Jabiru Bad experience
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(Over the last 12 months for various reasons there has been dramatic increase in compliance to the Service bulletins/ Letters and maintenance procedures issued by Jabiru This combined with Jabiru engine training workshops has resulted in fewer incidents and has put Jabiru engines well ahead of Rotax for reliability, the standard by which CASA based their aggressive actions.)
Surely you jest (If your comparing 912/914 4 stroke and not two stroke)
Absolutely no comparison,, the Rotax beats them hands down no question.
Surely you jest (If your comparing 912/914 4 stroke and not two stroke)
Absolutely no comparison,, the Rotax beats them hands down no question.
Hi Zac, can you please provide a link or cite the evidence that suggests that Rotax are "hands down no question" are more reliable than Jabiru engines?
Thanks.
Thanks.
That's the data that is a problem... it's the skewed data that CASA used to put limitations on Jabiru engines that included fuel exhaustion and other non-engine related stoppages.
The blue text above has been quoted from Jabiru directly in an email that went out to operators. They have been working closely with CASA and the ATSB to go analyse the information and to carefully monitor each and every failure and document it, including since the release of said data. The result of this has been a more accurate set of statistics that I believe based on what I've heard from higher sources will prove what is written above.
At a guess, we are not likely to see an update of these statistics any time soon, just through regular reporting.
The blue text above has been quoted from Jabiru directly in an email that went out to operators. They have been working closely with CASA and the ATSB to go analyse the information and to carefully monitor each and every failure and document it, including since the release of said data. The result of this has been a more accurate set of statistics that I believe based on what I've heard from higher sources will prove what is written above.
At a guess, we are not likely to see an update of these statistics any time soon, just through regular reporting.
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No Bob its from Jabiru/casa/atsb themselves and is built into most recent head inspection SB
Majority of engine failures were in flight training aircraft, mostly 4 cyl and almost all hydraulic lfter type
The link with poor maintenece is misleading. This problem is that concept forms the basis of keeping restrictions on experimental and modified aircraft. They have to "upgrade" to latest spec to hve them remove I think
Majority of engine failures were in flight training aircraft, mostly 4 cyl and almost all hydraulic lfter type
The link with poor maintenece is misleading. This problem is that concept forms the basis of keeping restrictions on experimental and modified aircraft. They have to "upgrade" to latest spec to hve them remove I think
Last edited by Jetjr; 21st Jul 2016 at 10:52.
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S7700,,
2200 hours training and mustering in a 912 trouble free while I watched the Jabber's fail one after another with very low hours. But I won't fly a 2 stroke either !!
2200 hours training and mustering in a 912 trouble free while I watched the Jabber's fail one after another with very low hours. But I won't fly a 2 stroke either !!
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On a standard Jabiru the battery can fall out of the plane and the engine will run normally till the fuel runs out.
Fixed
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....or it drops a valve, frees a valve seat, overheats or has a bottom end through bolt related failure, which ever comes first.
Fixed
Fixed
Jabiru's major problem was that many owners chose to ignore the notifications.
The truth of this was spelled out when RAA/CASA (I think it was) came up with the idea that the aircraft's engine maintenance log had to be sent in with the annual licence fee. Of the first 70 or so sent in only 3 engines fully complied with the factory service bulletins, maintenance schedules and maintenance procedures.
The great improvement in reliability has come about because the licence renewal is withheld until the engine is compliant.
Most owners are not engineers and they don't fully grasp the complexities in designing a completely new engine. Even giant companies have teething problems with new equipment. Airbus 380 and Boeing 787 come to mind.
I realize it was just a throwaway line but I wonder if Young Mic understands the real reason the through bolts were failing and what the factory had to do to identify the cause. (If you don't understand the cause of a problem anything you do to fix it is just a guess)
Two things to note. I am not an engineer and I don't own a Jabiru plane or engine. I've always had an interest in engineering and I think Jabiru should be given a fair go as they appear to be a company doing the right thing by their customers which is more than can be said about Continental and Lycoming.
I just had my Rotax 912 iS alternator stator replaced with an upgraded version (Thicker wires for alternator B). Total cost zero. Does Jabiru run a recall and upgrade program or is it all at owners expense?
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Rutan Around
An interesting spin.
My casual understanding of the matter is the exact opposite of what you have stated, I believe many would agree with me.
Numerous cases of Jabiru engines failing not long out of factory O/H and just to really tick the customer off and add insult to injury they follow up with often pretty poor support.
Was it not the case that CAMit (the original Jabiru engine builder) had been pushing Jabiru for some time to incorporate their mods to solve some of the inherent engine issues. I understood they were ignored time and time again. Now they are marketing the Jab engine under their own name with the necessary mods and doing very well as I understand.
