ATSB report into light aircraft engine failures

[Old Koreelah]

Yep, the guvmint should doo summit about it!

 

 

[fly_tornado]

Bruce, you should get the boys together and pass the hat around and see if you can get a $50K sweetener for Barry O'Sullivan to make this problem go away.

 

 

[gandalph]

$50k to make FT go way..... Bargain!

 

 

[fly_tornado]

I'll do it for a lot less, I'll even endorse Jabiru

 

but you know I'll only do it because I know how much you boys love a rebuild

 

 

[gandalph]

Sorry Mate - No plans to rebuild you.

 

 

[gandalph]

I'll even endorse Jabiru

As if they don't have enough trouble already.......

 

 

[Oscar]

Sorry Mate - No plans to rebuild you.

Pity.... could have re-started his personality from scratch.

 

 

[kasper]

Sorry Mate - No plans to rebuild you.

But with some things you never want to rebuild to original form ... replace or upgrade options???

 

 

[fly_tornado]

I woke up this morning wondering how much longer will CASA continue to keep the public safe from Jabiru curse.

 

I live day by day

 

 

[gandalph]

I live day by day

Not if the contract is accepted......

 

 

 

[REastwood]

The RAA Training syllabus requires the pilot to follow the Pilot Operating Handbook for the aircraft. The POH for the Jabiru - Pre-flight Inspections Step 1 Engine requires Check oil and Pull through engine checking compression of each cylinder and listening for any odd noises. If not conducted then the pilot is in breach of the POH and not adhering to the RAA standards requiring the pilot to follow the aircraft POH.And as far as being 2016 - Jabiru have made improvement to the engines with improved through bolts and valves as well as a move to roller cams to eliminate identified failure modes. Withstanding a long history of engines with a wide range of configuration since 1992 the ATSB report has not found a problem with the latest spec through bolts or roller cam valve train. Even using ATSB's figures at least 20% of the Jabiru engines in service have the larger 7/16 through bolt. So obviously not all Jabiru engines are the same.

 

Operating within the manufacturers limitations and following their specified maintenance schedule and procedures is absolutely a requirement for ongoing successful operations.

I notice that the Jabiru 230D POH still says that the CONTINUOUS Maximum cylinder head temp for the 6 cylinder is 356 deg F (180 C) yet I was told by one of the tech guys inside Jabiru that it should NEVER go over 270 F (132 C). How can Jabiru tell you "you ran the cylinders too hot, that's why your engine failed" yet it never exceeded the MAXIMUM CONTINUOUS values specified in the POH LIMITATIONS section (3.7 of 230D POH), so which part of the POH should we follow and which part should we ignore?

 

 

[planesmaker]

132'C ? Any body got a jab engine that does not go past 132'C especially climb out on a hot day? Really interested to know.

 

 

[Keenaviator]

132'C ? Any body got a jab engine that does not go past 132'C especially climb out on a hot day? Really interested to know.

Yes, the hottest it gets is on the ground.

 

 

[Oscar]

Not if the contract is accepted......

Wouldn't have thought you'd get much in the way of offers - there must be a considerable queue of people prepared to do it for free...

 

 

[jetjr]

Once you consider easily possible 40+ degrees measurement error, many Jabirus run too hot.

 

Plenty dont even know what their cht for each cylinder are

 

Cooling isnt an engine related problem but installation and up to owners to sort out.

 

Current engine runs around 120-140 deg C in cruise, one creeps to 150 on a hot day on take off

 

Sitting on the ground they can go to 180 pretty easily with some rpm

 

 

[SDQDI]

Old K our local jab engine runner was talking to me the other day (must have been a real low moment for him:sad:) and was saying that his jab guru down Cessnock way says 140C should be max, I think Old K said that talking to CAMit though and they said 180 or 200 (I was listening but my memory is not 100% confident on which it was.

 

I would certainly be aiming for the lower figure.

 

 

[Oscar]

132'C ? Any body got a jab engine that does not go past 132'C especially climb out on a hot day? Really interested to know.

This is actually a topic that deserves far more research and assembly of facts than has been carried out so far.

 

We know - anecdotally at least - that there are some FTFs that experience repeated failures of Jab. engines at quite low hours ( the log books of my own aircraft for the FTF operating it before its last EFATO and crash that, eventually, bought it into my hands demonstrate that very convincingly), while others - such as Gawler - have had a long history of highly successful operation of numerous engines to 1000 hrs and beyond with nary a hiccup. This cannot be just a fluke - in either case - but something that deserves examination of ALL the relevant factors: operating profile, maintenance effectiveness, fuel supply, etc. I don't believe that anybody has assembled a coherent picture of the differences that may exist between those FTFs that have a 'troubled' history of Jab. engine operation and those that have a 'satisfactory' history. It needs an epidemiological study, and Jabiru ought to conduct such a study. In fairness to Jabiru, its recent 'risk assessment' strategy is a first foray into this field.

