Another Jab bites the dust.

[Thirsty]

Thanks frank. Yeah we do leak downs every 50 hours as well and on the first aircraft the figure was something like 75 over 80 whereas on the other it was about 68 over 80. I make a habit of taking the head off and re-seating the valves if the leak down indicates that's required, its so easy to do so might as well.

 

 

[frank marriott]

Thirsty

 

With those leak down results - blows my theory out of the water. Thanks for the reply anyway.

 

FrankM

 

 

[Guest Maj Millard]

On leakdowns,... I have done a few over the years on all types, having worked in GA for over 40 +years now.

 

This is what I have learned : They must be done with the engine warm/hot !!....to do them cold is a waste of time. This is because there are often up to a dozen different metals types used in an engine, and they all have different rates of expansion for required proper sealing etc. IE: The metals used in piston-rings, pistons, valves, cyl-heads, valve-seats, valve guides, valve push-rods, and engine-cases are vastly different in thermal-expansion rates. What you are testing here after all, is the engines' ability to seal properly, and hold compression, at engine operating temperature !!...

 

Compressions done cold will always be 5-10 psi less, and totally unreliable IMOP. Do your engine warm-up and pre-service engine performance checks, drop the oil, and while it is draining, do your compressions checks before the engine cools.

 

Additionally,... avgas use will produce carbon/lead buildups, and can deposit material under the valve seats which will affect readings. There are simply ways used in the industry to remove carbon build-ups under the valve seats during checking, without the need to remove any cylinder-heads.

 

Blow-by, which is heard by the hissing of escaping air pressure and a slowly dropping indication on the guage, is located by putting your ear to either the exhaust outlet, or crankcase breather outlet. This tells you if the blow-by is from worn rings or cylinder cracks, or, (as is more common) from non-sealing exhaust or intake valves. I often see unnecessary and expensive significent work done on engines because of unreliable cold compression readings, where there was no problem in the first place !...

 

Simply having the guages to do the job is no good if you don't have the skills or experience to interpret the results, or the knowledge on how to rectify the faults found...........................................................Maj...

 

 

[jetjr]

Totally agree Maj

 

From the engine manual - Standard leakdown is to be done with oil temps between 30 and 70 deg.

 

CHT and EGT tell you in real time if something is changing (like a build up or randomly sticking valve). No one suggests these as an alternative to leakdowns or gaining skills to read and respond results

 

I do hot AND cold leakdowns, differences are huge and cold is more likely to indicate problems from my tests. Quite often under a hot test problem disappears.

 

Head torque, plug inspections and valve adjustments are done cold, not much more effort to run leak test then too.

 

Wouldnt be without full EGT and CHT now Ive seen the temp spread across my and others engines.

 

 

[Guest Andys@coffs]

I always worked on the principle that they had to be done hot, and in fact I never was comfortable that hot (being fully hot all engine parts) could be achieved with just a ground run. I usually go and do 5-6 circuits and then do the leakdowns.

 

JetJr I struggle to see how cold could work? (Not that I claim to be anything other than an avionics tech....)given that oil distribution around the cylinder walls etc cant be guarenteed until run??? If I did mine cold and I did once to see what I could see, In that case I would have had to pull all heads off reseat all valves and then likely still would have failed....... Which might indicate I have a problem developing/developed...

 

I Also pull the heads and reseat valves etc when indicated on a hot leakdown test, but I wonder if there is a way of measuring the volumes of gasses that bypass the rings etc, Others have spoken about increasing oil consumption, but isnt that in our J engines simply a symptom of increased air/gas blowing past the rings? If I could measure the volume of gas coming out the overflow pipe then to me that would tell me how much is getting past the rings

 

But as said Im an engine novice and thats being kind....

 

Andy

 

 

[Guest Maj Millard]

Additionally, it is handy to record your leakdown readings each time you check, traditionally on the valve cover of each cylinder . This allows you to compare how much of a drop you have at each check, if there is any drop at all. If all show a small drop, (normal) and one a large drop, then that one may have a problem, and now you know where to look.

