the aftermarket manufacturers.

The latter is irrefutable....they are imposing sanctions against the most reliable products, whilst leaving the statistically least-reliable OEM product untouched.

rutan around

21st Apr 2014, 10:55

Commercial bias against the aftermarket manufacturers.

The latter is irrefutable....they are imposing sanctions against the most reliable products, whilst leaving the statistically least-reliable OEM product untouched.

Dare I ask if $$$$$$$$$ might be changing hands. Calculate what it would be worth to the remaining players if a major competitor was knocked out of the ring. How much were cylinders before a bit of genuine competition came on the scene? Is this what is meant by the current popular term " Government- Business Partnership "
RA

cockney steve

21st Apr 2014, 20:35

If something stinks, there's usually a reason......something rotten somewhere?

Creampuff

21st Apr 2014, 21:31

Problem for Australia is that there may be no one with sufficient time, expertise and objectivity in the regulator to properly analyse the data and refuse to adopt this AD verbatim.

As usual, owners will have to pay to address a remote risk that is patently clearly not of their making and, more bizarrely, is patently clearly a more remote risk than the failure of the OEM’s product. All in the name of ‘safety’. :yuk:

No Hoper

21st Apr 2014, 21:35

Something rotten..... In Denmark?
Cracks at to the screw thread are not new as Walter has said.
How many cylinders in Aust are affected?

yr right

21st Apr 2014, 22:53

If the AD comes out it is auto on our system. Yes oem cly cracked but let's compare apples to apples. Ie hours to hours. The older the cly the more likely it is to crack. So are these 1st service life cly that are failing or second or 3 rd time around the block. If they are 1st then not hard to see why the looking at them careful. Funny that is why we do a leak rate check one of the things we also look for but some think a leak rate is not relevant
Cheers

Creampuff

21st Apr 2014, 23:42

CASA has discretion:39.004 ... (2) For paragraph 98(5A)(b) of the Act, CASA may, in writing, on its own initiative or on a written request by a person:

(a) approve, for a particular aircraft or aeronautical product, a means of compliance with an airworthiness directive other than that set out in the airworthiness directive; or

(b) subject to subregulation (5)—exclude a particular aircraft or aeronautical product from the operation of an airworthiness directive.

yr right

22nd Apr 2014, 00:09

Casa won't go against another country's AD. They will not do it for litagation
Cheers

Creampuff

22nd Apr 2014, 00:22

Sadly, I think you are correct. The GA sector in Australia doesn’t have sufficiently united brains or brawn to make CASA exercise its powers on the basis of objective data.

(PS: Great to see the incredible improvement in your usage of apostrophes, yr right. ;) )

No Hoper

22nd Apr 2014, 01:02

Creampuff,
You may remember the Bell47 Main Rotor grips that were downgraded to 1200 hour life. In Australia we convinced CASA that an eddy current inspection of the threads allowed us to retain the original hour timex.
So it has been done before

LeadSled

22nd Apr 2014, 01:06

Problem for Australia is that there may be no one with sufficient time, expertise and objectivity in the regulator to properly analyse the data and refuse to adopt this AD verbatim.

Creamie,
Too true.
The last engineer (as opposed to LAME) who had serious knowledge and experience with piston engines retired quite some time ago.
The AOPA US developed failure statistics showed the illogical position of the FAA clearly, why a proper cost/benefit analysis was bypassed has never been explained.
Sadly, high level administration of the FAA is seeing fever and fever people of serious aviation expertise, and more and more "career" public servants.
Tootle pip!!

Creampuff

22nd Apr 2014, 01:39

You may remember the Bell47 Main Rotor grips that were downgraded to 1200 hour life. In Australia we convinced CASA that an eddy current inspection of the threads allowed us to retain the original hour timex.

So it has been done beforeYes, but how many decades ago?

There is no doubt it could be done again, but it would require a level of unanimity and commitment that, sadly, I think no longer exist in GA in Australia. :(

yr right

22nd Apr 2014, 02:06

They used to look at all ADs and make there own judgement now they don't and we lost a great deal of good ones when they started that allowed everyone to know where they should. Now it's just a mess a system that is useless and still not common to anything or any where. It's a disgrace.
Cheers

No Hoper

22nd Apr 2014, 03:33

Compliance with Airworthiness DIRECTIVE of the NAA of the OEM or TC or STC holder is a requirement of Australian regs. CASA promulgates the foreign ADs in Part 39. Note they are no longer issued as Aust ADs.
Indeed Creampuff, time passes in the blink of an eye, was in the 1990s

Creampuff

22nd Apr 2014, 03:47

Compliance with Airworthiness Data of the NAA of the OEM or TC or STC holder is a requirement of Australian regs. …Did you mean ‘Airworthiness Directive’ rather than ‘Airworthiness Data’?

If you meant ‘Airworthiness Data’, what is your definition of that term?

No Hoper

22nd Apr 2014, 06:11

Creampuff
Airworthiness Directive is what I meant
At the risk of thread drift and tailwheel taking us all out the back of the hangar for a damn good flogging I am willing to discuss the differences. Remember though I am just a dumbass mechanic from Tennant Creek who failed matriculation

Creampuff

22nd Apr 2014, 06:34

In that case, you are correct: There is an automatic obligation to comply with what the CASRs call a ‘foreign State of Design airworthiness directive’ (as well as comply with an ‘Australian airworthiness directive’). That’s because CASR 39.002 imposes an obligation to comply ‘airworthiness directives’, and the definition of ‘airworthiness directive’ in CASR 39.001A covers both ‘Australian airworthiness directives’ and ‘foreign State of Design airworthiness directives’.

I merely reiterate that CASA has the discretion to approve a means of compliance with an AD other than that set out in the AD, and CASA has the discretion to exclude a particular kind of aircraft or aeronautical product from the operation of an AD: see CASRs 39.004(2) and 39.004(3).

Read all about it here: Civil Aviation Safety Regulations 1998 (http://www.comlaw.gov.au/Details/F2014C00220/Html/Volume_1)

The approved maintenance data for an aircraft and the maintenance schedule applicable an aircraft are related but different regulatory concepts. Read all about them here: Civil Aviation Regulations 1988 (http://www.comlaw.gov.au/Details/F2014C00219)

And BTW: I too am just a dumbass who left school at 15 to start an apprenticeship. :ok:

LeadSled

22nd Apr 2014, 06:57

And BTW: I too am just a dumbass who left school at 15 to start an apprenticeship

Creamie,
Such excessive modesty !!:)
Tootle pip!!

Creampuff

22nd Apr 2014, 08:16

No Hoper and Leaddie: Check your PMs!

yr right

22nd Apr 2014, 12:12

What amazes me is at what cost do you put on safety. You seam more worried that FAA is using it powers for evil. I would think that the cost should not be brought into it. I known the FAA dose costing and have done for a long time which is a lot different to what we have here.
Dick smith had a affordable safety. I know how dangerous that was when a pilot that was normally bright and bubbly was as white as a ghost. He nearly had a mid air late at night. When I ask how close was it he pointed to the top of the hangar wall. Luck was riding with that night as we'll as the crew down the back.

So at what point dose it stop. I think this is a very basic AD. Not much to it. As I've said earlier at what point have they being failing. If first life I can see why. I never seen or heard of an OEM cly failing at a 1st life.

rutan around

22nd Apr 2014, 20:40

What amazes me are the idiotic decisions that are made in the name of safety. When a decision is made that can't be backed by data the powers that be bellow "SAFETY" to shut down any further discussion. Those who think there is no such thing as affordable safety have a very poor understanding of risk management.
If "affordable safety" is abandoned it follows that even a cessna 150 should be fitted with a zero zero ejection system and that Malaysian Jet should have had personal ejection seats for every passenger + a life raft equipped with VHF and HF radios and 2 weeks of food. If you think this is nonsense then you actually do believe in affordable safety and the discussion then becomes where to draw the line.
Cheers RA

No Hoper

22nd Apr 2014, 20:55

Rutan
That is what is called an Absolute
Have been considering Walter's bait
Without the screw thread the head would depart on the first runup
It is a combination of the screw thread and interference fit that retains and locks the head to the cylinder

rutan around

22nd Apr 2014, 21:33

No Hoper
Without the screw thread the head would depart on the first runup
It is a combination of the screw thread and interference fit that retains and locks the head to the cylinder
Do you have Data that shows this to be true? I always thought the above to be true. In fact I didn't even know there was a shrink fit involved.:{
Having now read Mike Busch's article (Link post 10 ) I tend to believe a cylinder manufacturer probably knows more about how they work than I do. I do know that train wheels seldom fall off and they don't have a threaded section to help hold them on.

Creampuff

22nd Apr 2014, 21:34

I agree with Rutan: It’s amazing how the word ‘safety’ can turn some people into gibbering idiots.

I’ve posted this in the threads about DAMP and the proposed SS terminal AD, but it’s about this ECi Cylinder AD. Well known expert and aviation journalist Mike Busch said this, in part, in response to the NPRM for the AD: On August 12, 2013, the FAA published a Notice of Proposed Rulemaking (NPRM) in the Federal Register for a proposed Airworthiness Directive (AD) that would basically legislate more than 30,000 ECi cylinders out of existence, forcing the owners of about 6,000 Continental IO-520, TSIO-520 and IO-550 engines to perform $14,000 top overhauls. The total cost to affected aircraft owners would be $83 million, making this one of the most costly general aviation ADs in history. The FAA’s rationale for this Draconian AD is that they’ve received reports of 30 head-to-barrel separations in ECi cylinders (out of a population of 30,000, a failure rate of 0.1%).

This proposed AD is one of the most unwarranted, inappropriate, punitive and generally boneheaded rulemaking actions I’ve ever seen come from the FAA. Here’s why:

- At 0.1%, the reported head separation rate of ECi cylinders is the lowest in the industry, lower than for Continental factory cylinders. Why is the FAA picking on ECi jugs?

- There have been ZERO accidents and ZERO injuries resulting from the reported head separations of ECi cylinders.
…My all-time favourite comment on this proposed AD (and any other one for that matter) is: I am an emergency physician of 35 years experience with extensive involvement in helicopter EMS and a private pilot flying in the back country of Idaho. I understand, in detail, risk mitigation.

I wish to point out that based on available information the risk of appendicitis in FAA employees is much higher than having a ECI cylinder fail inflight. Following the FAA's assessment model, immediate prophylactic appendectomy is indicated for all 47,000 FAA employees.

Immediate appendectomy is particularly indicated for the 30,000 FAA employees involved air traffic control, as an appendix "failure" while on duty can affect the lives of hundreds people inflight.

I can provide the supporting calculations if desired.You see, yr right, if the probabilities and consequences of ECi cylinder failures justify this AD, it follows that other risks with similar probabilities and similar consequences must justify similar regulatory action.

For example, people with learning difficulties should be prohibited from conducting maintenance on aircraft. Even though there may have been zero accidents and zero injuries from their activities, they could cause a big accident by misunderstanding some important maintenance data. All in the interests of ‘safety’, old boy. Surely it’s a cost you’d be willing to pay? I’d be amazed if you disagreed. Have been considering Walter's bait
Without the screw thread the head would depart on the first runup
It is a combination of the screw thread and interference fit that retains and locks the head to the cylinderIs that your guess, No Hoper, or a conclusion supported by data?

No Hoper

22nd Apr 2014, 21:57

Seems basic engineering
A screw thread retains and then it is locked if in a high load situation.
Lock nuts come to mind, wouldn't work without the screw thread
Although in the olden days was split pinned or wire locked.
One can also wire lock the bolt heads in a blind bolt situation

Creampuff

22nd Apr 2014, 22:13

My guess is you are correct. However, I don’t have any data to back that up and, like many things in life, the correct answer could be counter-intuitive.

I’m hoping Walter A or John D will enlighten us with the results of their research. :ok:

yr right

22nd Apr 2014, 23:06

Well everyone has leaning problems for a start. You may be an academic but can you true a screw driver generally no. I know off a very clever fella that once fixed his 210 in to a 182 buy glueing his u/c handle into the down position or one friend that I will assure you all that make you like a primary school kids but put a nut on and his lost.
Where is the data that these are failing at are they 1st life, like ive said cly failure on general don't happen on a 1 st life engine OEM and separation happens at the end of the screw thread.
Now this also proves that it is a between the inter fit and the screw thread that hold the head on. With out either that don't stay on. Manufacture's wont do unnecessary work like fit a screw thread for know other reason. Also there is nearly always a sign before separation, you need to know the signs.
Why did we never use R1340 engines cause when they have a head separation the engine stops and in a R985 the engine looses performance and allows you to get back. We never had a head separation because we always always always checked during the day on shut down and ever night on return to base.

So why do you think that FAA wont these cly out of service.

And why don't I have a problem because I check recheck and check again that's why im good at my job. That's why im get ask all the time what im doing , that's why im sent all over the place to work.

Cheers

Creampuff

22nd Apr 2014, 23:19

So why do you think that FAA wont these cly out of service.That’s what most of the world’s experts are wondering.At 0.1%, the reported head separation rate of ECi cylinders is the lowest in the industry, lower than for Continental factory cylinders.Something stinks… to high heaven. And why don't I have a problem because I check recheck and check again that's why im good at my job. That's why im get ask all the time what im doing , that's why im sent all over the place to work.But going on the logic that has resulted in this AD, your zero accident and zero injury history is not enough. You have a known problem that could cause accidents and injuries in the future. You must be stopped, in the interests of 'safety'.

And BTW: I reckon you work for CASA. ;)

yr right

22nd Apr 2014, 23:30

Me casa I think not. My family would disown me if I went to the dark side. Soypu also should be stopped as your own disability is far worse than mine.

So once again go f yourself. I deal in common sence you still not said when these cly are failing

Creampuff

22nd Apr 2014, 23:40

Yep: You and me both should be stopped in the interests of ‘safety’.

You and I know why the cylinders are failing: Excessive leaning. ;)

Pilots of aircraft with engines fitted with ECi cylinders run them excessively lean. When one of those cylinders fail, the pilots do a forced landing and sneak over to another aircraft with engines fitted with stock CMI cylinders and sledge hammer the heads off two cylinders. Thus the logical regulatory response is to mandate replacement of ECi cylinders. It all makes perfect sense ...

... on the Planet Coosbane. :ok:

rutan around

23rd Apr 2014, 03:34

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

Walter Atkinson

23rd Apr 2014, 04:49

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.

No Hoper

23rd Apr 2014, 07:38

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

yr right

23rd Apr 2014, 09:25

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.

onetrack

23rd Apr 2014, 10:13

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.

gerry111

23rd Apr 2014, 10:39

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? :mad:

So perhaps warm the engine correctly, take off into wind and lean to LOP in the cruise... :ok:

(My apology for the thread drift.)

rutan around

23rd Apr 2014, 11:21

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.

Why bother when good temperature control solves the problem? Just how hot do you want to run them? A better idea would be to have engineers write the POH instead of leaving it to the marketing department.Mike Busch has over 4,800 hours on 9 of his 12 cylinders simply by having an alarm sound whenever any cylinder passes 390*F and then taking immediate action to prevent the temp going higher.

yr right

23rd Apr 2014, 11:55

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

004wercras

23rd Apr 2014, 12:04

Great thread :ok:

http://m.youtube.com/watch?v=hSb7mlz7Hag

peterma

23rd Apr 2014, 12:49

Hi Creampuff

May I respectfully ask if you once worked with CASA? Thanks.

rutan around

23rd Apr 2014, 13:10

I recall Germanys worst train accident was caused by a wheel failure.

