CASA - Draft Proposal for Jabiru Aircraft

[Dafydd Llewellyn]

OK then Dafydd, leave the oil pressure out of it, what do you think about the resonance?

In regard to what? As far as the through bolts are concerned, it's got nothing to do with torsional resonance (tho there might be some "bowstring" resonance in the Jabiru design, I've not looked at the detail for a while); but everything to do with a number of factors that accumulate to cause loss of pre-load; and also to flexure of the cylinder base flange (take a good look at the cylinder base flange design on a Lycoming - they had trouble there, too). Every time a cylinder fires, the force trying to pull the cylinder base away from the crankcase is about 3.5 tons. Things flex under that sort of hammering.

As far as the "flywheel" bolts on the 3300 are concerned, I suspect it does contribute - and that can be improved considerably by removing the permanent magnet rotor from the engine - which reduces the moment of inertia of that end of the crankshaft assembly - and replacing it with a belt-driven alternator, which does not contribute to the "flywheel" inertia, but instead supplies some dynamic damping at the torsional frequencies likely to be responsible.

 

The propeller is the principal "flywheel" and its attachment MUST be capable of handling the transient loads that involves - just as in any direct-drive Lyconental. So putting a Rotax donut between the crankshaft and the propeller is right out. It works (for a while) in the Rotax because the individual firing impulses are relatively small, and at twice the frequency. The Rotax gearbox pinion would fail very quickly without some sort of cushioning effect between the crankshaft and the propeller.

 

 

[motzartmerv]

Do we know how the failed engines were run. With one operator getting 3 failures, it would be good to compare his method of operation with other operators.

The aircraft in question was used primarily for training. Run on 98 octane Mogas.

 

Always flown IAW the poh with regards to speeds etc.

 

Cht ( single probe) was always notably low for a jab. Indications were generally sub 150 degs during normal operations.

 

The engine lasted till 800 hours when we were forced to change the through bolt nuts IAW a jabiru AD ( I forget the ad number) for bigger nuts.

 

40 hours later the front stud bolt sheared off and was found during a preflight inspection.

 

The engine was returned to the factory for a top end and the factory stated the cause of the bolt failure was

 

" incorrect bolts supplied by the factory" .

 

The top end overhaul was completed by the factory and the engine re installed by an L4.

 

250( ish) hours later the fly wheel screws sheared. Only 2 remained intact. This was picked up again during a pre flight inspection.

 

The screws showed signs of being " reused" from the top end overhaul evidenced by multiple fitting and wear points on each screw .

 

80 hours later another through bolt was found sheared during an inspection after pilot reported rough running during run ups.

 

Note. The new even bigger through bolts were NOT fitted during the factory top end overhaul. We don't know why, and requests for this info have not been .... Handled.

 

The j170 this engine is fitted to as I said has been used fr training on a short, grass runway. In order to obtain speeds IAW with the poh idle approaches are generally used, particularly after jabiru released an AD which reduced the amount of flap available.

 

We teach VY climb to 1000ft agl followed by a power reduction and an increase to 80-85 kts indicated for " cruise climb" with regular clearing of the nose by lowering to cruise attitude every 1000 ft during the climb.

 

 

[01rmb]

It is good to see the robust discussion of the mode of failures and analysis of the potential solutions. There is a huge amount of information available from an in depth analysis of the failures. The information from facthunter, motartmerv, Dafydd, Oscar and many others here is critical to gathering information on the failures to determine the route causes of the problems. From what I have observed it would appear that Ian Bent (CAMit) has progressed a lot of this but I still believe that there is more to the problems being experienced.

 

Yes, Jabiru should be doing this. In spite of my open criticism of the CASA actions which I see as using a sledge hammer to repair a precision instrument, I have also argued directly with Jabiru that they should be doing more analysis of not just of the identified failures but also of the out of schedule maintenance being conducted, to determine the root cause of the problems and be doing something to fix the problems. A more reliable, robust and less reactive maintenance engine is a great thing for all who sit behind one and for those that pay the costs of maintaining them.

 

By uncovering the underlying reasons for failure and implementing changes (operation, maintenance and components) it will lead to improvements in reliability and thus safety.

 

 

[motzartmerv]

The first aircraft (first through bolt failure) was a 160. I cant recall the hour state of the engine, but the total time was 1200 ish. Training aeroplane that had extensive time spent at bankstown.

 

It has pent its life run on AVGAS but had recently been changed to Mogas when the failure occurred, I wold guess maybe 3 months .