 

Rarely do you see leakdown figures increase between checks, except on new engines which may show increased readings in the 100-200 hour checks due to the improved seating/sealing of the piston-rings in the cylinder. This is normal, but don't be dissapointed if you don't see an increase, as some engines seal well, right from the start....................................................Maj...

 

 

[jetjr]

Andy

 

No you dont do anything about cold leakdown results, so long as close to limits, ie say >60 but can give idea of a cylinder which might have an issue, always confirmed with hot leakdown of course. You hope all problems go away.

 

The cold test was recommended to me as an extra check not instead of a hot check. If the plane has flown recently it shows some sort of repeatable result.

 

It was also as the solid lifters lash are adjusted cold, ie BEFORE hot test done...... so to pick up a small valve problem - like a bit of caught crud under a valve - is highly important before you go and adjust clearances. Its also why you have to do head torques before valve clearances too.

 

Im no mechanic either but it all fits in the process without much extra effort. So Im there with cowls and ducts off, rockers open, heads torqued and Im removing plugs for inspection, I just leave one plug out of each pot and run the leak test cold, all ~ ok then adjust tappets, refit plugs and wires, rocker covers, warm up with 5 min run outside, remove 6 plugs, leak down test gear is setup and working so run the test again hot - can open oil drain whilst doing this.

 

Recording and watching trends is very important. Maj idea of writing on heads is a good one. Think Ill take it up

 

To go for a few circuits means reinstalling all covers and ducts. With cowls off I can get CHT up to 100 deg easily and oil temps over 50. Nearly too hot to work on and as cowls and ducts already off you can test them faster. They cool down quite quickly.

 

Where the leak is coming from is critical before pulling a head or doing much, exhaust, intake of sump. Sump is the most benign, its just ring leakage and yes it could use oil but thats about it. A leak thru exhaust is deadly, can burn a valve in no time but EGT guage should see this well before its a problem.

 

The size of the leak eg past rings (hissing from dipstick hole) is in relation to the leakdown figure you are seeing. So you sort of are measuring volume of leak.

 

 

[diablo]

Ahh jabiru ...

 

If only they would listen. It's no wonder sales have, plummeted. Good plane but rubbish worldwide service.

 

Sorry to say the cookie has crumbled for jab au ...

 

 

[j230]

i must add too, well done to the instructor/student.I too am a low hour newly minted 'pilot' and seriously, as much as i love flying and aircraft, if someone offered me a ride in a jab powered aircraft, i think i would give it a miss! I know a failure can happen to any powerplant, not just jabs. I'm a diesel fitter/motor mechanic, and i've seen some catastropic engine failures in industrial motors like cat 3126's that are supposedly bulletproof, but jabs now have such a bad record, i dont think its worth tempting fate honestly. Give me Rotax or lycoming. Hell, give me a greatplains vw, or a subie ea81! I had a subaru brumby with an unopened ea81 with 400k k's on it!

 

My 2c worth

To my 2cents worth

Well you sound just like a typical jab noker. Firstly i had an engine failure and it wasnt a jab moter it was a Rotax but i dont nock Rotaxs as there are plenty of good ones out there. I personly know a jab nocker who had a Savanah with a 100 hp rotax and also nocked jabs even his wife shit canned them.In saying that they now have a j230 and state its the best thing they have ever done and have never had an ounce of trouble with it. I have been flying jabs for 17 years and have never had to put down because of engine trouble. I also fly a j230 and have flown it just about all over Australia and it has never missed a beet . A lot of time it has to do with the way they are treated . If you want to climb them out at 60 or 70 kts yes you will have trouble with them as they get to hot. I know of a j230 that has been continualy climbed out at those speeds and has cooked it 4 times the last time pistons were blue not the moters fault but operaters fault. I know of another 230 which is hamered all the time but climbed out at 90 to 100 kts and has never missed a beet so its more to do with operater missuse or ignorance and not knowing the correct operating procedures. It sounds like you have never owned a jab only taken notice of the bashers. Yes they do have some problems but so do they all and rotax has the same problems exept people dont talk about it so much. THe fly in to Wentworth the other week end and in landing at Renmark there were 20 Jabiru,s there only 3 other brands of aircraft so i gues that must say something At our airfield there are 5 jabs 2 other aircraft and one of the other aircraft even has a jab moter in it. None of us have had an ounce of trouble. You dont see glider tugs with rotaxs in them but you see 170 and 230 jabs towing up full size gliders ,maybe before you can a product you should buy one and treat it correctly and then make up you mind. If you want to come to Kadina airfield i will be only to happy to take you up and you can then make up you mind if you should never get back in one. No im not just a jab lover i have an open mind on all brands of aicraft and engines. Hope your flying goes well in what ever you fly in.

