Another Jab bites the dust.

[motzartmerv]

I think we all need to go make a coffee and relax for a while. The purpose of a thread such as this is to inform, educate and arm people with knowledge. We all know Jabiru have issues and those issues aren't confined to the reliability of their engines. When we look at the statistics (thanx tubz) its quite clear that pretty soon some major steps are going to need to be taken. But remember, we are the consumer here, in any other industry the consumer holds the power because its the consumer that has freedom of choice to chuck his money where he see's fit. In this case nobody could argue that Jabiru offer cheap, factory built aeroplanes. Unfortunately, this bottom line does seem to effect the quality of the product. This business is like any other, you generally get what you pay for. Sad when peoples lives are at stake, but true.

 

The issues are not new, and I have operated these aircraft in the toughest of settings for a number of years now. And the aeroplane has stood up well. The engines do require constant tinkering mainly with minor issues, but we have to accept the risk associated. Its no different to operating any other type.

 

As an operator in a training setting all we can do is hope for the best and plan for the worst. Train people to a high standard, be thorough with maintenance and ward off complacency.

 

I would like to see Jabiru take major steps in rectifying the problem, they seem to have a very 'reactive' attitude towards engineering rather than 'proactive', ie, they bring out mods, ads, fixes after the fact. The J170 with the ghastly looking ventral fin mod is but one example. I would like to see nothing new come from them for a few years, and then the release of a "finished" product, rather than sending out aircraft for people like me and you to test in the field, and then fix the problems later.

 

But finally, I would like them to listen to the consumer. And this I believe is Jabiru's biggest problem. We have been telling them for years..... Please arrange the cockpit better, please offer a choice of engines, please offer a choice of propellor, please please please...But as yet..We still fond ourselves in threads such as this. The reputation of the brand has suffered tremendously, and I wonder how much further it can sink. I know of a couple of owners who are selling now before their aircraft are worthless in an open market.

 

All of the above is not knocking. It is observation from someone who operates multiple Jabirus in what could be considered the toughest testing grounds, a school on a short, narrow, grass (mud) field. And like I said, the aeroplanes have stood up to the test. Until now I have had no engine failures (with the training aircraft) in approx 5000 hours of operation (total school).

 

I have however had numerous U/S periods during that time due to maint issues that if not discoverd by rigerous checking, could well have ended badly.

 

I am trying to offer a balanced view here.

 

cheers

 

 

[Stewy]

And I think that you have done a great job in providing that view Motz

 

I have only flow Jabs during my training and since (About 80 hrs in total) and have never had any reason to doubt them.

 

My instructor is like you in that he is religious with maintenance and has done plenty of tinkering with his engines. Current engine is a test engine from Jab, has done about 500 hrs I think and runs really smooth

 

He has about 15000 hours in them so I do trust him and i enjoy flying them.

 

I am not going to ground myself because I have a Jab engine up front I will continue to look for emergency landing spots as I fly no different than if I had a Rotax or any other engine up there as I was taught, and practice my emergency procedures as taught as well. Life is full of choices and as adults we can make those sort of decisions and should be able to discuss them openly. Sounds a shame Jab dont seem to listen but i have never owned a plane so dont have that problem hope they help you with this problem.

 

Regards

 

Stewy

 

 

[fly_tornado]

So does a flying school end up saving that much money when they buy a Jabiru over say something like a Technam?

 

 

[motzartmerv]

Of course they do.

 

 

[M61A1]

Jab may need top end overhaul early - so what, parts are cheap, easy to work on. Im told not many Lycoming or Conti go throught to TBO without some heads or cylinder being worked on.When adjusting valve clearances (or tensioning lower head bolt) look closely for exhaust burn in the rocker chamber, monitor ALL EGT and CHT, re jet if needed, do regular leakdowns.

Some choose to do top end every 300hrs. Still cheaper than Rotax alternative depends how much effort and time you can spend on it.

 

What is the maintenance framework in RSA? Having so many more around means LAME are more experienced spotting problems and maybe do more than standard on services.

 

Im not sure the 2200 is a big seller there though.

