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Yenn

Jabiru mixture

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Doesn't make sense to me. The cost of labour to strip an engine, AND NOT replace All wearable parts, is a waiting game, as it Will need those parts replaced at a later date. !.

O K if owner is doing the work & not counting their hours of labour.

Who on the old Ford / Holden motor's never put new "valve stem seals" in their motor as the old ones never gave trouble,?.

spacesailor

Most engines had/have their own component cycles.

The example I gave was one or two valve grinds before the complete pull down, and what I said was the valve grinds were not TBO.

Another might be an exhaust manifold cracking every 250 hours; on which case you'd probably fit a new one every 200 hours (the "on-condition" which both Facthunter abd CASA mentioned), but you'd still run the engine out to its specified TBO, and you wouldn't use the cracked manifold to suggest the engine "didn't make TBO" as someone was doing to make a comparison with a recreational engine.

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Just a mo, I read this & assumed the writer was correct.

" "Every engine must be totally disassembled and the wear and tear of each part evaluated separately" (Source: Sapling.com)".

Each part"evaluated" If spending tens of thousands of dollars. I would expect NEW parts. Not IT'LL be allright,!.

I don't know "Sapling . com".

spacesailor

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Doesn't matter whether you agree with me, you have to agree with CASA, and this CASA definition is pretty much the same as the one I gave you

"Time Between Overhaul (TBO), which specify how long they consider their product should remain in service. These recommendations are based on average utilisation and conditions and usually recommend that the item be fully stripped and returned to the original specifications. "

 

The CASA definition came from this link which has more information on TBO

AWB 02-1 Issue 1 - On-condition maintenance

 

Ha ha! Good Joke!! bureaucracies may force regulations on the public but when it comes to keeping up with changes in technology/expectations, they are more often than not, way out of date.

Purchasing power will ultimately dictate what engines are bought. The consumer will purchase engines that have proven reliability/minimum in service cost, not what CASA or any other bureaucracy define TBO as.

Routine major surgery/component replacement (read $$$$$) will never be accepted where alternative lower cost/hr options exist.

 

This debate started around Jabiru's - You purchase a cheap engine, then over multiple short intervals, change out all sorts of "bits" and its still within TBO!!!! ???. The analogy I would use is that of "Granddad's Axe" - all original, every part has been replaced but its still Granddads Axe .

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I don't know "Sapling . com".

No problem, just go to the other link from C-A-S-A

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Operators are not fools. If a POT fails on a low hours motor you just FIX it as long as it hasn't affected the motor generally. Nev

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If a manufacturer claims it is a normal maintenance exercise to rebuild heads and reseat/replace valves and valve seals in 2019 before tbo, they are abusing the definition of the term "tbo" as an excuse for a poorly designed and/or manufactured engine.

These problems were sorted long ago with modern metalurgy, casting and machining techniques.

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Operators are not fools. If a POT fails on a low hours motor you just FIX it as long as it hasn't affected the motor generally. Nev

Fair enough BUT if a high percentage of "pots" on this series/mark of engine fail, it becomes a routine maintenance item to keep a poorly designed/constructed engine in the air - to me this engine has failed to make projected/claimed TBO. In effect it becomes Granddads Axe - a con!

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You are not really listening. . that's your privilege.. Nev

I'm with Downunder on this - Your privilege to stick with an outmoded & potentially costly concept of engine service life (is this whats called a tradition?)

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I'm with Downunder on this - Your privilege to stick with an outmoded & potentially costly concept of engine service life (is this whats called a tradition?)

I don't think you're wrong and I don't think Facthunter is wrong just your English practical history vs ours where the heat and dust factors changed our attitude to service. Also you are correct on today's liquid cooled auto engines where no internal repairs are expected during ownership and most will exceed 500,000 km and many 1,000,000 km without a full rebuild, and Facthunter is correct on aircooled aircraft engines where fuel standard plays a major part.

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A

I don't think you're wrong and I don't think Facthunter is wrong just your English practical history vs ours where the heat and dust factors changed our attitude to service. Also you are correct on today's liquid cooled auto engines where no internal repairs are expected during ownership and most will exceed 500,000 km and many 1,000,000 km without a full rebuild, and Facthunter is correct on aircooled aircraft engines where fuel standard plays a major part.

 

A win win then - however me thinks that those that accept such costly & involved replacements as routine maintenance are 1. failing to recognise that technology can, if applied, give much longer intervals/reliability between overhauls and 2. in accepting this maintenance model from manufactures, are accepting an on going cost structure designed/or evolved to benefit the manufacturer.