 

Regards Ray

 

P.S dont take this to hart but try to keep an open mind in flying and not listen to much to the nockers on any aircraft .

 

 

[turboplanner]

If you want to abuse posters as Jab bashers it would pay to understand a little about product reliability statistics.

 

I've mentioned several times on here that engine reliability is measured in terms of failures per 100 engines. There's no emotion in it, the statistics are the statistics whatever the brand of engine.

 

How you would demonstrate that in one short flight at Kadina airfield?

 

 

[dazza 38]

If you want to abuse posters as Jab bashers it would pay to understand a little about product reliability statistics.I've mentioned several times on here that engine reliability is measured in terms of failures per 100 engines. There's no emotion in it, the statistics are the statistics whatever the brand of engine.

How you would demonstrate that in one short flight at Kadina airfield?

Im with Tubs on this. It doesnt matter who the manufacturer is.They only true way of knowing the reliability of a Rotax, Jabiru ,Continental ,Lycoming or even Billy Bobs Victa mower. Is that all the failures of all the engines in the fleet must be collected as Data.Then the average Mean Time Between Failure (I have mentioned this before) can be established per engine model. Or same brand different models. eg-Solid lifter verses Hydraulic lifter etc. That way the Friday afternoon and Monday morning engines are thrown into the mix with the Wednesday built engines.ATM It appears that a certain brand of engine has a lower mean time between failure rate than other brands. The only way to confirm or deni is that we need ALL the data collected . The number of engines in service and the number of hours flown and the number of failures and what were the specific component or components that failed.

PS- Mean time between failure - is actually a PREDICTED failure time.Is predicted by Data that has been collected.

 

 

[Hongie]

To my 2cents worthWell you sound just like a typical jab noker. Firstly i had an engine failure and it wasnt a jab moter it was a Rotax but i dont nock Rotaxs as there are plenty of good ones out there. I personly know a jab nocker who had a Savanah with a 100 hp rotax and also nocked jabs even his wife **** canned them.In saying that they now have a j230 and state its the best thing they have ever done and have never had an ounce of trouble with it. I have been flying jabs for 17 years and have never had to put down because of engine trouble. I also fly a j230 and have flown it just about all over Australia and it has never missed a beet . A lot of time it has to do with the way they are treated . If you want to climb them out at 60 or 70 kts yes you will have trouble with them as they get to hot. I know of a j230 that has been continualy climbed out at those speeds and has cooked it 4 times the last time pistons were blue not the moters fault but operaters fault. I know of another 230 which is hamered all the time but climbed out at 90 to 100 kts and has never missed a beet so its more to do with operater missuse or ignorance and not knowing the correct operating procedures. It sounds like you have never owned a jab only taken notice of the bashers. Yes they do have some problems but so do they all and rotax has the same problems exept people dont talk about it so much. THe fly in to Wentworth the other week end and in landing at Renmark there were 20 Jabiru,s there only 3 other brands of aircraft so i gues that must say something At our airfield there are 5 jabs 2 other aircraft and one of the other aircraft even has a jab moter in it. None of us have had an ounce of trouble. You dont see glider tugs with rotaxs in them but you see 170 and 230 jabs towing up full size gliders ,maybe before you can a product you should buy one and treat it correctly and then make up you mind. If you want to come to Kadina airfield i will be only to happy to take you up and you can then make up you mind if you should never get back in one. No im not just a jab lover i have an open mind on all brands of aicraft and engines. Hope your flying goes well in what ever you fly in.

