J120 drops oil @ YCRG. Very lucky timing

[Oscar]

Phhht, if the Jab had a Camit engine it would be as close to VTOL as you could get.I heard Chuck Norris designed them.

By which comment, you demonstrate the level of your competence to appreciate proper engineering. You were doing somewhat better with your: 'and NEXT week, I'll have the answer to all the world's aero-engine problems!'

 

Stick to your day job. CAMit engines are flying and turning in excellent results. All we have from you is some photos of crankcases..

 

 

[bexrbetter]

Stick to your day job. .

Come in spinner ...

 

The post wasn't aimed at the competence of Camit in anyway, I was however taking a poke at your constant flooding of the forum about them.

 

Hope that helps.

 

 

[Oscar]

Update for anyone interested:Went for a spin the other week and took the 120 up with a brand new motor (recon, I assume) fitted after it failed again, but on different head bolts, less than 12hrs after my incident and repair. Lucky for them they were only in circuits.

TT=844hrs before 2nd failure.

 

Hopefully this new reco won't suffer the same fate....

In Post #9 you stated that the LAME had replaced the through bolts - that is NOT a factory rebuild, that is a field rebuild. Now you tell us that it failed again, but: 'on different head bolts'. WHO did the 'repair' before it failed 12 hours later? Replacing head bolts has no systemic connection with the failure of through-bolts; however, head warping through over-temp operation and through-bolt failure resulting from detonation as a result of operation in an over-temp condition has a very definite systemic connection. New head-bolts will NOT correct an over-temp damaged head.

 

The necessity for forensic examination of damage is NOT some idle conceit of forum members, it is a necessary condition for understanding what has happened, what remedial action needs to be done and what lessons can be learned. Rather than simply throw out shallow commentary, would it not be in your OWN interests to help in the process of improving the engine you might, one day be flying behind over Corryong? The only insult here is one you give yourself by not (apparently) being bothered to find out all the relevant information before posting- and presenting that information so that others can contribute to the information-gathering process.

 

'recon, I assume'? Since you don't know, how is it that we are supposed to accept as completely accurate the rest of the information you have supplied concerning the operational history of the engine(s) concerned? You state that it's not your aircraft, so to be fair in your commentary, surely you should add the source(s) of your information regarding the actual condition, work etc. done on the engine(s) so forum members can evaluate the reliability of that information.

 

You are in a position to provide useful information to all Jabiru engine owners and users - including yourself. The end result of good information could be improvements in the engine that you - like many others - fly behind.

 

 

[Oscar]

Come in spinner ...The post wasn't aimed at the competence of Camit in anyway, I was however taking a poke at your constant flooding of the forum about them.

 

Hope that helps.

No, you are transparently self-interested in denigrating the work of any engine manufacturer, despite the fact that you have no product to offer. You don't even bother to correctly attribute CAMit. It's called 'trolling', and it's recognised as one of the lowest forms of contribution to on-line discussion, the modern equivalent of xeroxing your buttocks at the Office Christmas party.

 

 

[Dafydd Llewellyn]

Come in spinner ...The post wasn't aimed at the competence of Camit in anyway, I was however taking a poke at your constant flooding of the forum about them.

 

Hope that helps.

Well, no, actually it doesn't. It's off topic and provides no enlightenment. This occurrence should be able to be used to provide some useful information; but what we're getting is obfuscation. If the engine was repaired in the field, that's an important piece of info. Exactly who did what to the motor, and when?

 

 

[SDQDI]

Cheer up people fair dinkum he was making a joke and having a bit of a dig no need to tear him to pieces

 

 

[Oscar]

Cheer up people fair dinkum he was making a joke and having a bit of a dig no need to tear him to pieces

Sorry, but that's not good enough. Engine reliability is a life-important issue; that sort of self-serving cr&p from a clown way outside where the buses run of serious development work for the benefit of every Jabiru engine owner is nothing but ambush advertisement for his own (unrealised, and as yet completely unproven to even exist) product. You are being conned.

 

 

[SDQDI]

Sorry, but that's not good enough. Engine reliability is a life-important issue; that sort of self-serving cr&p from a clown way outside where the buses run of serious development work for the benefit of every Jabiru engine owner is nothing but ambush advertisement for his own (unrealised, and as yet completely unproven to even exist) product. You are being conned.