 

RSA engines come off same production line as ours as far as I know. There are some guys doing upgrades and improvements over there even on new engines. EFI is being developed.

 

I feel the EGT/fuel distribution problem is a core problem, cylinders can severely lean under different throttle settings and different altitudes (To some extent this might be what Rod S is eluding to) This has been an issue since the first of these engines was developed. Until EFI, even most automotive engines had the similar issues, only water cooling masked the problems. Every engine has differences which needs adjustments and tuning. Rigidly sticking to the book isnt good enough, you have to trawl through websites and forums to learn much of how to make them run well and reliably. With this in mind Jabiru do need to more to enable certified use of the engine.

 

They arent Lycoming or Rotax but a small volume engine maker with problems and benefits that brings, but they are good value and generally perform well but not always.

 

I have one cylinder which goes lean at wide open throttle whilst rest of engine cools as it is supposed to. Punching out repeated circuits with this problem would definitely see it fail. In cruise it all settles out OK.

 

Without EGT monitor would have no idea there was an issue. Ive been doing 25hr leakdowns expecting to see a problem and yep it finally reached limits, had the head sent away, back in five days with new valves, guides tested and head lapped, all I paid was freight.

 

It is annoying to see those on here refusing to fly a Jabiru because of these problems, many with little experience in them. There are many thousands of Jab engines out there and only a few problems. Flying RAA or experimental aircraft is one of the highest risk activities you can choose to do. Id say engine failure isnt the top of the most likely things to go wrong. By far the greatest risk is the pilot, their capabilities and decisions they make.

This sort of information is gold to me Piston aviation engines will never be as reliable as automotive engines, as they are built lighter and have higher demands. They continually evolve (hopefully), and a good maintenance tech will quickly learn to interpret what the machine is telling them. You cannot ignore the signs and then say you weren't warned. It may be that, because this particular engine type is used for recreational aviation that the evolution has been slower, due to the the lack of research. Research & development that would occur much faster if the engine was used for business purposes (ie:passenger/freight).

It would appear that those that get the best results from these engines, understand and listen to what these egines are telling them, and then do something to sort it, regardless of what the factory has to say about it.

 

So I guess what that means is, if want to get the less expensive engine, you best be prepared to spend a bit of extra time on your maintenance, and be very familiar with your engine failure procedures. (all aircrew should be familiar with their engine out drill, regardless)

 

 

[motzartmerv]

M61. I would disagree. Mainstream GA engines have changed very little over the years. There seems to be much more movement in the light sports engine department, from my limited knowledge, but there seems to be very little development of the lycomings etc, they already have a proven product.

 

 

[motzartmerv]

If it aint broke, dont fix it...;)

 

 

[damkia]

M61. I would disagree. Mainstream GA engines have changed very little over the years. There seems to be much more movement in the light sports engine department, from my limited knowledge, but there seems to be very little development of the lycomings etc, they already have a proven product.

Not quite true.

 

There has been some improvements in GA engines, but the issues and costs related to re-certification of every modification means they tend to be lumped all together (ie., new metallurgical products, new head designs, turbocharging, and FADEC on some engines) in one big redesign, versus the RAA engines which are more incrementally improved with time.

 

 

[fly_tornado]

how many jabiru variants are there?

 

http://en.wikipedia.org/wiki/List_of_Lycoming_O-360_variants

 

 

[motzartmerv]

Yes ft, one would expect quite a few variants on a 50 year old design. It's interesting to note, if you read the differences, that a variant number can be generated by things like changing between different series of magnetos, or a change in carby model number. Hardly what you would call substantial development. I'm sure if jab changed the variant number everytime they changed a nut or a bolt then the variants would be countless..;)...

 

 

[fly_tornado]

Thats only the 360. Do you reckon a twin carby version of the 2200 would sell well?

 

 

[motzartmerv]

For those that are interested, heres what the cylinder looks like when this occurs.

 

 

 

[dutchroll]

This sort of information is gold to me Piston aviation engines will never be as reliable as automotive engines, as they are built lighter and have higher demands.

