Yet another Jab down.....

[Dafydd Llewellyn]

In lobbying Jabiru to conduct an in depth investigation into these engine issues and share the results.RAAUS allows the registration of the aircraft, if there is such a major issue and the manufacture isn't doing anything then surely the board with the Tech Manager can issue a directive that no new aircraft fitted with this engine shall be provided registration until it's improved?

Read CAO 95.55,

POST EDITED AS IT DOES NOT ADD VALUE - MOD

 

If the product meets the criteria, RAA has no option - it MUST register the aircraft (and vice-versa, which was the case with the Ibis).

 

In the case of an aircraft coming in under CAO 95.55.1.8, I would suggest that the authority rests with CASA, not RAA, because the aircraft must have a special C of A under CASR Part 21.186; unless RAA has an authority from CASA to issue such special Cs of A, that has to come from CASA.

 

 

[Guest Andys@coffs]

Lets be clear there are 2 classes of members:-

 

1) jabiru owners, the minority, who I believe, would want things dealt with, but in a softly softly way so that long term their aircraft is valuable and available for use.

 

2) Non Jabiru owners, the majority, who would want things fixed because the Jabiru's are perceived by them to represent clear and imminent danger to their freedoms. If a regulator acts, he is unlikely to operate with a scalpel, rather more likely (at least the perception is that) to take up a Husky chainsaw and go to work....the fear is spill over collateral damage......

 

Those 2 groups overlap for some areas of concern(fix it), and are at direct opposites for others (2 wants it fixed yesterday, what ever that takes!, 1 wants it soon, but don't stop me flying in the meantime)

 

The board has to operate for the good of the members which given the diverse views for some aspects means some will be disappointed, maybe all, because the best case might be a middling one.....if there is an issue

 

Andy

 

 

[facthunter]

, as can be done,Valve "washers "?? Collett retainers or something but NOT washers. If they are soft get rid of them. Probably made from free cutting steel.

 

In making any recommendations one gets involved in something they have no (or limited) control of. The manufacturer is in a similar position. They have made a lot of recommendations over the years, and a lot of it good sense, BUT the idea that ALL problems are with the operators/maintainers is not convincing. The engine is obviously sensitive to occurrences that make an unsatisfactory number of them unreliable. When repaired,(from the factory) engines don't last long you start to worry. Some operators HAVE managed to get quite satisfactory runs from their engines .

 

One of the first things to do is collate as much of the damage records , as can be done, and look for a pattern of failure, and get as many FACTS (not emotion) as possible. ALLOW mods that address deficiencies and are superior to the existing items to be installed ( this can be done now in some aircraft, already). Where it can be shown they (reasonably) cannot be inferior. In other words have advantages and unlikely to have extra risk. This can be done by testing and evaluating each item carefully. I would still like to see what torsional vibrations exist in these engines in the rev ranges they operate. I have never seen any figures at all. Nev

 

 

[motzartmerv]

Read CAO 95.55, friend. Then read it again, and maybe get somebody to explain the big words to you.

POST DOES NOT ADD VALUE - MOD

 

 

[facthunter]

It's not productive, so I agree Merv. Plenty do it... Nev

 

 

[Dafydd Llewellyn]

Valve "washers "?? Collett retainers or something but NOT washers. If they are soft get rid of them. Probably made from free cutting steel.In making any recommendations one gets involved in something they have no (or limited) control of. The manufacturer is in a similar position. They have made a lot of recommendations over the years, and a lot of it good sense, BUT the idea that ALL problems are with the operators/maintainers is not convincing. The engine is obviously sensitive to occurrences that make an unsatisfactory number of them unreliable. When repaired,(from the factory) engines don't last long you start to worry. Some operators HAVE managed to get quite satisfactory runs from their engines .

