CASA - Draft Proposal for Jabiru Aircraft

[Old Koreelah]

Choice of fuel? Mogas vs avgasChoice of warm up prior to applying full power ( I know a guy who has had an engine failure who didn't know for three years that jabs should not have full power applied till engine temps were over 50 degrees. He used to take off at any temp over 15 degrees. ( the minimum operating temp)

Climb out speeds

 

Cruise settings - many opt for fuel economy but that runs engines hotter

 

Probably more

At cruising altitude (7500+) and 2800 rpm the fuel flow on my 2.2 gets down around 11 litres or even less. I'm told that's asking for trouble, but CHTs seem within limits and I dare not pour on more power- I'm already cruising near VNE.

 

 

[Dafydd Llewellyn]

Much to my distaste, I have a question. It may at first seem irrelevant to the subject, but it is not:

 

Just how worried are the contributors to this thread, about the wings of their aircraft falling off? I've not heard such a commotion as is evident on this thread, about that risk. In fact, I'd venture that nobody here has any idea of what the statistical probability of that might be, or even thinks about it.

 

So if we're going to make such a fuss about statistics, let's put them into some sort of perspective:

 

I note that the CASA document refers to "an extraordinary high rate of partial and complete engine failures".

 

Pray, what is the statistical rate that is "extraordinary high"?

 

I see reference to a rate of engine problems per aircraft movement, for Jabiru aircraft, from RAA data, of 0.03% - is this correct?

 

How does this translate into a rate per flying hour? If, for example, the average flight time per movement were, say, 20 minutes, then the rate would surely be 0.09% per flying hour, would it not? For the sake of this discussion, let's round that off to 0.1% per flying hour , i.e. a probability of one in one thousand per flying hour.

 

How does this compare with other relevant probabilities? One that is surely relevant would be the probability of a wing falling off due to a structural fatigue failure. The liklihood of surviving an engine malfunction or complete failure is vastly better than of surviving a major structural failure, so this is a conservative comparison.

 

The "safe life" criterion that applies to the majority of GA aeroplanes flying in Australia to-day, was CAO 101.22 Appendix II (No, you won't find it on the CASA website, it's been superseded - but it was relevant up to about 2004 or thereabouts). That specified a safe life of one fifth of the calculated mean time to failure, and was supposed - if I recall it correctly - and taking into account not only the variability of the fatigue life of a structure, but also the inherent inaccuracy of estimating the loading spectrum that causes it, to give a probability not exceeding 1 in 1000 per flying hour - i.e. 0.1%. More modern standards set the bar a bit higher, but they are not yet in general application for the GA fleet, let alone recreational aircraft.

 

Standards for recreational aircraft such as CAO 101.55, BCAR S, ASTM F2245 etc, do not even mention fatigue life. There is no requirement whatsoever in these standards for any estimate of the safe structural life to be calculated. So the possibility of a structural failure may well be higher than 0.1% per flying hour - yet all you people blythely ignore this.

 

RAA is, I can just about guarantee, completely unconscious of this. The airworthiness authorities that drafted those design standards were not, however - they knew the score; but they did not consider it sufficiently important, for a recreational aircraft, to bother with putting such a requirement into the product safety standard.

 

So how consistent is it for the RAA to protest to CASA about a failure rate for the Jabiru engine, that is of the same order as the probability of a catastrophic structural failure, which they considered insufficiently important to bother about? How consistent is it for the protagonists on this thread, to focus on the engine alone? I would suggest that nobody here is exhibiting anything remotely able to be considered either competent or logical.

 

This being the case, I do not see that the rate being reported by RAA for Jabiru engine issues, warrants the action proposed in the draft Instrument. It would seem that the sports office in CASA is equally ignorant and inconsistent. You can vote with your cheque books, after all.

 

Isn't it about time people started to look at the big picture? And be just a little bit consistent? We are, after all, talking about a recreational activity that has been defined as "inherently dangerous" by the courts. How does 0.03% compare to other "inherently dangerous" recreational activities?