It probably ran over one of those ECI cylinder heads raining from the sky.
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.:ugh:

cockney steve

23rd Apr 2014, 13:37

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.

gerry111

23rd Apr 2014, 14:43

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.." :E

No Hoper

23rd Apr 2014, 21:16

The maximum combustion pressure I can find for cyl is under 2000 psi.
Where did the 20000 psi come from?

Creampuff

23rd Apr 2014, 21:25

May I respectfully ask if you once worked with CASA?Me? I’m just an acne-stipled, wheelchair-bound geek from Hicksville USA. Flying and airplanes scare me! ;)

Weheka

23rd Apr 2014, 21:35

The maximum combustion pressure I can find for cyl is under 2000 psi.
Where did the 20000 psi come from?

"Using 232 psi as the maximum observed cylinder pressure results in a combustion force of 3,488 lbs."

The above is from the testing of a 1910 engine used by the Wright Bros, I think it was around 20 to 30 HP.

Creampuff

23rd Apr 2014, 21:57

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. :ok:

Weheka

23rd Apr 2014, 22:03

Thats right Creampuff, no where in his post did he say 20000 "psi". Still some people are determined to try and trip him up, good luck with that.

yr right

23rd Apr 2014, 22:21

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.

yr right

23rd Apr 2014, 22:48

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.

No Hoper

23rd Apr 2014, 23:30

Weheke
This is an engineering discussion. 20000 pounds is not a force it is mass or weight relatively speaking

Creampuff

24th Apr 2014, 00:14

So, an engineering question from a mere academic. ;)

When a doctor puts one pound per square inch pressure on the thumb plate of a syringe, what is the pressure at the tip of the needle?

When the pressure inside a cylinder of an IO 520 is 800 pounds per square inch, what is the pressure on the surface area of the thread between the head and the barrel?

OZBUSDRIVER

24th Apr 2014, 00:34

If I have it right. There is about 900psi evenly loaded on the thread. 30000psi shear for Al and things are pretty good. Given 6in bore, at least ten winds of thread...more winds equals less pressure, and 1/8th thread depth.

Does that sound about right?

If its an 8in bore that goes out to about 1300psi evenly applied.

Jabawocky

24th Apr 2014, 00:44

Turn the pressure on the head into a force (F) in Newtons or Lbs, whichever is your flavour of choice then apply the force to the thread area. Less any opposing forces of course.

Another way is by comparing areas but then you miss the value of knowing the forces. :ok:

LeadSled

24th Apr 2014, 00:53

Train wheels don't fall off because both components, the hub and the steel tyre, are made of the same metal.
Onetrack,
Not quite true, the axles and hubs/wheels tend to be something like EN40B, while the removable tires are an SG iron. If I remember correctly, the expansion co-efficient of the hub/wheel is actually higher than the SG iron, so heating during running actually tightens the interference fit.
Tootle pip!!

Creampuff

24th Apr 2014, 00:54

Frankly, I’m jiggered if I know!

My understanding of Mr Atkinson’s point is that it doesn’t matter. My understanding of his point is that the ‘squeeze’ caused by the interference fit is what holds the head on, rather than the strength of the threads.

If I get a bolt and clamp it in a vice and tighten the vice as far as I can make it go, it ain’t the threads on the bolt that stop me pulling that bolt out of the vice …..

Weheka

24th Apr 2014, 01:26

No Hoper.

This is an engineering discussion. 20000 pounds is not a force it is mass or weight relatively speaking

I am certainly not an engineer.

I think Walter said roughly 20000 lbs of force is applied to the threads as a result of combustion?

You said, Where did the 20000 psi come from?

Why did you misquote him?

Correct me again if I am wrong, but I think combustion results in a force being applied to something, be it pistons or whatever?

Walter Atkinson

24th Apr 2014, 01:33

It's beneficial to understand how the head and barrel are mated. The head is heated to expand and the barrel is cooled to contract. The head is then screwed on to the proper alignment. As the two metals reach temperature equilibrium, the interference fit is attained. The design is to allow for adequate strength absent the threads (which will shear at a much lower pressure) by the interference fit up to the design redline temp. The shear strength of aluminum is fairly low (can't recall the exact value). BTW, the interference fit is NOT at the same place as the threads. It is below the threads. The threads do not hold the head on during operation.

As Yr Right as alluded to but not exactly explained accurately, the cyclical fatigue on the aluminum is the issue that results in failure over time--NOT the time in service. If the cylinder is operated below about 380dF, the time in service will be MUCH longer than if the metal gets hotter. In addition, if the internal cylinder pressures are controlled (and by our best estimate based on a LOT of test data) and kept under about 800 psi peak pressures, the longevity is vastly improved.

Remember, the enemies of metal are heat and pressure. Control those and the design parameters are adequate. Operating at high CHTs (above about 380dF) and with high ICPs and the metal will fatigue and fail much earlier.

ROUGH, back of the napkin calculations:
Diameter of the cylinder approx. 5"
Area of cylinder head approx. 20 sq. in.
ICPs during a various mixtures range from 600psi LOP to 1100 psi at 50dF ROP.
20 x 600 = 12,000 pounds of force down on piston and up on head.
20 x 1100 = 22,000 pounds of force down on the piston and up on the head.

NOTE: These are peak pressures (stress) not mean pressures (HP).
Both of the above stress scenarios can actually produce the same HP!!
The former will have CHTs lower by about 50dF.

In which scenario is the cylinder going to last longer?

pcx

24th Apr 2014, 01:39

AH, but have a think about what would happen if the jaws of the vice had a thread of the same diameter and thread form in them as the bolt, and the bolt was clamped into this thread.

Now assume that the vice is tensioned up to clamp onto the thread so now you have the frictional resistance caused by the pressure of the vice on the thread and also the shearing force required to strip out the thread, to be applied before you can pull the bolt from the vice.

I am neither an engineer nor a LAME but I suspect that, in the case of the cylinder heads under discussion, both the thread and the shrink fit are required to ensure that the cylinder head remains on the cylinder barrel. I always believed that the thread was the primary way that the head was secured with the shrink fit ensuring that the thread both on the barrel and in the head remained very tight so that there was no tendency for the head to fret or move during operation, especially as they are subject to such varying temperatures.

Again see my disclaimer above and I certainly will be happy if I have this wrong and someone with accurate information (data) sets me straight.

The 20000 pounds of force mentioned by Walter is just an approximation of the measure of the surface area of the cylinder in square inches multiplied by the maximum cylinder pressure in PSI and is the force being applied to the cylinder head during each power stroke. This is the force that the head to barrel connection must resist, with the appropriate safety margins to allow for changes in temperatures etc.

Edit: I posted this while Walter was posting. I have just learned some more. Thanks Walter.

yr right

24th Apr 2014, 01:44

Forces on a thread are not distributed evenly across the whole of the thread face. Meaning say the nut at the closest point to the surface it mates against takes more load than at the end where the nyloc is. This is why cly crack at the start of the thread and not at the end

Creampuff

24th Apr 2014, 01:57

This is very important: BTW, the interference fit is NOT at the same place as the threads. It is below the threads. The threads do not hold the head on during operation.This, too, is very important: ICPs during a various mixtures range from 600psi LOP to 1100 psi at 50dF ROP.
20 x 600 = 12,000 pounds of force down on piston and up on head.
20 x 1100 = 22,000 pounds of force down on the piston and up on the head.

NOTE: These are peak pressures (stress) not mean pressures (HP).

Both of the above stress scenarios can actually produce the same HP!!

The former will have CHTs lower by about 50dF.Thank you Mr Atkinson! :ok:

yr right

24th Apr 2014, 02:11

Fatigue is a matter of time and / or cycles. You may have a high time engine with low hours or a low time engine engine with high cycles it evens out. That's why Qantas aircraft at high hours low cycles. That's why we log starts cycles hours.

No Hoper

24th Apr 2014, 02:41

Walter,
Thanks for the explanation, so the threads are not part of the equation only the area below the threads

Creampuff

24th Apr 2014, 03:45

Fatigue is a matter of time and / or cycles.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…. )

No Hoper

24th Apr 2014, 04:24

Creampuff
The ones fitted with wagon wheels or train tyres?

Old Akro

24th Apr 2014, 04:50

As a rule of thumb the first 3 threads of any fastener bear pretty much all the load. This is pretty much fastener design 101.

If a part fails at the beginning of the thread my first assumption would be that it is caused by a stress concentrator resulting from the manufacturing process of the thread forming. I assume that cylinder head threads are cut rather than rolled (bolts are rolled threads about 99.9% of the time). Rolling a thread is a process analogous to forging and produces a stronger thread and doesn't introduce stress concentrators from the thread cutting process.

There are formulae to calculate the thread strength. But, I doubt that its an issue because its worked successfully in aircraft engines for decades. I'd be pretty confident that the AD is the result of a material or manufacturing defect.

Properly torqued threaded fasteners do not come loose. Full stop. But typically we use fasteners tightened below the proper torque. Hence the need for Nylok nuts, lock wires, loctite, etc.

My guess would be that the shrink fit of the cylinder head to barrel is more to do with sealing than it is mechanical strength.

yr right

24th Apr 2014, 05:11

As in life there are no guarantees. If the engine is run as per the book you generally don't have problems. As I said before this is really not a lop issue. 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. That's why you have reduced cruise power settings.

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.

yr right

24th Apr 2014, 05:16

I've only seen lock wire work once. It didn't stop the bolt from loosening but it stop it falling out of the hole after the thread failied in a magnesium case.

Creampuff

24th Apr 2014, 05:25

No, that won’t do at all. Learning difficulties are no excuse for deliberate obfuscation.Fatigue is a matter of time and / or cycles.

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?

It’s not a hard question, and it won’t hurt you to answer it.

yr right

24th Apr 2014, 05:32

They both may or may not make o/h. If you gong to continue with personal abuse two things will happen you decide. If the engine is run to its book it will and should make o/h. Cly px have not much bearing on head failure period. Detenation which has the most extreme px will damage the bearing first

Old Akro

24th Apr 2014, 05:47

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.

Its not that easy. It depends on how close this is to yield strength.

Creampuff

24th Apr 2014, 05:51

I beg to differ: It is easy.Detenation which has the most extreme px will damage the bearing first I'm pretty sure pre-ignition causes more extreme pressures than detonation.

andrewr

24th Apr 2014, 05:53

Which of those two engines is more likely to have a cylinder failure first?

It’s not a hard question, and it won’t hurt you to answer it.

Your hypothesis is that reduced internal cylinder pressure reduces the likelihood of cylinder failure.

It actually IS a hard question to answer. You might assume that it is true, but you can't provide a definite answer without running a LOT of cylinders to failure. A proper answer for the question should include a p-value.

No Hoper

24th Apr 2014, 05:54

Creampuff
All else being equal one would surmise that the lower pressure would be more benign environment, but I suspect all else isn't equal

Creampuff

24th Apr 2014, 05:59

The answer is in this thread.

Please read Mr Atkinson's post at #68, twice. :ok:

Weheka

24th Apr 2014, 06:03

yr right, in my experience operating skydive aircraft, 470s and 520s, many, many thousands of hours, I never had a cracked cylinder. To be fair nearly all the engines were factory remans. Always carried power in the descent i.e. 2300 rpm 23" when down to certain height, straight in approach reducing power as required.

If people are cracking cylinders in skydive ops then they need to look at how they are managing the engine.

andrewr

24th Apr 2014, 06:15

Please read Mr Atkinson's post at #68, twice.

I have. He outlines which you would expect to fail earlier, but do the actual results agree?

What is the p-value?

Creampuff

24th Apr 2014, 06:29

Do the actual results agree? Yes. They are all piled up in yr right’s hangar.What is the p-value?I have NFI but, given the assumptions of the question, it makes NFD.

Weheka

24th Apr 2014, 06:33

You can drag a horse kicking and screaming to water....but

yr right

24th Apr 2014, 06:43

As I've said before there are pilots and there are operators. If you abuse the engine it will not last. The myth and that's all it is that lop is a magic fix for all is just that. If it wasn't no engine would make o/h at all with execption to a lop engine and this is clearly not the facts. Cly press is not the cause of a head failure at all. As I said before. Learn se basic engine knowlege on any hangar floor. Yes but a lot of meat bombs don't do a power decent. By adding power you are not getting shock cooling across your engine. And factory o/ h engines have what. New cly as standard.

Weheka

24th Apr 2014, 07:00

Well as far as I was concerned heat was my enemy, so on operations, hard climbs and descents, up to 27 per day, 1000 + hours per year I used a lot of fuel. With the TO rpm at 2700 (noise abatement) full throttle I liked at least 26gph, rest of climb always on the rich side of rich, didn't like cylinder head temps anything over 380 and that seemed to work well for me.

However when I was ferrying or cross country I ran LOP, was amazed how low the cylinder temps were while burning a lot less fuel. My speed was also reduced so maybe I didn't save much at all in the scheme of things, probably needed more coaching in LOP operations. Anyway I liked it, smooth running engine, low cylinder head temps, great!

43Inches

24th Apr 2014, 07:01

I have never seen a cracked cylinder due shock cooling on a training aircraft. We had a few cracked pots, all were due to metallurgical, manufacturing or installation defects, granted high temp variations can aggravate these issues. All our aircraft were treated with large high to low power variations during engine failure practice, from small 100hp engines to 350hp turbo engines. It definitly was not good for the engine life, but I disagree it causes cracking, otherwise just shutting an engine down after each flight would crack it.

If cylinders are coming off engines it's generally not something the pilot instigates unless he's doing something really exceptionally bad.

Jabawocky

24th Apr 2014, 07:08

43"

Exactly :ok:

Aussie Bob

24th Apr 2014, 07:10

I am thinking that shock cooling is a myth in some aircraft. With an engine monitor I see similar temps on descent with throttle closed that I see with a good dose of descent power.

That equates to a drop from around 370 to around 300 regardless of power used, excepting remaining at cruise. The biggest shock cool is always at engine shutdown.

43Inches

24th Apr 2014, 08:20

I think it's the opposite maltreatment of engines, from low to high power when the engine is too cool that causes the most damage. Applying full power from the end of a long glide or having done the incremental long cool down of your Navajo, then suddenly applying full power such as in a go-round. It's better to keep the temps up and cool down taxiing in once on the ground prior to shut down.

The other thing that will do a lot of damage is rapid throttle/rpm changes that throw the engine balance out. I would add excessive vibration to temp and pressure as engine killers.

OZBUSDRIVER

24th Apr 2014, 09:18

By 1918 Heron and Gibson had designed, manufactured, and tested cylinders that consisted of open-ended machined steel barrels with an external thread on a portion of the upper end and a mounting flange on the lower end. The finned cast aluminium head, which was fitted with valve seat inserts and valve guides, was internally threaded. The pitch diameter of the internal thread on the head was slightly smaller than that of the external thread on the cylinder barrel so that the head had to be heated in order to allow assembly. This resulted in a joint that was mechanically secure at the cylinder's operating temperature and provided the best escape path for waste heat. In concept, if not in exact detail, the modem air-cooled cylinder had arrived, but not everyone was ready to accept it, possibly because of the “not invented here” syndrome prevalent in some companies.

Modern technology!

Still interested in finding a link to actual assembly of a modern cylinder. I dare say, little would have changed. From this snippet it would appear the entire barrel enclosed by the casting becomes an interference fit...including the threaded portion.