One of the first things to do is collate as much of the damage records and look for a pattern of failure, and get as many FACTS (not emotion) as possible. ALLOW mods that address deficiencies and are superior to the existing items to be installed ( this can be done now in some aircraft, already). Where it can be shown they (reasonably) cannot be inferior. In other words have advantages and unlikely to have extra risk. This can be done by testing and evaluating each item carefully. I would still like to see what torsional vibrations exist in these engines in the rev ranges they operate. I have never seen any figures at all. Nev

The requirement re torsional vibration comes under JAR 22H (now CS 22H) para 1843 - see attached. This was done for the 2200J engine by ETRS at Rocklea; the requirement can be satisfied by strain-gauging the exposed barrel of the propeller hub and verifying that there is no resonant frequency up to the maximum RPM required (as I recall, the test was taken to 3600 RPM for the 2200J engine. The other models of Jab 2200 use the same shaft.) I don't know what was done for the 3300, because it's not certificated.

JAR 22H.doc

 

JAR 22H.doc

 

JAR 22H.doc

[Dafydd Llewellyn]

Daffyd, your input is invaluable, please dont take your brothers 'line' with people, do you really need to get personal?

Apologies - I was merely trying to make the point that it needs hard data, not waffle. The example was pertinent. I do get irritated when people are too lazy to read the rules.

 

 

[rhysmcc]

Read CAO 95.55, friend. Then read it again, and maybe get somebody to explain the big words to you. If the product meets the criteria, RAA has no option - it MUST register the aircraft (and vice-versa, which was the case with the Ibis).In the case of an aircraft coming in under CAO 95.55.1.8, I would suggest that the authority rests with CASA, not RAA, because the aircraft must have a special C of A under CASR Part 21.186; unless RAA has an authority from CASA to issue such special Cs of A, that has to come from CASA.

CAO 95.55 covers the rule set to allow an aircraft to operate under the RAA umbrella, however it does not force RAA to accept the registration of an aircraft. I don't see how RAA could say they it's out of their hands, they are the authority that provides registration to these aircraft, I think it's more then acceptable to expect they work with the manufacture to improve.

 

 

[Dafydd Llewellyn]

, as can be done,Valve "washers "?? Collett retainers or something but NOT washers. If they are soft get rid of them. Probably made from free cutting steel.In making any recommendations one gets involved in something they have no (or limited) control of. The manufacturer is in a similar position. They have made a lot of recommendations over the years, and a lot of it good sense, BUT the idea that ALL problems are with the operators/maintainers is not convincing. The engine is obviously sensitive to occurrences that make an unsatisfactory number of them unreliable. When repaired,(from the factory) engines don't last long you start to worry. Some operators HAVE managed to get quite satisfactory runs from their engines .

One of the first things to do is collate as much of the damage records , as can be done, and look for a pattern of failure, and get as many FACTS (not emotion) as possible. ALLOW mods that address deficiencies and are superior to the existing items to be installed ( this can be done now in some aircraft, already). Where it can be shown they (reasonably) cannot be inferior. In other words have advantages and unlikely to have extra risk. This can be done by testing and evaluating each item carefully. I would still like to see what torsional vibrations exist in these engines in the rev ranges they operate. I have never seen any figures at all. Nev

Let's get some soft ones, and find out what they are made from. Send one to ETRS (or whatever they are currently known as) and ask for a material ident.

 

 

[facthunter]

I haven't been able to open that link Dafydd. Why did the Sensenich composite prop have problems? Nev

 

 

[01rmb]

Lets be clear there are 2 classes of members:-1) jabiru owners, the minority, who want things dealt with, but in a softly softly way so that long term their aircraft is valuable and available for use.

 

2) Non Jabiru owners, the majority, who want things fixed because the Jabiru's are perceived by them to represent clear and imminent danger to their freedoms. If a regulator acts, he is unlikely to operate with a scalpel, rather more likely (at least the perception is that) to take up a Husky chainsaw and go to work....the fear is spill over collateral damage......

 

Those 2 groups overlap for some areas of concern(fix it), and are at direct opposites for others (2 wants it fixed yesterday, what ever that takes!, 1 wants it soon, but don't stop me flying in the meantime)

 

The board has to operate for the good of the members which given the diverse views for some aspects means some will be disappointed, maybe all, because the best case might be a middling one.....