Regards Ray

 

P.S dont take this to hart but try to keep an open mind in flying and not listen to much to the nockers on any aircraft .

no mate, i dont own a jabiru, and no, i wont be buying one, 'to make up my mind'. Seems a rather expensive exercise to me. My mind is made up (for now, see end of post), and i dont see why because you own a jabiru, you have taken my comments as a personal attack on you, because that is not how it is intended. But i stand by what i said. Especially with my luck, I wouldnt want to tempt fate (if something is ever going to go wrong with any product, it will be the one I get). I Appreciate your offer of a flight, but i must decline. I'm only dissapointed that I cant place my trust in Jabiru motors, becuase i would love to be able to support an Australian company. If you are happy to fly them, go for it, more power to you. Its like the old Ford vs. Holden, Nissan vs Toyota. Everyone is entitled to an opinion about a product... but ones opinion about a product means jack all about people who use it.

 

And, you could be well right about problems being attributed to how the engines are being treated, but I cannot draw conclusions from that, not having 1st hand knowledge, or knowing the owners/operators of them. I can only go on statistics. I only wish I could actaully get some solid figures, and have the time to go through a pile of accident investigations. Im happy to be proven wrong, but until then, i will be staying out of jab powered aircraft.

 

edit: to anyone who has access to figures, it would be great if you could compile a list, and populate a time/failure graph.

 

also, does anyone know the failure rate of the 3300? I personally havent heard of many of them failing?

 

 

[Yenn]

We have heard a lot of fuss about a lot of motors, but nowhere have I seen the real statistics as suggested by Dazza.

 

Until I see the statistics I like to make up my own mind and not try to rubbish any brand of engine.

 

 

[Old Koreelah]

They only true way of knowing the reliability ... the average Mean Time Between Failure ... can be established per engine model.

You are right, Dazza. The only way to settle an argument is via hard facts. Years ago the French started adapting diesels for aircraft use. To establish their service life, one bloke (who must have worked for PSA) tested a batch of Peugeot diesels to destruction. He set TBO at 10,000 hours after the first engine failed at 12,700 hrs (dropped exhaust valve).

 

I doubt Jabiru, or any other small engine builder has the resources to do this work.

 

Just like our pioneering forefathers, I will always fly with care, aware that things may go quiet at any moment, but I'm happy that I could afford to buy a fairly reliable, very light Australian-made engine. I have no complaints about factory support.

 

 

[facthunter]

I personally don't know one 3300 engine failure. That doesn't mean much, but a lot of the talk around here doesn't mean much either . Unless you take some trouble to determine the cause of various failures you don't get far with an analysis.. For instance early ea falcons were overheating but it was people crossthreading the threaded water reserve bottle and the coolant was escaping under pressure. ( as an example)

 

These Jab engines operate out in the field under uncontrolled conditions where just about anybody spanners them and you don't know what stale/ contaminated fuel goes into them, how long they sit in sheds. etc Some of the engine failures mentioned here have NOT had all the required AD's etc done. An aero engine has to be right. It's not like some clapped out ute that you can jump into and go to the pub each day for 30 years running on half of the cylinders. Any fuel out of an unsealed drum is unsuitable for a certified engine technically.

 

I've never heard a discussion on spark plug heat range with these motors. Does everybody tension the plugs with a tension wrench" When you put a heat sensor under a plug washer you change the temp a plug will run at.

 

Hands up who has ever checked the valve to guide clearance.? Who really knows how to retension the bead bolts. The L2 who "does" your motor. is he any good? I've seen plenty who think they are, but they don't have much affinity for engines ,just regurgitate the smoke and mirrors magic stuff that gets around perpetuating the myth of their mystic powers .

 

Very few shops do good engine work on the more 'real" engines either, which cost something like $3500 per cylinder assembly and you will spend something like $27,000 for a rebuild Lyc and it may be pretty unreliable, if it isn't done right.

 

The older motors like the gipsy major would need a "top" every 300 hours or so when used regularly. Used the way they are used today they are even less reliable, but a pilot then would feel the 'soft" cylinder when priming it, and prop swinging it, and have it serviced.

 

Other engines like Pobjoy's, Warner Scarabs, Menasco Pirates needed special care and attention to keep them going. and even then it often wasn't long.