Can't say that I entirely agree with that. While aviation engines are indeed designed lighter (because they simply have to be to satisfy the performance vs weight equation) and do have more demand on them than the average car engine, they also frequently use higher quality components, and components subject to much more rigorous quality control procedures than automotive engines. It is rare for aviation engines to fail when they are treated and maintained well and have proper components fitted, considering the demands put on them. Now cut to my useless EF Falcon of many years ago, which was always regularly serviced, driven responsibly, and experienced a litany of costly failures throughout its life, the final one being its death knell.

 

 

[damkia]

Aviation piston motors are routinely run at 75% full power or greater for extended periods of time. The fact that we get this level of reliability at high output power levels out of such a lightweight collection of parts is really quite remarkable.

 

Automotive engines rarely see this level of sustained driveline stress, mostly operating at the 15-30% full power (you don't drive continuously under near WOT). Even then they are less reliable and generally do not fare well when operated in the same sustained high power environment as an aviation piston motor.

 

 

[Guest Andys@coffs]

Automotive engines have a whole series of design objectives that can clash. For example today its an important part of the decision process to buying a new car to understand the fuel efficiency of one variant over another yet most males want a car that has as much if not more power on call than the last chariot, equally its legislated and we expect that emissions are controlled and minimised as much as possible.

 

A broadbrush statement for both of those aspects when it comes to aircraft engines is that we will never knowingly trade off reliability or significant weight for fuel efficiency or emmision controls etc. Case in point close to this whole discussion is the J lean running mod that was relatively quickly reversed and in fact went further the other way when it was seen that it was further degrading reliability.....

 

Rightly or wrongly the saved cost of additional fuel or "Percieved cost of extra emissions" (by todays community standards) pale into insignificance when we factor aircraft engine replacement cost or repair costs. (Not to mention the risk to life that accompanies the experiment)

 

Andy

 

 

[eightyknots]

Hi guys. Here's a flight path mock-up. Props to Motz, he's taught me everything I know. I hope you all have as good an instructor as I do.Cory.

 

[ATTACH=full]17398[/ATTACH]

So glad you weren't over tiger country and that you're both OK!

 

For those that are interested, heres what the cylinder looks like when this occurs.[ATTACH=full]17404[/ATTACH]

Ouch, that looks both nasty and costly!

 

 

[jetjr]

My 2 cents on the photo Motz

 

The problem with the normal through bolts was thought to be that during normal tensioning the first threads can strip. Adding longer nut adds more threads so in theory more hold on the bolt. Not sure I agree though.

 

It seems in this case the entire threaded end has let go, based on the crack appearing on this side of the cylinder its possible the bolt was the secondary event. Heavier bolts may not have helped.

 

Looks awfully like detonation could have caused this. Did the engine suddenly stop? Did you have EGT equipment fitted?

 

In terms of repair, what are the maintainers saying? Might not be costly as you expect.

 

Many EMS setups log and record engine and flight details for many hours and would add greatly to sorting these sort of failures out. A lot dont have this feature turned on!!

 

 

[motzartmerv]

Hi Jet. Thanx for the comments. Two engineers so far have differing opinions on the head cracking and bolt failure sequence. The bottom through bolts retained the base of the cylinder after the issue. There hasn't been any proper look into it yet, but what seems to make sense to me (and I am no engineer) is that if the cylinder cracked first why would this put extra undue load on the through bolts? What looks like may have happend (to me) is the top two bolts let go but the bottom two tried to retain the head, the head then isn't flush and straight with the cylinder which is still doing its thing and cracked the head.. Thats my opinion, but like I said, I am certainly no expert in this area.

 

I think the aircraft will be going back to Jab, they will no doubt get to the bottom of it... (sense my sarcasm)...

 

I can say that this particular pot had attracted the attention of my engineer who contacted Jab about the symptoms. He was told to check the torques which he did. Everything was spec.

 

We dont have a EGT guage fitted to this engine unfortunately. The CHT info shows no anomaly.

 

 

[motzartmerv]

The right hand bolt failed about 10mm back from the nut, while the left bolt failed right at the base of the nut. Which one went first is anyones guess.