Whilst all this was going on CASA stirred from its slumber, rubbed its collective eyes, looked at what was going on, called a meeting or 2, weren't satisfied so slapped a heap of operating restrictions on Jabirus.
Now a blind man on a galloping horse could see what will happen next....100's of Jabiru owners just had their asset devalued.
Hardly a company deserving of great credit at the moment.
I have been watching the development of the 3300 for some time as that engine might be a great replacement for my O-200 but sadly it just isn't getting the run tally up.
I'm not sure what iteration of Burt's you own but you would be a braver man than I to take flight with 2200/3300 bolted to the back.
It is a great credit to the Jabiru Company that as their engines evolved they actually addressed any problems that were found.
My casual understanding of the matter is the exact opposite of what you have stated, I believe many would agree with me.
Numerous cases of Jabiru engines failing not long out of factory O/H and just to really tick the customer off and add insult to injury they follow up with often pretty poor support.
Was it not the case that CAMit (the original Jabiru engine builder) had been pushing Jabiru for some time to incorporate their mods to solve some of the inherent engine issues. I understood they were ignored time and time again. Now they are marketing the Jab engine under their own name with the necessary mods and doing very well as I understand.
Whilst all this was going on CASA stirred from its slumber, rubbed its collective eyes, looked at what was going on, called a meeting or 2, weren't satisfied so slapped a heap of operating restrictions on Jabirus.
Now a blind man on a galloping horse could see what will happen next....100's of Jabiru owners just had their asset devalued.
Hardly a company deserving of great credit at the moment.
I have been watching the development of the 3300 for some time as that engine might be a great replacement for my O-200 but sadly it just isn't getting the run tally up.
I'm not sure what iteration of Burt's you own but you would be a braver man than I to take flight with 2200/3300 bolted to the back.
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The truth of this was spelled out when RAA/CASA (I think it was) came up with the idea that the aircraft's engine maintenance log had to be sent in with the annual licence fee. Of the first 70 or so sent in only 3 engines fully complied with the factory service bulletins, maintenance schedules and maintenance procedures.
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By that logic, then every Rotax engine owner is keeping on top of, and is well trained in maintenance of their engines? just Jabiru owners who dont care for maintenance.
All I know is that since proper servicing and maintenance has been virtually forced on owners there has been a rash of reliability to the extent Jabiru's recent record is now better than Rotax's.
I realize it was just a throwaway line but I wonder if Young Mic understands the real reason the through bolts were failing
PS. In the earlier pages I didn't know either thus the long bow theories back then.
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Well Mic???
But what's your point?
3.2 Contributing Factors
A number of factors can contribute to through-bolt failure. The following list contains a few examples but there are many other, smaller, factors which can have an impact.
a) Detonation or uneven combustion. Detonation or uneven combustion can be caused by incorrect tuning, induction system leaks, stale or incorrect fuel or a number of other factors. The result is increased engine vibration.
b) Operation. Engines which work hard with high engine temperatures tend to have more issues than others.
c) Maintenance. In some cases through bolt failures have been caused when a person has tightened them beyond the design tension. Poorly calibrated torque wrenches and poor understanding of tools like the “crowsfoot” torque wrench extension also contribute.
Last edited by youngmic; 24th Jul 2016 at 12:16.
Contributing factors? My ass! The additional metal to ensure there are no such failures at all, under basic maintenance, is insignificant. Begging the question of alloy selection, heat treatment, surface modification (shot peen,, etc), let alone using "waisted" bolt designs.
Stuff like through bolts should not fail EVER! ..under responsible maintenance anyway.
this is a pet peeve of mine, I know weight costs $100 per pound, arbitrarily anyway, but it annoys me when designs fail at multiple points for want of an extra 20 grams of steel, alloy or carbon in the right place.
Then of course there is the F27 landing gear story of how cracking failures were eliminated by removing metal.
Stuff like through bolts should not fail EVER! ..under responsible maintenance anyway.
this is a pet peeve of mine, I know weight costs $100 per pound, arbitrarily anyway, but it annoys me when designs fail at multiple points for want of an extra 20 grams of steel, alloy or carbon in the right place.
Then of course there is the F27 landing gear story of how cracking failures were eliminated by removing metal.
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For clarity, there is no requirement to submit maint logs to RAA, it was an audit done randomly which found poor log book compliance. Very few even replied, dont think it was anything to do with Jabiru but checking the service records of all makes.
It is relevant however as without accurate records, little should be drawn from data like casa used to make their limitations
Jabiru have always claimed problems are servicing related, now they have regulatory backing to force owners to upgrade to latest iteration of their engine.
It is relevant however as without accurate records, little should be drawn from data like casa used to make their limitations
Jabiru have always claimed problems are servicing related, now they have regulatory backing to force owners to upgrade to latest iteration of their engine.
