Oscar

No, not really - with the dowels, the larger bolts and the steel starfish arrangement, I am under the impression that flywheel bolt failure is now a rare occurrence - sufficiently so that one should be looking for a specific cause of this specific failure. The 'buried' reference is to the fact that a number of things could cause such a failure, including a bad batch of bolts, installer error, prop imbalance, an occurrence of detonation etc. - even someone hitting the starter while the prop is turning. If you have a close look at the photo showing the ring gear, there is a badly chewed-up set of teeth just to the left of the 6 o'clock position, with the tooth just to the left of the trigger plate looking badly bent and the one two further around appearing to have the top snapped off.

 

 

Yes, it's a PITA; with multi-point EFI and EGT monitoring mixture control, it should be possible to get very close to the button for all pots. If we didn't need to keep our beastie 55-reg I think I'd be looking at EFI right now; as I said earlier, the official (FAA etc.) attitude to electronic EFI seem to me to be based on 'possible' failure, rather than looking at the broader picture of relative likelihood of failure of the EFI in the context of the alternatives..

 

 

Oscar, if jabiru didn't change this bolts during overhaul then they certainly have violated their own manual. Install of that engine was as per the manual as all ways, inclusive of the propellor. The environment at Nowra is very corrosion friendly and that level of corrosion is not uncommon.

Absolutely agree, new bolts are the requirement in the repair manual. There has to be a reason, but perhaps it is just buried somewhere.

 

 

Russ, a Part 21 engineer can do this for you, though you may have to use a TSO'd device ( though I'm no expert). However, I believe that RAA is examining the whole 'who can authorise mods.' thing and there may be some changes in the not too distant future.

 

 

One would certainly hope so! Did Jab. do the overhaul? It just seems strange that there is so much evident corrosion on those specific bolts; I'd assume that you get a fair bit of sea air at Nowra, but there surely has to be a reason why those bolts only have that evident problem. And you're absolutely correct re the prop bolts - was the prop installed with the beleville washer pack? Of course, the other known cause of flywheel bolt shear is detonation, and if the bolts were on that engine when it broke the through-bolt, they'd have likely been cactus..

 

 

Those flywheel bolts look very suss to me - why the corrosion on them and not on any of the other bolts on the flywheel? Were they possibly re-used and originally from a flywheel that did not have dowel pins, and thus quite possibly cracked before they were installed?

 

 

JJ, absolutely correct, the hoops that have to be jumped through to get any form of certification are not for the uncourageous..

 

Your distribution problem is interesting, but of course totally known with Jab. engines. I think - but am in no way sure - that there were some tweaks to the intake plenum done some time ago, but again, Ian Bent will have the answer. Whatever HAS been done to get even distribution can't be just a one-off result, has to be repeatable - but the trick is, as always, knowing what has made the difference!

 

 

Certainly, a very professionally done and attractive kit. If it were me thinking about installing one - and I'm very pro the idea - I'd be having a long chat to Ian Bent though first,simply because he knows better than anyone how changes do/can affect the engine in ways that may not be foreseen by anyone without his depth of knowledge. The old adage that a silly question costs less to answer than a silly mistake costs to fix applies here, and I am a firm believer in the principle of 'do it right and do it once'. If everyone who installs a CAMit engine communicates effectively with CAMit, then we'll all benefit from the rapid accumulation of knowledge about how to get the very best results and I for one would trust CAMit to provide the best distilled wisdom they can muster from users, which will be a far better and more reliable channel than 'paddock gossip'.

 

 

I'm sure the billet 'cases on the jabiru are not as good as the cast* cases on the 914... everyone knows castings are better than billet *Rotax use die castings, which inevitably suffer some degree of inclusions and shrinkage stress.

Rudi's mob (at Sale) have a much better weld repair process, but these days CASA couldn't handle extending the approval to Rotii, even if Rudi were willing to have a go (he might be?).

From what I hear, Rudi is pretty much out of the game these days - but my info. is not authoritative there.

 

 

Given the odium heaped on Jabiru engines and customer support by certain forum members over a considerable period and the upholding of Rotax as a gold standard for both, this comes as somewhat of a reality check...

 

 

Not necessarily a reason for universal rejoicing. This could add weight to the judicial idea that recreational aviation is 'an inherently dangerous sport' and until the ramifications of that are teased out and evaluated, I think we should be cautious. I can certainly see some potential downside in terms of insurance rates and airspace access, just for openers.

 

And as Turbs has said, it removes the defence for training organisations that they have operated according to the mandated standard so any situation potentially becomes a candidate for litigation.