 

This engine was a "hot runner" with two bank CHT monitoring. regular running temps around 160-175 degs (CHT)

 

Semi powered approaches were generally flown IAW with POH and carefull monitoring of temps during climb was always needed.

 

Quite often requiring levelling off and relaxing the engine to allow it time to cool before entering the climb again.

 

for this reason the aircraft was seldom used for navigation training.

 

There was no reason given for the failure other than the fact the owner had not had the through bolts changed IAW with an AD (that expired 9 days before )

 

The reason for the failure from then on was " We didnt do AD". Subsequent years and continued failures have proven this not to be the case, but as I said, its the only reason ever given.

 

 

[fly_tornado]

Jabiru should have "gifted" camit the engines along time ago. Concentrated on the brilliant airfames, developing them further with better options (yokes?).Camit could have concentrated on and develped the engine with a known income in Jabiru airframes.

Win win?

 

Someone mentioned Jabiru as a "family business". That may have been an advantage early on but has fast became their achilles heal I think.

 

I think Jabiru are making decisions based on emotion and sentimental attachment (how dare you say our engine is bad) instead of a defined pragmatic business approach.....

People often wonder why Jabiru are the only manufacturer in Australia to survive for as long as they have.

 

The obvious answer is that the engine rebuilds is their bread and butter that gets them through the slow sales. No wonder really they aren't in any hurry to fix any issues with the engines.

 

 

[facthunter]

I'll take this opportunity to ask Dafydd "do you think the starter engagement has any effect on the flywheel attachment. failure" . It should be on the front of the engine near the prop.

 

ft has anyone suggested the parts prices are too high? That's a pretty outrageous suggestion if you think about it. Keep it dangerous TO MAKE MORE MONEY!!!..Nev

 

 

[Russ]

People often wonder why Jabiru are the only manufacturer in Australia to survive for as long as they have.The obvious answer is that the engine rebuilds is their bread and butter that gets them through the slow sales. No wonder really they aren't in any hurry to fix any issues with the engines.

I'm hoping that's a joke.......unreal

 

 

[motzartmerv]

Further to the above post re the 160 failure. (and I offer this NOT as a Jab bash, but a practical example of some ststements regarding jab service)

 

After the failure jab washed their hands of the engine realising that the AD not being complied with meant they were free and clear of any responsibility. So they told us to " do what you like with the engine"

 

My engineer at the time requested that the factory check the engine for a cause, but was met with " you didnt do the through bolt mod" .

 

I think THIS case is a perfect example of how the factory's attitude has lead (in part) to the current climate.

 

For the sake of some shipping costs, the factory could have had a 'dead engine' to give an autopsy, but instead, washed their hands of it once they had their "out". This is (IMHO) an example of a reactive rather than pro active mentality.

 

Another example, just TODAY, I recieved a call from the Jab factory asking if I run jabiru engines in my flying school.

 

I answered no, the last engine is broken with little or no chance of being repaired. The previous 4 jab powered aircraft have also 'broken' and are no longer online. The girl on the phone said " Well, ok, theres no need for you to do our survey if your not running jabirus anymore." Ummm.. I was dumbfounded. I just told you I have broken 4 jabs at my school, and you dont think this is statistically important?

 

Anyway. Todays dealing has sealed the deal with me. Nobody can now convince me that they truely care. IMHO, they are only "reacting" still.

 

 

[Dafydd Llewellyn]

I'll take this opportunity to ask Dafydd "do you think the starter engagement has any effect on the flywheel attachment. failure" . It should be on the front of the engine near the prop.ft has anyone suggested the parts prices are too high? That's a pretty outrageous suggestion if you think about it. Keep it dangerous TO MAKE MORE MONEY!!!..Nev

I doubt it is significant - but I agree, the ring gear would be much better located at the front of the engine, at least on the 3300, but not for the reason you suggest; it should preferably be where its mass adds to the propeller flywheel effect, not to the flywheel effect at the opposite end of the crankshaft. I've said all this before, several times. This should not be taken to mean that I consider the current location to be a design fault; it would be a desirable design improvement, which is not the same thing.

 

 

[facthunter]

You are only dealing with the office girl probably in this instance but I can understand your frustration. The situation with the parent company and CAMit must complicate matters (for them). It should not be to the customers detriment, Over the years I have heard many good deals done by the company. I guess there must be an end to many good things. Nev

 

 

[motzartmerv]

Don't you find this spikes the EGT? (Climbing at lesser power)

It causes a slight rise in egt but no where near limits.