 

I would be obliged if the moderators could refrain from interfering with this post.

 

(Ok so far we wont, however we reserve the right to edit any post that contains material contrary to the rules as per our brief....mod)

 

 

[Bigglesworth]

"Tweak the cooling", heard that one before from Jab getting out of the factory setup being not good enough.

 

Apparently you need full temp monitoring and then cardboard and sticky tape. And then your plane is no longer certified.

 

Not saying this wouldn't work, but its not the right answer from a certified supplier.

 

Andy (motz) is right; there is no way to baby through bolts. Especially when Jab says that their motors like running at full power. (Especially at run in)

 

 

[bexrbetter]

Just how worried are the contributors to this thread, about the wings of their aircraft falling off? I've not heard such a commotion as is evident on this thread, about that risk.

http://en.wikipedia.org/wiki/AMD_Zodiac#Safety_incidents_and_grounding

 

 

[Peter Tapscott]

Club has a j160c which was using up yo 150 ml of oil per hr. Our lame mechanical engineer stripped top end and torque plated barrels and heads for honing and valve face cutting because of distortion. Minor work on rocker arms sorted guide wear. These jobs have been done without going out of jabiru specs. It has been a journey but we are getting things sorted. It has done over 200 hrs since top end overhaul .

 

 

[acro]

http://jabirucrash.com/

[planesmaker]

So could anyone confirm to me that the throughbolt failures occur only on the lower rows next to the pushrod tubes (as Bruce pictured above) please?

Bex,

 

No, I have just replaced thru bolts on 2200 that had broken a top bolt. Flying school using avgas and maintained to the letter. Done about 400 hrs from factory bulk strip / repair where ,if I recall correctly , new thru bolts were fitted. Tom

 

 

[Jaba-who]

Multiple people have posted a response but not an answer to my question " what are the stats" so won't quote each of you but ....

 

. The RAAus figures quoted are not usable statistics. They are just some partial figures that leave more questions than answers. I don't think any attempt has been made to factor in that there will certainly be unreported events and also unreported hours/movements where no events have occurred.

 

They reflect only one part of the fleet (RAAus) and do not define how much of the fleet they involve. Ie: They don't include experimental nor any certified GA jabirus.

 

They have elected to use "malfunctions per movement". I have not seen a definition of what is a malfunction nor what is a movement. How useful is using movements as the denominator? The rest of aviation uses events per hour of flight. Is a movement a start up to shut down without consideration to what happens between the two?

 

If one movement consists of one ten minute circuit flight with one take off and landing it can not be compared to someone else's movement consisting of a four hour cross country flight with one take off and landing. Nor can either be compared with eg ten touch and goes, a flight at varying power and settings and a few practice engine failures.

 

Next i think ( could be wrong) they have used events this year whereas the other used events in full 12 month period.

 

And worst of all these were all relying on self reporting of events. I am aware of at least one failure that was not reported to authorities. I am also aware of many pilots whose reporting of flights and hours per year for CASAs are just guesses as to what they think they flew without actually getting their log books out.

 

I'm a reviewer for a medical journal and review stats and manuscripts and if an prospective author presented stats like those we would reject their paper without further reading.

 

 

[bexrbetter]

Bex,No, I have just replaced thru bolts on 2200 that had broken a top bolt.

Thanks Tom, appreciate your time.

 

 

[jetjr]

A big issue is the lack of data, all RAA (or anyone else) is landings vs reported failures. Should have flight hours too i guess.

 

Other info is coming from people and anecdotal reports, notorious for emotion and bias.

 

I suggest CASA and ATSB have nothing more which is what gives Jabiru argument room.

 

Its been discussed to death here ove time, you need full cht and egt monitoring or you have NO IDEA if your overheating heads or running lean.

 

This was recommended to me some 6 years ago so isnt news.