 

This could well turn out to be a case of 'be careful about what you wish for'..

 

 

Dodo, I used to fly gliders from Polo Flat until we were squeezed out; it's not a bad spot at all. I think Mike Apps has a school there?

 

Currandooley very limited on height (used to be 1500 top) and I think is now a wind farm anyway.

 

 

The technology available to the common man has streaked ahead of aviation, which is burdened by an overly-conservative attitude. We should be able to replace magnetos, carbies and brick-sized transponders with more efficient and more reliable equipment.If CAMit could offer a good simple EFI option they'd have to expand the factory.

It's a pretty damn good size of factory... some of the CNC machines are bigger than the caravan park unit my co-owner and I were staying at when rebuilding our engine at CAMit, and we had separate rooms..

 

 

Why not keep the carb as a backup?Phil.

Yep, that's an option - you'd need to have two fuel systems though, one for the high pressure to the injectors, one low pressure to the carby. That's do-able, it's just a question, I think, of working out the best option(s).

 

Carby,s etc, have served us well for umpteen yrs, why go and complicate things. "EFI" was in part, to lessen pollution, to increase power etc, we are bound by regulated max weights, and the 80.........120 hp most use, does the job just dandy.My gyro is "EFI" , prob is, the slightest hiccup, is a nightmare to trace.....and folks can get a head shake from workshops because it,s an aeroplane install, they want nothing to do with it.

Carby,s .....easy as.

 

As to "limp home mode" if the ecu is not happy with a sensor input, limp home is about 20% power......at best. Yet to see aviation get you home on 20% avail power.

 

Keep it simple is my preferred.

I suggest that for peace of mind, one should assume that any problem with the primary fuel delivery system should be considered 'total loss', and a secondary system should be independent of the primary. We're getting reports of the 912 EFI system being a right cranky thing despite being dual-channel (or whatever they call it). No doubt Rotax will get that sorted, but my experience of 'German' (ok, they're Austrian, I know, I know) engineering is that it tends to assume that a 'clever' approach is preferable to a simple if less efficient one. Just a general observation from having worked on Porsche, BMW and Mercedes cars, a little bit.

 

Going EFI is a value-judgement thing. There are undeniable benefits from using EFI: better fuel consumption ( i.e.: more range for the fuel load at MTOW), automatic compensation for varying fuel quality, even mixture supply to each pot, no icing problems. All of that makes for less engine management stress on the PIC and a happier life for the engine. There is a huge amount of experience now of EFI systems - I suspect that the incidence of EFI problems in motor vehicles is extremely rare in normal use. Is there ANY new, or recent, motor vehicle on the market that still uses carbies?

 

I grew up with carburettored cars, raced them and worked on them for many, many years. One thing I can say with some confidence is, that IF you have a problem with a carby - say, a needle circlip breaking, a slide jamming because of an errant strand of wire in a broken accelerator cable, a return spring breaking etc. - from an aircraft POV, you're on the ground to fix it just as much as you will be if the motherboard for an EFI system goes to Silicon Heaven. I know that I don't have the skills to diagnose and rectify problems with an EFI system whereas I think I do for most carburettors (well, Weber, Dellorto, Solex, S.U., Rochester and Holley, anyway - Bing is an adventure yet to be traversed), BUT: I'm not going to fly any more happily over tiger country with an engine with any of those attached, as I would with an engine with an EFI system.

 

Why? - simply because there are too many factors that can contribute to an aero-engine ceasing to turn the whirly bit out the front reliably anyway - of which an EFI system would be just ONE. I'm a glider pilot by experience, I don't trust noise to keep me aloft.

 

If one assumes that the noisy thing can cease to be noisy for any one of a considerable number of reasons and flies accordingly, then the EFI vs. Carburettor argument comes down to expected failure rate vs. advantages in non-failure mode. I believe that a decent EFI system has advantages that are seriously worth considering, and with the caveat that one should NOT assume that an EFI system will never fail, those advantages may well be very attractive.

 

 

Pretty easy and cheap to use an entirely self-contained back-up using a megasquirt with one or a pair of suitable injectors in the plenum chamber, and I'd be surprised if you couldn't get decent duration from a simple and light LiFePO4 battery ( less than I kg). Plus, you can carry a spare injector for the main system for en-route replacement..