Oil temp and cht remain optimal with this method.

 

 

[facthunter]

Thanks Dafydd. I have had Harleys move the mainshaft in the flywheel because of the starter engagement shock so it can be a significant force. I agree totally about the flywheel effect. Should be one end only. Nev

 

 

[bexrbetter]

Thanks Planesmaker we just need to see if there is any pattern to these bolt failures . we have found the resonance problem and eliminated about 90% of it in several jab engines , since then [18] months ago we have had no trouble 1 eng 800 hrs at least 2 others around 700 hrs all still operating, engines run smoother /50 deg cooler climb small increase in power, 200 hrs was about all you could expect out of these engines before a major repair, used in F.T.S . 2200 hydr lifter . the way the bolt has broken certainly indicates[ cyclic loading ] , even if they increased size to 5/8 would probably still fail. the base cause needs to be addressed, rather than just beefing up bolts , seems to be an Australian manufacturers trend, if it breaks , just make it bigger.Your bolt failure position and the other one I have ,ARE ALLREADY indicating a pattern that I suspect would be associated with this resonance . bit like the violin and glass trick. I'v been engine remanufacturing since 1976 full time , I have seen large diesels have ends break off cranks 4"diameter all because of resonance.

So again , thank's for your reply. ALL other bolt failure position indications would help ANYONE !. Could be a goose chase , but who knows , has to start some where.

 

A.D.

As I said TVs and I fully agree with your position. There are a number of famous engine's TV or resonance cases throughout engine history, the Holden Grey engine crankshaft breakages being one of them.

 

I am also underwhelmed at whoever at Jabiru decided not to use case clamping bolts outside of the camshaft, also a possible origin of some resonance.

 

I have a friend who was Lotus's NVH chief engineer and now a chief engineer in Ford Australia I'll see if this interests him.

 

 

[Dafydd Llewellyn]

Thanks Dafydd. I have had Harleys move the mainshaft in the flywheel because of the starter engagement shock so it can be a significant force. I agree totally about the flywheel effect. Should be one end only. Nev

Did the Harley have a starter of the modern form, in which the solenoid pulls the gears into mesh before it makes electrical contact, or was it a simple Bendix gear that threw-in by inertia? There's a considerable difference in the impact torque, I think you will find.

 

 

[jetjr]

Might explain some variability, failures vs starts?

 

Wouldnt resonance be totally different in 3300 vs 2200?

 

Merv every time you relate the stories, which are good info, i see your people were let down by poor service and maybe engine building NOT the engine design itself.

 

Exactly why an approved parrallel option is required.

 

Take a 912 put together wrongly using old parts youll get the same thing but far more expensive rattles.

 

Not making excuses for Jabiru, but didnt the AD run for 12 months? Owner wasnt 9 days late?

 

 

[Dafydd Llewellyn]

It is good to see the robust discussion of the mode of failures and analysis of the potential solutions. There is a huge amount of information available from an in depth analysis of the failures. The information from facthunter, motartmerv, Dafydd, Oscar and many others here is critical to gathering information on the failures to determine the route causes of the problems. From what I have observed it would appear that Ian Bent (CAMit) has progressed a lot of this but I still believe that there is more to the problems being experienced.Yes, Jabiru should be doing this. In spite of my open criticism of the CASA actions which I see as using a sledge hammer to repair a precision instrument, I have also argued directly with Jabiru that they should be doing more analysis of not just of the identified failures but also of the out of schedule maintenance being conducted, to determine the root cause of the problems and be doing something to fix the problems. A more reliable, robust and less reactive maintenance engine is a great thing for all who sit behind one and for those that pay the costs of maintaining them.

 

By uncovering the underlying reasons for failure and implementing changes (operation, maintenance and components) it will lead to improvements in reliability and thus safety.

I suggest you go and see what Ian Bent has been doing (except he's frantically busy right now, with this undeserved crisis to his situation) - you'll find he's light years ahead of this discussion.

 

 

[Dafydd Llewellyn]

Might explain some variability, failures vs starts?Wouldnt resonance be totally different in 3300 vs 2200?

Yes, of course it is.

 

 

[01rmb]

Further to the above post re the 160 failure. (and I offer this NOT as a Jab bash, but a practical example of some ststements regarding jab service)After the failure jab washed their hands of the engine realising that the AD not being complied with meant they were free and clear of any responsibility. So they told us to " do what you like with the engine"

 

My engineer at the time requested that the factory check the engine for a cause, but was met with " you didnt do the through bolt mod" .

