Not sure XXX. Id be very reluctant to send anything to the factory that i wanted back:)
Thank you for the positive comments regarding putting the planes on line with another school. The owner just needs to advertise for a school that uses a crystal ball to know exactly when a normal operating engine will go super nova in 5 seconds time huh?
if your looking for a copout on not IAW with jab manuals then your barking up the wrong tree.
This maintainer was ANAl about that, and even helped jab FIX some of their discrepancies in their manuals which we discovered existed after following them during install and finding that they had been put in backwards. Very clear, simple F@#up by jabiru. Discovered after yet ANOTHER component failure.

The logbooks on all these aircraft have been inspected on several occasions during RAA audits and insurance claims.

Cheers

XXX your confusing two different aircraft here mate, The independent report is for the 3300 in my 230, the reason there was no log book at jabiru when it was independently inspected was because it wasn't requested, Jabiru did however request extracts from it! Yes of course the engine was maintained by the book and torque checks of the thru bolts conducted at the settings advised by the factory (if I recall somewhat lower than initial settings)


Only number 4 head from that engine reached a temp above 200c, shows how invested Jab are in the facts when plying their facts on failures.


The cracked heads and the valve seat failure are from the 160 all within 300 hours from Top end overhaul and no this engine was never at Bankstown since they O/H'd it.


Its not a falling out with Jabiru mate, I am posting my experiences as stated previously to inform people, yes they are entitled to make up their own mind either way and im not trying to sway it, just the raw facts!


I am so sick of people wading in accusing a Jabiru owner of incorrect maintenance or operation, give me a break please its getting old.

I have had 4 engine failure in my 6600hrs experience.

All four in Jabiru 2200 aircraft.

Two engines cut out short final when power reduced to idle for landing.

One cut out during a stall practice at 4000ft in training area accompanied by a wing drop at the stall. Exciting! Restarted ok.

Final one was loss of oil pressure in circuit on downwind. We landed immediately and the engine started vibrating wildly on touchdown.
Subsequent investigation found that on downwind the oil pump jammed up with pieces of valve tappet adjuster screws that had shattered, and engine went completely out of timing on landing.

You will never ever get me back in that piece of $hit wing cracking, engine failing, random flap retracting, small wheelled uncomfortable aircraft.

Z.:ok:

Zanthrus, can I use that bottom line? very funny, thinking of ideas for side stripes on the 160...

XXX,
heres two of the reasons Jabiru gave me for the J160 heads failing, the other was to accuse me of running an additive. I quote Sue woods the business manager:-


"The word from the engine section regarding the heads is that there is evidence of overheating of the exhaust port areas probably from leaking exhaust pipes. This overheating has resulted in the valve seats dislodging and valve stem damage. They suggest the installation of EGT monitoring as an early warning for leaking exhaust pipes. Also carburettor jetting can be checked against the EGT measurements on the Mogas, Avgas and mixture of Avgas and Mogas. The cracks in the heads may have been caused by the overheating though they don’t appear to have contributed to the engine failure. For any more information speak to Mark in the engine section."


XXX, point of note a full brief of equipment fitted and conditions at the time was sent, they missed the fact that it had the desired sensors, also if you read the report into my other engine, the 3300 you will note that Jabiru state that the seats will start to fall out at 250c. also they found that one head had an exhaust leak at the flange, gripping at straws if you think that effected all heads... So I politely pointed out the inconsistency in their conclusion and got this:-


"Hi Chad

The engine section has examined the heads and the piston and cannot see any manufacturing defect that has caused this damage therefore we will help as far as providing the 2nd hand heads as quoted. If you want to send us the EMS data file we would be interested to see the EGT measurements against what fuel was in use. "


I have considered driving the 7 hours to get the EMS file for them, but I can guarantee it will show that they have been kept within limits! further all Jabiru would say if I tried to use that as evidence is that its a non calibrated instrument.


Sue has informed me that they will not be returning my heads, only after I requested them back for a third party to inspect and report on, she quoted her requirement to hold them in quarantine for one year so CASA can inspect. I provided her with this from the section head of defect investigation at CASA:


Hi Chad,

This email formally notifies you that under Civil Aviation Regulation 52B(3) that your Jabiru cylinder heads are not required to be kept in a state which allows CASA to investigate the defect.


Still refuses to return my property.