 

What other engines normally have to accept full throttle after a minimum warm up every time they are used, and sit on 75% power most of the time.. They are also built to a minimum weight and size and price in low volumes that would be lucky to be commercially viable.

 

Learn to properly look after your engine. ( I didn't say that is easy) appreciate it and enjoy it. C'mon people, even having a thread named "another Jab bites the dust". Is it really that bad? You don't realise how lucky you are to have this stuff and be allowed to use it. Get a life.. .Nev

 

 

[Mick]

You dont see glider tugs with rotaxs in them but you see 170 and 230 jabs towing up full size gliders

Have a look at Tocumwal where they use a Sportstar and a Eurofox with Rotaxs as tugs.

 

 

[turboplanner]

I personally don't know one 3300 engine failure.

If you go back to #57 on this thread you'll find that from Pilot Notes covering a total of 35 mechanical failures on Jabirus, 7 were 3300 engines.

 

I agree the aircraft engines of the 1920's had short life cycles, but we've moved on from there.

 

I agree with you that the selection of fuels and oils is appalling.

 

I also agree that service standards are so bad that CASA should apply the same safety standard used in GA and ensure engines are maintained by a qualified person.

 

However, having said that, the same demographic group are flying roughly the equivalent number of Rotax engines.

 

When I get a minute I'll pull the Rotax engine failures from the same magazines I used for Jabiru, so we have a reasonable month by month failure rate.

 

Let's not forget that the statistics from #57 referred to 28 forced landings from the 35 failures, and sooner or later someone isn't going to make it or their passenger isn't going to make it, so the frequency of the failures needs addressing.

 

 

[facthunter]

You still need to go into the nature of the failures. and why. Some could be fuel exhaustion for all I know. It is not a controlled situation to be making conclusions from. Any two stroke I have flown would have to be a lot more likely to fail that any jab I've flown. and as Ive said elsewhere the only times I have landed for engine related factors the engine was a Rotax 912. On those occasions I am not blaming the engines design or manufacture but the servicing. I have no idea whether this likewise is a factor with a lot of the jabiru problems but I suspect it is. jabirus require more hands on servicing than the Rotaxs hence more opportunity for error. Nev

 

 

[eightyknots]

Thanks for reminding us about this post w-a-a-a-y back on page 3 of this 24-page thread. To assist with the thread's continuity and what you have written above, I have placed the info in the space below (:thank you:Thanks again Turbz for going to the trouble to compile the stats!):

 

These statistics come from 48 RAA/Sport Pilot magazines between May 07 and March 12, so they represent a random period of 48 months.It appears that not all forced landings make it to Pilot Notes, so the numbers may be under representing what's actually going on.

Only aircraft with Jabiru engines are listed.

 

There were 35 mechanical failures (Unbelievably there were about 3 more where the cause was no oil in the sump)

 

Of these, there were:

 

28 forced landings

 

6 found "on the ground" - which if the pilot had been alert should have been forced landings (one case, not included, was where a crankshaft broken in half and the pilot flew home on the front half cylinders and crank)

 

1 "landed", which probably should have been a forced landing

 

26 were 2200 models and 7 were 3300

 

Of the 35 incidents only one injury was reported, a serious one

 

Of the 35 incidents there were:

 

16 thru bolt failures

 

6 valve failures

 

6 exhaust valve failures

 

3 seized

 

1 conrod failure

 

1 catastrophic engine failure

 

1 cylinder crack

 

1 misfire and shudder

 

The standard of reporting in Pilot Notes (which comes from RAA reports) leaves a lot to be desired and itself tends to mask what the problems exactly are - for example, conrod failure, seizure, catastrophic engine failure, cylinder crack are results rather than failures, and misfire and shudder is a sympton, not a cause.