Did you hear about the 912 recall that meant that owners were up for up to half of $12k for a new crank case because their engines were of a particular serial number range? The operator I know of got away with $6,000 on his half life engine as Rotax funded half of it.
How much will a rebuild cost on your $26k? engine Sunfish, perhaps around $23k?!?! Jab used to rebuild engines for $6.5k for flying schools.
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Youngmic asked
Mic I'm sorry if I caused you to jump through hoops but the question was posed to 'start the conversation' ( in pollie speak). I also apologise for my tardy reply . This working till we're 70 is the pits. WORK- the curse of the drinking class.
You quoted valid possibilities from the Jabiru Service Bulletin and Sunny mentioned shortfalls in alloy and steel strengths. I'd heard all of these reasons in various pilot BS sessions and generally in more colourful language about Jabiru.
I couldn't understand why the bolts were breaking. They should have been plenty strong enough given that 3/8 bolts will yield at 2.5 to 5 tons. Nor could I believe that in this day and age Jabiru would choose some inferior alloy for their engines. Detonation, severe operation and over torquing didn't explain it either as the bolt problem was fairly widespread and those scenarios aren't all that common.
I never did guess the real problem. I recently found out while visiting Bundaberg and got talking to people involved with solving the mystery.
It was that old nemesis of aviation - harmonics. The natural frequency of the long 3/8 through bolts was found to be excited at certain high power settings.
Once excited, the bolt makes like a sine wave vibrating the bolt and of course the ends with the nuts. Eventually the vibrating nuts & washers chew into the alloy they're up against and the bolt becomes loose. Mr pilot tightens the nuts and tells anyone who will listen that the alloy is s#*t. With enough repeats of the above the bolt would break. Then Mr Pilot tells everyone the bolts are weak.
Harmonics, flutter, divergent resonance are part of the dark arts in engineering engines. It's a science in itself and is complicated. Even now some GA engines have no go rev ranges. A Grumman I flew had (from memory ) 2,000 - 2,250 no cruise area. Many normally aspirated Continentals have a recommendation to not cruise below 2,300 rpm.
Back to Jabiru. The bolt only resonated at high power settings. Hence Flying Schools going to full power more often, or a bigger % of their flight time, were more likely to experience failure at lower hours than the rest of the fleet.
The cure is to install the 7/16 bolts which don't flutter in the rev and load range ever likely to be seen by a Jabiru.
But what's your point?
You quoted valid possibilities from the Jabiru Service Bulletin and Sunny mentioned shortfalls in alloy and steel strengths. I'd heard all of these reasons in various pilot BS sessions and generally in more colourful language about Jabiru.
I couldn't understand why the bolts were breaking. They should have been plenty strong enough given that 3/8 bolts will yield at 2.5 to 5 tons. Nor could I believe that in this day and age Jabiru would choose some inferior alloy for their engines. Detonation, severe operation and over torquing didn't explain it either as the bolt problem was fairly widespread and those scenarios aren't all that common.
I never did guess the real problem. I recently found out while visiting Bundaberg and got talking to people involved with solving the mystery.
It was that old nemesis of aviation - harmonics. The natural frequency of the long 3/8 through bolts was found to be excited at certain high power settings.
Once excited, the bolt makes like a sine wave vibrating the bolt and of course the ends with the nuts. Eventually the vibrating nuts & washers chew into the alloy they're up against and the bolt becomes loose. Mr pilot tightens the nuts and tells anyone who will listen that the alloy is s#*t. With enough repeats of the above the bolt would break. Then Mr Pilot tells everyone the bolts are weak.
Harmonics, flutter, divergent resonance are part of the dark arts in engineering engines. It's a science in itself and is complicated. Even now some GA engines have no go rev ranges. A Grumman I flew had (from memory ) 2,000 - 2,250 no cruise area. Many normally aspirated Continentals have a recommendation to not cruise below 2,300 rpm.
Back to Jabiru. The bolt only resonated at high power settings. Hence Flying Schools going to full power more often, or a bigger % of their flight time, were more likely to experience failure at lower hours than the rest of the fleet.
The cure is to install the 7/16 bolts which don't flutter in the rev and load range ever likely to be seen by a Jabiru.
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FYI, Grumman Tigers are not allowed to be descended at 1850 and 2250 RPM due to engine/prop harmonics. This was only an issue in the standard McCauley props. Sensenich probs did not have that issue. Later Tigers used the Sensenich props as factory stock.
Last edited by AbsoluteFokker; 27th Jul 2016 at 13:15.
Interesting about the harmonics .... It would appear that Jabiru, like other aero engine builders in modern times has used the end customer as the R & D dept.
Last edited by Aussie Bob; 28th Jul 2016 at 06:25. Reason: Rutan's points noted