 

ATSB has conspicuously failed, in my opinion, to do anything even resembling that - it has assembled statistics taken from reporting of highly dubious quality. While it is not unreasonable for people to be somewhat cynical of the evident self-interest in Jabiru's response to the ATSB report, Jabiru has nominated a number of instances where the fact that the failed engine was used in FTF operation, unrecognised by ATSB: that is clearly able to be checked and proven/disproven.

 

Does the type of operation make a significant difference to the likelihood of engine failure? I believe that there are reasons to believe that it does.

 

Ground running is the Archilles Heel for Jabiru engines. If held for any significant period of time across-wind ( e.g. at the holding point for the active runway, while the student goes through the pre-take-off checks, talking them through with the Instructor), temps on the downwind side of the cowl intakes can rise very seriously. THEN: with several pots really hot - the take-off and initial climb at full power and low speed adds significantly to the heat loading in already nearly over-temp cylinders. If the circuit requirements are for a tight and high climb to avoid encroaching on the local area, or because of topographical factors - a Jab. engine is set-up to fail.

 

Can we all be realistic here for a moment? There are operational environments where a Jab. engine is simply NOT appropriate. Just as anybody with a modicum of intelligence wouldn't choose a Lancair 320/360 as their PNG Highlands runabout, or a Holden Maloo ute as their tradie vehicle for servicing the Olgas, it's horses for courses. As a Jabiru owner, I would NEVER recommend them for training out of, say, Wedderburn. Out of Clifton: NO worries ( and that's what they use up there, very successfully).

 

Next issue: the actual cooling performance of a 'standard' Jab. installation can vary very considerably with apparently small differences in installation. I recently spent some time discussing installation issues with someone down at Camden, who has meticulously researched and modified his cooling baffles and cowl extraction in a research project that has taken him months - and has been conducted superbly: even down to wool-tufting and borescope-camera recording of the airflow within individual ram-ducts. His work has been of laboratory quality, and it shows that 'fine-tuning' the cooling airflow requires finesse beyond the factory tolerances - but when correct, produces excellent results: a max. of about 5C between heads right across the flight speed range, at any ambients. He is one happy Jab owner... and Jabiru could do FAR worse than ask his advice!

 

Old K our local jab engine runner was talking to me the other day (must have been a real low moment for him:sad:) and was saying that his jab guru down Cessnock way says 140C should be max, I think Old K said that talking to CAMit though and they said 180 or 200 (I was listening but my memory is not 100% confident on which it was.I would certainly be aiming for the lower figure.

CAE heads are a different - and better - alloy. Keith Rule at Cessnock's comments are absolutely on the money, AFAIK, and so are CAMit's. But you need to recognise that they are talking about different heads!

 

 

[jetjr]

He is correct, camit heads can handle more temp and it is measured better too. Numbers are higher when using their probes

 

180 max continuous or ground running, 200 absolute max climb

 

Recommends 140 max in cruise

 

 

[Old Koreelah]

Old K our local jab engine runner was talking to me the other day (must have been a real low moment for him:sad:) and was saying that his jab guru down Cessnock way says 140C should be max...I would certainly be aiming for the lower figure.

The numbers I got from CAMit and Jabiru were not that high, SD, but I agree on caution.

Last week after ground-running my engine I found that I shouldn't rely too much on my new guage.

 

Admittedly the heads were in cool-down mode, but my MGL guage (shielded sensors between plugs) showed 18C less than what a laboratory Mercury thermometer read under the head. This presumably means that the heads can get hotter than even a good digital temp monitoring system tells you.

 

To be on the safe side, I plan to keep it under 140C.

 

 

[Oscar]

OK, if that mercury thermometer was placed between the bottom of the head and the top fin of the barrel, it would be getting a considerable boost of heat from the barrel. There is a very considerable 'hot-spot' right at the top of the barrel, where the majority of combustion is concentrated.

 

Calibration testing of the CAE thermocouples back to MGL Stratomaster Infinity instruments ( with don't operate through an RDAC with ambient compensation) in a proper installation ( engine test cell, I think you have seen it?) showed a very close tolerance. It is important for accurate reporting that the cold junction is not subject to elevated ambient temp. or the gauge will under-read - the early Jab cht installations were really, really bad for that.