 

Air-cooled engines (particularly petrol) will probably always suffer from wide operating temperature issues that will impact on wear , tolerances, life span, etc - liquid cooled and oil cooled (BMW) engines have been around for ever (proven benefits) but somehow aviation is stuck in this comfortable air cooled rut.

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Comparison between an aero situation and a road engine doesn't really cut it. The "Problem " with the aero engine is weight must be the absolute lightest possible and other variations to operating environment and installation that are hard for the designers makers and rule makers to manage. It's a totally different design now being aircooled which is still probably the most reliable and cheapest for the operating environment. IF you put it in a car it would be a joke. (noisy mechanically hard to cool and not a high revver or high HP/Litre. but in a plane it's still the best concept unless you go turbine which is also not good in a car, expensive and thirsty.

Every possible bit of metal is pared from it , (or it's too heavy) and it runs in a totally different environment to a car engine which spends most of it's time loafing is invariably liquid cooled and built stronger, is capable of very high revs and managed by microprocessors and often VVT. It's intake air is heated and well filtered. it spends long periods near idle and cruising at low revs and power. An auto engine with faults can continue on for years and drop a lot of power and still go back and forth where the Aero one has to stay completely on song and deliver full power on every takeoff, RELIABLY right up till the time you remove it for overhaul. It starts each day on full power and then nearly full power climbing to cruise at 75% power without let-up till descent.

To make it worse the aero engine is never going to be high volume so will have a high labour cost % and should be user friendly as to fault diagnosis in a country as big as this one is, (which is nothing like Europe with its access to servicing. and survive intermittent usage in a realistic way.. Plenty of plane engines get treated as badly/ neglected as lawn mowers at a time when the average person is less mechanically savvy than 80years ago.. Cars are disposed of in a relatively short time frame these days so the innards of the motors hardly ever get disturbed. They are not designed for rebuilding at all, with heads that don't allow for resurfacing as it upsets the engine dimensions and you buy a new one or wreck the vehicle. They are literally throw away and a major engine fault is a vehicle write off same as a significant shunt. Nev

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So whats your explanation for the liquid cooled aero engines that 1. are still with us ? 2. have come & gone?

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Makers are free to do what they think will work in the market . That's their choice... IF it's an auto conversion chances are it will be liquid cooled as you won't find an aircooled one easily that's current... No one is suggesting the 'task" is simple. Many have failed including Porsche and Bugatti.

Simplicity, reliability, light weight and price are the main factors.. I believe the engines have to be designed specifically for the task with good support from the factory assured for many years. Adapting something else has severe drawbacks. like hard to mount properly and the prop drive and the inevitable reduction gear needed is a design critical part. Using parts of the engine from the current market (piston valves. conrods etc compromises the whole design concept and eventually is not available as the source product becomes obsolete and is usually compromised as to suitability from the beginning.

Liquid cooling has to be justified as it's more costly and adds complexity. .For higher specific output for capacity (BHP/ Litre) engines or multi (4 valves /cylinder) heads it's virtually mandatory and also entails going back to the REQUIRED reduction gear to use the higher engine revs on a normal prop . For fuel efficiency you don't need high revs. Friction squares when you double revs.

Building a complete complex high rpm engine in low volumes for U/L use is probably assured of market failure This leaves the ONLY likely source as an adapted automotive engine and a few of those have been tried with some limited success. I also find high RPM engines tiring on a long trip. and more likely to have sheet metal accessories/ rigid pipes, crack and screws coming undone from vibration. A liquid system has to have a higher pressure cap for higher altitudes as it works on a differential and the boiling point lowers when the pressure is lower .Nev

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Makers are free to do what they think will work in the market . That's their choice... IF it's an auto conversion chances are it will be liquid cooled as you won't find an aircooled one easily that's current... No one is suggesting the 'task" is simple. Many have failed including Porsche and Bugatti.

Simplicity, reliability, light weight and price are the main factors.. I believe the engines have to be designed specifically for the task with good support from the factory assured for many years. Adapting something else has severe drawbacks. like hard to mount properly and the prop drive and the inevitable reduction gear needed is a design critical part. Using parts of the engine from the current market (piston valves. conrods etc compromises the whole design concept and eventually is not available as the source product becomes obsolete and is usually compromised as to suitability from the beginning.