It may be a long, long time ago for me since I graced the halls of the Mechanical Engineering department of the old QIT but I still get curious about how things work.

cockney steve

24th Apr 2014, 10:41

Which brings us back to my intuition-led hypothesis.
the thread acts as a physical restraint on the head, during the low-power warming-phase....we've already established the alloy head expands faster, but when the barrell is also up to the sama temp. the interference- fit is restored (within the plastic and elastic limits of the alloy, it being the softer, weaker material)

The wall- thickness of the cylinder, is effectively reduced to the thickness at the root of the thread...the thread is strongest at this point,being the base of an essentially triangular section....again, during differential expansion,the "overlap" of the threads, male and female, will diminish....in extremis, the alloy thread would ride up the flanks of the steel thread and either slip off, or the crests would shear each other off...essentially a broaching-action.
No doubt the size of the interference-fit collar has ben determined to give sufficient frictional grip to make the threads redundant under normal operating conditions.

I am an afficionado of Scott motorcycles....this unique 2-stroke twin has a central-flywheel with overhung cranks in 2 separate crankcase compartments.....the flywheel is furnished with a tapered bore each side...the crankshafts are pushed in, each having a matching taper...the assembly is pulled tight with a long draw-bolt.
These engines run sucessfully and dismantling often shows the tapers have cold-welded to each other...do not discount the frictional grip of metal against metal!

Aviation alert! The Scott engine was an option to power the Flying Flea (Pou de Ciel )

Creampuff

24th Apr 2014, 11:00

This thread is at risk of descending into rational objectivity. Shame on you, OzB, 43, AB, J, Weheka, Cockney S et al!

My understanding is that the most wear and tear on a bog standard piston aero engine occurs at …

Startup. (This is consistent with yr right’s point about the number of ‘cycles’.)

Cold engine and high RPM too soon after start = badness.

So, it’s probably smart to maintain very low RPMs after start until the engine is sufficiently warm.

However, my understanding is also that if you want to do even more damage, you should…

Set 25/25 in the climb (if it’s an injected engine).

Disabling the enrichment function and moving PPP closer to TDC = worseness.

So, it’s probably smart to climb at wide open throttle and higher RPM.

But let’s ignore this silliness and get back to reality.

Thrash cold engines on the ground and climb at 25/25! And if you want to really ‘take care’ of your engine, set 40 degF ROP, in accordance with the POH. That will put you in the Pantheon: “I’ve been doing this for 20,000 hours / 40 years and therefore my opinions about engine management / maintenance are objective truths.”

We had a few cracked pots, all were due to metallurgical, manufacturing or installation defects.That’s crazy talk! All engine problems are surely due to ‘excessive leaning’. :confused:

Jabawocky

24th Apr 2014, 11:20

Creamie.....those Peroni's see to make you a genius :ok:

Walter Atkinson

24th Apr 2014, 14:09

This oughta stir the pot:

Shock cooling is a myth (unless your CHTs start at redline and you chop the throttle and descend in the yellow airspeed arc--in that case, you *might* shock cool it).

If you are concerned about shock cooling you'd better NEVER fly into rain. Think on that.

I can explain where the myth originated, but I don't have the time right now. Maybe later.

jdeakin

24th Apr 2014, 14:25

If the engine is run as per the book you generally don't have problems.
If you run at or below 60% of rated power (maybe 65%), and if you pay a little bit of attention to cooling (baffles), and if you don't care about wasting 2 to 3 GPH (7.5 to 11.3 LPH), and if you don't care about running about 30℉ (17℃) hotter, then you are correct.

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.A true statement.

The bearings will fail before the head.
Got data? I've never seen bearings fail, except from catastrophic events (Oil starvation, Crankshaft failures, or a mechanic who fails to put "keeper" on the engine when a cylinder is removed, etc.)

Rapid cooling is something else which is hard on an engine. Flight schools and meat bomb aircraft suffer the worst cracking.Exactly the opposite. Those aircraft generally go to TBO and beyond, mostly (entirely?) because they spend their whole lives at full power and properly ROP in the climb, OR idle power, where mixture is not important. "Shock Cooling" is a myth.

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. I'm trying and failing to see any relevance to the subject at hand. But if you operate any aircraft designed for 8.5 psid at ambient pressure (0.0 psid) instead, you will generally have more problems with the pressurized aircraft due to the pressure (The Aloha "Pop-Top" comes to mind). But with proper maintenance and corrosion control, you probably won't see cracks at all in either aircraft.

John Deakin
jdeakin // at // advancedpilot.com

jdeakin

24th Apr 2014, 14:39

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…. ) Ahh, a man who "gets it." Thanks!

(But you forgot to specify "at the same power.")

jdeakin

24th Apr 2014, 14:47

I've only seen lock wire work once.How do you know? All those tens of thousands of safety-wired nuts that last from an hour to 100,000 hours, and have to be cut off, how do you know they are not working?

John Deakin
jdeakin // at // advancedpilot.com

LeadSled

24th Apr 2014, 14:49

Flight schools and meat bomb aircraft suffer the worst cracking. Folks,
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!!

gerry111

24th Apr 2014, 14:55

Jaba, Rest assured that when I Bo travel with Creamie, the beers are indeed Coopers Pale Ale!

jdeakin

24th Apr 2014, 15:13

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. :)

gerry111

24th Apr 2014, 15:32

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! :ok:

And also for the pilots that managed to fly them safely IFR.. :sad:

Walter Atkinson

24th Apr 2014, 19:27

***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. :ugh:

Jabawocky

24th Apr 2014, 21:17

Anyone remember this thread a few years ago....I collected the data....the cooldown rate was impressive for its lack of anything. :hmm:

http://www.pprune.org/pacific-general-aviation-questions/493896-shock-cooling-myth-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!

Aussie Bob

24th Apr 2014, 21:43

All any doubter needs to do is observe the CHT. While an engine monitor helps, a standard gague will suffice. Very slow small drop regardless of power setting.

No Hoper

24th Apr 2014, 22:02

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

Creampuff

24th Apr 2014, 22:16

Unless you are being deliberately disingenuous, NH, you too have a substantial learning difficulty.

(But you forgot to specify "at the same power.")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.

Jabawocky

24th Apr 2014, 22:22

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?

Tankengine

24th Apr 2014, 22:42

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!:rolleyes:
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!:confused:
We have even gone to Chevies to try to find a solution.:ugh:

421dog

24th Apr 2014, 22:45

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...)

421dog

24th Apr 2014, 22:58

I kinda hope Awblaine wants to assert dominance here...

yr right

24th Apr 2014, 23:22

Just got back from dawn service. Now now of to breakfast. Listen to real story's from real people with out the need for data.

Lest we forget.

Jabawocky

25th Apr 2014, 03:16

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 :ok:

Some good reading here from Mike Busch How Do Piston Aircraft Engines Fail? « Opinion Leaders (http://blog.aopa.org/opinionleaders/2014/04/09/how-do-piston-aircraft-engines-fail/)

John or Walter....Mike was a three time APS student was he not?

Walter Atkinson

25th Apr 2014, 03:27

!!!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.

Walter Atkinson

25th Apr 2014, 03:31

***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!

No Hoper

25th Apr 2014, 03:54

To add to summary, anyone questioning self appointed gurus has only half a brain.
Do not rest on arms reversed with fixed baynets, which has as much to do with ECi cylinder AD as some of the posts here

yr right

25th Apr 2014, 04:23

Mmm nasty cut may we assume lol. Know one has said when these cly are failing yet either. 1,2 3,4 life what when how. Anyone can produce data. That's why it's published and reviewed in medicine and science. But more on that later. I'm ahead $140 on two up. Mmm what are the odds on that.

So it can be taken that creamie not in the USA and more than likely not in a wheel chair either.
Cheers

yr right

25th Apr 2014, 04:45

As a red head lady said please explain

http://www.shamrockairservices.com/images/LEANING%20TECHNIQUES.pdf

yr right

25th Apr 2014, 05:02

Or maybe
Tcm sb
M89-18
And
Sb03-3
And
Mandatory sb m91-6

But what would they know there data is published.

Cheers

yr right

25th Apr 2014, 05:20

There are no free rides.
Cheers

Weheka

25th Apr 2014, 06:04

Whats with the "shamrock" web site? Why not take the link directly off the official Lycoming website?

Anyway the fact that I am able to run LOP successfully makes a mockery of the statement that for 98% of pilots it would be very hard to get right. If I can do it anyone can.

Weheka

25th Apr 2014, 06:12

When I click on the highlighted Lycoming web site on your post yr right, it takes me nowhere?

When I go to the proper Lycoming web site yr right, and put in search SSP 700, nothing comes up?

Whats goin on yr right??

yr right

25th Apr 2014, 06:19

just tried it works for me.
cheers

Weheka

25th Apr 2014, 06:27

Yep I just logged into shamrocks site and it is just something they have taken the liberty of making up themselves.

Mind you they have been in business since 2006 so would have a massive amount of data to back up their b/s? As the Tui ad says...yr right!

yr right

25th Apr 2014, 06:29

Maybe it's a cheap Chinese nock off what you think ? There are no old bold pilots.

Now where is the data on these head failures that started this post before it became another free ads campaign.

Cheers

yr right

25th Apr 2014, 06:33

It's a real document and you all know it is. But no have yr $10 and gamble it's your life's not mine.

Weheka

25th Apr 2014, 06:33

Just goes to 404 error? Lycomings web site doesn't have dot textron in it. You must have a special computer yr right?

Weheka

25th Apr 2014, 06:39

It's only real in shamrocks rotax world. Anyway i've had a good anzac day (thanks to all those who made it possible, including my father) and am now sitting down to a cold beer while I watch the Blues hopefully beat the Waratah's.

Hope you've had a good day yr right, your in one camp and i'm firmly in the other as far as LOP goes, nothing too serious though.

Creampuff

25th Apr 2014, 06:42

What I don’t understand is why you trolls think that your pretence is not obvious. If you are able to comprehend documents like the Lycoming one at the link in yr right’s post, you are able to comprehend other documents with big words.

From the Lycoming document at the link in yr right’s post:Lycoming recommends cruise operation at peak EGT or TIT, which is the point where the best economy range starts. …But hang on a sec’… I have a POH that says:Continuous operation is recommended at 25 degrees F or more below peak EGT only on the rich side of peak.Those recommendations are patently irreconcilable.

Given that you apparently put implicit faith in any document published by manufacturers (despite those documents being produced primarily for marketing and a*s-covering purposes), which one of the above recommendation do you support? They are both arrant nonsense to me, but you real experts will know which is the better way to protect the clys…

Standing by to be underwhelmed by the usual dullard impressions. :=

yr right

25th Apr 2014, 06:48

Once again you shun what's in front of you. Now are you in a wheel chair simple question yes or no
Cheers.

Creampuff

25th Apr 2014, 06:54

Of course I'm not in a wheelchair, any more than you have a learning difficulty.

The difference between us is that, on matters technical, you are being deliberately deceptive under the guise of being a dullard.

Troll :=

yr right

25th Apr 2014, 07:03

Weheka

25th Apr 2014, 07:20

Settle down yr right...settle!

Are you by any chance in the Ag Industry or the Survey Industry?

Also going back to one of your other posts, where in Australia would you pre heat the oil and the engine before first start of the day?

Creampuff

25th Apr 2014, 07:50

You are a low life sack of ****. And yes I am dyslexic. Any one that says they in a wheel chair has some sort of mental illness and those of you that knew he was are just as bad.
Me a troll no sir you are the troll. A gutless prick is what you are.All of which has nothing to do with the ECi cylinder AD and none of which is an excuse for your deliberate failure to answer the technical questions that you understand, perfectly.

On matters technical, I’m not being deliberately deceptive. I have no reason to be: I am not trying to sell anything to anyone. I’m motivated only by a strong sense of mortality while flying behind a single piston engine.

You, on the hand, are being deliberately deceptive on matters technical.

Creampuff
(Defence Force Service Medal With First Clasp; Australian Service Medal (SE Asia); Australian Defence Medal)

BTW: It’s a very serious offence to falsely claim military awards, so I’ve just committed a very serious offence if my claim is false. You being big and brave and me being a gutless pr*ck, I assume you’ll take this up with the authorities.

I won’t be holding my breath.

Troll. :=

andrewr

25th Apr 2014, 08:10

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.
Super cooled fuel? Really? I'm not sure whether this is serious or in jest.

Have you worked out how little energy it takes to warm the fuel compared to the energy being routinely generated and removed from the engine via normal cooling?

What temperature did the fuel get down to in the tanks?

Lets assume -20F as a suitable definition for super cooled, and 40F as a "normal" fuel temperature. It takes more than 200x as much energy to vaporise the fuel as to raise the temperature 1 degree F. Fuel at -20F will only take about 15% more energy to vaporise than fuel at 40F and therefore provide 15% more fuel cooling (making some assumptions about boiling point).

But fuel cooling would be a tiny proportion of the total energy. The energy to raise gasoline from -20F to 40F is about 30BTU/lb. If gasoline provides 19000 BTU/lb, and about 12% of that energy is removed through the fins, then supercooled fuel might be able to account for about 1% of cooling.

If a lean mixture fixes the problem then it is the difference between a rich and lean mixture that is important. Lets say a rich mixture is about 30% more fuel, so the cylinder cracking is from increasing the cooling by 1/3 of one percent?

Even worse, this is assuming cruise fuel flows. If you reduce the power setting for descent, you reduce the fuel flow and the fuel cooling even more. However, cooling via the fins is controlled by temperature, so until the engine cools down air cooling will be providing an even larger proportion of cooling.

Supercooled fuel doesn't seem to be a plausible cause of cracking - although I am happy to have any errors in my calculations pointed out.

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.My flame suit is on in preparation to receive incoming from those with no data.I didn't see any actual data in your own post. I would be very interested to know:
1) what was the measured temperature of the supercooled fuel and
2) how much it warmer it gets when you start your descent 100 miles out, vs. the actual descents they were doing.

yr right

25th Apr 2014, 08:58

By the way. You don't have data. You have observations. There is a large difference. You cannot use any of what you are saying in a court of law if anything goes wrong. Data is provided by manufactures that in our case MUST be used. Not something you have found in the back shed. You will be legally liable if someone dose a course that as you have said is not approved. God help us if someone hurts them selfs by a miss calculation and has an accident and they not used the correct data but what you have said. The insurance for a start will be null and void.
You shown nothing just said we have it all
Why did I say rotating valve seat and cabin px because it shows what little knowlege you know in the real world. I even gave you all the engine but still have to ask. And why cabin px. Because if you don't operate the aircraft in the way the manufacture has designed it you will break it. Px in the cabin supports the airframe in flight. A Saab 340 for example has chemically milled skin that on the ground you can nearly push your finger though. But in flight is as solid as a rock.
You had a go at me for saying about the lock wire. But you never said anything about the orginal post. You gone out off your way to discredit me as much as you can to be called a troll because I don't agree with you and as has been shown I been right all along and you have not had to pay for it. I was called dangerous how low was that all I've said is you must follow was is in the poh once again this was to try and discredit me.
The information I have give is factual for years on the floor real life. You also given zero credit to what the manufactures have done in the world of reliability.
You have stated that if you run lop your engine will last to o/h. Guess what if you run it to the book you will as well.
Now as I recall hazeltons ran there tsio 540 to 3500 hours on rpt with a cly change mid life ie top o/h why cause the bottom end was not a cause of any problems but the valves where and guess what they never ran lop either. Jaba has also said that his wife would not allow anyone in her org to run outside the poh. So you have to ask yourself why would he like you to run it. Because he is making $$ from you. Oh you will safe an engine o/h in fuel cost that is each time you put that money in the bank.
But you won't. Then you have to fit a trend monitor muti cly now you have to buy it fit it maintain it for the life of it in your plane. You would save more fuel just by preheating your engine before flight.

It's a shame that this post has had to turn out like the last one hijacked.