 

Ive argued to Jabiru this should be std equipment, but cost is a problem for them. Looking at cht is only one part of the issue, fuel flow doesnt help much either. The spread of fuel and air coolong needs work. id be surprised if this isnt allowed under LSA. Manuals state the limits it mist be run too.

 

Saw two with it fitted and logging turned OFF. It can be a vital tool in any fact finding or warranty issue

 

 

[ieadave]

CASA is responsible for aviation matters in Australia. Many Jabiru engines are found in SLSA aircraft manufactured outside of Australia. Separate and independent from SLAS are Jabiru engines flying worldwide as experimental. Data is data and to be useful statistics must be determined though the whole production line. I don't think we will ever get a full picture. Do SLSA failures happen behind Jabiru engines outside of the shores of Australia? You bet they do! Do they get reported to the proper authorities? Maybe no maybe yes. Many NEVER get reported back to Jabiru Australia because of poor responses. As I read what is happening in Australia, CASA is limiting ( and rightly so) it's study and to review of national data. Here is my question: of the total production run how many Jabiru engines were exported beyond CASA authority? How will other regulating bodies react to the events playing out in Australia?

 

Dave

 

 

[ianboag]

Have a look at the "for sales" on the RAA and Jab sites. A third (give or take a bit) of the engines seem to have had a top overhaul at about 500 hours TTIS. I know that my aircraft had a new engine fitted at TTIS 500 hours (long before I owned it) because of crankcase fretting ....

 

Go figure.

 

 

[dutchroll]

So how consistent is it for the RAA to protest to CASA about a failure rate for the Jabiru engine, that is of the same order as the probability of a catastrophic structural failure....

I have no clue how you can arrive at the conclusion that the probability of catastrophic structural failure of a Jabiru is about the same as that of an engine failure in the same aircraft. There is nothing about that concept which makes sense from either a theoretical or real world perspective.

 

 

[kgwilson]

The stats that have been released are extremely broad brush and meaningless. How many full failures, how many partial, what was the actual problem and more importantly what was the cause. If they have 27 to 29 incidents it can't be that hard to provide more details than they have.

 

All CASA has said is what I asked them in my submission. Are the causes design faults, are they assembly faults, are they pilot induced (no warm up, overheating due to slow climb out, detonation, pre-ignition fuel starvation etc) are they poor adherence to maintenance procedures, are they just poor maintenance or poor quality maintenance, is the fuel of correct grade, quality & freshness. The list goes on and then there are the comparisons with other engines again without any detail or specific statistical evidence. So from an initial knee jerk reaction to a "we are know thinking about things" 2 page soother document adding an extra week there is still no more information available to the Jabiru engine owners and the rest of the flying fraternity than before.

 

 

[Guest Bruce Knowles]

I have no clue how you can arrive at the conclusion that the probability of catastrophic structural failure of a Jabiru is about the same as that of an engine failure in the same aircraft. There is nothing about that concept which makes sense from either a theoretical or real world perspective.

reading that article one would think the Jabiru was a glider and the engine was irrelavent

actually when you think about it a very successful glider

 

perhaps we are looking at it from the wrong perspective

 

 

[motzartmerv]

How can a pilot " handle " the jab engine in a way to minimize through bolt failure?Genuine question.

I posed this question because I have a genuine interest in it and its ramifications, particularly for an engine marketed and sold as " a training platform".

 

Everybody that replied is correct . Things like:

 

* Adequate warm up time

 

* Engine monitoring (with non standard instruments)

 

* Increased climb speed to increase cooling

 

* Correct mixture ( Automatic, not manual)

 

My point is, NONE of this is new. None of those techniques are anything a pilot shouldn't do with ANY aeroplane engine. Students have been flying manual mixture control engines since the 50's,in numbers that make Jabs totals pretty negligable. and im not aware of a significant recurring failure mode in the major engine types relating to the same problems we are having here.

 

A well trained student will NOT take off until T's and P's are green (IAW POH)

 

A well trained student will monitor climb temps and climb with an increased airspeed to improve cooling

 

Any half trained mechanic can spot a lean or rich mixture during maintenance on ANY engine.