Liquid cooling has to be justified as it's more costly and adds complexity. .For higher specific output for capacity (BHP/ Litre) engines or multi (4 valves /cylinder) heads it's virtually mandatory and also entails going back to the REQUIRED reduction gear to use the higher engine revs on a normal prop . For fuel efficiency you don't need high revs. Friction squares when you double revs.

Building a complete complex high rpm engine in low volumes for U/L use is probably assured of market failure This leaves the ONLY likely source as an adapted automotive engine and a few of those have been tried with some limited success. I also find high RPM engines tiring on a long trip. and more likely to have sheet metal accessories/ rigid pipes, crack and screws coming undone from vibration. A liquid system has to have a higher pressure cap for higher altitudes as it works on a differential and the boiling point lowers when the pressure is lower .Nev

I agree with "reliability" would change "light weight" to high power to weight ratio and of course the consumer will shop for the biggest bang for his/her buck (cost).

Yep! engines must be designed for the task(s) and we all hope that our engienes will continue to have factory support for years to come (that's where they make a lot of their $$)

In general I do not advocate auto conversions BUT there is much the aviation engine industry could learn/adopt from this area.

The KISS principal in all things, is an admirable philosophy but should not block development where an acceptable increase in complexity has significant "payoffs" in efficiency, longevity, etc

You may not NEED high rpm for fuel efficiency but looking at the automotive market would suggest otherwise - is it not about volumetric efficiency rather than capacity??

"Building a complete complex high rpm engine in low volumes for U/L use is probably assured of market failure " - Soooo the Rotax 912/914 range is a market failure then ??

"high RPM engines tiring on a long trip. and more likely to have sheet metal accessories/ rigid pipes, crack and screws coming undone from vibration" - my 912ULS is almost turbine smooth way better than the LyCons I used to drive.

"A liquid system has to have a higher pressure cap for higher altitudes as it works on a differential and the boiling point lowers when the pressure is lower " - sounds logical Nev but again my 912 uses a Ducati motorcycle radiator cap (as specified by Rotax ) cant recall its pressure rating but so far it has done the trick in the Australian environment (I may have sneaked up over 10K on occasion) & seems to be okay to fly over the Rockies/Alps without adverse comment.

 

I put this to you - the the market has never been entirely free - all to often the buyer has been "educated" (brainwashed) by marketing to accept a certain product. Sometimes the old product is spiffed up, repackaged , some trendy and unlikely terminology applied, all to convince the buyer he/she is getting the latest & greatest. Often the objective is to have a long (read unchanging) production run, to maximise profit (retooling etc) manufacturers will try and bluff the consumer with hype. I believe this is especially prevalent in GA level aircraft industry which it so happens is dominated by a super conservative Uncle Sam. I wish I could offer a constructive solution but when the USA dominates a small international market , we have no choice other than to go with the man. (Go Austria/Rotax!!) In the economic war between the USA & China we may benefit/or not somewhere down the track.

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Stick with your Austrian solution , you are unlikely to change. A complex High rpm engine is not a Rotax 912 type. . That particular engine is a push rod two valves per cylinder engine that was the best (in it's then 80 HP form) by a mile compared with what else was available when it was introduced now many years ago.. It DOES have some issues and is nowhere near a perfect motor as there's no such thing.

. USA does most of the light aircraft flying in the world and aviation people generally are a little more educated than you give them credit for. Stuff has to stack up out there in the field. where it's an open book as far as information is concerned. for those who care to look. It's never been really easy to get FACTS.. .

The flying scene is always ready to look for new ideas. Always has and that's the nature of it. Just because a modern Lycoming looks like one of it's ancestors doesn't mean any of the innards has remained constant during that entire time. Four cylinder flat motors don't get close to the smoothness of the six cylinder versions but the smaller ones are inevitably fours.. Maintaining quality control is always a difficulty where parts supply is farmed out for any manufacturer. Going liquid cooled is the big consideration. for the aero scene The Rotax is PART liquid cooled . Four separate heads cooled only. A lot of extra complexity just for that aspect of it. So is the awkward dry sump oil system where they chose to not have a scavenge pump to return the oil. but rely on engine blow by which pressurizes the engine itself to do it... Wet sumps are perfect for flat engines. Nev

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So is the awkward dry sump oil system where they chose to not have a scavenge pump to return the oil. but rely on engine blow by which pressurizes the engine itself to do it... Wet sumps are perfect for flat engines. Nev

 

I don't understand your obsession with the 912 oil system, it is a simple system that has worked well for 25 years. Crankcase pressure never fails and costs nothing. The reason they would have done it is to reduce the depth being a geared engine, also the pilot has to pull the prop thru each day that can't be a bad thing.