 

Of the 35 total time in service (TTIS) was:

 

0 - 200 hrs - 3

 

201 - 300 hrs - 4

 

301 - 400 hrs - 5

 

401 - 500 hrs - 6

 

501 - 600 hrs - 1

 

601 - 700 hrs - 3

 

701 - 800 hrs - 2

 

801 - 900 hrs - 3

 

901 - 1000 hrs - 4

 

1001 -1900 hrs - 1

 

Not specified - 2

 

In looking at these statistics we have to be mindful of the fact that we know because of open discussions on this forum and others that:

 

A percentage of owners do not use specified oils and do not change oil at correct periods

 

A percentage of owners do not understand filter technology

 

A percentage of owners are not mechanics, and so settings on some engines will be permanently incorrect

 

A percentage of pilots do not monitor operating temperature as they should

 

...and so on

 

Conclusions

 

28 forced landings in 48 months represents about 7 per year, and we could maybe double that if we include forced landings not reported in Pilot Notes

 

46% of these are due to thru bolts

 

34% are due to valves

[turboplanner]

Some could be fuel exhaustion for all I know.

It wouldn't have hurt you to read the post; thanks 80.

 

There's no way I would have listed fuel exhaustion as an engine failure, and I also did not report other issues which were not engine failures.

 

And bringing Rotax two strokes into the discussion when they clearly are not being used in two place touring aircraft is only going to crowd the issue. Of course they will have a shorter TBO, but they haven't been figuring extensively in Pilot Notes.

 

 

[facthunter]

That goes some part of the way . It is common knowledge that exhaust valve failure is often mentioned. hence my mention of valveguide wear check. the spark plug reference and overtemping and stale fuel relate to through bolt failures. the newer bolts and compression lowering may assist this, but Jabiru have always emphasised top end attention. IF you have to run the mixture a bit rich to make sure the leanest cylinder is not critically lean, there may be more carbon build up than desireable in the richer cylinders

 

 

[dazza 38]

The biggest promblem I think is A- Not all engines that fail are recorded and B- nobody can realy put a percentage figure on the number of abused/not maintained well engines that fail.This makes it realy difficult. To get a true figure on what is actually going on.Regardless of the manufacturer.

 

 

[dazza 38]

Roll Royce paid QANTAS 95 million dollars in compensation for the QF 32 engine failure. Big Dollars.Sorry for being off thread but it goes to show though, getting it wrong in the big league costs alot of money. Just as well we are the little league.lol

 

 

[facthunter]

Some of your remarks are a bit offputting turbo. How can you be sure that some of the failures are not fuel "lack of supply"? there is a lot of variation in just where the selector is left with the Jabiru's . some could have been selected wrong..Any attempt to analyse this is fine, but do it right. If you get this engine grounded you "won't know what you have lost till its gone". It hasn't reached that stste by a long way , in my view. I am not a Jab basher or a supporter . Just realistic I hope.. Nev

 

 

[Camel]

If you go back to #57 on this thread you'll find that from Pilot Notes covering a total of 35 mechanical failures on Jabirus, 7 were 3300 engines. I agree the aircraft engines of the 1920's had short life cycles, but we've moved on from there.

 

I agree with you that the selection of fuels and oils is appalling.

 

I also agree that service standards are so bad that CASA should apply the same safety standard used in GA and ensure engines are maintained by a qualified person.

 

However, having said that, the same demographic group are flying roughly the equivalent number of Rotax engines.

 

When I get a minute I'll pull the Rotax engine failures from the same magazines I used for Jabiru, so we have a reasonable month by month failure rate.

 

Let's not forget that the statistics from #57 referred to 28 forced landings from the 35 failures, and sooner or later someone isn't going to make it or their passenger isn't going to make it, so the frequency of the failures needs addressing.

I have seen a lot of LAME that have done unairworthy , rough and untidy work. I am a motor mechanic and an L2, if they stop me doing my maintenance I will not fly any more as I certainly will not put my life in the hands of so called AME under a LAME who signs out rough as guts work that I have had done on my GA aircraft in the past, I fly RAA because I do not want anyone else to maintain my aircraft. I owned a C172 for 9 years and will never own a GA plane again unless I build it so I can maintain it. In saying that not all LAME's are bad, but that doesn't help after you have gone to a bad one. I have a Jabiru 230 and a Sportstar, I know the pitfalls of both and I maintain to a very high standard and inspect more regular than recommended. Motor Mechanics are just as thorough as most AME or LAME. Do not think that regulating maintenance will make it safer. People need to seek assistance and know their mechanical limits not experiment. This is what needs to be educated not regulated.