Why would they need a log book to explain how and why an engine failed? Its simple. They pull it apart, find the broken bit. The blaming of the operator (need for log book) would come later yea? Thats the usual routine isnt it?
"oh, youve overheated it"
" umm, no I havnt, I have 4 channel EGT/CHT for entire life of (rebuilt) engine which clearly shows always in specs."
"Oh, well, in that case, you used the wrong fuel additives"
"Ummm, no, i dont use fuel additives"
Oh...fair enough, well, then im afraid youve overheated it"..
"Ummm..havnt we been over this?"..
"oh yea, sorry, i got confused who i was talking to. You must understand we deal with a lot of these failures every week, I got confused"
"ok, so can you please tell me why my factory engine died at 300 hours?"
" Yes, we probably can..But..Not right now..We want to quarantine the parts so casa can see them...one day..maybe."

"Ok, just let me know please..Now, can you put me through to the sales dept..i need to buy some new parts to fit to my factory engine that doesnt work anymore"
"yes certainly sir"


While you may think this is a joke, i assure you its not. every part of that conversation I have witnessed first hand.

I chuckled when I read this, so you have had one genuine engine failure that can be attributed to the condition of the engine.

Adjustment of the idle stop is hardly a fault of the engine or engine manufacturer !

Yea, hafta agree. It seems your engines were idling to slow.
I once did the testing for a Jab powered homebuilt. For some reason, the engine would idle normally on the ground, but in flight would idle down and stop. Was strange and counter intuitive. I cant recall the reason. Sorry, getting old..

Well I would happily look at it for you, but can I say that there is no such thing as an EGT within limits, except when talking about a TIT, but that is not relevant here.

Have you been using Avgas? Mogas? and which sort and where from?

And just in case you are wondering ....which do you think has the highest EGT and which is the better off the two?

And just before you think I have any involvement with Jabiru, I do not. But I might be able to offer rational understanding of engines the data and they fuel used. ;) Gidday Wally! :ok:

Jabbawocky,
mogas, higher EGT than avgas.

M,

My best 'guess' would be induced prop drag due airspeed. I used to operate a C206 that would slow the idle when turning right due (I'm told) to gyroscopic propeller influences. Never occurred when turning left.

An aerodynamicist or engineer may have a more qualified answer.

Deadstick 1 you have one more guess. I'll let Jabba explain why. Cheers RA

Hint:- Compare what happens after the spark event using the two different fuels. Especially look at peak pressure and where it occurs and what happens to CHTs The timing and RPM should be the same for both fuels when you do the comparison.

Nothing like judgement by your peers :ugh:

The two J160's I have time in both have a peculiarity. If the idle is set correctly and a ham fisted pilot heaves the throttle shut the engine stops. If the idle speed is set high so the engine can't stop with a hard yank on the throttle then excessive braking is required or you need to instruct to pull the throttle very hard and keep the pressure on. There is a flex in the system somewhere that I have NEVER encountered in any GA aircraft. Gifted engineers have looked at these two aircraft, the best they come up with (failing modification) is a compromise, high idle or an engine that can be stopped by hauling hard on the throttle.

I know the problem Zanthrus, I have seen it, having a prop stop on final or on the runway is not really my cup of tea.

That said, both aircraft have had no engine problems, both have 2200 hours and both have had engines replaced (in lieu of a top overhaul) every 1000 hours.

hey Bob. No judgment mate. Just a possible explanation to his woes..Which you subsequently provided further evidence for. Judgment? or discussion..?

Ive not come across that problem in jabs. You must have some strong handed pilots there, pulling on that throttle.

Rutan around..... :ok: Good work there. Clearly not rutanaround at the back of the class were you. Unlike a couple of other ppruners :E

deadstick
The shorter latency of mogas Vs Avgas means that the peak pressure is higher and so is the CHT. Neither of these things is optimal.

The spark timing is fixed at 25DBTDC and being a direct coil on the flywheel system this will mean the spark (in theory) will fire sooner than that of a conventional magneto, but only a little. It could be said that the plugs location partially offsets this, but I do not know that for sure. (Flame front propagation).

High CHT, poor fuel quality, and with MOGAS there is not guarantee, there could be increased peak pressure and thus CHT. Add to this induction leaks and or the ordinary fuel distribution and how you know what was happening.

My suggestion is that with Mogas compared to Avgas all things being equal, you had higher CHT and lower EGT.

