"Jaberoo" down (Mildura this time)

[turboplanner]

It has as far as I'm concerned; I've not been active on the website all that long. Please give me an indication of the thread on which you gave those data. I have to say, getting meaningful information is like getting blood out of a stone.

I gave you the link to RAA which has all the data; it is published in the Association Magazines month by month. I've asked Ian a couple of times for better indexing but his position is that people spend more time on the site if that isn't done, rather than just finding their information and leaving. I can't remember the threads I posted the data on, so I'll post it again.

 

 

[Dafydd Llewellyn]

Ta. Firstly, as I have repeatedly stated, I'm NOT a member of RAA - I was so disgusted by what I learned as an expert witness for Carol Smith, that I let my membership lapse, and went back to the GFA. Secondly, I do not have the time to spare to wade through years of RAA reports; so I will be most appreciative to see your results.

 

 

[turboplanner]

This is a batch of 35:

 

The typical report goes like this one:

 

Jabiru LSA 55, Engine: Jabiru 2200,358 hrs ttis.

 

The aircraft had completed several circuits and was at a height of approximately 150 feet when two loud bangs were heard and the engine failed.

 

A forced landing was carried out in a ploughed paddock where the aircraft flipped over and came to rest inverted. The pilot and passenger suffered abrasions and cuts requiring sutures

 

Inspection of the engine revealed that a cylinder had separated from the crankcase.

 

Probably not enough for you, but enough to categorise the failure.

 

Just for the moment disregard totals for the timeframe because it only represents about half the reports. I now have the balance and have dragged the magazines out on to my desk.

 

EXX22.pdf

 

EXX22.pdf

 

EXX22.pdf

[turboplanner]

But as been repeated again and again, those stats doesn't say whats wrong , just what happened or what was the end result.

The taxpayers got smart and stopped funding what had become a self indulgent industry, costing the taxpayers millions, decades ago.

 

These days the government specifies performance standards, and the manufacturer has to spend the millions doing the research and ensuring his product is ft for purpose. If not, it's his problem to do the research and development or get run over by the competitors.

 

The stats we are getting do point to specific areas for the various aircraft and engines, and if a build up of numbers occurs in safety related areas, then the manufacture has a job to do.

 

 

[Dafydd Llewellyn]

Ta - yes, even that much helps to narrow it down somewhat. I wouldn't expect more from RAA data.

 

I wont, hes busy running through oscars log books and stuff ay?

Aye, belike.

 

 

[turboplanner]

Typing............

 

 

[geoffreywh]

I found it interesting to browse through this month's mag and check out the difference between the Airframe hours and the Engine hours on the (Jabiru) aircraft advertised. Looks like 400 hours is about as far as they go (with a notable,wonderful exception) without a replacement or major work... That too is my experience. My take on problem reporting? It's my estimate that less than 50% of incidents get reported, so the RAA figures will not be a whole lot of help in building a statistic base.......

 

 

[Ron5335]

If there is some sought of inquiry it will be interesting to see what figures are marched out..........

 

For 19 owners, they have they option to go with mods from Camit, Bent, Rotec and others, and a lot have chosen this option, and are building up uneventful hours.

 

The Jab factory says if you use any of the above mods, then it's not a Jab engine anymore, and you should send your engine plate back.

 

When push comes to shove, will the factory use the "Non Jabiru" engine numbers & hours to guild the lily??. where it should be restricted to the 24 & 55 reg aircraft , where the owners have no options and will reflect a true account of the engines performance, and will reveal the truth whether the modifiers are on the right track or simply Pi$%^ng in the wind.

 

 

[Oscar]

This is a batch of 35:The typical report goes like this one:

 

Jabiru LSA 55, Engine: Jabiru 2200,358 hrs ttis.

 

The aircraft had completed several circuits and was at a height of approximately 150 feet when two loud bangs were heard and the engine failed.

 

A forced landing was carried out in a ploughed paddock where the aircraft flipped over and came to rest inverted. The pilot and passenger suffered abrasions and cuts requiring sutures

 

Inspection of the engine revealed that a cylinder had separated from the crankcase.