 

 

[facthunter]

Most limits relate to affecting the heat treatment of the head material. Any high temp (say above 160 but depends on where measured ) makes fuel quality more critical, as detonation more likely. Water cooled engines run cooler than desired for max efficiency, often. Nev

 

 

[Old Koreelah]

OK, if that mercury thermometer was placed between the bottom of the head and the top fin of the barrel, it would be getting a considerable boost of heat from the barrel. There is a very considerable 'hot-spot' right at the top of the barrel, where the majority of combustion is concentrated...

You're probably right about that, Oscar. When I took my readings the Al. heads were rapidly cooling, particularly on the top edges where the probes are located. I found it 18C hotter underneath the head close to the steel barrel, which would have been cooling down at a much slower rate. This realisation probably vindicates the MGL monitoring system, but prudence tells me to allow for some parts of the alloy heads getting hotter than the Guage reading.

 

...Calibration testing of the CAE thermocouples back to MGL Stratomaster Infinity instruments ( with don't operate through an RDAC with ambient compensation) in a proper installation ( engine test cell, I think you have seen it?) showed a very close tolerance. It is important for accurate reporting that the cold junction is not subject to elevated ambient temp. or the gauge will under-read - the early Jab cht installations were really, really bad for that.

My junctions are sealed inside the BRS compartment, so that probably moderates temps.

After that test I enlarged the cooling air exits by 37%. The next flight showed a reduction in climb-out temps, but not as much as I'd hoped. The next step is get the oil cooler's hot air out of the system. Tomorrow I plan to shamelessly copy your oil cooler duct design.

 

 

[aro]

Interesting report. I have a few concerns about some of the statistics.

 

I would like more explanation of why they limited the GA study to <800 kg MTOW and the effect this might have had. Superficially it seems reasonable to compare similar aircraft, but if you are comparing engine reliability MTOW is not necessarily the best way to select your population. You would be better to try to get aircraft involved in similar operations. 800 kg MTOW excludes all C172 and PA28, so you probably exclude most of the GA training fleet, while Jabiru do a lot of training hours. The only common GA training aircraft that seems to be included is the C152 (and the Tomahawk, if you consider it a common training aircraft). I don't know which way that would skew the statistics. You also exclude some common amateur built aircraft e.g. RV-7 and RV-8 (although not RV-6 or RV-9).

 

I think you can work out average aircraft hours/year from failures per aircraft and failures per 10,000 hours. If I did my maths right it comes to:

 

Jabiru: 52

 

Rotax: 30

 

Lycoming: 40

 

Jabiru utilization is significantly higher (75% higher than Rotax, 30% higher than Lycoming) which again suggests to me that the operations may not be directly comparable.

 

The report states:

 

It should be noted that when comparing the VH and RAAus occurrences in Figure 5, there is always the possibility that reporting rates for engine failure or malfunction occurrences may differ between VH and RAAus communities.

 

However, it seems unlikely that this would bias any manufacturer in particular.

 

 

Figure 6, however, shows that there is something significantly different about reporting of Jabiru failures. Jabiru engine failure reports seem to have much more detail. The quality of the reports is different enough that I think you can no longer assume that the Jabiru numbers can be directly compared to other manufacturers. It seems possible that if details of the failure are more likely to be reported, failures themselves might also be more likely to be reported.

 

It looks like Jabiru reports are about 50% more likely to include detailed information about the failure. Does this mean that failures are also 50% more likely to be reported? Or maybe reports with insufficient information are a similar percentage of actual failures, which would mean that Jabiru failures are about twice as likely to be reported. It's all guesswork until you can explain why the Jabiru numbers in figure 6 are so different.

 

Some sort of verification needs to be done to make sure that you are comparing apples with apples.

 

Overall I'm disappointed in the lack of analysis of the figures. I think you can conclude from the report that there are some common failures with Jabiru and MAYBE they fail more often than other engines - but exactly how often it's hard to say.

 

It would be interesting if they had used the FAA methodology discussed in a previous thread, where a number of failures was deduced based on the number of accidents. That would have been an interesting way to cross check numbers.

 

 

[coljones]

And there probably should be a review/audit of the reported and recorded hours and movements of each engine across the fleet. It is one thing to count dodgy faults but if the fleet total hours and movements are also suspect then the resultant stats are rubbish.

 

 

[greybeard]

While everyone is arguing the details/numbers/stats/rubarb rubarb/waffle/ mines bigger than your's etc back on topic, too many engine related failures are occurring. If it's an issue with the design (regardless of who make the damn thing) or the numb nutz manipulating the throttle then maybe some of the NASA scientists with all of the answers could put a smidgen of their efforts into sorting out the problem(s). Rather than excrementing over and over about the exact percentage of who cares.

 

Or maybe just go flying.......