Still no data on why the other cly have failed though I case anyone hasn't noticed.

Cheers

43Inches

25th Apr 2014, 09:53

Px in the cabin supports the airframe in flight. A Saab 340 for example has chemically milled skin that on the ground you can nearly push your finger though. But in flight is as solid as a rock.

Not quite sure how you get that, it's bonded aluminium like most other modern transport aircraft. I've seen enough things banged into them to see it's strong with or without pressurisation and you can fly them de-pressurised if necessary due faults.

yr right

25th Apr 2014, 10:26

The skins between the frames a chemically milled. Check it out. It is near on freighting how thin they are. Yes you can fly it un px as any aircraft but then there are limitations on that.
Cheers

43Inches

25th Apr 2014, 10:33

I have been involved with the type in the past, there are no limitations for de-pressurised flight, except those for oxygen limitations for pax and crew. You can even operate them with passengers de-pressurised under the MEL.

The centre fuselage is constructed in four parts. The skin is aluminium, bonded to the frames and other parts. These are then riveted together. There is no magic potion in the skin. Kevlar composites are used for flight control surfaces, fillets and some other bits.

Creampuff

25th Apr 2014, 10:35

So anyway

andrewr has raised some important technical questions. I confess to also being interested to know how fuel that's been pumped through the heat-soaked EDP and subsequent fuel system components ends up being 'super cooled' at the cylinder.

Still, my understanding is that the 777 that impacted short of London HR had issues with fuel and temperature. (But my understanding may be inaccurate.)

Oracle1

25th Apr 2014, 10:36

Don't waste your bandwidth on yr wrong, everything he says is total dribble

yr right

25th Apr 2014, 11:03

777 for a start uses jeta and water is held in suspension that is why you use prist. And was pre Edp. Fuel at the nozzle is post Edp and for a start when you compress something you get a heat rise plus the transfer of heat from the engine via the base of the pump. But as the fuel exits the the nozzle heat is instantly taken from the air and fuel vapourizes and cools the intake charge in the same way a aircon works. Fuel dose not enter the chamber in liquid form.

Ocky I forgotten more than you no.

Cheers

Creampuff

25th Apr 2014, 11:05

Exactly! :ok:

PS: Troll!

jdeakin

25th Apr 2014, 12:22

As a red head lady said please explain

http://www.shamrockairservices.com/i...TECHNIQUES.pdf (http://www.shamrockairservices.com/images/LEANING%20TECHNIQUES.pdf)This was the infamous, asinine, "Experts are Everywhere" letter put out by Rick Moffet, of Lycoming. I think he was "Chief Engineer" at the time.

He was once quoted as saying in the test cell, "That's the first time I've ever touched the mixture control, we usually just leave it full rich, here."

He's made some stupid misstatements in public, and we've sent him data to demonstrate the "difference from reality." He never responded, and like "yr right", I don't think he ever read it, either. It's called a "closed mind."

He is gone now, and I think Lycoming has withdrawn that ghastly document, as I cannot find it there. It's only left on a few oddball websites, now.

John Deakin
jdeakin // at // advancedpilot.com

Lumps

25th Apr 2014, 12:40

jdeakin

25th Apr 2014, 13:14

What about all those aircraft in WW2 flying for hours in the flight levels? Pretty sure their fuel would have been supercool, wouldn't have this issue come up well before cessna made a turbocharged twin?

By this reasoning shock cooling due fuel would have cracked many heads as I'd imagine a P-47 or equivalent escort aircraft would go from high altitude cruise to combat down to low levels, mixture control pushed into auto-rich. Excellent point!

1) The fuel in those engines entered the air charge at the blower inlet and had a considerable distance to travel and heat up before getting to the combustion chambers. Walter is talking about the Cessna system where raw fuel gets sprayed directly on the cylinder, inside the inlet port, and the sudden change in temperature caused by the increased flow of very cold fuel.

2) "Auto-Rich" and "Auto-Lean" (big radials) were both RICH MIXTURES, that is, on the RICH side of peak, and therefore the change in cooling would not be quite as much. (Except for the B-24, which had the mixtures set for LOP in "Auto Lean." That's the reason for their astonishing range, compared to the other aircraft.)

(I'd like to think the ghost of that man who set up the B-24 carburetors that way is hovering up the rafters of our classroom, smiling in approval. :D)

John Deakin
jdeakin // at // advancedpilot.com

yr right

25th Apr 2014, 13:28

Fuel goes though a stainless steel line of a controlled length across the top of hot engine it less than 1/8" inside dia how hot is the fuel going to be. Answer is sfa,
I never ever heard of this before with exception to Jets using jet A

yr right

25th Apr 2014, 13:35

And to dismiss the lyc document wtf it would have gone past how many sets of eyes and lawyers desks to get published , Give us a break you also said nothing about the tcm doc btw
Or more likely doesn't suit your model so you dismiss it like anything or anyone that doesn't agree with what you said, maybe next you mate is a famous actor and you belong to some cult that says it is a church

jdeakin

25th Apr 2014, 13:56

"yr right" said:
Fuel goes though a stainless steel line of a controlled length across the top of hot engine it less than 1/8" inside dia how hot is the fuel going to be. Answer is sfa,
I never ever heard of this before with exception to Jets using jet A Those lines run above the engine with OAT air flowing over them, blasting the heat away and downwards. Inflight, I'd guess the fuel coming out of the injector nozzles is pretty much the same as it was in the tank. It might pick up a couple of degrees from the fuel pump.

I don't understand your abbreviation "sfa."

The fact that you, or I, or anyone, or no one has ever heard of something before isn't relevant. Some, even today believe the earth is flat, that no man ever walked on the moon and that Lycoming and CMI POH's are holy writ, divinely inspired, engraved in stone, straight from Mt Sinai - or even more authoritative, CASA. I consider them all fools, but that's just my opinion.

John Deakin
jdeakin // at // advancedpilot.com

Walter Atkinson

25th Apr 2014, 13:58

NOte that the Lycoming graph is not real data, but "idealized" traces. The Experts are Everywhere doc was NOT reviewed by a cadre of eyes but only Rick Moffett who was the lawyer who wrote it… It has become a source of major embarrassment to Lycoming due to its inaccuracies and they've removed it from their website. That took a while to accomplish!

As for the cold fuel hitting the hot metal, does anyone think that's a good idea? At least we have an explanation for the phenomenon. The observable fact is that the cracks were in the intake ports, not in the cylinders. So, if that's the case, how does rapidly cooling the cylinder with air, form the outside, cause cracks INSIDE the intake port?

There are none so blind as those who will not see and none so ignorant as those who will not think.

I offered the information. Do with it, think about it, or not, as you please.

gerry111

25th Apr 2014, 14:37

John Deakin, SFA is an Australianism meaning 'Sweet f##k All'.

jdeakin

25th Apr 2014, 20:44

"yr right" said:
And to dismiss the lyc document wtf it would have gone past how many sets of eyes and lawyers desks to get published , Give us a break you also said nothing about the tcm doc btwLet me see if I can cover them all at once.

Both CMI ("TCM" is several years out of date) and Lycoming have built their engines pretty much in isolation for decades. If a cylinder fails, their first step is to try and deny any responsibility, either warranty or otherwise. Either way, they grab a new cylinder off the line, ship it out, and melt the old one down. No checking, no "What happened to this cylinder." Into shipping, onto the junk pile, off to the ovens to recover the metal. I have my doubts, but I've seen the pile. Out of the box, and onto the pile. Out of the box, and onto the pile. ZERO interest in it.

Hardly the attitude of "Let's figure out what happened to it, and make it better." They very proudly show the pile off, saying, "Look, we don't re-use any of this, it all get melted down!"

Until very recently, no one at either factory was qualified to FLY any of their engines, and the very idea of doing that appalled them, repelled them. Until very recently, NO ONE at either factory had ever seen an engine monitor, much less used one. Bill Ross, the honcho at CMI has taken our course, and liked it so well he subsequently sent four more CMI employees. All have had their eyes opened, but when they go back, they run into the same bilzzard of misinformation and little gets done. That was last year, and there HAS been some progress. Not enough, but some.

Put yourself in CMI's shoes. They have produced what, a thousand different models of engines, with a manual for each? As they become dimly aware that their manuals have errors in them, only the most egregious errors get revised, because they simply don't have the manpower.

The manuals you're looking at are 50 years old! I say that because they take the old language from the old manuals, and blend it in with the text that goes with the new, often badly, same old text, year after year, decade after decade. I refer to the "How to operate," and not the LIMITATIONS, those are pretty good.

NO MENTION of MODERN engine monitors! We've had 'em for 30 years and more, and neither of the engine factories even mention them, much less tell you what to do with them! THEY DO NOT KNOW.

"Not invented here" and "We've done fine without 'em for 100 years."

Not their job. Their job is to turn out engines that pass the FAA required 150 hours on the test stand at full power, near the CHT redline. Then ship 'em out.

John Deakin
jdeakin // at // advancedpilot.com

cockney steve

25th Apr 2014, 21:00

John Deakin, SFA is an Australianism meaning 'Sweet f##k All'.

Err, actually, it's a British expression "sweet Fanny Adams" or Sweet Fanny Ann"
It is , of course, also taken to mean the same as the convicts translated it.:}

yr right

25th Apr 2014, 21:01

Now if the airfraft is to be flying above an altitude that is going to get into this so called super cooled fuel range then it's going to be turbo charge. Now also the heat is transferred now remember that the nozzle is brass and the cly head temp will be around 300 deg or so and the upper deck line is pumping air into the nozzle ( pre intercooler) and remember why we use inter coolers and remember what happens when you compess a gas and it already picked up heat energy from the Edp as it passes that then the diverter valve you still going to say that the fuel is going to be super cooled.

Now we still don't know why these after market heads are failing.

Cheers

yr right

25th Apr 2014, 21:03

Yeah convicts ha ha how dumb where them dills sending us out here. Was 20 deg C hers yesterday morning and I was looking for a jumper.

Pmsl
Cheers

jdeakin

25th Apr 2014, 21:30

maybe next you mate is a famous actor and you belong to some cult that says it is a church If I can catch my breath from laughing so hard at that, I'd like to tell you a little story.

Twenty years ago, we WERE kind of a cult, although without the religious overtones. Very much in the minority, with only forgotten history and facts on our side. We're mainstream today (at least in the USA), which isn't nearly as much fun.

Doug Ranz, one of the top programmers in the world, is a dear friend to all three of us, and is possessed of a helleva sense of humor. Without us knowing about it, he wrote off to the central registry of all churches in the USA, and registered us as "The Church of the Lean of Peak," with us as the principals. "Bishop Braly," "Deacon Deakin"," and "Reverend Atkinson."

I kid you not!

I thought it was a joke for a long time, but Walter went down to the local Parish (Parish is "County" in Louisiana), to see about getting set up as a local minister. First the girl checked the master registry, and sho' nuff, there it was, the "Church of the Lean of Peak." Walter told me it nearly killed him to "maintain his dignity," and I couldn't have done it. The girl then asked about "The Church," and Walter made up some BS story on the spot. The nice little gal nodded her head and said just as serious as she could be, "I believe I've heard of that!" She handed him a form or two to fill out, and a few minutes later he walked out a fully certified minister, qualified to conduct weddings, funerals, and all the other ceremonies of an ordained minister!

Which he promptly did! I think he married one couple in his Twin Beech on the way to the Bahamas.

Now me, I'm still not 100% sure of the authenticity of the whole thing, and I'm just a wee bit nervous, a'feared that a bolt from the blue would seek me out for impersonating a holy man - which I am definitely not. Ole George ("The Bishop") is kind of ambivalent over the whole thing, he just smiles weakly, and says nothing. I think he's a little upset that Walter and I have so much fun with it.

John Deakin (Deacon)
jdeakin // at // advancedpilot.com

andrewr

25th Apr 2014, 23:27

Those lines run above the engine with OAT air flowing over them, blasting the heat away and downwards. Inflight, I'd guess the fuel coming out of the injector nozzles is pretty much the same as it was in the tank.

Interesting point about the lines over the engines. I'd guess there was enough surface area/volume and enough airflow that the fuel temperature would be close to OAT regardless of the temperature in the tank - depending on fuel flow. Lower fuel flow (power settings) would be closer to ambient temperature.

Without measuring however it is only a guess.

Creampuff

25th Apr 2014, 23:36

I think the APS or other folks have put multiple temperature sensors and air flow tufts under the hood. Not sure whether any sensors were put on the injector lines though.

andrewr

25th Apr 2014, 23:37

As for the cold fuel hitting the hot metal, does anyone think that's a good idea?

This is the intake tract for an engine. Without fuel, it's not much good to anyone. Presumably we would have many more problems if fuel in the intake tract was a problem. By my calculations, the temperature of the fuel has very little effect.

You're an engineer - I don't expect that "does anyone think that's a good idea?" was a substitute for calculations in engineering school. Do the calculations and tell me if I'm wrong.

Or, fire up your test cell and measure the difference in temperature of the internal intake tract walls when using supercooled fuel vs. room temperature fuel.

yr right

26th Apr 2014, 00:17

If this so called super cooled fuel was a problem how come we don't see it now. Nothing has changed in relationship to the injector placement in the cly or the atmosphere or airframe mmm strange I have never seen any cracking in the inlet port other than from the plug. Once again seams wildly strange. I've also ask a few friends if they heard of this or seen this and they also have said no.

Now the fuel is atomised as it leaves the nozzle if it so cold this will not happen and the loss of power will be noticed. If it's to hot it vaporise in the system. So it has to be just right.

But still no answers to why in the first place why these cly are failing.

Cheers

yr right

26th Apr 2014, 01:03

Or maybe assume the position.
Now follow me
Kneel down
Bow head
Raise hands above your head to the sky
Raise head
And repeat
Praise The Lord of lop
Praise The Lord of lop

You are the masters of all knowledge.
Praise you

Old Akro

26th Apr 2014, 01:20

fuel gets sprayed directly on the cylinder, inside the inlet port

John, not trying be be a smart*rse, but you might want to rethink this wording.

Aircraft fuel injection is what is called "piss & dribble". Aircraft injectors are mis-named really. They are brass fittings with a hole in them. Fuel flows out of these injectors continuously. Its as simple, basic and reliable as you can get.

You can see this about halfway through this Avweb video. There is no "spray pattern".

https://www.youtube.com/watch?v=tN6gOuAmZdQ

Cars stopped using this system in the 1950's. Until about 10 years ago, cars used a timed, high pressure spray injection into the inlet manifold. Initially done mechanically (the old Lucas & Spica systems), then open loop electronically without any mixture feedback (Bosch L-jetronic), then with mixture control feedback using an oxygen (lambda) sensor (Bosch Motronic), then with refinements on spray pattern and spray timing using higher and variable fuel pressure. About 10 years ago, very high pressure injection directly inside the cylinder was introduced. Alfa was pretty much the first production company to do this with the 2.0 JTS engine.

Back, to aircraft. Try opening the under wing fuel drain and time draining a few litres into a bucket. For my aircraft its close to its climb consumption. Its a good trick to visualise exactly how much fuel your aircraft is using and the amount of fuel going through the injection plumbing.

Typically, "injectors" are located to spray (pour??) fuel onto the back of the valve. This is to a) cool the valve and b) help vapourise the fuel. The intent is that the fuel vapourises inside the inlet manifold so only vapour goes into the cylinder. This is what gave GAMI a business, because (especially Continental) inlet design is poor and the inlet air flowing past one cylinder will rob fuel vapour from one (making it leaner) and delivering it to another (making it richer). Hence tuned injectors. GAMI supported a guy to do his PhD thesis on this. Its an excellent paper and available on-line if you look hard enough.