Well what about hearing from you in nearly every thread about CAMit? Is that not counted as ambush advertisement? I know engine reliability is an important issue and I appreciate all the serious discussion including your inputs in regards to CAMit's work but when someone makes a joke don't take it so serious.

 

 

[Dafydd Llewellyn]

All right, let me see if I have this right:

 

1. The aircraft flew about 820 hours on the original engine, before having the through-bolt Service Bulletin incorporated.

 

2. The aircraft flew about 5 hours after the SB was incorporated, then broke two through-bolts on January 9.

 

That suggests to me that the SB was incorporated late last year. However, that's quite a while AFTER Jabiru's 12 month offer to do the job free of charge. If correct, that leads to three rather pertinent questions:

 

(a) Why was the SB not incorporated when Jabiru was making that offer?

 

(b) Was it incorporated because the original through-bolts had failed; or was the engine still servicable when the job was initiated?

 

© Was it incorporated by somebody other than Jabiru, since the factory offer had expired?

 

(Do, please, correct me if I have this wrong; I'm trying to get at the facts.)

 

If I do have the sequence correct, then there are a couple of deductions:

 

Firstly, the through-bolts fail primarily because their pre-load has diminished sufficiently to expose them to cyclic loads each time one of the cylinders they secure fires. There are a number of potential causes for the loss in pre-load - but it is inescapable that the original assembly was good for 820 hours, on through-bolts that Jabiru were requiring to be replaced.

 

Secondly, if the original bolts had failed, a condition must have developed that caused it - and simply replacing the through bolts obviously did nothing to correct whatever that condition was. Whether that indicates inadequate practice on the part of whoever performed the replacement cannot be deduced from this; it would require that forensic analysis to clarify that.

 

 

[geoffreywh]

from that can I take it that it does not fall under warranty.................................

 

 

[Dafydd Llewellyn]

Well, we ain't got the full story, by a long shot; however Jabiru SB JSB031-1 (which is a maintenance directive, for a Jab 120, since the J120 is under LSA rules) was dated 14 April 2011, and it says, inter alia:

 

 

If it had 820 hours on 9 January 2014, on the original through-bolts, where does that place it in regard to the above? Work it out yourself . . .

 

 

[Oscar]

Well what about hearing from you in nearly every thread about CAMit? Is that not counted as ambush advertisement? I know engine reliability is an important issue and I appreciate all the serious discussion including your inputs in regards to CAMit's work but when someone makes a joke don't take it so serious.

There are CAMit engine owners out there reporting on their experiences. There is a guy with precisely zero runs on the board throwing ordure. Who are you inclined to believe?

 

 

[alf jessup]

Phhht, if the Jab had a Camit engine it would be as close to VTOL as you could get.I heard Chuck Norris designed them.

Yep like if your Grandmother had B@lls she'd be your Grandfather too

 

 

[jetjr]

Well, we ain't got the full story, by a long shot; however Jabiru SB JSB031-1 (which is a maintenance directive, for a Jab 120, since the J120 is under LSA rules) was dated 14 April 2011, and it says, inter alia:[ATTACH=full]28861[/ATTACH]

 

If it had 820 hours on 9 January 2014, on the original through-bolts, where does that place it in regard to the above? Work it out yourself . . .

Interesting

My 3300 solid was rebuilt by jab weeks before this was announced, took it back and had bolts replaced no probs. they did not do nor was it in the instructions for others (somewhere is a set of instructions) to do the studs as mentioned above, to do these means splitting case I think. New nuts are fitted

 

 

[Dafydd Llewellyn]

Hi Dafydd,1,2,3,4 - not sure, I'm not the owner or the LAME. Nor do I thoroughly check the logbook, it's not my plane.

 

I provided an estimate of engine hours, that's all I know.

 

I'm not sure it's worth anyone's time or effort to attempt a forensic analysis of this incident via a forum.

 

My post was to inform the aviation community in a more general sense.

 

I can only refer you to the RA-Aus incident report register...

 

9 Jan:

 

"...Subsequently discovered that the engine through bolt on cylinders 3 and 4 had failed...."

 

Engine TT: 826.7

 

9 March:

 

"...inspection revealed a fractured through bolt on No1 cylinder.the reporting pilot advised this was the second through bolt failure in the previous 5 hours of operation, engine repair work had been previously conducted by factory...."

 

cheers

 

R

 

ps. Calm down, it's insulting to both you and me.