 

Probably not enough for you, but enough to categorise the failure.

 

Just for the moment disregard totals for the timeframe because it only represents about half the reports. I now have the balance and have dragged the magazines out on to my desk.

Turbs - do you have that table in a spreadsheet? This is seriously useful stuff and some statistical analysis would likely be very instructive. It would need more background information on the circumstances of failures to really pinpoint causes rather than just results, but it's a hell of a good start, and RAA - and Jabiru engine owners - owe you one for the work that you've put in.

 

Your 'typical example' is remarkably close to an entry in the logbooks for my aircraft. From having dismantled and rebuilt the engine from the last failure - that ended in a tip-over (as described almost perfectly what happened) it is evident that a forensic examination of that aircraft's history shows that it has a pattern of engine failures that need to be considered in terms of the operational parameters under which it was used, that that particular engine (a zero-timed rebuild) should never have been returned to service, and that by examination, the maintenance work undertaken on the aircraft was seriously deficient in quality if not quantity.

 

We need to get beyond the philosophical conundrum of the assertion that 'All elephants are grey, this animal is grey, therefore it is an elephant'. We need to look at the difference in all the factors between a Jab engine that fails at, let's say, 358 hours and one that runs to 900 without any problems at all. Your research shows that there are examples of 900+ hours TTIS (indeed, up to 1900 hours!), and examples of 155 hours TTIS. A fundamental design problem does not produce differentials of that sort of magnitude.

 

If we can get the sort of detailed information that would allow us to even put boxes around failures so we could identify 'at risk' vs 'safe' operational parameters, that would be a major improvement in the knowledge base.

 

 

[Dafydd Llewellyn]

This is a batch of 35:The typical report goes like this one:

 

Jabiru LSA 55, Engine: Jabiru 2200,358 hrs ttis.

 

The aircraft had completed several circuits and was at a height of approximately 150 feet when two loud bangs were heard and the engine failed.

 

A forced landing was carried out in a ploughed paddock where the aircraft flipped over and came to rest inverted. The pilot and passenger suffered abrasions and cuts requiring sutures

 

Inspection of the engine revealed that a cylinder had separated from the crankcase.

 

Probably not enough for you, but enough to categorise the failure.

 

Just for the moment disregard totals for the timeframe because it only represents about half the reports. I now have the balance and have dragged the magazines out on to my desk.

OK, here's my tabulation of it:

From the total no. of hours, the average TIS was 602 hours. As far as I can determine, 14 of the occurrences were through-bolt related. What the data do not say, is how many of those occurred because the operator did not comply with the relevant Jabiru Service bulletins (there were about three of them) within the specified time; and how many represent failures that have occurred after all service bulletins were incorporated.

 

Apart from the through bolts issue, the next principal fault was exhaust valve failure (12 cases). I haven't yet looked up the Jabiru Service Bulletins on that one. I suspect that some of these may have been due to a dud batch of valves from the supplier. If so, that's a quality assurance issue, not a design issue.

 

There are two instances of cracked cylinder barrels; that's part of the through bolt problem; it occurs due to flexure of the cylinder base flange. That's a design issue, in my opinion.

 

The three instances of seizure have me scratching my head; were these due to insufficient oil, or what?

 

What I tentatively get from this, in conjunction with the previous "guesstimate" analysis (which I'll try to revise when more data comes from Turbs), is that the panic over the probability of an engine failure is over-played; the probability is likely to be about one in a thousand for a four-hour flight. That's one quarter of the probability of a structural fatigue failure for an aircraft that is nearing the end of its permissible fatigue life; the "safe life" of an aircraft is set by the probability of a failure reaching one in one thousand per flying hour.

 

The real issue is the short average service life; and that's what Ian Bent has set out to address.

 

Jab engine failures.doc

 

Jab engine failures.doc

 

Jab engine failures.doc

[coljones]

snip snip snipThe real issue is the short average service life; and that's what Ian Bent has set out to address.