 

Andy

Andy - I agree that the board must operate for the members as a whole but actions by the board and RAAus does not have to adversely affect one group over another. There is a large number of people not directly but will very likely be indirectly affected by what will happen. Any action by CASA is going to be anything but surgical - other engines or aircraft are not immune from problems so any approach will affect more than just the minority of Jabiru aircraft owners. Jabiru might be the start but then any engine or airframe issue would get the same treatment.

My observation is that there are a few people that push their own agendas for their own purpose with no consideration of others. I believe you are more balanced in your views and approach but I can't say the same for everyone. I am happy for the association to be as heavy handed as needed - but in public and armed with facts - to work with the manufacturer to identify and resolve the issues. Don't make it public and don't drag the regulator into it because that does not help the minority or the majority when the arbitrator takes their indiscriminate actions.

 

 

[Old Koreelah]

Do we have statistics for fatal crashes resulting from engine failures Jabiru vs Rotax?

Good point, KA. I'd predict that a survey of flying styles might show much more risk-taking by Rotax pilots. Flying behind a Jab engine requires careful piloting.

 

 

[facthunter]

The engine that won't fail hasn't been built yet, but the PT 6 comes close. Abuse of it and complacency reduces it's reliability too... There are LESS reliable engines out there than the Jabiru, that I would still fly behind, but not over populous areas, that I couldn't glide clear of. That's why multi engines are common. (But not in our field).. Nev

 

 

[Dafydd Llewellyn]

I haven't been able to open that link Dafydd. Why did the Sensenich composite prop have problems? Nev

What link? If you can't find ETRS (I think they call themselves something different nowadays) try http://www.alfatest.com.au/

I don't know anything about the Sensenich composite prop; however the vibration clearance of a propeller for use on a particular model of engine, requires strain-gauge testing of the propeller, not the crankshaft. Any direct-drive aero engine produces substantial torque pulses as each cylinder fires. Problem with a composite prop is that the elastic modulus of the material varies with temperature, and therefore so do its natural frequencies. Fixed-pitch wood propellers do not require strain gauging, because wood does not fatigue (in its normal-use stress range). All other forms of propellers need to be strain-gauge tested for each engine type on which they are to be used; look up any metal propeller Type Certificate Date Sheet on the FAA website; at the back of it you will find a listing of the engines for which it has been vibration-cleared.

 

 

[facthunter]

I'm aware of the specificity of the testing requirements. engine to prop.. Sensenich are a respected manufacturer but their composite has problems on the Jab and not other engines. If there were no issues with torsional vibration in the rev range why the prop damage and loosening problems and the flywheel retaining problems?. A wood prop forgives many sins. How much must it forgive on the Jab? Nev

 

 

[Dafydd Llewellyn]

I'm aware of the specificity of the testing requirements. engine to prop.. Sensenich are a respected manufacturer but their composite has problems on the Jab and not other engines. If there were no issues with torsional vibration in the rev range why the prop damage and loosening problems and the flywheel retaining problems?. A wood prop forgives many sins. How much must it forgive on the Jab? Nev

What other engines are we talking about? The 912 has much lower peak instantaneous torque input than the Jab, because of its rubber coupling; and also the frequency is much higher because of the gearbox reduction ratio. So it's much kinder to propellers.

The Jab 2200 shaft tested free of resonance in its required range; however the 3300 is another question, to which I do not have any knowledge. The CAMit belt-driven alternator definitely acts as a torsional vibration damper on the 3300. I have never liked the flywheel or propeller flange connections on the Jabiru engines; however they passed the required JAR 22H endurance run on the Jab 2200 J and C engines, so they work if everything is right. The 3300 has the same bore & stroke (uses the same cylinders) so its peak torque should be no greater.

 

Wood propellers must be driven by friction between the propeller and the flange; and again, I suspect the margin is not great - tho it certainly works if everything is right. On the Seabird Seeker, the propeller flange (Lycoming 0-360) is definitely too small to be reliable with a wood propeller (which the Seeker has, because it's a pusher and the propeller works in dirty air, which causes problems with metal propellers), so it has a propeller extension that has an 8-inch flange diameter, with eight bolts, not six - and each bolt has nine Belleville washers, to maintain the clamping pressure. Few manufacturers go to that amount of trouble - and the Seeker has problems, because well-meaning but ignorant maintainers persist in over-tightening the Belleville washers.