You would be shocked to learn how high the inlet manifold air temperature is. Its nowhere near OAT. In a non-intercooled turbo engine it could be 200 degC. Cars use water cooled inter-coolers to try and get the inlet air temperature DOWN to 100 degC.

Some raw fuel may enter the cylinder, but it will only occur during the time that the valve is open. This is maybe 10 - 12 % of the time.

Fuel from the tanks will be at OAT and cold fuel handling can cause problems. It can cause problems in cars too that are hot, but fuelled from cool, underground tanks. BUT, there is a fair bit of plumbing in warm parts of the aeroplane and the injector itself will basically be at the same temperature as CHT. I struggle to see that cool fuel injected into a hot inlet manifold is a real issue.

And, I would suggest that most cylinders are replaced not because of cracking, but because of valve seat problems or cylinder dimensional problems - out of tolerance big, oval, taper or "barrelling"(fat in the middle). All of these can be improved with the APS techniques.

If there was a problem with a Continental engine, it may be that they made a mistake with injector alignment. There is a car manufacturer paying the price for a similar mistake at the moment.

No Hoper

26th Apr 2014, 01:24

Yr Right
Just now found the NTSB report released November 2013, whilst they question FAA requirements I noted that the cylinder cracks are at the roots of the THREADS, not at some other place below the threads. One of the failures was 4 out of 6 cylinders. With current litigation issues in USA and elsewhere the FAA is damned either way

Old Akro

26th Apr 2014, 01:26

I think the APS or other folks have put multiple temperature sensors and air flow tufts under the hood.

Don't know about APS, but if you spend some time in the NASA Langley library or looking through the proceedings of the AIAA conferences, there are quite a few guys who have studied cooling airflow in GA engines.

Most of the work is done with manometer lines, not wool tufts. The holy grail is pressure recovery.

Roy Lopresti was probably the leader on cooling design. Hence the Mooney 201 cowl redesign and the Lopresti "Wholey Cowl".

yr right

26th Apr 2014, 01:40

You forgot about crank angle for internal airflow into the cly. This is why gami injectors work as they give a better f/a into the cly by matching the fuel flow. Inside the brass shell is a stainless metered orifice.
The nozzle flows At 90 deg to the valve. We don't see if any intake valve problems lop dose not effect the intake valve.

Cheers

Old Akro

26th Apr 2014, 01:57

Just now found the NTSB report released November 2013

I can't find this, but I found an FAA whitepaper on the subject.

file:///C:/Documents%20and%20Settings/Administrator/My%20Documents/Downloads/Doc_3_-_Cylinder_White_Paper_-Final_June_17_2013_signed.pdf

This is inside the dockets folder. If it doesn't open, look here:

Regulations.gov (http://www.regulations.gov/#!documentDetail;D=FAA-2012-0002-0430)

This makes it pretty clear that the cylinder cracking issue is a manufacturing problem that is independent of operating technique. It also makes a pretty strong inference that ECI did not have the engineering talent to understand what it was doing.

yr right

26th Apr 2014, 02:02

mmmm or here

http://www.google.com.au/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=0CDEQFjAB&url=http%3A%2F%2Feaa.org%2Fnews%2F2013%2Freleases%2F2013-11-13_national_transportation_safety_board.pdf&ei=ORJbU6DzGoXSkwW7t4C4Ag&usg=AFQjCNH8rc1j9eS45reYlezWmmh4KoDAVA&bvm=bv.65397613,d.dGI

OZBUSDRIVER

26th Apr 2014, 03:12

Yr right, thanks for the link. Manufacturing fault. Insufficient interference fit at shrink band and wall thickness around head and threads as well as being over hardened....manufacturing faults...since part number 61177 in 2009 THERE HAS NEVER BEEN ANOTHER FAILURE!!! Sounds like something TCM/CMS should have done with their failed jugs years ago...if they did, the likes of ECI would never have got a start.

LeadSled

26th Apr 2014, 03:20

is that the 777 that impacted short of London HR had issues with fuel and temperature

Certainly did!! All such FAR 25 aircraft have, in limitations, a minimum fuel tank temperature, set at 3 degrees above the freezing temperature of the fuel in use. If you get to that tank temp., you either have to increase Mach No. of descend to warmer air.
On the day the BA B777 had the problem, the air mass over Russia had been particularly cold, as a result of a combination of circumstances, the fuel filters became partially blocked.
Thus, insufficient fuel flow was available when power was required.
It was the inspired action of the Captain, in reducing the flap setting, and reducing drag, without much change to lift, that enabled the aircraft to clear rows of houses and a major road, and make the grass just short of the runway.
Tootle pip!!

Old Akro

26th Apr 2014, 03:24

OZBUSDRIVER

read the FAA whitepaper. It goes into a lot more details including comparative failure rates of TCM & ECI and details af the respective manufacturing processes. It makes ECI look like clowns.

yr right

26th Apr 2014, 03:24

Lyc and Tcm have made big improvement's over the 10 years or so, ive been saying that. The amount of cracks has deceased, however two things still stand out. The pilot and the fact they don't last for ever. Like ive been saying 1st and 2nd life you really don't have a problem.
When we ran r985 we had to change a few this was because of there age and they to cracked. had when you cant get new ones. Then we got some believe it or not new old stock cly new and second life cly and never had a problem.

Then we got new engines twice a big and never had a problem with them either.

At o/h if you get new cly you wont suffer from this type of cracking and if you do you will get warranty on it. But it depends how much you fly. If you like most don't even do a 100 hours a year well I guess you need to think about it, if you doing a 1000 then its not a hard choice for reliability.
At the end of the day however I know which way I would go

cheers

yr right

26th Apr 2014, 03:31

Negative ghost rider as I recall it was not the fuel filters it was the fuel oil cooler became blocked due to the tube protrude the surface thus allowing a build up of ice. Since been modified so the tubes are much closer to the heat source so a build up of water /ice held in suspension cannot from across it and block flow .

jdeakin

26th Apr 2014, 03:46

Deakin said: fuel gets sprayed directly on the cylinder, inside the inlet port Old Akro said: John, not trying be be a smart*rse, but you might want to rethink this wording.
I don't think I've ever taken your wise words as those of a smart***, and I'm not now! :)

I do however have a slight quibble. I don't think we're in disagreement here. The injector dumps it's fuel into the intake port short of the valve, where it "piles up" until the valve opens, as you say. It is atomized by the "aspirator," a small screen around the injector. This screen allows outside air in (NA) or upper deck air in (TC and TN). The "inlet port" is a cavity in the cylinder. Thats what I meant when I said it's part of the cylinder.

Aircraft fuel injection is what is called "piss & dribble". Aircraft injectors are mis-named really. They are brass fittings with a hole in them. Fuel flows out of these injectors continuously. Its as simple, basic and reliable as you can get.
I agree.

Cars stopped using this system in the 1950's. Until about 10 years ago, cars used a timed, high pressure spray injection into the inlet manifold. Initially done mechanically (the old Lucas & Spica systems), then open loop electronically without any mixture feedback (Bosch L-jetronic), then with mixture control feedback using an oxygen (lambda) sensor (Bosch Motronic), then with refinements on spray pattern and spray timing using higher and variable fuel pressure. About 10 years ago, very high pressure injection directly inside the cylinder was introduced. Alfa was pretty much the first production company to do this with the 2.0 JTS engine.
Thanks for the historical detail. No quibble.

Typically, "injectors" are located to spray (pour??) fuel onto the back of the valve. This is to a) cool the valve and b) help vapourise the fuel. The intent is that the fuel vapourises inside the inlet manifold so only vapour goes into the cylinder. This is what gave GAMI a business, because (especially Continental) inlet design is poor and the inlet air flowing past one cylinder will rob fuel vapour from one (making it leaner) and delivering it to another (making it richer). Hence tuned injectors. I'm extremely well aware of that. I was there when George made that discovery. He calls it "an occult transfer!" :)

You would be shocked to learn how high the inlet manifold air temperature is. Its nowhere near OAT. In a non-intercooled turbo engine it could be 200 degC. Cars use water cooled inter-coolers to try and get the inlet air temperature DOWN to 100 degC.
No shock here a'tall. Very well known.

Fuel from the tanks will be at OAT and cold fuel handling can cause problems. It can cause problems in cars too that are hot, but fuelled from cool, underground tanks. BUT, there is a fair bit of plumbing in warm parts of the aeroplane and the injector itself will basically be at the same temperature as CHT. I struggle to see that cool fuel injected into a hot inlet manifold is a real issue. In this conversation, I'm ONLY talking about a long-ago issue, where pilots were following an unusual POH suggestion to go full rich for the descent. We theorize that was the cause of some very unusual cylinder cracks that developed IN THAT AREA. This long-ago (sixties?) procedure was the direct cause of the INSANE procedure of starting the descent much sooner, and reducing manifold pressure no more than 1 inch per two minutes.

It has NOTHING to do with the rare cracking in the SAP cylinders, which triggered the current AD in the US. It has NOTHING to do with any other cracking. I was only attempting to give the REASON for the "inch in 2 minutes procedure, nothing more.

And, I would suggest that most cylinders are replaced not because of cracking, but because of valve seat problems or cylinder dimensional problems - out of tolerance big, oval, taper or "barrelling"(fat in the middle). All of these can be improved with the APS techniques.
I'd love to take credit here, but I must, with respect, disagree. It has nothing to do with our procedures, either for or against. Most (all?) of the cylinder removal for valve problems are due entirely to INSTALLATION ERROR, and they take about 400 hours to show. Why else would we be able to correct the problem in just the errant cylinder (or 2, rarely 3), and go to TBO without further problems? Why else do some pilots who don't want valve problems send their BRAND NEW cylinder off to be checked, with a small percentage being found OUT OF LIMITS, repaired and installed, and THOSE engine usually go to TBO?

John Deakin
jdeakin // at // advancedpilot.com

No Hoper

26th Apr 2014, 05:07

Thanks Old Akro and others for trying to keep this thread on topic
John this is not an APS thread
Yet again you blame the installers for problems with valves etc
If you wish to provide valid data that repudiates FAA and NTSB research please go ahead. We don't require your email address

Old Akro

26th Apr 2014, 05:13

It has nothing to do with our procedures, either for or against. Most (all?) of the cylinder removal for valve problems are due entirely to INSTALLATION ERROR, and they take about 400 hours to show. Why else would we be able to correct the problem in just the errant cylinder (or 2, rarely 3), and go to TBO without further problems?

John, this is where it gets interesting!

I have a suspicion that we have one cylinder location (TSIO 360) that causes a problem. (Its a recent hypothesis, the logs are 100km away and I haven't been back to check). I have assumed that this is a cylinder whose mixture is out of step with the others (no, the aeroplane doesn't have an analyser - yet). If this is the case, it could play straight into your "red box" area.

I have looked at a number of removed cylinders and most have sunken valve seats. It looks to me like a material problem and the race engine shop next door to me agrees.

This gets us back to a point you made on the previous closed thread about an engine running happily with a 5/80 compression. Clearly you understand that the valve springs are there to make the valves follow the camshaft and not seal the valve. The cylinder pressure does that.

When I was young and building engines, I'd grind valves until my hands were sore. Coarse paste, then fine paste, them tooth paste. I'd fill the combustion chambers with kerosene and leave them to see which leaked. Then do more grinding until they didn't. Now the shop next door does all the head work (including porting & valve seats) on a 5-axis computer controlled mill. He says its better to leave the inlets a bit rough and that grinding paste does more harm than good. sigh.

Continental valve seats and seat profiles are not particularly good. I assume that your 5/80 cylinder is one where one or both valves don't seat properly under the pressure of the spring. But, if you are suggesting that a 5/80 cylinder can run happily then how do you reconcile that with your statement about installation problems causing the cylinder to not make TBO?

The other reason we have had cylinders replaced is that they "barrel" ie, the bore gets bigger in the middle. I had assumed that this condition could be improved by more attention to cooling management. Are you suggesting that it might be just a material issue and the luck of the draw?

I like your logic. But we, as pilots, like to think we have more control! :)

yr right

26th Apr 2014, 06:27

Oldeee is it a io 360 tcm. if you like some help pm as mush info as you have and I'll tell you the fix for it.
Cheers

Creampuff

26th Apr 2014, 07:22

But, if you are suggesting that a 5/80 cylinder can run happily then how do you reconcile that with your statement about installation problems causing the cylinder to not make TBO?My understanding is that the rules require a cylinder with those numbers to be repaired/replaced, because it’s not within specification.

The alternative is to get approval to run the aircraft in the experimental category. My understanding is Mr Atkinson did that with his 5/80 cylinder. :ok:

Walter Atkinson

26th Apr 2014, 14:17

That is correct. We were trying to prove (and did prove) that a static compression which would cause one to change the cylinder was not necessarily an indication that the valve was leaking while running. It clearly was not leaking while running. That was all there was to the issue. If one realizes that a static leak does not equal a dynamic leak then this is useful knowledge. If one is not willing to think about this in these terms and insists that ANY leak is a leak and do not care whether or not the problem is real or imagined, then this exercise was useless.

We use compression testing ONLY because for decades it was all we had. It is a suboptimal test and not nearly as accurate as engine monitor data. Eventually the FAA and CASA will catch up and change the rules for the poor mechanic who can't make the call on his own.

I have not, and do not recommend running an exhaust valve AT ALL which is leaking dynamically, it will soon fail. But I do know, intellectually, that just because it is leaking during a very poor test, that it does not mean that it is leaking while running.

"Those who insist that something is impossible, should not get in the way of those who are already doing it."

That is all. You may now return to your regularly scheduled programming. :D

jdeakin

26th Apr 2014, 14:23

Thanks Old Akro and others for trying to keep this thread on topicAgreed!
John this is not an APS threadI'm aware of that, but realize it's terribly difficult to avoid mentioning it from time to time, as that's where most of the research has been done. More correctly, GAMI/TAT does the research, we just teach it.
Yet again you blame the installers for problems with valves etcYES! BECAUSE THAT'S WHERE THE PROBLEM IS! Factory (predominantly CMI) and overhaulers though, not the person who simply puts them in. Not always, but a large percentage. It is the rule, not the exception, on the failures. Not the overall production, which is pretty good.

The machining that takes place regarding valves is one of the most exacting and difficult tasks in the engine. The valve guide must be straight and true and precisely aligned with the seat, everything must be concentric, and the valve must end up precisely centered in the seat with the contact area exactly equal all the way around. The tiniest mistake in any of that machining will result in a valve destined to fail at 400 to 600 hours.

Take the matter of a valve where the machining process puts the valve microscopically off-center. The valve-to-seat interface will have a contact surface a bit narrower on one side. We used to think that's ok, because it does make contact, it passes a compression check fine, the Kerosene check is fine. A couple hundred hours, it works well. But all the time, the valve is NOT EQUALLY COOLED AROUND THE CIRCUMFERENCE, because most of the heat passes through the valve seat. Eventually, the unequal cooling causes the valve to actually begin to warp, and at 400 to 600 hours (approx) a tiny bit of the valve no longer seals properly, and now a bit of the 3500 degree combustion event can partially leak out during the time the valve should be sealed. At that point, the poor valve hasn't long to go. It takes about 75 hours of operation from the first sign of this to failure. We have borescope pictures, EMS data, pilot descriptions, and the remaining parts from these failures. All the way from first indications and prophylactic removal to failure and engine destruction.

This is just one of the failures, there are others.
We don't require your email addressI'm aware of that. I post that in case someone wants to contact me outside the forum (special format to evade the internet 'bots that collect addresses for spam). You don't require real names, either, more's the pity. It would be much more polite forum if you did.