Is your average service life the service life of those with a failure or the service life of all engines of that class - which would include those that haven't yet failed - all part of MTBF. Of those which have not yet failed , what life can one expect.

 

The really important failure rate is failures per hour run NOT failure rate per aircraft (whether on the register or not)

 

 

[Oscar]

I wont, hes busy running through oscars log books and stuff ay?

Ah, I wish it were so, in terms of getting my aircraft back in the air.

 

But in reality, Darren has much on his plate, including trying to get a better system of assessing risk for amateur-built aircraft systems so we don't - hopefully - have the losses of life that happened at Moruya repeated. That is way more important than the progress on my aircraft, if perhaps we can leave snide comments aside for a moment. Also, I have the opportunity of contributing in some small ways to the improvement of Jabiru engine reliability, which has obvious implications for my own Jabiru. To me, that seems a worthwhile distraction.

 

 

[Dafydd Llewellyn]

It's simply the total hours to failure divided by the number of samples, for that 35 specimen example that Turbs provided. So it's definitely NOT an average life expectancy for Jabiru engine in general. I agree this is of limited value, but that's all I can get from that sample of data.

 

 

[Oscar]

Is your average service life the service life of those with a failure or the service life of all engines of that class - which would include those that haven't yet failed - all part of MTBF. Of those which have not yet failed , what life can one expect.The really important failure rate is failures per hour run NOT failure rate per aircraft (whether on the register or not)

I don't believe we have any figures for the service life of all Jab. engines, just those that have been the subject of failure. There are something like 2,000 Jabs. in current service in Aus, these figures tabulate the history of 35. I would not suggest that there are not a considerable number that have been 'retired' early in their expected life as a result of inspection in maintenance, but I think it is a rather small statistical survey from which to try to draw definitive conclusions.

 

 

[turboplanner]

This reminds me of a time when I was designing semi trailers which look simple but are quite complex when you are starting from a blank sheet.

 

I would be drawing and working the scale rule and drawing, and the workshop foremen were coming in looking over my shoulder and writing down the dimensions as soon as I put them on the drawing, and giving them to the welders. There was no time for an Oh Sh$t moment, or redrawing. If I made a mistake I had to adapt the design, and I often had to move to a different part of the drawing for a foreman who wanted to order steel, or set up some components.....with him patiently looking over my shoulder - not a word, just patient waiting.

 

That was some pressure.

 

I've managed to extract 54 months of reports covering 40 Jab failures and 7 Rotex failures.

 

You'll see the Rotex failures have more to do with tuning and poor maintenance than base mechanical failures.

 

I'll try to upload the data as an Excel File

 

 

EXX22.xlsx

 

EXX22.xlsx

 

EXX22.xlsx

[turboplanner]

Here's a novel idea..As the assessment base is only 1000 odd..

If possible... Why not approach ALL Jabiru engine owners directly for input.

 

That way the correct data required should be able to be obtained, not the guess work from the limited RAA data.

 

It should be in the interest of All Jabiru engine owners to assist.

Good job for you Arron, start writing

 

 

[turboplanner]

It would need more background information on the circumstances of failures to really pinpoint causes rather than just results, but it's a hell of a good start, and RAA - and Jabiru engine owners - owe you one for the work that you've put in.

You can imagine the RAA representative's difficulty even getting the person's name let alone the bare minimum of detail, the "Ah, haven't looked it yet mate", or the many which are not reported at all, so don't expect to get more detail soon unless RAA were given a lot more powers.

 

You're expecting the same as Jetjr, and even some of these results are vague. We could tell an awful lot with metallurgy reports, but do you want the members to fork out several million dollars a year in forensic analysis, or is the present system better, where CASA force the manufacturer to do that at his expense. I've seen aviation reports costing millions just to find that something like a latch arc did not engage a pawl fully in an aircraft which went out of production 5 years ago.

 

What we do need to be concerned about is that 40 Jab pilots had lucky escapes, and that can't last forever, and something needs to be done about it by the manufacturer.