 

 

[facthunter]

Thanks for that. There is still a severe pulsing concern because of the lack of flywheel effect and common to all flat or inline four cylinder engines, That of having all 4 pistons stationary at the same time twice per revolution. A well designed Vee 4 is better in that respect and with the optimum Vee angle, particularly so.. Surely the starter helps the retaining screws/bolts on the flywheel to move also. Nev

 

 

[Dafydd Llewellyn]

Thanks for that. There is still a severe pulsing concern because of the lack of flywheel effect and common to all flat or inline four cylinder engines, That of having all 4 pistons stationary at the same time twice per revolution. A well designed Vee 4 is better in that respect and with the optimum Vee angle, particularly so.. Surely the starter helps the retaining screws/bolts on the flywheel to move also. Nev

Yes, I like the Vee layout; but it does not really come into its own with less than six cylinders, because it's very difficult to get a good compromise between even firing intervals and optimum inertial balance. There's a definite advantage on the six-cylinder engine to having the ring gear at the propeller end of the engine.

Vee engines tend to need fairly substantial crankshaft counterweights. The flat four and flat-six layouts get away without counterweights, so they can result in a lighter engine. That's why they are so common, I suspect.

 

 

[facthunter]

Radials are the ones with substantial counterweights. Yes most aero engines don't counterweight where they can get away with it , to save weight, but a bit of extra bearing loading happens then, which stresses the crankcase more.. I think we could get away with a slight variation from even firing impulses in a vee. I notice most of the upgraded VW aero conversions run counterweights. Their cases aren't strong.. Nev

 

 

[Dafydd Llewellyn]

Radials are the ones with substantial counterweights. Yes most aero engines don't counterweight where they can get away with it , to save weight, but a bit of extra bearing loading happens then, which stresses the crankcase more.. I think we could get away with a slight variation from even firing impulses in a vee. I notice most of the upgraded VW aero conversions run counterweights. Their cases aren't strong.. Nev

If you care to look up the crankshaft counterweight requirements for a 90 degree V-twin with common crankpin, you will find that it can have complete primary force balance (one per rev) and complete secondary (2 per rev) force balance in the plane of symmetry; but a small secondary out of balance force at right angles to the plane of symmetry. This makes it far superior to an "in line" engine, and also to a boxer twin; however this requires fairly substantial counterweights. Take a look at a Peugeot 604 crankshaft sometime. That had uneven firing intervals (90 degrees/150 degrees), but that's not really an issue with a direct-drive propeller, tho it evidently is with a vehicle transmission at low RPM, high manifold pressure.

To the extent that one can "build up" a multi-cylinder engine (in principle) by "stacking" two-cylinder units, it will be possible to delete part or all of the intermediate counterweights - completely, in the V-4 layout - but the V4 firing order is pretty wild. You'd find the armchair pundits blaming it for all sorts of things.

 

 

[facthunter]

You are onto it. You don't need the centre bearing if that is done. Having cylinders individually bolting onto the crankcase without deep spigots lacks rigidity and requires a strong base flange with quite a few bolts in lieu.. The one piece approach starts to look good structurally. Nev

 

 

[Camel]

Can you supply some part numbers or identify the parts as having come from Jabiru, together with hardness values? Jabiru has, I think, put out a service bulletin on this (I don't follow them, not being a Jab. owner). The point I'm trying to make, here, is that if you want CASA to sit up and pay attemtion, you have to give them factual information - like a defect report (used to be - maybe still is - CASA Form 404 - go to the CASA website and look it up; or maybe RAA has its own defect report form). You also need to produce the defective hardware and its history. CASA does not deal in hearsay.

POST EDITED AS IT DOES NOT ADD VALUE - MOD

 

Jabiru have a SB to check the washers, they know they wear out and drop valves ! Because the were ok to start with then changed them and now they are soft and wear out, the problem is a committed manufacturer would have recalled and replaced them and discontinued the part !

 

POST EDITED AS IT DOES NOT ADD VALUE - MOD

 

but I think this way, if there is a problem fix it NOW not later or when someone gets hurt !