 

What makes this engine any different? If the engine requires full CHT EGT monitoring then that instrument should be standard equipment.

 

If the engine cant be climbed IAW with the POH, ie, VY at max continuous (FULL POWER) CHT not exceeding 180 deg's for more than 5 mins,then change the bloody thing.

 

On a 230 that went thermo nuclear on one cylinder, we had 6 channel monitoring on CHT and EGT.

 

Right up until the moment it went mental, it had NO over temp indications (IAW Jabs specs). ie, it never went more then 180 deg's for more than 5 minutes (IAW POH)

 

It never exceeded 200 deg's c (IAW with poh) and yet, turning xwind the thing went nuclear.

 

I have two contentions, after suffering every common Jabiru engine failure.

 

1. The engine can NOT tolerate operating at 180 deg's (CHT) as stated in the POH

 

2. During normal circuit operations, the heads cool too quickly.

 

Im no engineer. Im no mechanic, but I reckon those two things are playing a huge part in this saga. I have no DATA to suport my notions, other than the facts gathered by operating many Jabs, in many locations and NONE of them making TBO.

 

Some L2 maintained, some LAME maintained. Most run on 98 octane mogas, some run on Avgas.

 

 

[Keith Page]

So could anyone confirm to me that the throughbolt failures occur only on the lower rows next to the pushrod tubes (as Bruce pictured above) please?

What are you thinking?

Could be? Could not it. A very good pick up.

 

Regards

 

KP.

 

 

[Dafydd Llewellyn]

I have no clue how you can arrive at the conclusion that the probability of catastrophic structural failure of a Jabiru is about the same as that of an engine failure in the same aircraft. There is nothing about that concept which makes sense from either a theoretical or real world perspective.

I didn't say it was. I said, people are unconscious of the fact that the design standards for such aircraft do not address this aspect; and as a result, the probability is uncontrolled and could be as high as 0.1% - or higher. It may also be lower - and since Alan Kerr did some fatigue work on the Jabiru 160C, the probability, in its case, may be several orders of magnitude lower (but keep an eye on the lift strut end fittings). The higher risk is likely to occur in a rivetted aluminium airframe, especially one having cantilever wings.

 

 

[gandalph]

[quote="Dafydd Llewellyn, post: 460202, member: 8952......if we're going to make such a fuss about statistics, let's put them into some sort of perspective:......

 

I would be obliged if the moderators could refrain from interfering with this post.

 

(Ok so far we wont, however we reserve the right to edit any post that contains material contrary to the rules as per our brief....mod)

 

Thanks Dafydd for raising some interesting points. Good to see you back here.

 

I note with some concern the moderator's response to your request to not have the post censored. I found the tone of that response more than a little intimidating - perhaps just my reading or perhaps I'm just sensitized by the amount of moderating that has been occurring lately. I would like to discuss some issues with you by PM but I would like to be assured by Ian and or the Mods here that private messages between site members are not monitored.

 

Note to Ian: Nothing subversive intended Ian here and no criticism implied re the site. I'd just like your assurance that private messages are just that.

 

 

[Bandit12]

I'm a reviewer for a medical journal and review stats and manuscripts and if an prospective author presented stats like those we would reject their paper without further reading.

Me too (ed psych not medical though) - if there is real data out there, it is not being shared publicly and what has been shared is neither valid nor useful. Not that I think Jabiru deserves a free pass here, but a little more transparency and a whole lot more quantified data would go a long way.

 

Anecdotally, I have seen a lot of mention about people approaching Jabiru with a failure, only to be told it was caused by poor maintenance or operator error. Has an alternative response ever been received?

 

 

[Bruce Tuncks]

"Tweak the cooling", heard that one before from Jab getting out of the factory setup being not good enough.Apparently you need full temp monitoring and then cardboard and sticky tape. And then your plane is no longer certified.

