New Cylinder AD's released by FAA

[jdeakin]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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%20Setting...013_signed.pdf

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

Regulations.gov

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]

mmmm or here




http://www.google.com.au/url?sa=t&rc...65397613,d.dGI

[OZBUSDRIVER]

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]

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]

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]

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]

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]

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]

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]

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!