 

Maj, the Ibis was one but there were a few other Australian manufacturers.

 

 

[Dafydd Llewellyn]

So Dafydd, you say" put up or shut up ! " You are missing the point, Jabiru have a SB to check the washers, they know they wear out and drop valves ! Because the were ok to start with then changed them and now they are soft and wear out, the problem is a committed manufacturer would have recalled and replaced them and discontinued the part ! You are very quick to read out the rules like CASA, that's because you think like CASA ! but I think this way, if there is a problem fix it NOW not later or when someone gets hurt ! Maj, the Ibis was one but there were a few other Australian manufacturers.

I thought Jabiru put out an SB on them; what did it say? Are you chasing something that has already been dealt with? My point was, IF you have a part that you consider defective, PUT IN A DEFECT REPORT ON IT.

 

 

[Camel]

I thought Jabiru put out an SB on them; what did it say? Are you chasing something that has already been dealt with? My point was, IF you have a part that you consider defective, PUT IN A DEFECT REPORT ON IT.

Service letter JSL 008-1 basically says that wear because of dust. Any excuse will do. Issued 21 dec 2012. Valves are still dropping.

 

Mine have not worn out yet so not cant do anything yet except inspect them. While pushing around with screwdriver it marked the washer significantly, obviously not hard.

 

Posted this before.

 

Valve Spring Washer Adverse Wear

 

Posted on April 22, 2013 by Roger Lewis

 

On account of 2 incidents, Jabiru issued JSL 008-1on the subject. Reading the service letter we are led to believe that in each incident, the failure of the washer was due to the aircraft being operated in dusty conditions. To support this we are shown a picture of a carburettor.

 

While ingestion of dust may be a contributing factor, I find it is difficult to believe that it is the major factor. Engines have been running for many years in all sorts of conditions without these washers failing. So what has changed within the engine to make it more susceptible to this type of failure?

 

1. Older engines have oil feed lubricating the valve guides and collets. Engines fitted with hollow push rods do not have oil lubricating the collets.

 

2. Older engines have G&S valves and collets. Newer engines use different valves and collets which sit differently on the valve washer.

 

3. Older engines use heavy duty valve spring washers with different cross sectional profiles. New engines have lighter duty washers. The picture shows both types:

 

 

Inspection of both types of washers removed from serviceable engines operating in the UK show witness marks on both types of washers. However, the curved profile of the heavier duty washers appears more resistant to possibility of a total washer failure.

 

While the letter is advisory, during top end maintenance it is well worth removing the valves and inspecting the underneath of the washers. Look for radial wear caused by the spring. If the washers are of the light duty type and the wear is significant then replace them. Also smooth off any sharp ends of the spring that could be causing the wear.

 

For those contemplating ‘upgrading’ to hollow pushrods, think of the consequences of removing the oil flow over the valve stems and guides.

 

 

[Dafydd Llewellyn]

OK, I saw that before. So, you have in your engine a set of washers (or Collett retainers) that you consider defective. Next step - beg, borrow, purchase or steal a replacement for one of them, install it, and send the one you remove from the engine to a laboratory (e.g. Alphatest, Brisbane http://www.alfatest.com.au/ ) and pay them to give you a material ident and a hardness. That will give you a certificate from a NATA laboratory that states the material and heat-treat condition of the part you have, whose history you know.

 

With that, you can do one of two things - either send the part, plus a copy of the certificate off to CASA with a filled-out CASA defect report; you will have to say that you consider the part defective because it wears too fast, and argue that the Jabiru SB proves your point. You could possibly consider having the lab. test an automotive equivalent part, to get a comparative composition and hardness.

 

Or, you can try to find out what the Jabiru drawing for that part calls for by way of material and heat-treatment. You could perhaps ask Ian Bent, if Jabiru will not answer.

 

If you can prove that the part is not in accordance with the drawing, you will have some solid evidence. If it is in accordance with the drawings, but inferior to an equivalent automotive item (as shown by test results) you will have a different argument.

 

This process is standard practice to justify a substitute component

 

POST EDITED AS IT DOES NOT ADD VALUE - MOD