Are you a sysop or forum administrator?

John Deakin

jdeakin

26th Apr 2014, 14:56

I have a suspicion that we have one cylinder location (TSIO 360) that causes a problem. (Its a recent hypothesis, the logs are 100km away and I haven't been back to check). I have assumed that this is a cylinder whose mixture is out of step with the others (no, the aeroplane doesn't have an analyser - yet). If this is the case, it could play straight into your "red box" area. Yes, both cylinder position and unbalanced fuel flow can cause that. Baffling will help the first, GAMIjectors often solve the latter. An EMS will tell all (or nearly all.) That's the true value of an EMS. Not leaning.

I have looked at a number of removed cylinders and most have sunken valve seats. AIRCRAFT ENGINES????? CMI AND LYCOMING???? Please, tell me more! You've got my full attention! I've read old reports of that, but those are due to either "soft seats" or timing issues related to below standard octane fuel. We should never see that today!

This gets us back to a point you made on the previous closed thread about an engine running happily with a 5/80 compression. Clearly you understand that the valve springs are there to make the valves follow the camshaft and not seal the valve. The cylinder pressure does that.
True. I don't know how long Walter did that, so I don't how "happy" the engine would have been in the long term.

When I was young and building engines, I'd grind valves until my hands were sore.Thanks for the memories - NOT! When I was a tadpole (15?) and a lineboy, the boss would make me "lap valves" just as you describe. I felt like an Indian, trying to start a fire! Only thing on fire were my hands. An evil chore.

Now the shop next door does all the head work (including porting & valve seats) on a 5-axis computer controlled mill. He says its better to leave the inlets a bit rough and that grinding paste does more harm than good. sigh.
One brand name is "Surda?" Spelling may be off, that's phonetic. I'm unsure why, but that may be the cause of our problems. I'd like to visit one of the shops that have a nice little sideline business of correcting new cylinders, and find out more.
But, if you are suggesting that a 5/80 cylinder can run happily then how do you reconcile that with your statement about installation problems causing the cylinder to not make TBO?It ran 5/80 for some time, but NOT 400 hours, and strictly as a test. I've answered the rest in a message just before this one.

The other reason we have had cylinders replaced is that they "barrel" ie, the bore gets bigger in the middle. I had assumed that this condition could be improved by more attention to cooling management. Are you suggesting that it might be just a material issue and the luck of the draw?I'd take a wild guess that your intial assumption is correct. Heat and Time are the enemies of our engines. The more we see, the more we like 380℉ as an operating maximum for long periods. We've got a LOT of data that shows these engines will take redline temps for short periods, even to 500℉ with no apparent damage, and go on to TBO. But at and above 500℉ we invariably see damage in the very short term, just a few minutes. 380, 400, maybe 420 seem to be the dividing line.

John Deakin

No Hoper

26th Apr 2014, 20:42

John D
No not doing mods job, you are making valued contributions here and would be a pity to lose you from the thread.
Reference valve and seat installation, are you suggesting that it is the overhaul shops not using the correct technique or the OEM?
CASA has given advice to the industry through ADs and AWBs about boroscope evaluation etc to assess cylinder condition when compression is below the 60/80 differential.
I have seen comp as low as 20/80 improved to an acceptable level by running the engine and rechecking.
Low compression from blow by can be simply a matter of the ring gaps aligning, well that was one theory.

ericferret

26th Apr 2014, 21:00

OLD AKRO

While a touch of thread drift is involved with this I would add the following story to your compression comments.

While carrying out diff comp checks on a Lycoming 0-320 installed on an R22 helicopter that had just flown in with no reported defects I was confronted with
0/80, 0/80, 0/80, 0/80.

Obviously the compression tester was u/s so I used a second one. 0/80, 0/80 e.t.c.

Obviously I was having a brain storm so I had a second engineer check the engine. Same result.

We dropped the exhaust and watched the exhaust valves closing and it was apparent that at slow rotation the valves were hanging in their guides due to excessive guide wear and with no inertia were not seating properly. That this amount of wear had no apparent effect on the engine performance when running was startling, a helicopter hovering at high gross weight will normally reveal any engine abnormalities.

jdeakin

26th Apr 2014, 22:11

Reference valve and seat installation, are you suggesting that it is the overhaul shops not using the correct technique or the OEM?I think both. I think once in every 10 or 20 cylinders "something happens" to make one out of limits in one way or another. Perhaps a compounded error, where both parts are within tolerances, but when assembled together they're not. I don't honestly know, but we didn't see much of this on cylinders manufactured before about 1991. CMI (TCM then) had a strike, where managers went down on the floor, and it was also about then that some machinery upgrades were done. Some very old machinery that had been doing the work right might have gotten replaced by "modern" machinery that wasn't so good. All supposition, but the results are clear. Efforts to blame LOP are nonsense.
CASA has given advice to the industry through ADs and AWBs about boroscope evaluation etc to assess cylinder condition when compression is below the 60/80 differential. Depending on how that's implemented, it's probably a good thing! Borescopes have been around a long time, but it's only in the last few years they've been cheap enough for even owners to have. Under $200, with digital picture-taking ability direct to a computer. If a shop or a mechanic doesn't have one, I'd look for another mechanic.
I have seen comp as low as 20/80 improved to an acceptable level by running the engine and rechecking.
Low compression from blow by can be simply a matter of the ring gaps aligning, well that was one theory. YES! One of our slides shows compressions all normal (rough engine). A second compression check was done after flipping the prop through few times, and that test was 0/80. Sticky valve, of course, sticking on some strokes, but not others. A single compression check should NEVER be taken at face value. Always borescope it, if that's good, run or fly the engine, or fly it hard, and check it again. CMI did good, with the latest SB. It's now obvious that we've all pulled far too many cylinders based on compression alone for the last 100 years! :)

John Deakin

Old Akro

26th Apr 2014, 23:17

CASA has given advice to the industry through ADs and AWBs about boroscope evaluation etc to assess cylinder condition when compression is below the 60/80 differential.

I have a very high grade borescope. We have used it for a number of automotive investigations (mainly catalytic converters and chassis cracks inside a box section). I have fooled around with it with aircraft engines, both complete engines and (with my favourite LAME), diassembled engines so that I can look through the borescope then remove the pot and look directly inside to compare.

In my opinion it requires a very high degree of skill & proficiency to diagnose developing issues with a borescope. If you have part of a valve missing, its pretty easy - but you don't really need a borescope for that. I'm prepared to bet that the guy at CASA who wrote this has never done it. I'm interested to hear from Walter or John, but at 60/80 I don't believe you are likely to get any useful information from a borescope.

And back on the compression test, the ones I have witnessed rarely seem to get the same number twice. LAME's do it by feel a bit, rocking the prop until they get a number they like. Any test that is this inconsistent is questionable. Its also highly dependant on piston ring orientation. Like yr right's valve seats, piston rings rotate also. Every now and then all the piston ring gaps line up and the compression goes to hell. Run the engine or just leave it till next time and you get a completely different number.

Old Akro

26th Apr 2014, 23:41

AIRCRAFT ENGINES????? CMI AND LYCOMING???? Please, tell me more! You've got my full attention! I've read old reports of that, but those are due to either "soft seats" or timing issues related to below standard octane fuel. We should never see that today!

The first 100 hourly after I bought into the Seneca we replaced 6 pots. I wasn't part of the decision and I was new to the joys of Continentals. But, I took all the old pots back to my workshop and took them next door to my engine guy. Both the seats on the valve looked horrible and worn with the contact part of the seat worn into the valve and the seat in the head looked similar. With the valves in place they looked "sunken". Unfortunately, I've thrown them all out now.

At the time, I had quite a lengthy discussion about valve seat design and we compared the valve seat geometry with a number of modern car engines. It was quite interesting. The view was that the CMI design is quite old fashioned and not as effective at heat dissipation as modern designs. The CMI design was as I remember valve seats when I used to hand lap them. Angular and geometric, whereas now they tend to be more like compound curves.

This aeroplane has had the same owners since 1985 and (from memory it has done 2 engine rebuilds in that time). No-one remembers what brand these cylinders were. It may be that they were a bad batch. I have a recollection that CMI cylinders were not available and that they were another brand. We replaced them with CMI cylinders.

BTW, the 5 axis CNC machine is made by Centronic in the USA. Its spooky to watch it doing a cylinder head. It will change the cylinder head shape, do a port job, skim the head and cut valve seats all in one go.

One of the advantages of race engines is that they get torn down a lot. So its easy to try a change, then see how it performs.

I spent some time with a drag race guy a year or so ago. The drag guys use no data logging at all. They don't need to because the pull the engine down after every race and they can look directly at the parts. They also use the almost forgotten art of "plug cuts" and reading insulator colour to set mixture.

No Hoper

26th Apr 2014, 23:48

Old Akro
The engine is "pumped up" with cylinder pressurized to ensure the rings are seated. Also ensures piston is at TDC as this affects comp as well.
Boroscope is an art but not that difficult on piston engines, more skill required for turbine engine inspections though.
Do you know the chap who wrote the AWB?

Walter Atkinson

26th Apr 2014, 23:51

I ran the low compression cylinder for over 250 hours. The only reason I stopped was that the engine was overhauled (not for that reason).

It is pretty easy and straightforward to see a valve that is leaking while the engine is running through a borescope (not using the borescope while it's running!!). A heathy valves will have a very even, donut appearance to it where the heat is evenly distributed as it leaves the valve for the head. A leaking valve will show a very definite change in the circular pattern. CMI (TCM) put out a SB on this with pictures, etc.

ANYONE can see this change with even a cheap borescope. Any LAME who does not have a borescope should get one-- they are very inexpensive and an invaluable tool. There are many A&Ps in the US who now take a quick peak at the valves every time they gap the plugs. We are not removing cylinders nearly as often as we used to as a result. According to CMI's SB, compression below 60/80 is no reason to remove the valve unless the borescope shows the burning pattern. In addition, as the OEMs catch up to the A&P/pilot population's knowledge about how to use the engine monitor for this (it is even better) we will likely begin to see recommendations that we have been teaching for over 14 years adopted about how to determine whether or not a valve is leaking form inside the cockpit during flight. We've been doing this quite accurately and successfully for well over a decade.

We will be happy to have the OEMs, engine builders and FAA join the party of knowledge. More and more are doing so.

Our recommendation:
1) NEVER run a cylinder with a known leaking exhaust valve--it is soon to fail.
2) Verify this with a borescope or engine monitor data and, if it is NOT leaking, no need to stop running it.

The above has been our recommendation for well over a decade, so those who have been misquoting my recommendation might want to read the above again.

yr right

27th Apr 2014, 00:01

OK lets have a think here'

We do a leak rate test iaw manufactures procedure's lyc and tcm are different.

They say no leak past the valves is excepted period.
Regulators enforce this in LAW

Now you have four places for a leak to occur
Rings evident via the breather for a leak
Exhaust valve via the exhaust
Inlet valve via the inlet track
Crack head via a leak in the head

All give a different result. And there are techniques that we use when a valve is leaking to try and get it to reseat before we remove a cly. There are also limits via SB for the wear on a valve guild. A worn guild can lead to a dropped valve due to uneven loading on the valve during closing
.
Next and this is important.
We do this test at the end of a m/r and before issue of a new m/r unless there is a problem the engine may develop a problem 1 hour into a m/r our 1 before the end of the m/r.

Now they ran a 5/80 after finding it. So how long was it running before this was found and in the other thread they said how long they ran it for.
Now it can be safely assumed that they where trending the engine before this had taken place and it wasn't pick up . So why not
Instrument wasn't calibrated
Instrument wasn't fitted
They didn't know how to read the instrument
The instrument didn't pick the defect up
What did the instrument say when they knew of the defect
or a small bit of carbon under the seat
Did you do retesting during this period
And the list can continue.

Now this leads me into thinking why or why would you run the risk maybe to yourself but the risk to others. And unless you flying over nowhere like here you pose a risk to someone on the ground however small that risk is.
So what was the wrong with the cly in the end did you change it or just leave it for Devine intervention or send it to the healing room.

Now despite them saying a leak rate tester is not a really good tool its a very powerful tool and used correctly can and will lead to stop an engine failure.
Boros are a great tool even the little cheap ebay one I had a selection of small mirrors now I don't, I ha at my disposal a $1000 one to a $75k one all singing all dancing But the leak rate is still a better tool to see if a valve is leaking.

Cheers

yr right

27th Apr 2014, 00:05

Sorry forgot to add
Only leaks passed the ring is allowed.
Cheers

No Hoper

27th Apr 2014, 00:15

Yr Right
Can't fault your what you just posted, except to add that with leaks I have also found it benificial to throw some soapy water at the cylinders, on two or three occasions have found cracks around the head as well as ring leaks

yr right

27th Apr 2014, 00:24

Yeah soap in water to find bubbles just didn't put it all in sorry. I know tcm say to do that in there SB as we'll
Cheers

Walter Atkinson

27th Apr 2014, 00:30

Now they ran a 5/80 after finding it. So how long was it running before this was found and in the other thread they said how long they ran it for.

Watched it descend below 60/80 and kept an eye on it every 25-50 hours.

Now it can be safely assumed that they where trending the engine before this had taken place and it wasn't pick up . So why not

It was picked up.

Instrument wasn't calibrated

Yes it was.

Instrument wasn't fitted

Yes it was.

They didn't know how to read the instrument

Yes we do.

The instrument didn't pick the defect up

Yes it did.

What did the instrument say when they knew of the defect

The correct values.

or a small bit of carbon under the seat

No.

Did you do retesting during this period

Constantly. Every 25-50 hours.

And the list can continue.

No it can't. We were doing research. We were very careful. We learned a lot. Sorry you don't "get this."

yr right

27th Apr 2014, 00:36

Oldee I was a drag racer. We even made our own fuel injection. Now whilst a lot dont use data loggers a lot do. That's why you can have a N/A 500 ci suspension car running faster than nitro TF cars in the earlier 80s
And btw I also can pretty much tell you how to fix your plane. Is it a turbo model ?

Cheers

yr right

27th Apr 2014, 01:12

So research then hey. We'll let's look at that again. You claim data I've already said it's not data it's obverations. Now 5/80 is not research at all. Un less it carried out on a calibrated dyno how can you ever say what power the cly is producing.
Compression = power
A low cly will not make as much power as a cly running at 70/80. That's why we have limits. That's why tcm and lyc have different methods of performing a lake rate test. And different tesster one with a calabrated orifice and one with out. You can use a tcm on a lyc but you can't use one that has not got a cal with out useing the external orifice on a tcm. Why is that then.
And whist a low comp generally will not be picked up by a pilot it will how ever be picked up at
So now this low cly all thought making power isn't making what it should be making.
The whole reason for doing this is to make the engine safe. So now what is your option of an un safe engine.
And of course it's all in the name of research but I'm sorry I don't subscribe to this theory as I have people's life's in my hands and I take that responsabity extremly seriously.
And now you are say I give miss quotes we'll no you given out dangerous information
Cheers

yr right

27th Apr 2014, 01:23

I also said at the start of this thread that the AD from what I read seam quite a normal response to a problem that has occurred. Then we going the Nstb report which supported the action of the FAA but did say we'll maybe not all the cly need to be recalled.
Everyone said what about Oem cly and I said compare apples to apples.
It would appear what I said in the start to be true.
Cheers

jdeakin

27th Apr 2014, 01:48

Now 5/80 is not research at all. Un less it carried out on a calibrated dyno how can you ever say what power the cly is producing.
You are demonstrating for all the world (again) your ignorance of internal combustion engines.