There is a large difference in Octane rating. So specifically which Mogas were they using and from where?

So getting back to the failure with a rapidly rising CHT and the two instructors on board, have you any photo's of the failed cylinder?

Hey := hold on, I was up the front :ugh:

There might have been a bit of rooting around but I got the most important question right :ok:

Do Jabiru certify mogas in their engines? If so are there any modifications needed (IAW with the maintenance manuals) to account for this issue?
Another question. How do other aircraft engines that allow both types of fuel handle the issue? Im assuming the engine manufacturers have similar or dare I say it, better knowledge about these problems?

There is a bucketload of material on this. Try this to start. You'll find more with the EAA, possibly AOPA and I think the Cafe Foundation.

Petersen Aviation | Auto Fuel STC

In short (aside from octane issues) Mogas compatibility has to do with fuel pump configuration and fuel line fitting metal composition. The engine itself doesn't care much, its all about getting it to the engine.

It is impossible to pull the throttle rotating mechanism past the stop located on the side of the carburetor, basic physics that one!

If the engine stops when the throttle is pulled out of the dash regardless of the strength of the pilot(s), then the idle stop is incorrectly set. Pretty simple really.

What will be wrong in the instances of stoppages mentioned above, is that the location of the cable assembly is incorrect both where it passes through the firewall and also through the holder attached to the carby. In all honesty if your mechanic can't get this right, they should stick to lawn mowers and I'm not referring to ultralights either. Failing that the problem will go away after replacing the throttle cable. I would be more than happy to demonstrate the correct fitting of the cable whenever I next pass through wherever this problem exists.


Would love to hear more on the wing cracking and random flap retraction. Both of those if reported would probably warrant an SB. As for random flap retraction, they are either manual flaps on an old LSA55 or electric in the J160 onwards and short of some shoddy maintenance I can't imagine why the flaps would randomly retract. No wonder these aircraft are getting a bad name when mechanics can't seem to look after them properly.

Yes yes. I get that. But, im saying that clearly there are engines that are designed to run on both types of fuel. My question is, what, if any measures do operators of these engines have to take when running the different fuels to account for these problems.. Apart from the rotax schedule of extra oil changes. Whats the difference. if its enough of a difference for some of you to blame the fuel for overheating the engine to FAILURE, then surely it would be enough of a difference to warrant standardised handling of the engines with different fuels.. of which there is non that im aware. Please tell me if im wrong.

Heat comes from energy. Its about how much power the engine produces and how effective the cooling, not the fuel that supplies the energy. I have only half been following this thread, but I think some of the failures may not fit the symptoms. I struggle to see how fuel type would play a role. Ignition timing might (come in Jaba).

As a rule of thumb car sump oil runs about 20 degC hotter than the water temp. Modern cars can easily run over 100 degC, so an acceptable operating temperature for oil is 120 degC (say 250 degF) for as long as you like. Use Synthetic and you'll go a lot higher. Higher temperature causes mineral oil molecular chains to break down. A modern car will happily do this on a synthetic blend oil for 30,000 km which equates to about 150 hours (an overall average of 50 km/h is a reasonable guess for an average suburban based driver with a mix of city, suburban and freeway driving). The Jabiru (I believe) uses automotive oil not the old mineral cr*p that certified engines use.

Oil is a major part of the cooling of any engine (even water cooled ones). I forget the proportion of cooling done by oil, but it might be circa 20%. Automotive oil will have better " wetting" properties and I would expect would transfer heat more effectively that aviation oils.

We should be able to design & build engines to cope with this and I struggle to see how through bolt issues are related to operating temperature. If I were to investigate this, I'd start by looking at the operating practices.

As I said, I haven't really paid full attention. These are off the cuff ideas. I might have something wrong.

Hey XXX

Glad I gave you a chuckle and I agree engine cuts on idle power may not be classed an engine failure. I can tell you it was a big surprise and very sudden. It was not as a result of ham fisted yanking closed either.

The flaps were manual on left side of roof. Half a broom handle and a bush which kept popping out of the hole holding the flap setting. Sudden bang and loss of lift which really scared the student in left seat!

Wing root cracks starting in windscreen. I was told that is just the gel coat she'll be right. Still not a good look and I never totally believed them. I have never seen this type of defect in other composite ga aircraft. Seems ultra light are a different breed.