Not saying this wouldn't work, but its not the right answer from a certified supplier.

 

Andy (motz) is right; there is no way to baby through bolts. Especially when Jab says that their motors like running at full power. (Especially at run in)

The through-bolts, even the older small ones, don't need babying. At normal combustion max pressure the small bolts have a tensile stress of 157 MPa due to the combustion itself. The bolts are 270 MPa yield strength steel.

 

What you can't do to this or any engine is have detonation or pre-ignition or both. An air-cooled engine is more likely be run hot and this and/or poor fuel can cause detonation with 3 times the pressures.

 

Also, the detonation can be subtle, for example only happening in one cylinder for part of the time.

 

( Having said that, the new bigger bolts are stressed only to 115MPa by normal combustion, and would take a fair bit of detonation)

 

How can Jabiru be held responsible for the fuel and how the temperatures are managed?

 

On tweaking cooling systems, I personally didn't pay enough for the plane to have this sort of detail done by the factory.

 

My guess is that the latest fine-finned heads and latest ducts probably don't need to be tweaked, but the older setups did. The best reference for what to do is on the Limbach site, a German certified engine based on the Volkswagen.

 

Monitoring all the temperatures is obviously sensible, especially if you rent the plane out. And way cheaper than going to liquid cooling.

 

There are a couple of unhappy Rotax owners around here, it costs about $4000 for the regular ( 5 year) mandatory hose replacement job, even if the old hoses are good and the hours are low. (Now there is a sum of money a Jabiru owner can spend on monitoring. ) I'll soon be $12,000 ahead on that detail alone, which happens to be the sum I paid for my engine years ago.

 

 

[facthunter]

Going "thermo nuclear" doesn't tell me much. We have to get facts, and figures. I've seen temps rising and just lower the nose, which I would see as a "normal" operation . It was a 42 degree day, on one occasion.. On climb you should monitor temps and pressures. You have no cowl gills, so speed variation is all you have (or restrict climb)

 

The 180 degree is probably a POH recommended limit. Staying under it doesn't guarantee the engine will cop anything else wrong .. If you run the heads too hot the heat treatment is gone. You (or someone else) only has to do it ONCE.

 

If the heads cool too quickly then you are getting too much airflow at that point. ( Higher airspeed less power). There's not a lot of mass in a Jab head, so it's likely to be a persistent problem, IF it is a problem.. The heads are not at an even temp anyhow. The exhaust port would be a lot hotter than any other part, on higher power outputs.. If they are not cracking excessively, it is acceptable. Nev

 

 

[motzartmerv]

Not sure what your getting at there Nev?

 

Too much airflow on approach when doing a normal approach 6 or 7 times an hour, over hundreds of hours, not alot I can do about the extra airflow, all we can do is operate it inside the specs in the POH, ie, appch speeds etc. Again, this is sold as a a training aeroplane, if I cant do a normal cct in it for fear of the heads shrinking then I would argue its uselfull ness as a trainer .

 

We do ccts in all types, I think you have missed my point entirely. My question is " What is so different about a Jab, that it cant handle the treatment for which it was supposedly designed?"

 

Should I limit circuit operations in jabiru powered acft? Should I modify how we fly an approach? Fly out 5 miles and do attitude approaches on the power all the way in with a flat profile to keep heat in the heads?

 

Thermo nuclear means it had a runaway in CHT on one pot. Went to 230 deg's in a matter of seconds. The factory could not provide an explanation for this, nor could an independent assesment.

 

 

[Guest john]

http://jabirucrash.com/

The reports & images contained in this thread tell the whole story once & for all for CASA,RAA, owners & pilots of Jabiru aircraft & any new potential buyer interested in purchasing this type of aircraft.

Or in other words 'THE CHICKENS HAVE NOW COME HOME TO ROOST"

 

 

[Teckair]

OK, Jab did recieve federal grant money at some time in the past...or low- interest loans

I think over the years they have had a lot of tax payer money.