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A complex High rpm engine is not a Rotax 912 type. " I dont think its particularly complex but compared with your "usual" aircooled direct/ drive, it is marginally more complex and definitely high (factor of 2.1 I think) faster than your run of thew mill LyCon and still faster than a Jab.

 

"It DOES have some issues and is nowhere near a perfect motor as there's no such thing". Agreed its a mechanical device it will have problems but I think we are making comparisons her and for my money the ([email protected] range seems to be less troublesome than the Jab and proabaly the pot changing LyCon's.

 

" ............aviation people generally are a little more educated than you give them credit for......." I doubt that the marketing /propaganda people care a jot for/education or intelligence - we can all be influenced and very easily. Just look at the political BS currently on show or the suicide bomber who has a pHD.

 

" The flying scene is always ready to look for new ideas. Always has and that's the nature of it" - generally true in the past however, in recent times, the baton of innovation seems to have been taken up by the experimental amateur..

 

"Just because a modern Lycoming looks like one of it's ancestors doesn't mean any of the innards has remained constant during that entire time. " - what are we looking at here 70 plus years of hidden development. Your pulling my leg. Not saying there have not been refinements but compared with the auto world (I know its unfair but what other comparisons are there?) they have been at a near standstill.

 

"Four cylinder flat motors don't get close to the smoothness of the six cylinder versions but the smaller ones are inevitably four"s - why have 4's why not 3' & 5's?

 

. Maintaining quality control is always a difficulty where parts supply is farmed out for any manufacturer - excesses!.

 

" Going liquid cooled is the big consideration. for the aero scene The Rotax is PART liquid cooled" - so?.

 

"Four separate heads cooled only. A lot of extra complexity" - I agree on this point. One liquid cooled head/barrel (2 cylinders) per side would likely be a better way to go.

 

"So is the awkward dry sump oil system where they chose to not have a scavenge pump to return the oil. but rely on engine blow by which pressurizes the engine itself to do it... Wet sumps are perfect for flat engines" - you may not like it (it's very KISS) but its stood the test of time and gives flexibility of oil reservoir and cooling location that may be limited with a wet sump design (just speculating)

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There are several things from Austria beside Rotax engines: Adolf Hitler, Arnold Schwartzenegger, the sound of music and Glock pistols. I can give them all a miss.

As for Rotax engines, they have mandatory CALENDAR replacement intervals on various expensive bits. So regardless of condition, you need to spend big money replacing things or be illegal.

And turning the engine over in the morning until it gurgles takes quite a long time and you don't feel much in the way of compressions because the gear reduction interferes with the feel.

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There are several things from Austria beside Rotax engines: Adolf Hitler, Arnold Schwartzenegger, the sound of music and Glock pistols. I can give them all a miss.

As for Rotax engines, they have mandatory CALENDAR replacement intervals on various expensive bits. So regardless of condition, you need to spend big money replacing things or be illegal.

And turning the engine over in the morning until it gurgles takes quite a long time and you don't feel much in the way of compressions because the gear reduction interferes with the feel.

 

Guday Bruce - where on Earth did you get all that from. I cant speak for certified Rotax engines, however I have had the pleasure, reliability and economy of using AND maintaining, by the book, a non certified 912 ULS for the last 10 year's. Leaving aside your totaly irrelevant tirade against Austria, lets take your Rotax 912 statements one by one:

 

"Rotax engines, they have mandatory CALENDAR replacement intervals on various expensive bits." - True! for certified engines but only recommendations for non certified like mine. However I go by the book so do the calendar maintenance -

5 year rubber replacement costs me about $6-700 to replace All rubber components associated with the engine (except mounting blocks) and I go over the top with higher specified tubing than required.

100 hr or 12 month (annual) service whichever comes first. Basically an oil & oil filter change, intensive inspection (addressing any issues that are found such as an air /fuel filter clean, etc) not much different to any other aircraft engine. Cost: Engine oil $45 +oil filter $20 + sundries lets go over the top $50 for a total of $110

There will be a gear box inspection at 1200 hrs but I haven't got there yet. Soooo no cost at this time. This is NOT a calendar requirement but I do expect it to be costly$$$

I have replaced the Sprag Clutch ($1300) again not a calendar matter and in my case probably as a result of not understanding the implications of using weak batteries and a poor starting technique - not everyone will experience this and later engines have been fitted with "soft start" systems that will further reduce the occurrence..