 

 

JJ, CAMit are working on a combined upgraded oil pressure relief valve (a known finicky area on standard Jab engines) with a TOCA cooler take-off; I'm not sure whether it is in production status yet but it's certainly on the way. Ask Ian Bent at Natfly... Once again, it's a likely benefit of CAMit's research that will have 'flow-on' benefit: the requirement for extended idling to get the oil temp up initially will be significantly cut, and thus the possibility of one side of the engine not getting decent cooling airflow if you happen to be holding in a cross-wind situation will be - at least - reduced.

 

The possibility of an efi system on Jab engines is also tantalisingly closer than one thinks; I've seen a set of intakes with injector holders on them (ain't saying where..) on an engine destined for drone use. The intransigence of the authorities to accept that the possibility of modern electronics failing is, on balance, less of a general risk to flying than the problems of not having an efi installed is a bitch, in my opinion. Remove carby icing problems AND mixture control problems in one fell swoop just has to be (I think) a positive trade-off for the apparent vulnerability of electronics to electricity power supply issues, and it should be possible to provide independent back-up power to keep injectors running using a LiFePO4 battery for little weight and complexity. The progress here is likely to be slowed by convincing 'authorities' to accept a solution rather than any difficulties in actually producing a decent system.

 

 

It certainly sounds attractive, but in practice I believe you need to design the engine from the start for one type of cooling or the other. A hybrid - and obviously a Rotax is a hybrid - needs to have both efficient barrel cooling AND efficient head cooling in the form of a radiator (or heat exchanger), plus oil cooling, all integrated into the design. So the cooling airflow requirements for all three components need to be considered; and if there is a water-cooled element in the equation, a form of pump to circulate the water. There will be a weight and cooling drag penalty for the additional water-cooling element, plus an additional mechanical complication element: hoses, pump, heat exchanger. To do the job properly, you'll need to substantially revise the 'old' cooling airflow arrangement to both provide decent barrel cooling and a sensible airflow past the heat exchanger - while not affecting the oil cooler operation..

 

If you add weight to the engine and the FWF installation at the front of a Jab., you may well need to add more ballast at the tail to keep the c/g range the same, so it's not just the added weight of the engine and heat exchanger that counts. That MAY affect the stall speed, so proper performance testing to ensure the POH is correct MAY be needed.

 

All do-able, at a cost. Not an option for non-certificated LSA aircraft I believe ( i.e. for Jabs. that are not 'C'-registered 24-aircraft); may require an Experimental certificate and the requisite hours of flight for unrestricted operation.

 

All of which is not to say that it isn't a viable option. However, if there is a simpler way to go that is comparable in results and better in cost and the CASA etc. embuggerance factor, which to choose? What we need here is for someone to actually do the LCH conversion and report back on the details and cost of the project.

 

 

Andy - if more people would actually go through the exercise you are going to do with (I assume) Keith Rule, I am personally quite sure that there'd be a far better body of information out there for all Jab. owners. Perhaps, when you have the results, you can share them - maybe on the 'Jab Cooling' thread?

 

The whole question of whether Jab. engines are 'fit for purpose' or not, is absolutely open to debate. Jabiru, of course, maintain that they are - if operated within the prescribed limits. I think it is a fair proposition that Jabiru is prima facie correct in that assertion; they have testing that demonstrates compliance within the standards required. However I think it is equally a fair proposition that the prescribed limits are damn difficult to adhere to and it is frankly too fine a tolerance for 'reasonable' operation. If we are to assume that most owners do NOT willfully operate outside limits and make their best efforts to fly conservatively, (people who continue to use their engine with one pot without compression when cold excepted..), entirely too many owners are experiencing problems they simply should not be having. I would agree with you that there are deficiencies in the current Jab. engines that are unacceptable for operation in real life, where factors that are outside the control of the operator (such as variations in fuel quality) mean that damage occurs through what should be expected minor transgressions of the 'prescribed limits'.

 

Ask any aero-engineer involved with engine performance testing and you will be told that cooling airflow performance for air-cooled engines is one of the most difficult areas for design and certification. It looks simple: stuff enough air past the barrels and heads, and it should be ok. It just doesn't work like that, and worse: what may look efficient, may in fact not be. It's arcane science at its best: you need velocity, distribution, lack of stagnation points, heat transfer rates etc. all to align.

 

From what I have seen of the CAMit mods, they will build in a very considerable improvement in tolerance to operation a bit out of limits to the standard Jabiru engine and they will resolve a number of other problems not directly related to cooling performance. However, it would be ridiculous to suggest that any mods to the engine can negate a fundamental fault in the cooling airflow, so the exercise you are currently undertaking is of great value.