Z!

Yea, sudden uncommanded flap retraction makes the aeroplane unserviceable in my opinion. If you flew it in that state...more power to ya brother. :)

JR

You did indeed. Nice to survive that test! Rutanaround was in the BN class though. More ratbags per sq M.....ohh hang on, no there were a lot from SA.

Merv, they do say they are OK on Premium Mogas, and they may well be. They approve them for 98RON, but I am not sure nor does it really matter about what they were certified with, but it would have been avgas at the time.

Old Akro The engine may not care much, but it does notice, but just like the STC's for many of the small HP carby engines, the engine will will see a change in the thetaPP no mater what. The fuel does not know the engine. It may well be fine on the PULP.

OA, think about this a bit more especially with hot heads. ;)

The jab engine was designed around 100MON avgas. It may well be fine on BP/Caltex 98 and they do say in factory SB's that 95+ is OK, but lord only knows what was being run in it so far in this thread, hence my question.


PS : OAThe latency off the fuel affects the effective timing. In other words the sparks go off at 'X' DBTDC but the peak pressure and ThetaPP are directly affected. Longer latency of Avgas will mean lower ICP as a result of the later ThetaPP. As for heat and the energy produced, yep 100% agree.

The heads are your property. They are not entitled to keep them. Period. I'd give them a solicitors letter and a deadline.

If you wanted an expert witness, there are a few guys from the engine labs of Toyota, Holden, Ford & Orbital that would be well qualified. I think you'll struggle to find an experienced engine calibration guy outside of Melb (or Perth for Orbital). For the purpose of preparing for a potential court appearance, I'd stick with a professional engineer.

I thought the hot heads were on the Dick Smith thread???

I'd argue that the head temperature is a product of the power output (& cooling airflow) and largely independent of fuel. Indeed Mogas probably has a lower specific energy than Avgas, so might be a bit easier on the heads.

We must catch a beer. I'm in Brisbane in early Feb.

I should add that I suspect part of Continental's problem is poor valve seat design which does not transfer heat from the valve to the head well. Thus the valve gets too hot and the seat wears causing valve recession. So, that's an area that might deserve investigation on the Jabiru engine.

The engine we are talking about was run on 98 Mogas.
Was this what caused the valves to fail?

Merv, not the valve failure needs to be determined as to how it failed. Valves generally fail due to poor machining of the head/valve seat and the guide. Valve guide wear through rocker geometry or through poor fit and then cargo or lead oxybromine ingress, then sloppy guides mean a rattly valve and then the head breaks off.

To make matters accelerate the CHT will not help if it is very high. There is no doubt the shorter latency of mogas Vs Avgas will have an impact but I doubt it has a serious impact if the cooling airflow is sufficient, but it does not help. There is a big difference from Avgas at about 110RON and 98RON that may well be a bit lower.

Getting back to the rapidly rising CHT, I am not saying it could not ever happen but a rapidly rising CHT is indicitive of a preignition event and not a valve failure.

Valve failure is not normally associated with a rapidly rising CHT. It can often be seen coming with the EGT races in the EMS. But even there not always. We had a C340 owner in a class once with a failed valve and no warning. That is a TSIO 520 Conti.

So was this failure a preignition event or not?

I wonder what the oil change interval was?

I think the valve geometry could be better, the guide material better. Are they post reamed and nice fit?

So many variables and the same is said for the maintenance of them. Don't get me wrong, my IO540 is my preference but many a jab engine does not get the life it should from external factors. But on the other side of the coin the cir clip events showed how easy things come undone too.

1.
2.
3.
QED

Jaba. There are two separate engines being discussed here.
The J230 was a CHT overheat event. I highly;y doubt it was pre ignition or detonation as the engine gave no rough running sympotm at all, The only indication was the flashing light warning me the CHT was over 180 deg's. That was late upwind, about to turn xwind on a normal 80 kt climbout on a 28 deg day. By the time the turn was completed the CHT was 210 deg's, then 220. That was when I levelled out, reduced power and returned to the strip.Where it subsequently stopped.
My questions relate to the valve failure at 300 hours in the 2200 with an engine that has logged history in 4 channels on CHT and EGT. None of which show anomalies. no overheat issues indicated. jab quote that valve seats start dropping out at 250 degs (see engine inspection report).
When we have one engine that fails at 220 degs, and jab saying 250 is where the seats let go. Why, has this 2200 engine dropped a seat with NO over tempt issues.
Thats the 64000 dollar question

Notes inserted below in RED

Generally the engines approved for lower octane fuels have relatively low compression and were originally designed for low octane fuel. Apart from lead polution higher octane 100LL does no harm as the slightly slower combustion event finishes a few degrees later safely after top dead centre. Peak pressure is well after TDC making it lower and easy on the valves and cylinder heads. As peak pressure occurs in a good place mechanically very little power is lost.