We know that unequal power from the six cylinders produces engine roughness. The fact that Walter ran his engine at 5/80 and it was absolutely smooth is proof positive it was producing full power.

Compression = power
A low cly will not make as much power as a cly running at 70/80.Absolute rubbish. CMI once left the rings out of either an engine (or a cylinder, I forget), and it produced very close to rated power. It sure did burn a lot of oil, though.

And now you are say I give miss quotes we'll no you given out dangerous information I don't think you addressed that to me, but it certainly indicates my thoughts.

John Deakin

yr right

27th Apr 2014, 02:04

So you said a low cly will produce roughness then you said it won't which is it.

Creampuff

27th Apr 2014, 02:31

yr right

27th Apr 2014, 02:53

I'm me no one else but myself. However I know who you are and your past. I'm no troll.
You sir as I've stated before and there is no change to it.

An ex military know it all that could not make it in the commercial world and ended up where you all do and damage the aviation community.
Go back to your hole and under your bridge. You added very little as you have zero understanding of what is what on this subject.

But still no answer how you said one thing at the start and a second at the end so which is it.

Cheers

yr right

27th Apr 2014, 02:56

Maybe puff dady is on the payroll as we'll. gee one wonders what would have happen to an engineer here if they let a cly go like that. ?

yr right

27th Apr 2014, 03:15

And points that I put out are because what is said is wrong. I'm not a sheep I have a brain and I'm allowed to use it. I notice they quick to cya in an event that I find them lacking in and then try to discredit me.
Notice nothing back on leak rate or sb or stuff like that. Yet it shows he made two references that opposed each other.
I just would like a balance debate. Not a you will do cause we said. And remember it's NOT data it is obverations they have. Data is produced by manufactures and others that have there findings approved and an a STC issued. I and every other engineer cannot do work unless it is approved Data. Check casa out on this hey creamie
Cheers

OZBUSDRIVER

27th Apr 2014, 04:30

Yr right= David Brown?????......YEHRIGHT!

Aussie Bob

27th Apr 2014, 05:19

And remember it's NOT data it is obverations they have.

Data: Facts and statistics collected together for reference or analysis.

With all due respects yr right, these people have way more data than you could ever comprehend.

Check casa out on this hey

yr right CASA are mostly a bunch of Wallies. Your continued references to them puts you in the same camp.

yr right

27th Apr 2014, 05:50

With respect bob I'm sorry but is not data that can be used that's the point. Data must be approved to be able to use. In this case it's observed only. If it is approved data via an stc then it can be called data.
We don't and can't deal with what ifs it very simple.

Yes casa bunch of wallowing wombats you don't have to tell me that. I have to deal with them daily. However they set the rules and as such I have to obey by them.
I alone have so much dirt on them I can wright a book.

And just because they on another level to me dose not mean they have the answers to all as has been shown. Ie super cooled fuel I think not.
Sorry I am not a sheep. They also said we don't think maybe they need to revisit that subject as we'll cause a lot of us do. Do you know why most lames don't comment on pprune cause they can't put up with the bs that said. I've struck true to what I have said but I notice the other side back tracking. I also note note nothing said about saying one thing and then another.
And another thing don't even know a David brown
But a debate is good just don't be a sheep and be lead. Think about stuff look at it. Funny how it's been hijacked again.

Cheers.

Oracle1

27th Apr 2014, 05:54

yr wrong you are a waste of bandwidth

http://i875.photobucket.com/albums/ab320/oracle1_2009/WastingBandwidth.jpg (http://s875.photobucket.com/user/oracle1_2009/media/WastingBandwidth.jpg.html)

yr right

27th Apr 2014, 06:22

Occy the person that didn't know what wf meant pmsl.
Cheers

Oracle1

27th Apr 2014, 06:33

And you deduce this how?

yr right

27th Apr 2014, 06:40

Go play with your Lego blocks son.
Cheers

yr right

27th Apr 2014, 06:51

You have not made one constructive comment. Your so brave behind a computer. Once again like creamie you act as a troll.

Cheers

Creampuff

27th Apr 2014, 09:23

So anyway, we all know what the 1940's-based leak check procedure and the 1940s-based maintenance rules require when the procedure results in a number that is beyond specification.

The APS/GAMI people are merely trying to help bring GA into the 1990s. For some, that's too big a change.

That's one of the reasons GA's in inexorable decline in Australia: Too many people and too many rules stuck in the last century. :ugh:

Jabawocky

27th Apr 2014, 09:31

yr right, you have a short memory. Very short.

I am David Brown. Although we may not have met you knew exactly who I was right from the start. Who are you?

I am afraid you are wrong on the approved data front. That is from a maintainers perspective (thats you when doing a specific task accoding to CASA requirements) not from a scientists perspective. All the gathered data that folk like Walter and John and myself refer to is actually in support of the data that has been collected since pre WWII. And support is that of TCM and LYC, P&W, CW and and and......

Your lack of willingness to learn from it is where the problem is. Not in the data or its acredited source. And by the way much of the data we are refrring to has been collected for the FAA's certification work on many different things, including the future of unleaded avgas. Trust me on this, I have seen far more approved data for the FAA than you are likely to ever want to see.

So cut the Willy wagging, I have no desire to get into that as I figure you can trump us all with that :ok:

BTW, Walter and John have over the last 20 years been involved in as much or possibly way more than me. So get over it.

What bothers me is I could learn something from you, but clearly you can't learn anything from anyone else. It seems the rest of the Army is out of step. :rolleyes:

jdeakin

27th Apr 2014, 10:39

So you said a low cly will produce roughness then you said it won't which is it. Are you deliberately misunderstanding, or just ..., Never mind, forum rules, and all that.

A cylinder that is producing LESS POWER than the others (from different mixtures, bad plugs, etc., will cause ROUGHNESS. Fairly noticeable. For example, one cylinder's mixture LOP, the rest ROP, will produce roughness. If all cylinders will run LOP smoothly, then you have pretty good fuel balance. If the fuel is really well balanced, then the engine will not run rough no matter how lean you make it, it will just slowly lose power and die.

My TNIO-550 was like that.

Weak compression (from rings and valve leakage) will generally NOT cause roughness. I say generally, because valve DAMAGE (a chunk of valve missing), or a hole in the piston from Preignition certainly will!

John Deakin

jdeakin

27th Apr 2014, 10:58

Mr Deakin: It's not worth your or Mr Atkinson's time responding to this troll. It is obvious to me that yr right understands, with crystal clarity, the points you are making. He has to understand them in order to choose, with surgical precision, the points about which he pretends to disagree."John" will do. Thanks for your kind support and concern. I've never run into anyone quite like him, in 35 years on the Internet. It's mind-boggling to think anyone is quite that malignant. I'm not convinced it's an act, but maybe.

My main concern is that he spreads trash in almost every message. Someone may accept what he says as truth. That's the only reason I've been as persistent as I have.
That's why a number of us initially thought yr right was David Brown in disguise! I know David Brown's identity here, and that's not it. He has a wonderful sense of humor, but not a sick sense of humor. Now, I know anyone can have multiple identities here (pity!), but I'd bet a fair amount of money that's not one of his.

John Deakin

Oracle1

27th Apr 2014, 12:04

It's mind-boggling to think anyone is quite that malignant. I'm not convinced it's an act, but maybe.

That's because he is a troll. This troll is far more sophisticated than any we have encountered before and he has spent a good deal of time establishing credentials to ensure his credibility. When he gets lazy he drops the contrived dyslexic act that he has cultivated so carefully.

For a practising LAME he seems to have a great deal time on his hands to contribute to the forum. Last time I looked LAMES spend every minute of the day trying to survive. Strikes me that he is a public servant with a computer at hand, probably someone who didn't make it the real world and took a government job instead. Remember this forum is a hot bed of resistance to the idiocy of CASA and this white ant is doing a wonderful job of perverting and skewing the agenda through at least two aliases. The signs are easy to recognise if you know what you are looking for. The malignancy is typical of the cancerous culture of CASA.

Sophisticated though he may be he is still a troll and easily dealt with. Ignore him and stop contributing to any discussion he may join, don't give him oxygen, his outrageous and provocative statements will soon cease. The mods will soon realise that he is dropping the hit count and lowering the tone of the forum and they too will lose patience. We are being played like fiddles people!:=

yr right

27th Apr 2014, 13:01

We'll occy I am dyslexic and have been all my life. I was in A for maths and G for English. I am no Casa spy I have no interest in being in Casa. I am however a hard working lame slut.
A troll you calle why because I'm not a sheep that has to follow I think not. You not said one word execpt to down grade myself. Why because it so far over your head.
Jaba sorry didn't make the connection. So keep putting me down I don't care. The reason your so worried is I speak the truth and put holes in what you are saying to the point you say one thing then another in the same post.

What you can't get over is what your being told is not what is sermon the hangar floor.
The last two weeks I've put my name to over 42 cly inspections how any have you all done and that's not including the Turbine and airframe work.

It's your way or the hwy. now on data I can't even print of a section of the m/m without having to stamp it sign it and date it. So your work is not data that can be used you have not had an stc on it etc etc.

What you can't seam to get over is the fact that what I've been saying is true and correct. Someone in the middle of now where where all there is sand and flys.

So as you state stuff if it's wrong I'll let you know. And I've found a lot wrong and you know it.
But to be called sofizicated fu&k me have you got it all wrong.

Cheers

yr right

27th Apr 2014, 13:05

And sir I'm not spreading trash. I'll leave that for yourself. I said I follow the data I'm given and the law that I have to follow. As we'll. you don't and have openly said so on this forum.

And all I've really said I will not advise anyone to operate outside the poh.
Where you have.

Cheers

Walter Atkinson

27th Apr 2014, 16:05

About 40 years ago, TCM (now CMI) ran an IO-520BA on their test cell with no rings installed in any of the six cylinders. It made rated power with a static compression of 0/80. It could only do so for a relatively short time, since it was blowing oil out of the breather rather quickly, but it, nonetheless, made rated power. That's why engines with low compressions due to leaking rings still produce power.

This information came to me directly from the director of the test facility at the Mobile, Alabama, TCM factory. Of, course, that's not "data", it is simply his observation…. oh, wait, that's what data is, isn't it? The observation of a phenomenon and the recording of it during a scientific test.

An opinion is a conjecture without supporting observation during a scientific test. I don't give opinions unless I so state.

Oracle1

27th Apr 2014, 21:29

No dyslexia here,

And sir I'm not spreading trash. I'll leave that for yourself. I said I follow the data I'm given and the law that I have to follow. As we'll. you don't and have openly said so on this forum.

And all I've really said I will not advise anyone to operate outside the poh.
Where you have.

Cheers

Lumps

27th Apr 2014, 22:10

Keep up the good work yr right!

I can't see what good work yr right is doing except for providing us all with entertainment better than anything on TV right now.

As a layman pilot I have read a lot of interesting stuff from the other protagonists, and have read almost nothing of interest or value from our main antagonist. Except, paradoxically, that he has a hangar floor littered with evidence of failed clys from engines that have never failed, not one in flight shut down, nothing etc etc.

Those that hide behind the law (POH?) as holy script can often be left red faced as the law changes when presented with new evidence that replaced previous assumptions. Just sayin'. It happens, even in GA, sometimes.

Creampuff

27th Apr 2014, 22:31

Err, well no, not really. It might be classed as anecdotal, hearsay or maybe even OWT, without a proper, verified source.

Seems to be quite a bit of that put forward in the name of scientific data around here. Keep up the good work yr right!

Some confusion of concepts there.

OWTs are the invalid attribution of causation to (usually perfectly valid) observations and (usually statistically valid) data.

I took 1,000 cockroaches and as I put them on the table I yelled 'run!' I observed that they all ran.

I took the same cockroaches, pulled their legs off, put them on the table and yelled 'run!' I observed that none of them ran.

Statistically valid data and perfectly accurate observations.

I conclude that cockroaches hear through their legs. Invalid attribution of causation.

I took 100 piston aero engines and ran them at exactly the same power settings and operational circumstances for 500 hours. I stripped them down and observed that 98 remained within the manufacturer's specifications.

I took the same 100 piston aero engines and ran them at exactly the same power setting and operational circumstances, except with unleaded fuel.

I observed that most of the engines suffered valve damage within 200 hours.

Statistically valid data and perfectly accurate observations.

I conclude that lead lubricates the valves. Invalid attribution of causation.

OZBUSDRIVER

27th Apr 2014, 22:42

Err, well no, not really. It might be classed as anecdotal, hearsay or maybe even OWT, without a proper, verified source.

Would a "a proper, verified source" be classified as an engine test cell. A cell capable of even verifying an AVGAS replacement good enough for submission for certification?

yr right

27th Apr 2014, 23:00

No data is is what we may use in the course of doing or duties either as a pilot or engineer. Data is what is use for our against you in a court of law.
Now it's your choice how you preform your duties but if you go outside the data them you are on your own. It very simple. And if the poh is changed that's not a problem or an stc is used the same it's then approved data.

It must be approved to be able to be used.

As for me being dyslexic we'll I am affair it's very true. My phone auto corrects there are words you my phone will not pick up and as such I have a weighting style that is a little different. If you can't see that or can't unstandardised that we'll sorry.

I can also say once again I have nothing to do with casa my file has a Red Cross over it with open with caution.

Now of to do sience again.

Cheers

yr right

27th Apr 2014, 23:02

All work is preform with this

IAW

Cheers

No Hoper

27th Apr 2014, 23:34

Ofcourse lead doesn't lubricate the valves, it's the oil leaking past the valve guides
Tetraethyl lead, the snake oil salesman's friend

andrewr

27th Apr 2014, 23:48

Would a "a proper, verified source" be classified as an engine test cell. A cell capable of even verifying an AVGAS replacement good enough for submission for certification?

It's a start. Unfortunately, the history of science is littered with examples where something that worked perfectly in the laboratory and in small scale trials had unforeseen problems in the field.

What you really need is an experiment where you run many engines to TBO, some with LOP procedures, some with the old ROP procedures. The conditions need to be as close as possible to identical for each sample i.e. no significant difference in pilot population etc. You then compare the number of engine problems in each sample.

It's a difficult experiment to run. It needs massive resources. Probably the only practical way to do it would be to put the same engine in different aircraft types, and write ROP procedures in the POH for one, and LOP procedures in another.

Wait a moment - did someone say that some aircraft had LOP procedures in the POH while the identical engine in other aircraft specified ROP procedures? Maybe someone has been collecting data and evaluating LOP vs. ROP results in the field....

What would the results of this trial look like? The conclusion would be something like "LOP procedures resulted in a lower rate/higher rate/no significant change in engine problems reported"

In fact there is a document on the Advanced Pilot web site that quotes Lycoming: "the technique of operating lean of peak and power recovery was discontinued due to the resulting increase in service issues."

To which APS reply "Wrong". Well OK, I guess that settles it...

Just maybe Lycoming are not as dumb as APS like to make out. Maybe they have also tested LOP successfully in engine test cells, but found that it caused problems in the field. Actually, that is exactly what Lycoming say, as quoted on the APS web site.

It wouldn't surprise me if after Lycoming employees go to the APS courses, they go back to Lycoming and someone pulls a folder maked "Lycoming Confidential" out of the filing cabinet. They point out that Lycoming did the same engine tests with the same results 40 years ago, then produce the statistics from LOP field trials which show an increase in problems.

APS claim that extra education and instrumentation are required to run LOP. OK, no problem, but then you need to run another experiment where you compare the rate of problems LOP and ROP with the same level of education and instrumentation. Otherwise, any change could be due to the education, and you are not measuring the effect of LOP vs. ROP.