 

We can speculate, and that might help the manufacturer, and that would be a good thing.

 

On thing from these statistics which intrigues me is the number of seizures and a con rod failure; once a piston seizes, usually a con rod bends or snaps off and punches through the side, but if it is strong it can jack the barrels off the crankcase, and I wonder if that is telling us something.

 

 

[turboplanner]

Is your average service life the service life of those with a failure or the service life of all engines of that class - which would include those that haven't yet failed - all part of MTBF. Of those which have not yet failed , what life can one expect.The really important failure rate is failures per hour run NOT failure rate per aircraft (whether on the register or not)

Col most engine manufacturers would faint if you suggested even thinking of calculating a service life from such a small sample.

 

We know from this sample, and other reports on this forum that some failures have occurred almost on the way home from a rebuild, while the failure in the aircraft that started this thread occurred after nine years of use.

 

So attempting to get a failure rate per hour would be very misleading.

 

The sample is 4.5 years, you can't position the current number of Jab engines on the register against that and make any sense because:

 

(a) Many failures are unreported

 

(b) More years of data are required, and may show better or worse results. The inputs I made tonight showed a much lower rate of failure.

 

© Many aircraft in addition to the register will by now have been written off or sitting in sheds waiting for someone to earn enough money for an engine etc.

 

What we can do is look at the failures per year and try to cut that back. Wiping out mechanical based forced landings means a huge reduction in the risk of injury/fatality, and alsoa big improvement to the back pocket.

 

 

[Dafydd Llewellyn]

You can imagine the RAA representative's difficulty even getting the person's name let alone the bare minimum of detail, the "Ah, haven't looked it yet mate", or the many which are not reported at all, so don't expect to get more detail soon unless RAA were given a lot more powers.You're expecting the same as Jetjr, and even some of these results are vague. We could tell an awful lot with metallurgy reports, but do you want the members to fork out several million dollars a year in forensic analysis, or is the present system better, where CASA force the manufacturer to do that at his expense. I've seen aviation reports costing millions just to find that something like a latch arc did not engage a pawl fully in an aircraft which went out of production 5 years ago.

 

What we do need to be concerned about is that 40 Jab pilots had lucky escapes, and that can't last forever, and something needs to be done about it by the manufacturer.

 

We can speculate, and that might help the manufacturer, and that would be a good thing.

 

On thing from these statistics which intrigues me is the number of seizures and a con rod failure; once a piston seizes, usually a con rod bends or snaps off and punches through the side, but if it is strong it can jack the barrels off the crankcase, and I wonder if that is telling us something.

Insufficient data, I suspect. From what little I've seen so far, Ian Bent has already covered all those points, and he's into aspects to increase the TBO now, rather than the MTBF. Temperatures are the principal governing factor in that, especially insofar as they affect ring life. Ian's well-researched answers to the exhaust guide and the exhaust valve stem temperature are quite different to Bex's suggestion, by the way. I rather suggest that our speculation would prove to be way behind Ian's thinking. I have no idea whatsoever of what Rod Stiff may have up his sleeve; but Rod has been beset by "Wydonchas" from day one, which hasn't helped his receptivity to hypothetical input. I can't really blame him; everybody that came along had some idea as to how it could be done better; I'm amazed he managed not to scream.

The through-bolt and exhaust valve issues are very reminiscent of similar problems that Lycoming had, with the early 0-320s and o-360s, about 30 years ago. If you remove them from the picture, as Ian Bent's mods seem very likely to do, and reduce the piston and cylinder wall temperatures, so the ring life is what it should be, and use a more thermally-stable alloy for the cylinder head, the statistics will almost certainly jump into 912 territory. The sooner we can formally test one of Ian's engines, the better.

 

 

[Old Koreelah]

This reminds me of a time when I was designing semi trailers which look simple but are quite complex when you are starting from a blank sheet.I would be drawing and working the scale rule and drawing, and the workshop foremen were coming in looking over my shoulder and writing down the dimensions as soon as I put them on the drawing, and giving them to the welders. There was no time for an Oh Sh$t moment, or redrawing. If I made a mistake I had to adapt the design, and I often had to move to a different part of the drawing for a foreman who wanted to order steel, or set up some components.....with him patiently looking over my shoulder - not a word, just patient waiting.