 

 

[M61A1]

Can't say that I entirely agree with that. While aviation engines are indeed designed lighter (because they simply have to be to satisfy the performance vs weight equation) and do have more demand on them than the average car engine, they also frequently use higher quality components, and components subject to much more rigorous quality control procedures than automotive engines. It is rare for aviation engines to fail when they are treated and maintained well and have proper components fitted, considering the demands put on them. Now cut to my useless EF Falcon of many years ago, which was always regularly serviced, driven responsibly, and experienced a litany of costly failures throughout its life, the final one being its death knell.

I have quite the opposite experience with automotive stuff, inasmuch as I've seen it abused to the extreme, yet not hard fail, particularly old falcons & holdens, but that's stuff for other forums.

 

 

[damkia]

A few more things....

 

Out of curiosity, have the bolts been re-tensioned by way of removal and rebuild? Could they in fact be a "torque to yield" bolt that is designed to be single use? Could they have accidentally been used (designed) in a yield situation where they are in fact overstressed (seems utterly possible)?

 

One more thing, would it be possible to do a dye test for cracks around and through the bolt hole in the pot and crankcase? Is there is a possibility that there may be a bit of crush deformation of the hole allowing metallic "hammering" of the bolt?

 

Yet another possibility from left field is resonance of the bolt itself at particular engine revs causing metal fatigue.

 

Torque to yield style bolt/stud is commonly used in automotive head-block assemblies. Having said that there is also a common issue in (of all things) Mazda rotary engines where the long steel through bolts expand at a different rate to the aluminium housings causing similar issues if not torqued correctly with new bolts used each time causing the alloy to crush. This also happens with wheel studs and nuts and alloy rims that have been overtightened with a rattle gun (the reason they give you a ridiculously short wheelbrace - so you can't over-tighten them by hand when out on the road).

 

 

[jetjr]

Yep, anyones guess, but to have the cylinder and 2 bolts break theres been a big bang - might have all happened at once too.

 

It likely Jab will repair it, they cant give any solid answer as this is a real unknown for them I reckon. Strictly they believe they have fixed the problem with new bolts. Theres a long thread in Jabiru section on these bolts and how they break. Tests show they strip VERY close to tension point. A poorly calibrated torque wrench could see these being over stressed easily upon initial assembly.

 

Id suggest looking hard at a Dynon EMS unit. It takes up 1 large gauge hole only. It can show and alarm on many parameters and log everything including all 4/6 cylinder EGT and CHT. Others like MGL etc are good too but not sure if they can log everything.

 

Good for new flyers and aircraft renters as most things are alarmed and this helps when other issues are tying up brain resources. Would also be helpful with any warranty or insurance discussions if it came to that.

 

Jabiru can sell and fit these, I wish they did it as standard so these problems could be isolated and fixed.

 

 

[motzartmerv]

Damika, the head bolts have only been torque tested, not removed, since a factory top end rebuild. 270 hours ago.

 

 

[motzartmerv]

Yea jet, like I said, I really shouldnt comment on these things as I am not an engineer..or even a tinckerer..I brake them, you guys fix them...lol..

 

This acft is fitted with a dynon EMS, it just doesn't have the EGT probes fitted.

 

 

[turboplanner]

It's a bigger problem than just the thru bolts, judging from the photo. I think Facthunter probably has it.

 

The whole barrel is trying to come apart, and cracking at the weakest point.

 

In two strokes the barrel often cracks when a piston seizes up and digs in to the wall, and the rotating crackshaft and flywheel mass just pushes the barrel apart.

 

In this case, in my opinion, if you made the thru bolts from 25 mm dia hi-tensile steel, they would hold but the barrel crack would be much greater, or the barrel would part and move up with the piston.

 

So if it isn't mechanical lock up, then it has to be an unusually large force, hence I agree with FH.

 

So the issue may be manifold layout.

 

I usually eliminated manifolds and run one carby per cylinder on straight spigots on race engines so I don't have this problem, but wonder if a flow guy might be able to spot an issue with the manifold design.