Science is difficult like that. It is more difficult than just running engines in a test cell. You need expert analysis of the experiment and statistics to see whether they support the conclusions. It isn't clear to me whether APS employ anyone with a science degree, or a statistician.

In summary, I believe that engines can be operated LOP as shown by APS. I believe that they can be very reliable when operated by a fastidious owner.

I don't know whether they will be as reliable when operated by someone who was taught by his instructor who was taught by the flying school owner, who did the APS course but had a little too much lunch and dozed in the afternoon. Or the pilot who knows all about it because they read about it on the internet. Or someone who just follows the POH. Or whether LOP operations might be less tolerant of mistakes when under pressure and you have to make unexpected power adjustments etc. I don't know whether the fastidious owner would get better reliability ROP with the same instrumentation.

The Lycoming quotes on the APS website make me suspect that maybe Lycoming have gathered the data, and they do know at least some of this, and as a result do not in general recommend LOP.

rutan around

28th Apr 2014, 00:16

The Lycoming quotes on the APS website make me suspect that maybe Lycoming have gathered the data, and they do know at least some of this,
Is this the same 'ethical ' Lycoming company that decided it was cheaper to pay out a few grieving relatives than it was to replace the hundreds of dud crankshafts they knew were out in the field? At least it was cheaper until they were sprung.
Also does this all knowing company even have an engine development test cell?

43Inches

28th Apr 2014, 00:20

I have not operated for many companies that have followed the manufacturers recommendations for flight operations to the letter. Most if not all flying training organisations where I've instructed used their own generic check list and procedures handed down over time and incorporated into the Ops Manual, CASA approved. Nothing much has really happened as a result, the issue would only be if you tried to pursue the manufacturer over a problem you caused. As a pilot you get hung for not following the company ops manual and CASA flight rules, the company is responsible for whether the ops manual is correct.

From what I understand the Malibu and Cirrus engines are recommended to operate lean of peak in the cruise. These are relatively new aircraft and may be an indication that the manufacturers are changing their tune.

I would say if operating the engine the way the APS guys say did so much damage then they would have been sued out of existence, especially since their main domain is in the USA.

andrewr

28th Apr 2014, 00:58

Also does this all knowing company even have an engine development test cell?

According to the quote on the APS website they do:

"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."

Would you really expect that Lycoming would operate without a test cell?

I'm not saying that they are all-knowing. I'm just saying that it's possible that they know more about the engines they build than APS give them credit for.

I also doubt that they just ship engines out the door and never collect in flight data. I would expect that they work closely with airframe manufacturers, including analysis of in flight data for new or changed installations.

What would be the liability for Lycoming if they didn't? Or for Cessna if they didn't consult with the manufacturer? How would it look in the witness box after an engine failure accident?

No Hoper

28th Apr 2014, 01:07

AndrewR
According to some posters Lycoming and CMI data is OWT and not collaborated by organizations acceptable to APS
and ECi
I agree with your summation of the issue of running LOP in commercial operations, pilots have high enough workload without adding to it

43Inches

28th Apr 2014, 01:23

I agree with your summation of the issue of running LOP in commercial operations, pilots have high enough workload without adding to it

I suggest you go for a fly with a Navajo pilot on a commercial run to see how much workload he's under in the cruise. If they're struggling with the workload at this point they need to go back to a Warrior or something slower. What you will probably see from 10 different pilots is 10 different leaning techniques from peak EGT to 150 rich, to just GPH settings.

Jabawocky

28th Apr 2014, 02:20

What you really need is an experiment where you run many engines to TBO, some with LOP procedures, some with the old ROP procedures. The conditions need to be as close as possible to identical for each sample i.e. no significant difference in pilot population etc. You then compare the number of engine problems in each sample.

American Airlines had 400,000,000 of data collected and ran TBO's several times longer LOP than they or the military could achieve ROP. Deakin San is probably one of the few old enough to remember. (sorry JD :O)

If anyone had proof of which you seek they did. :ok:

jdeakin

28th Apr 2014, 02:32

Good message, incomplete data. :D:)
It's a start. Unfortunately, the history of science is littered with examples where something that worked perfectly in the laboratory and in small scale trials had unforeseen problems in the field.AMEN to that!
What you really need is an experiment where you run many engines to TBO, some with LOP procedures, some with the old ROP procedures. The conditions need to be as close as possible to identical for each sample i.e. no significant difference in pilot population etc. You then compare the number of engine problems in each sample.

It's a difficult experiment to run. It needs massive resources. Probably the only practical way to do it would be to put the same engine in different aircraft types, and write ROP procedures in the POH for one, and LOP procedures in another.Yeah, but as you say, that's difficult to impossible, and we really don't need it.
Wait a moment - did someone say that some aircraft had LOP procedures in the POH while the identical engine in other aircraft specified ROP procedures? Maybe someone has been collecting data and evaluating LOP vs. ROP results in the field....The 1985 Turbo Centurion "Information Manual" for the T210R has the following comment on page 4-26:

"The recommended cruise mixture is at peak TIT or 1750℉, whichever occurs first. Leaner mixtures may be used but are not recommended considering that only a very small gain in economy is possible, accompanied by a loss in speed and possibly cabin comfort. However, richer mixtures may be used as desired for smoothness or power at the expense of increased fuel consumption."

Now, the ignorant might say, "SEE, SEE, I told you so, it's right there in black and white, DON'T RUN LOP! And they slam the door of their mind shut. They say you've got to follow that advise to the end of time, OR go through an expensive re-certification process to get it changed.

We (George, Walter and John) look at that language from 1985, and think it's sorta like reading respected (in their day) technical journals that insist the Earth is flat (written a few years earlier).

Now look. The turbo (with the Inconel rotor) will take 1750℉ all day long, but you're asking for trouble with the EXHAUST PIPES, which probably won't. Run it richer or leaner but stay away from 1750. The ENGINE MANUFACTURER doesn't know what kind of pipes the AIRCRAFT manufacturer is going to hang on it.

It does say that LEANER MIXTURES MAY BE USED! It flat out permits it, but offers some caveats. With fuel a $1.00 per gallon, it may be cheaper to throw some more fuel on the fire by running it richer.

"Possibly cabin comfort."

We really scratched our heads over this. What could they possibly mean? I'll tell you, they meant "VIBRATION from a ROUGH RUNNING ENGINE! The factories to this day do not understand the problem, or the simple solution to it! It took the genius of George Braly to produce GAMIjectors, of which there are now over 22,000 engine-sets out there. If all those engines had six cylinders, that's 132,000 individual injectors!

Look at the February 1990 "Maintenance and Operator's Manual" for the TSIO-520-BE engine, for the original Malibu. At high power, the ONLY mixture setting is LOP! IT IS NOT AUTHORIZED TO RUN ROP! IT IS FORBIDDEN TO RUN ROP AT HIGH POWER, BY LIMITATION!

I'll give you a hint. There is one minor adjustment to the engine that turns it into a LOP-ONLY engine. Does any know what it is?

In fact there is a document on the Advanced Pilot web site that quotes Lycoming: "the technique of operating lean of peak and power recovery was discontinued due to the resulting increase in service issues."
What were these "service issues?" Engine roughness when LOP! We say fix that, and you can run LOP again. Lycoming did not know how, because they did not, and do not understand why the engine runs rough.

It isn't clear to me whether APS employ anyone with a science degree, or a statistician.
George happens to hold an Aeronautical Engineering Degree from Brown University. When he graduated, AEs were plentiful, and jobs were very scarce. So he went back to college, and got a law degree as well. He put himself through both by Flight Instructing. His first aero job was with Ted Smith aircraft, builder of the Aerostar. His initials are on the original drawings used to build that airplane.
In summary, I believe that engines can be operated LOP as shown by APS. I believe that they can be very reliable when operated by a fastidious owner.
Thanks. I'll quibble a little bit, because IF AN ENGINE CAN BE OPERATED LOP, it's easier to do so, and a good deal safer, with OR WITHOUT an EMS.

John Deakin

andrewr

28th Apr 2014, 02:51

American Airlines had 400,000,000 of data collected and ran TBO's several times longer LOP than they or the military could achieve ROP.
If anyone had proof of which you seek they did.

Ah, that old chestnut. It's misleading to claim the old radials are the same as a Lycoming. Sure, they work on the same principles and use similar materials, but so does an aircooled motorcycle engine.

Some things which might be different, which may or may not make a difference:

combustion chamber shape
combustion chamber volume
compression ratio
valve timing
ignition timing
duration of the power stroke
fuel specifications
frequency of power changes
power settings used e.g. maximum range settings

What manifold pressure did they run? Can I run that in an IO360? If not, maybe not all the operating parameters are directly transferable.

Walter Atkinson

28th Apr 2014, 03:11

***
Ah, that old chestnut. It's misleading to claim the old radials are the same as a Lycoming. Sure, they work on the same principles and use similar materials, but so does an aircooled motorcycle engine.

Some things which might be different, which may or may not make a difference:
combustion chamber shape
combustion chamber volume
compression ratio
valve timing
ignition timing
duration of the power stroke
fuel specifications
frequency of power changes
power settings used e.g. maximum range settings
What manifold pressure did they run? Can I run that in an IO360? If not, maybe not all the operating parameters are directly transferable.***

No, actually the motorcycle engine is the different one. Mainly due to the shape of the combustion chamber. All of the above issues are so close between the radial and the flat engine as to be non-issues. The truth is, that the radial is a bit tougher to run… mainly because the detonation margin is narrower than your 360. They both run under very similar ICPs which is the big issue.

Jabawocky

28th Apr 2014, 03:20

andrewr

The list of differences is almost nothing compared to the similarities. The fuel and oxygen do not know any different. The motorcycle engine is not that much different at all apart from chamber shape, but remember they are designed for vastly different rev ranges. Otherwise, the rest not much in it.

The big turbo radials ran a lot more MP, but that only means reduced detonation margins to your trusty 360. :ok:

Why not come along and learn why?

43Inches

28th Apr 2014, 03:23

What manifold pressure did they run? Can I run that in an IO360? If not, maybe not all the operating parameters are directly transferable.

IO-360 is a bad comparison, if you destroy this thing you have been running it too high RPM, not due to leaning. At one operation the ones we had in the Seneca and Arrow were near on indestructible except for the odd manufactured problem that was easily corrected once found. The main problem was an oil leak at the front end spraying into the alternator on the Arrows. We shock cooled the buggery out of them and leaning, who knows, was all over the place but they went through to overhaul. Same with our O-320 and O-235s. IF you could run them lean of peak was more the question than whether it damaged them. These were engines usually on goodness knows what life, at least one crankcase was the same since new in the late 70s, and almost all overhauls were cheap, whatever could be scavenged and put back was done. Only had one bad O-320, came back from a dodgy overhaul and never ran well and a O-235 that lost two cylinders due wrong parts fitted during overhaul.

Jabawocky

28th Apr 2014, 03:30

No Hoper
I agree with your summation of the issue of running LOP in commercial operations, pilots have high enough workload without adding to it

That statement to those who know what they are talking about will seem rather at odds with reality.

A properly set up conforming engine, is considerably easier to set safely LOP than it is to set an appropriate ROP power setting. I know how to do both properly and to apprpriate settings and I can assure you that setting a LOP setting takes a fraction of the time it does to setting the appropriate ROP setting.

43Inches seems to know exactly what I am talking about.
I suggest you go for a fly with a Navajo pilot on a commercial run to see how much workload he's under in the cruise. If they're struggling with the workload at this point they need to go back to a Warrior or something slower. What you will probably see from 10 different pilots is 10 different leaning techniques from peak EGT to 150 rich, to just GPH settings.

I would strongly suggest that you need to reconsider this opinion of yours by learning to do both properly. I have posted this before, I took the editor of Australian Pilot flying and with a one minute briefing and a 3 seconds doing, she managed an 83% power LOP setting with amazing precision. 3 seconds. When you get good at it 1-2 seconds is more like it :) I reckon by now she has mastered the art.

andrewr

28th Apr 2014, 03:31

What were these "service issues?" Engine roughness when LOP!

According to the quotes from Lycoming on the APS website: "Burned pistons, valves, ruined rod and main bearings were traced to the inability of pilots to utilize this technique with the instrumentation and distractions found in the typical general aviation aircraft."

George happens to hold an Aeronautical Engineering Degree from Brown University. When he graduated, AEs were plentiful, and jobs were very scarce. So he went back to college, and got a law degree as well. He put himself through both by Flight Instructing. His first aero job was with Ted Smith aircraft, builder of the Aerostar. His initials are on the original drawings used to build that airplane.

Scientists and engineers are both specialized but different fields. In general, a scientist is not an engineer, and an engineer is not a scientist. They are different degrees, and in different faculties at many universities. (For the record I am neither but interested in both, I probably know a little more about science than engineering.)

Statistics are important in science. They are the way to translate data into statements like safer, more reliable, less problems, lasts longer etc.

Way back in the thread I mentioned p-values. They are an integral part of science. Without a p-value or a similar test of statistical significance you can't say whether data has meaning or not. The p value tells you the probability that you would get this result if the item you are testing makes no difference at all.

It is influenced by the amount of data, the natural variability etc. If your p-value is e.g 0.2, the data basically doesn't prove anything (even if it looks like it does). If your p value is e.g. .05 or .01, you have strong evidence. This is a fundamental part of any scientific claim of a change in the frequency of an event (cylinder failures, engine problems etc)

yr right

28th Apr 2014, 03:55

LeadSled

28th Apr 2014, 04:28

Like most things in aviation it when it goes wrong when **** hits the fan. A friend was flying a citation jet two crew dick made it a single crew so he can fly it himself. My friend said yep that's all good till it goes wrong and when it dose it's two quick for you to catch. We'll he was right he had a big inceadent two crew and got away with it single not much chance.

yr right,
More ratbag assertions. Most small Citations were built for single pilot operation, only Australia made a big deal about two pilot operations. Based on your previous posts, the real problem would be that there was no Flight Engineer.
Tootle pip!!

yr right

28th Apr 2014, 05:16

Oh yes leads led back. Have you ever flown or flow in a biss jet I have. Do you no the incident I was referring to. The machine did not have one rounded pannel leading edge nose cone and the list continued.
Now last time I checked American Airlines didn't have a piston aircraft in its fleet. And as for military hours we'll if the book say 500 till o/h that's what it is not 501. They not paying for anything. They also have a set twist for lock wire per inch.

Cheers

Jabawocky

28th Apr 2014, 07:46

Now last time I checked American Airlines didn't have a piston aircraft in its fleet.

what more can I say..... :ugh::ugh::ugh::ugh::ugh:

Do you work for a LAME shop or do you own and run one?

What year were you born?

Simple questions and no follow up hidden agenda involved. I will get in first, no and 1968 for me :ok:

LeadSled

28th Apr 2014, 08:09

Oh yes leads led back. Have you ever flown or flow in a biss jet I have

yr right,
Enough people on this thread know my operational background, that I am not going to dignify your silly comments with an answer.

The machine did not have one rounded pannel leading edge nose cone and the list continued.

So, an aircraft had a serious encounter with hail, not all that rare an event. What has that got to do with single versus two (or more) pilot operation.

Are you now claiming pilot qualifications??

They also have a set twist for lock wire per inch.

By "they" do you mean the military? Where I came from, an apprentice had to achieve the correct twists per inch, depending on the gauge of the lockwire, and do it by hand, only then did they graduate to Milbar wire twisters.Such standards were not limited to the military apprentices.

As for your "comment" about AA, what has that got to do with the price of figs.

Tootle pip!!