Well, your initial post left out one extremely salient point - which was that the engine had been operated (if I read the information supplied correctly) some 326.7 hours longer than was allowed by a legally-binding Service Directive, namely JSD031-1.

It looks to me, from the second part of the RAA incident report, as though Jabiru should have scrapped the engine instead of replacing the through bolts; because the second failure says to me that the previous history had done damage that prevented the replacement through bolts from maintaining sufficient preload to prevent them from being fatigued by the cylinder firing loads. The peak cylinder pressure at full throttle is around 1000 psi; this acts on the underside of the cylinder head over the full area of the cylinder bore - so the force per bolt every time the cylinder fires would be of the order of 2000 pounds force - nearly one ton. This can only be resisted if the preload on the through bolts exceeds that value.

 

They would appear to have run 844 minus 826.7 = 17.3 hours; each through bolt gets the loads from two cylinders, and each cylinder fires once every two revolutions, so at 2900 RPM that would be around three million load cycles. That was in the face of pre-existing damage. Such damage tends to occur extremely slowly at first, and to gradually accelerate, progressing much more rapidly close to the end. So whatever that damage was, it would quite probably not have existed had the engine not been allowed to run that extra 300 odd hours.

 

 

[Oscar]

InterestingMy 3300 solid was rebuilt by jab weeks before this was announced, took it back and had bolts replaced no probs. they did not do nor was it in the instructions for others (somewhere is a set of instructions) to do the studs as mentioned above, to do these means splitting case I think. New nuts are fitted

jj - if Jabiru did not replaced the studs, then that is certainly not in accordance with either the 2011 (JSB 031-1) or the subsequent 2013 (JSB 031-2) Service Bulletins. Both of those require bolts and studs to be replaced, plus fitting oversize crankcase dowels. Further, putting the 'new' 12-point nuts on old studs would not allow the required thread engagement, which necessitates slightly longer bolts and studs. If the pre-tension on old bolts / studs has diminished enough to allow any movement of the cranckases there is the possibility of the Loctite case joining medium becoming damaged, which allows more crankcase movement which becomes cumulative damage over time, further reducing the bolt/stud pre-tension and allowing more destructive loading as described above - or in less technical terms, allowing the engine to effectively beat itself to death from the inside out, as it were.

 

Suffice it to say that CAMit have completely re-engineered the whole bolt/stud/nuts and crankcase joining technique system; it may look similar from the outside but it most certainly isn't!

 

 

[jetjr]

Yep agree BUT, this is where it costs a company lots (excessive) money.

 

There was a range of numbers subject to the problem, they increased range affected significantly to be safe, and it extended into Solid lifter engines - which I believe never have the issue.

 

With studs included, its no longer a simple upgrade but a full teardown. Had this been the case unlikely they could afford to cover the cost and owners left with whole cost.

 

Outcome could have been a lot of complete rebuilds for a non existant problem.

 

As the studs only support one cylinder was it a OK risk to leave them there? Maybe studs had never broken? Dont know

 

Im not concerned that they werent replaced, in fact wouldnt want a full rebuild on engine unless needed as then there are way more things can go wrong if this was done cheap or in a hurry.

 

All the same if this was the case why have it in the documents that studs need replacement.

 

At the time there was lots of discussion if this is a real fix or not, and was actually recommended to me NOT to replace them.

 

 

[jetjr]

Well, your initial post left out one extremely salient point - which was that the engine had been operated (if I read the information supplied correctly) some 326.7 hours longer than was allowed by a legally-binding Service Directive, namely JSD031-1.It looks to me, from the second part of the RAA incident report, as though Jabiru should have scrapped the engine instead of replacing the through bolts; because the second failure says to me that the previous history had done damage that prevented the replacement through bolts from maintaining sufficient preload to prevent them from being fatigued by the cylinder firing loads. The peak cylinder pressure at full throttle is around 1000 psi; this acts on the underside of the cylinder head over the full area of the cylinder bore - so the force per bolt every time the cylinder fires would be of the order of 2000 pounds force - nearly one ton. This can only be resisted if the preload on the through bolts exceeds that value.

 

They would appear to have run 844 minus 826.7 = 17.3 hours; each through bolt gets the loads from two cylinders, and each cylinder fires once every two revolutions, so at 2900 RPM that would be around three million load cycles. That was in the face of pre-existing damage. Such damage tends to occur extremely slowly at first, and to gradually accelerate, progressing much more rapidly close to the end. So whatever that damage was, it would quite probably not have existed had the engine not been allowed to run that extra 300 odd hours.