 

I guess that I'm expressing an article of personal faith here, but my co-owner and I have put our money on the line that the combination of the CAMit mods plus attention to the whole cooling airflow situation - to be developed through testing - will give us an engine we are happy to fly behind and will more than repay the upgrade costs for the engine. We have a lot of airframe work to do before our wee beastie gets back into the air, but I will be posting our findings. If you can help with providing information about your cooling airflow tests, I believe we can all contribute useful information, out of which hopefully will come a 'profile' for Jab. / CAMit modded Jab. engines to deliver the sort of performance all owners hope to get.

 

 

I would seriously suggest that the best sort of person to talk to Ian and 'report' back is someone who has worked on Jab. engines and has a decent amount of experience with them. The reason for this is, if one has the necessary level of technical knowledge and some detailed knowledge of Jab. engine-specific problems, Ian Bent can talk through the causal chain he has discovered for the problem and the measures he has adopted to address those - and in many cases, it's not just a seemingly simple cause but a 'set' of circumstances that need to be understood.

 

For instance, with the through-bolt issue, we've seen in various threads (no pun intended here!) people have talked about the size of the bolts, the type of thread (rolled or cut), the nuts, the material etc., some with high levels of conviction that they have found the 'smoking gun' and an apparently simple change would resolve the problem/s. Ian Bent can discuss every aspect of through-bolt performance (or failure) and explain all of the factors and why each one is important - right down to the actual disposition of thickness at varying places along the length of the bolt. It all makes sense to someone who has seen first-hand the types of failure that occur, because the 'simple' and seemingly apparent answer is not necessarily the correct one.

 

 

Then you'd better not go to Natfly (or send a mate there) and ask Ian Bent about the engines directly, because there's stuff I haven't mentioned that he's been working on that will be chocolate sauce and M&M's on top of the ice-cream...

 

And especially don't take a camera /send a mate with one to take piccies of anything Ian Bent might put on display...

 

 

Camel, as with quite a lot of debates, there is much truth on both sides! Your point that good basic flying practices that manage temps (and shock cooling too, completely agree) is essential to get a decent life from any engine - it's useless to know what's going on if one doesn't ACT on that information. And the manufacturer's recommendations aren' ALWAYS correct: Steve Wittman used to rev his small Continentals way over the recommended and pretty much always got good life out of them. However: he had a wealth of experience on which to draw.

 

The Jab cooling thread: http://www.recreationalflying.com/threads/jabiru-engine-cooling.112581/ is very instructive about just how 'finicky' and non-intuitive the whole cooling thing can be, it's worth reading. The obvious point about that is that without the information feed, one doesn't really know what is going on; I doubt that most people need to fly with their eyes glued to the gauges once they have the 'profile' of what happens established - but you can't get that established if you don't have the basic information. Jabiru themselves say clearly that one shouldn't make modifications without a full set of gauges, and you can bet that came from experience as they developed engines and cooling mods.

 

The thicker barrel bases on the CAMit barrels are a bit more subtle in effect than just 'not breaking off': what happens with the thinner bases is they bend under extreme load (especially detonation) and act as levers to magnify the force on the through bolts. If you look at used cases, you will frequently see indentations from the outer edges of the barrel flange imprinted in the cases from this effect, and it's that extra load that overstresses the through bolts. CAMit have taken a belt-and-braces approach to the whole through-bolt problem: increasing the size of the through-bolts, changing the nut base profile so full torque is applied to the barrels without introducing bending in the through-bolt shank at the nut AND eliminating the base bending problem (maybe that's belt-and-braces-and a spare belt as well!). Being CAMit, they've actually gone even further: by a complete re-design of the through bolts and the removal of the case dowels plus a new case joining technique, they've addressed two causes of case fretting - thus getting what one might consider to be 'triple-duty' of good effect from what at first blush appears to be an answer to just one problem: the through-bolt strength issue. It's that sort of thoroughness of approach that, when one has it all explained, gives one great confidence in the potential of the CAMit mods.

 

 

Camel, I'll bet your engine loves you and hopefully it understands just how lucky it is, but I'm absolutely with JJ on this one. There's decent evidence that chts can vary by 10C or even more (take you pick of how much of that is a result of minor variations in cooling airflow and how much uncalibrated CHT probes). Once you have actually established the cooling temp profile under use, then you will (as an obviously mechanically empathic person) know what's likely to be happening in the engine from one sensor BUT you need to be the sort of person who runs an 'engine performance' channel in your thought process (some people just do that, many don't).