That was some pressure...

Crickey Turbs, was there a war on?

 

 

[coljones]

Good job for you Arron, start writing

Turbs, thanks for your collation of the data. Airframe and engine hours data should be available already based on the renewals data provided to RAA on each plane.

The importance of digitalising the registrations is that RAA will be better able to extract data and do some statistical analysis to alert owners, users and manufacturers about the performance of the fleet.

 

 

[turboplanner]

Crickey Turbs, was there a war on?

More or less - we were breaking into new markets and every different semi had to be designed from scratch. After about 30 I had the benchmarks, and only had to add some specialised client request now and then. It was a very rewarding time.

 

 

[Dafydd Llewellyn]

Many thanks, Turbs. Here's my tabulation from the spreadsheet; it gives a MTBF (not counting engine that did not fail but were removed from service due to problems, or are still in service) of 588 hours. As for the previous version of the data, the two major faults were through bolts (42.5%) and valve/exhaust valve failure (30%). The remaining 27.5% of occurrences have insufficient data to assign any likely causes, except perhaps occurrence # 39 which looks like faulty maintenance.

 

So this more complete data set does not change the overall picture at all, really. Fixing the through bolt issue and the exhaust valve/valve issue (both of which have complex causes) would reduce the failure rate as shown by this data set, to about one quarter. It's not clear whether the various Jabiru service bulletins have accomplished this fully for the through bolts; the data are insufficient to allow that.

 

Issues such as loss of compression, causing engines to be withdrawn from service, are not covered by this analysis, as they do not appear in the data set.

 

I don't think we can get any more data than this, from the available RAA statistics; it would be useful to compare the total engine failure rate to the total hours flown, but I do not have the latter information.

 

Further analysis.doc

 

Further analysis.doc

 

Further analysis.doc

[Oscar]

Thanks to Turbs' effort (and mighty collection of the RAA mags.), this has to be one of the most useful advances in getting perspective on the whole story that we've had.

 

It does seem somewhat glaringly obvious that the depth of recording (and probably, I guess, reporting) of the circumstances of the failures has not provided much more than a simple 'this is what happened'. Again, I believe that Don Ramsay's call for better performance in both of these areas is likely to considerably advance the understanding of the situation, and even the development of a relatively brief pro-forma type of reporting that covers a wider range of information would help.

 

Preferably, this would be accomplished by on-line reporting in a format that would feed a database so that analysis can be quickly carried out, with I guess a paper back-up for those unable to access the on-line system. There'd need to be some explanatory material for entering the details so that common terminology is used, and also that we don't get the legendary 'electrical failure' [because the broken rod pushed the plug leads off]' type of entry..

 

While I suggest it is probably correct that some failures do go unreported (and certainly, there is anecdotal evidence for this), I'm not sure how much weight can be placed on that to suggest there is any vast pool of unreported failures. As far as I am aware, it is a requirement to report these and I wonder how many people fail to meet that requirement; there doesn't seem to me to be any advantage to not reporting such failures when it is a requirement. That some aircraft have been pushed into the back of the hangar/shed because the owner is concerned about the engine and 'will get around to it' someday I'd suspect IS certainly a factor in reducing potential failures - but we don't have data to either support or deny any of this. One could equally suggest that there are plenty of owner/operators who are unconcernedly flying along out there with Jab. engines who don't have anything untowards TO report - though perhaps 'unconcernedly' is not the right word, and I'd accept 'with due concern' (for their maintenance, operation etc.) as being more likely. However, as with other assumptions, this remains just that - an assumption.

 

The work done so far is a pretty quantum leap in improving the understanding of the whole Jabiru 'engine failure' raw numbers; a better reporting system that would indicate at least even general areas of 'cause' would be the next useful step.

 

 

[fly_tornado]

The numbers reinforce what we suspected, 500hours