(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.

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.

i think the ATSB has some data on engine failures by type per 100,000 flight hours.

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.

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

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 !!

.....or it drops a valve, frees a valve seat, overheats or has a bottom end through bolt related failure, which ever comes first.

Fixed :ok:

Exactly as you say Young Mic 'Fixed' It is a great credit to the Jabiru Company that as their engines evolved they actually addressed any problems that were found. As solutions were found notifications were sent out to owners detailing what needed to be done to ensure the engines performed safely. Sometimes these notices were to replace parts and sometimes they were operational and maintenance issues.

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. http://cdn.pprune.org/images/icons/icon8.gif

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?

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.

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.

I really can't comment on the accuracy or otherwise of your thoughts without reliable data.
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.


Well Mic???
PS. In the earlier pages I didn't know either thus the long bow theories back then.

I don't normally jump through hoops for little reason but I'll make an exception, I am not sure what the purpose of the question was but I pulled up the Jabiru SB and below is what it says. All sounds pretty normal to me with an insufficiently strong through bolt suffering metal fatigue likely due to cyclic loads to close to its yield point.

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.

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.

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.

You have a lot to learn young grasshopper Sunfish.

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.

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.http://cdn.pprune.org/images/smilies/boohoo.gif

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.

Fair enough.

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.

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.

. Fair go Bob. What about Lycomings little frolic in metallurgy when they altered the metal alloy used in their crankshafts to make them easier to machine with c&c machines. That killed quite a few people and cost our industry millions.

Then there was Continentals effort to reduce oil consumption by increasing the ring pressure against the cylinder walls. That experiment virtually stopped oil consumption but wore the cylinders out in about 400 hours. Yes you guessed it. Just out of warranty. Another R&D exercise that cost owners millions.

Neither Lycoming nor Continental came out of that smelling of roses. Their efforts to avoid rectification were disgraceful.
Both events occurred within the last 20 years.

I nearly forgot. What about Continentals ongoing experiment with little or no Quality Assurance when case hardening their cam lobes and followers.

That coupled with their hit and miss method of seating valves in their new and overhauled io520s and perhaps other models is trashing the company's name.

CASA is asleep at the wheel and some LAMES/ engine reconditioners aren't bothering to report such incidents because past experience has told them they're wasting their time and energy.:ugh:

Thanks Rutan for the reality check, post above edited ....

Hi X. ATSB research sums it up well in their massive research project into engine failures "ar-2013-107". ".......Aircraft powered by Jabiru engines were involved in the most engine failures or malfunctions with 130 reported over the 6 years. This represents about one in ten aircraft powered by Jabiru engines in the study set having reported an engine failure or malfunction. Reports from Rotax powered aircraft were the next most common with 87 (one in 36), followed by aircraft with Lycoming (58 – one in 35) and Continental (28 – one in 35) engines. When factoring in the hours flown for each of these engine manufacturers, aircraft with Jabiru engines had more than double the rate of engine failure or malfunction than any other of the manufacturers...."

You must also remember, The Rotax numbers also included the two-stroke engines.

This is why it was impossible to compare apples with oranges, nothing was counted correctly right from the very start.