 

I think THIS case is a perfect example of how the factory's attitude has lead (in part) to the current climate.

 

For the sake of some shipping costs, the factory could have had a 'dead engine' to give an autopsy, but instead, washed their hands of it once they had their "out". This is (IMHO) an example of a reactive rather than pro active mentality.

 

Another example, just TODAY, I recieved a call from the Jab factory asking if I run jabiru engines in my flying school.

 

I answered no, the last engine is broken with little or no chance of being repaired. The previous 4 jab powered aircraft have also 'broken' and are no longer online. The girl on the phone said " Well, ok, theres no need for you to do our survey if your not running jabirus anymore." Ummm.. I was dumbfounded. I just told you I have broken 4 jabs at my school, and you dont think this is statistically important?

 

Anyway. Todays dealing has sealed the deal with me. Nobody can now convince me that they truely care. IMHO, they are only "reacting" still.

I am fully sympathetic of your and the jab owners experience and agree you deserved a better response from Jabiru. I agree they should have done more to investigate the problems and searched for the underlying cause of the failures - maybe then this current situation could have been avoided.

 

When I visited the Jabiru factory I was impressed on what had been accomplished but disappointed on what could still be achieved. I still don't like what CASA is doing to the owners - but getting Jabiru to lift their game to better investigate problems is reasonable! If Ian Bent has at least some of the answers to improve the engine I for one will be lining up - if I can fit them within my registration limitations...

 

 

[turboplanner]

How many engines to CAMit have in operation?

 

 

[jetjr]

Thousands they built the lot,

 

Older Solid lifter types are the basis for their work so it isnt a scratch built concept.

 

The hours done on them counts for something, they "significantly report" to have much less problems

 

With the new upgrades, dunno, Oscar knows but he is banned

 

 

[01rmb]

I suggest you go and see what Ian Bent has been doing (except he's frantically busy right now, with this undeserved crisis to his situation) - you'll find he's light years ahead of this discussion.

When I was in Bundaberg last I had intended to visit Ian but between Easter and Anzac day holidays plus Natfly everyone was a bit busy. It sounds like he has made some great improvements and I welcome his hard work coming to fruition - just a shame about the politics.

In the discussions around the improvements Ian has proposed - do any of them consider the lead fouling problems caused by avgas? I know my own maintenance problems were related to fouled exhaust valves but also that 2 of the partial engine failures in the stats being used are directly related to the same issue.

 

 

[DCM]

How many engines to CAMit have in operation?

Fitted mine about 5 weeks ago it's serial number 0020 in the new engines but I don't know how many upgraded Jab engines are getting around

 

 

[Geoff13]

DCM Is it classed as a Jabiru engine or not in light of this proposed instrument. Or do you not know.

 

Cheers Geoff13

 

 

[poteroo]

Another example, just TODAY, I recieved a call from the Jab factory asking if I run jabiru engines in my flying school.I answered no, the last engine is broken with little or no chance of being repaired. The previous 4 jab powered aircraft have also 'broken' and are no longer online. The girl on the phone said " Well, ok, theres no need for you to do our survey if your not running jabirus anymore." Ummm.. I was dumbfounded. I just told you I have broken 4 jabs at my school, and you dont think this is statistically important?

Anyway. Todays dealing has sealed the deal with me. Nobody can now convince me that they truely care. IMHO, they are only "reacting" still.

Same here. When I advised her that I'd happily sold the aircraft a year ago, because of 2 engines and 2 total failures in 730 TT - the tone changed and she decided that it would serve no purpose if I did their 'survey'. Methinks the 'survey' will be very much skewed towards successes rather than failures. happy days,

 

 

[Guest Andys@coffs]

DCM Is it classed as a Jabiru engine or not in light of this proposed instrument. Or do you not know.Cheers Geoff13

The Question might well be moot....As Dafydd as suggested, and others have also agreed these engines can only, at present, be fitted to 19 or E24 class aircraft and as such, given that if you want you can fit a steam engine providing the aircraft continues to meet the limitations of the exemption we fly under, limiting these further as per the proposed instrument is nonsensical given that usage of E24 and 19 is already limited above and beyond 24 and 25 so double jeopardy??

 

Andy

 

Personal view not a board view, and I have no more knowledge than you do on which I base my view