 

The problem for most people in trying to do the best engine management they can, is the range of variables they need to reconcile all the time. For instance, we know that at different engine intake airflow rates, the mixture can vary considerably between pots - a full set of EGTs will show that up. I've seen the results of the Jab. installation on a motor-falke motor-glider and the nearly 18 months of testing, adjusting, testing again etc. just the intake tract airflow to try to get even temps at the 'normal' rev range, and even as little as 50 rpm. change on climb could make an appreciable difference to the distribution of temps between pots. Does it matter? - hell, yes; if you for instance get a 'bad' batch of fuel and happen to hit a particular intake velocity situation (basically, revs and load on the engine) that tends to send one or two pots high but not the pot with the cht/egt, you might never know that one or some pots are being hammered.

 

When idling in a crosswind, it's possible to get cooling airflow reversal from one side of the engine to the other, so one side can be doing just nicely, thank you, while the other is rapidly cooking. It doesn't take many minutes for that to become critical for damage. A full set of chts will alert you to that problem.

 

Finally, we also know from information supplied by Jab. engine users that seemingly insignificant changes to the under-cowl arrangements can make quite a lot of difference to cooling airflow, so if you change anything around (such as an oil-cooler hose routing, for instance) your previous experience of the engine may not provide you with the necessary information as to how it is faring after the change. A full set of chts will give you that information.

 

Finally, by having only a single cht and egt, you are relying on your previous experience that future situations will conform to the 'known' because you are applying the engine management techniques that have served you faithfully. That, of course, flies in the face (little aeronautical joke there..) of the Harvard Law:

 

Under controlled conditions of light, temperature, humidity and nutrition, the organism will do as it damn well pleases.

 

OK, I'm being a little bit facetious here. We know that some Jab engine owners consistently get excellent lives from their engines and others conversely get repetitively poor lives. Good management technique simply HAS to be a factor, it's not just a lucky-dip (though it has also to be recognised that some Jab engines just aren't up to scratch). I am rebuilding a very old Jab that has had hard use all its life, and the log-books show it has had a bad history of engine life - but I can say that other evidence from the airframe shows incontrovertibly that it has been subject to bodgey maintenance and extreme hard use. If you did not access the engine records and just looked at the airframe evidence, you'd expect the engine story to be less than wonderful..

 

A full set of cht and egt's will report the condition under operation for every pot. A fairly low-cost installation of full monitoring, out-of-limit warning and flight recording (we're looking at the MGL Extreme EMS for this) is less than the cost of a top overhaul and could easily save you that cost at 400 hours for an 'abused' engine vs. 1000 hours for a 'managed' engine. Plus which, it could save you having to recover your downed aircraft from the middle of buggery...

 

 

Yes, the whole NBN thing is a bloody mess. Anybody who thinks it's all about fast movie downloads has the cow by the wrong teat. The engineering company I consulted to, calculated the real cost of a one-day outage; with just a central office staff of around 65 engineers, it came to over $250k PER DAY in lost chargeable time - and that was 10 years ago.! With four State offices and two overseas ones, the nightly back-up across the network was over 3 TB (each office backed-up to servers in another office for data security reasons). For some of the remote projects, poor communications options had people flying once or twice a week to their nearest State office just to lodge their back-up from hard memory devices.

 

 

All routine administrative processing that is reportable electronically and requires only manual checking of some elements (such as the actual information content of photos) can be done in a virtual office situation.

 

It can be more difficult to work up policy that requires multiple inputs simply because the written expression of ideas etc. is not always immediately clear between different members of a group and version control of documentation often requires considerable juggling to ensure everybody is reading from the same, current version of the song-sheet; electronic conferencing is often the quickest way to achieve a consensus when one is required.

 

Once you have worked in a (properly-organised!) virtual office situation, you will never want to go back to a 'traditional' office environment because it is clumsy, slow, and far less efficient. The only caveat here is the absolute necessity for high-quality communications access - and I'm talking fibre-to-the-site between sites. It also requires some training in effective use of IT and a good network manager.

 

 

Comp, may I suggest a call to Ian Bent at CAMit, I think he has (or will very shortly have) some very encouraging news for you, if the 'C' in 170C means the Certificated version as per the 160C and therefore may be modified under an EO from a Part 21 engineer. Incidentally - and I am NOT a LAME so this is only an observation - if your engine was seriously cooked, I'd talk to a Jab engine specialist before doing just a top-end overhaul, you may need to split the cases and re-do the silastic, and also possibly replace the through-bolts and nuts.