"So regardless of condition, you need to spend big money replacing things" - Do you mean the aforementioned 5 year rubber replacement, and/or oil filters, spark plugs all of which have engine hour replacement recommendations ?? hardly in pristine condition after the specified in service interval and as indicated quite reasonably priced (if you do it yourself).

 

"or be illegal". - As I said my engine is a non certified unit, so I cant be 100% sure, but I dont think legality comes into maintaining it at all, just a love of life (no wish to cark it ), common sense, a bit of pride and responsibility for those ,on the ground and who ride with me, that my maintenance keep safe.

 

"turning the engine over in the morning" - Back in my GA days I was trained to turn over the engine (LyCon) befor the first start of the day to pre lube the innards and feel for compression differences between cylinders - so good airman-ship Same Same!!

 

"until it gurgles takes quite a long time" - True we like to hear the "gurgle" that's how a Rotax speaks to the initiated. Those that know how , can get her to speak, from 3-6 compression - so much for a long time.

 

"you don't feel much in the way of compression because the gear reduction interferes with the feel" - poor Bruce, the understanding/trained pilot knows what to look for - its the feeeeel of every cylinders compression, looking for a difference that may indicate a problem - the gear box does not interfere with a comparative assessment of this sort.

 

Last weekend, my nearly 900 hr Rotax took me on a 2 hr flight, cruising between 110 - 120 knots (indicated), 500 - 5500 ft, climb outs 1500 ft/min, 3 landings, at an average fuel burn, for the whole flight, of 13 L/hr ULP

 

How do your engine maintenance costs match up ???

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As a non Jab person, I always wondered about the ability of a single carburettor to deliver the same air/fuel mixture to every combustion chamber - particularly on the 6 cylinder models.

 

Probably the same way a Holden did. It's not rocket science. The idea of recreational flying is to keep it cheap for most of us 'plebs'. Cheap means simple and simple means easy maintenance and easy to understand. Only last week my mate was grounded because his two carbs were 'not in tune' (whatever that means) keeping is Savannah out of the air.

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Probably the same way a Holden did. It's not rocket science. The idea of recreational flying is to keep it cheap for most of us 'plebs'. Cheap means simple and simple means easy maintenance and easy to understand. Only last week my mate was grounded because his two carbs were 'not in tune' (whatever that means) keeping is Savannah out of the air.

 

The Holden 6 was a solid reliable "donk" that paid very little attention to efficiency. It persisted in Australia, way past its due date, when much better engines, in every respect, were readily available. I have little doubt, that amongst the multitude of factors that resulted in the demise of Holden, was its failure to compete with much more efficient engines fitted to its competitors when they were still using the old single carbi 6. The Australian attitudes of the 60-90's was probably about 20 years behind the rest of the west - I wonder if its changed all that much.

 

Your mates problems sound very much like lack of maintenance (or just bad luck) rather than an inherent failure of the Rotax carbi system.

 

I am continually astonished by those that infer the Rotax 912 is a complex maintenance nightmare - for me its a doddle with no surprises and I am far from a mechanical savant.

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Well said skippy, I guess I am biased in favor of Jabiru engines. I didn't know that there is a legal distinction for certified engines with respect to timed replacement of parts.

I reckon that I particularly don't like the idea that nothing comes out of Austria unless they have your money first, but this may be not true. Maybe you can have an account with Rotax.

On certified engines: Would a motor-glider, bought to do training and for hire, have to have a certified engine?

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Well said skippy, I guess I am biased in favor of Jabiru engines. I didn't know that there is a legal distinction for certified engines with respect to timed replacement of parts.

I reckon that I particularly don't like the idea that nothing comes out of Austria unless they have your money first, but this may be not true. Maybe you can have an account with Rotax.

On certified engines: Would a motor-glider, bought to do training and for hire, have to have a certified engine?

 

I also admit bias in favour of Rotax, largely because that is what powers the aircraft I have most hours in and so far (900 hrs) it has been remarkably reliable.

 

Australia used to "punch far above its weight" in the R& D department but successive Governments over the last 30 years or so, have failed to support education, science and innovation - the consistence - amongst many other fields aviation has languished and as far as I know jab is the only Australian engine maker/developer.

 

RAA training aircraft or aircraft available for hire do not require certified engines - dont know if the same is true for the gliding fraternity. ( may be if it can be registered RAA it would be OK)

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