All technically correct as always

 

BUT could way simpler answer

 

What if there was a cause of the breakage like leaking induction tubes, serious leaning and detonation or maybe just running too lean.

 

Bolting engine back together and running again will have the expected result.....same again.

 

As Oscar said no one said Jabiru did repairs and even if they did do they have skills to determine failure cause.

 

Supports the view that explanation for failures is critically important however often difficult, so data on engine operation becomes equally important......... were EGT and CHT being monitored?

 

Other point here is that isnt the first 50 hours after major work a common point in life for engines to fail?

 

 

[Dafydd Llewellyn]

Yep agree BUT, this is where it costs a company lots (excessive) money.There was a range of numbers subject to the problem, they increased range affected significantly to be safe, and it extended into Solid lifter engines - which I believe never have the issue.

With studs included, its no longer a simple upgrade but a full teardown. Had this been the case unlikely they could afford to cover the cost and owners left with whole cost.

 

Outcome could have been a lot of complete rebuilds for a non existant problem.

 

As the studs only support one cylinder was it a OK risk to leave them there? Maybe studs had never broken? Dont know

 

Im not concerned that they werent replaced, in fact wouldnt want a full rebuild on engine unless needed as then there are way more things can go wrong if this was done cheap or in a hurry.

 

All the same if this was the case why have it in the documents that studs need replacement.

 

At the time there was lots of discussion if this is a real fix or not, and was actually recommended to me NOT to replace them.

My understanding is that if the engine does not have a TC, (which the 3300 does not) then that Jabiru document is a Service Directive - i.e. it's mandatory. If the engine has a TC (which the 2200 J and C do have) the Jabiru document is not mandatory unless made so by an Airworthiness Directive. So regardless of its actual technical merit, I suspect that that SD is mandatory in law for the 3300.

 

 

[Dafydd Llewellyn]

All technically correct as alwaysBUT could way simpler answer

What if there was a cause of the breakage like leaking induction tubes, serious leaning and detonation or maybe just running too lean.

 

Bolting engine back together and running again will have the expected result.....same again.

 

As Oscar said no one said Jabiru did repairs and even if they did do they have skills to determine failure cause.

 

Supports the view that explanation for failures is critically important however often difficult, so data on engine operation becomes equally important......... were EGT and CHT being monitored?

 

Other point here is that isnt the first 50 hours after major work a common point in life for engines to fail?

Actually, the quote of the RAA report does say that the factory did the repair - see post #97. Doesn't say which factory; the Jabiru repair shop is NOT the manufacturer. Getting the info is like pulling teeth without anaesthetic. Yes, of course, the operating conditions could well be one of the uncorrected problems; and for sure, there are many factors involved, and they are all quite subtle - the most obvious one (and probably unmeasurable) is the case jointing compound. It only has to compress about 0.001 inches to have a significant effect on the preload. There are far too many unknowns to hypothesize.

 

 

[Oscar]

All technically correct as alwaysBUT could way simpler answer

What if there was a cause of the breakage like leaking induction tubes, serious leaning and detonation or maybe just running too lean.

 

Bolting engine back together and running again will have the expected result.....same again.

 

As Oscar said no one said Jabiru did repairs and even if they did do they have skills to determine failure cause.

 

Supports the view that explanation for failures is critically important however often difficult, so data on engine operation becomes equally important......... were EGT and CHT being monitored?

 

Other point here is that isnt the first 50 hours after major work a common point in life for engines to fail?

Absolutely agree on all points you make - and I think two of those are extremely important that they be recognised.

 

The first is - as many have stated on the various Jab. engine problem threads - that it is VERY important to determine what was the actual CAUSE. There has been way too much conjecture derived from the RESULT (usually that the through-bolts are simply too weak, and for the original 5/16 bolts, that's a pretty fair conclusion, but it certainly isn't the whole story).

 

And the second point you make that should be inscribed on the wall of every repair shop (including Jabiru's own) is that bolting the engine back together and running again will - highly likely - have the same result. Unless one can accurately determine a manufacturing fault (e.g. bad batch of components) or an obvious installation fault, then failing to learn from the lessons of history - and all that..