When lower octane UL fuel is used in engines designed for high octane fuel bad things happen.The spark occurs where the factory set it. The time from spark to completed combustion is shorter with UL so peak pressure occurs earlier in the cycle sometimes before the piston reaches TDC. This is very hard on the engine and it's a credit they hang together as well as they do.

One way to help the PP to occur later is to use higher revs. Now this is all very well for Jabba with his fire breathing monster engine fitted with a constant speed prop but for us mere mortals the only option is to lower the nose. It's unfortunate that engines fitted with fixed pitch props reduce revs just when they are working hardest ie in climb.The cooling air decreases and the PP occurs in the worst place creating more heat. The combination creates excellent conditions for detonation but by using low octane fuel detonation is not very well resisted and can quickly get out of hand.
Automobile engines get round the problem by having knock sensors which retard the spark in the above scenario.
Don't ask me past this point as the rest of the seminar was after the long liquid lunch and Jabba's dulcet tones put me to sleep.http://images.ibsrv.net/ibsrv/res/sr...ies/tongue.gif
Cheers RA

Detonation doesnt cause rough running?

not normally, might create an unusual sound as it get to heavier detonation, but mild detonation usually goes un-noticed.

the 2200 (J160 ) Failed on startup. ran rough and spluttered. pulling ther prop through by hand we found a cyliner to have zero compression.

Not till it gets out of hand. Some big bore turbo'd engines live with mild detonation for a lot of their operation. The high octane fuel prevents it running away (generally)http://images.ibsrv.net/ibsrv/res/sr...ies/boohoo.gif

from my understanding, the 2200 was the failed valve seat? the failure of the valve seat is irrelevent to EGT, or fuel type burned. and most lilely a manufaturing defect, even though Jabiru claim its valve seats fail at 250degC, which the 2200 never reached.

merv

as pointed out above detonation is unlikely to be noticed in an aircraft engine. I doubt the Jab engine will detonate anyway, although given the right circumstances with low octane, hot temps etc you might be able to. But not easily.

Preignition you will likely not hear or feel much there either until you have a trashed piston.

Your description of what you found is not very diagnostic at this level so maybe none of our collective somments are of any use.

The likely issues are valve guide wear then damage to the valve as a result. High temperatures will not help either.

Complete lack of data along with so many experts having their opinion along the ay mean finding the truth is almost impossible.

Recap gents,
the 230 suffered a cylinder head overheat on number 4 only no valve seat movement or valve failure, the subsequent bulk strip at the factory, revealed the bottom end was destroyed by the original inadequate thru bolt design.


The 160, dropped a valve seat whilst sitting at idle after the pre take-off mag checks. Upon inspection the cracks in the heads were discovered.


"The word from the engine section regarding the heads is that there is evidence of overheating of the exhaust port areas probably from leaking exhaust pipes. This overheating has resulted in the valve seats dislodging and valve stem damage."


The heads show cylinder creep (ridging) only around the exhaust port.


Fuel used primarily is Caltex 98, but when away, fuelling at other strips they use avgas.


Jabba, My experience on these engines and I have opened up a few, is that Avgas leaves deposits everywhere, the common issue I have noticed caused by it is ring sticking.


I have tried to post pics but cant figure it out, drop me your email and I'll send you some.


Request: can we keep it civil? accusations that the standard operating advice from Jab has not been followed are unfounded and completely wrong. It has been maintained and operate within the guidance and documented requirements set down by the manufacturer.


I get accused of this by Jabiru, always when asking for some kind of warranty or an explanation why their product isn't performing as it should.


But for the life of me can't understand why others have to belittle or be suspicious even after multiple denials, I have nothing to hide I have done everything that the factory has asked.
(My next step will to have a monk bless the bloody thing in hopes of 1000 trouble free hours).:rolleyes: