Yet another Jab down.....

[AVOCET]

I removed my rockers after running hollow pushrods for 15 hrs after reading about this ,

 

I carnt see how oil doesnt lube the collit

 

All looked fine , less oil than the old way , but thats a good thing ,

 

To much oil in the rocker gear ?

 

No signs of ware or metal dust on the floor , where all the crud used to accumulate ,

 

Looked clean , runs great hyd , lifter ,

 

Ian bent says leave it alone .

 

Mike

 

 

[facthunter]

It's a critical part not because the springs wear them out. I've actually never seen that happen in any other motor. The collets sometimes pull through the body due to high loads and soft metal IF the valve springs are strong. and the taper expanding or wearing. Nev

 

 

[Dafydd Llewellyn]

It's a critical part not because the springs wear them out. I've actually never seen that happen in any other motor. The collets sometimes pull through the body due to high loads and soft metal IF the valve springs are strong. and the taper expanding or wearing. Nev

do you have a failed one laying around?

 

 

[AVOCET]

When folk do the upgrade to hollow pushrods , its important to make sure that if new bushes are fitted that their drill ed and cleaned so no crud or flakes of teflon remain to partialy block oil flow , as well as checking theres no residue swarf in the pushrods ,

 

I checked under the rockers after a ground run and then again after 15 hrs

 

Mike

 

Ps if there fitted and not ground run and then checked, i suggest you find someone else to do your maintainance

 

 

[Guest john]

With the continual ongoing failures of the same internal components within the Jabiru engines, the time will be forthcoming in the not to distant future whereby if unfortunatley there is a fatality in this type of aircraft that is considered to have resulted from an engine failure & further more if CASA, RAA or Jabiru have done nothing about the known defects that may have contributed to the engine failure apart from tooing & froing & passing the buck & sitting on their respective hands, then in all probability they will be required compulsarily to give a PLEASE EXPLAIN to the Coroner in the event of a CORONIAL INQUEST being conducted, which may result in the CORONER making certain specific recommendations in order to prevent similar occurrences, which seems to be the only consolation at present to concerned Jabiru owners & pilots.

 

 

[Dafydd Llewellyn]

With the continual ongoing failures of the same internal components within the Jabiru engines, the time will be forthcoming in the not to distant future whereby if unfortunatley there is a fatality in this type of aircraft that is considered to have resulted from an engine failure & further more if CASA, RAA or Jabiru have done nothing about the known defects that may have contributed to the engine failure apart from tooing & froing & passing the buck & sitting on their respective hands, then in all probability they will be required compulsarily to give a PLEASE EXPLAIN to the Coroner in the event of a CORONIAL INQUEST being conducted, which may result in the CORONER making certain specific recommendations in order to prevent similar occurrences, which seems to be the only consolation at present to concerned Jabiru owners & pilots.

POST EDITED AS IT DOES NOT ADD VALUE - MOD

I'm trying to pin down exactly what components, and why are they failing. So far, no useful answers.

 

 

[rhysmcc]

The problem seems evident from some of the posts here. Owners are too afraid for the value of their aircraft or being completely grounded that they don't want to report deficit or problems, but rather pay jabiru for new parts and hope the company will come good.

 

There has been some good suggestions regarding allowing LSA owners to apply mods, maybe this is an area the association could focus on and collecting all possible information regarding issues members are having with these engines and encourage everyone to come forward. No one wants Jabiru bust or the aircraft grounded, but if there is an issue we need it addressed before someone dies and it's all over for RA-AUS.

 

 

[jetjr]

Only for interest sake, ill comment, i spent a lot of time and money trying different propellers on a 3300, in the process spent time talking to plenty of experts and manufacturers both here and overseas. Got rogered by a fench prop maker in the process.

 

Feeling was at the time the 3300 had no problem with inflexible carbon or composite props and had been running for long time with 3 blade options of various brands.

 

I was clearly warned that NO manufacturer had sucess with composite props on 2200, in fact EVERY prop maker had tried and failed with non wooden props on these 4 cyl engines. Was talk about harmonics, much over my head. This includd talking to Rod S too.

 

Subsequently a few years later Jabiru were testing composites on the same engine.

 

The belt drive altenators are the go, especially if a LiFe battery can be used to offset weight. Damping is a key advantage. This is what excites me most about Camits work, there are anumber of solid upgrades which could tip the balance to being a reliable option. Going to be expensive to upgrade though.

 

 

[01rmb]

The problem seems evident from some of the posts here. Owners are too afraid for the value of their aircraft or being completely grounded that they don't want to report deficit or problems, but rather pay jabiru for new parts and hope the company will come good.

That is BS. I don't believe anybody would ignore safety just to retain the value in their aircraft. If you got that from anything I have written here then you have misjudged me. I certainly have not got that message from anyone else.

 

My comments about not destroying the value in aircraft is that people should not act without proper consideration. I am certain the manufacturer does want reliable aircraft and will do what is needed to achieve that. There are a number of people quite happy to throw rocks, accuse Jabiru of not doing enough and generally trying to bring them down but those people don't seem to be able to come up with a constructive proposition to help remedy the problem. Fact based investigation of the root cause of the problems is the only way this can be achieved. There is a lot of innuendo and supposition about what the problems may be (most of it has no basis on fact). Some aircraft are getting many hundreds of hours of use without a problem and yes some are having some issues and proper investigation is needed to find out why. Treat machinery badly and it will fail. There are answers out there and a number of people are working on implementing real solutions.

 

I have been open about the issues I have had with the exhaust valves in my aircraft being fouled as a result of the lead oxide buildup from using avgas -my strong recommendation following investigation is to use mogas. I also recommend to always check compression by pulling the prop through before every flight and if there is any sign of an issue to not fly and get it checked by somebody who knows about Jabiru engines.

 

As I said earlier it is about risk - Flying has inherent risks, if it is too high for you then don't do it. You assess the risk before every flight and take appropriate mitigations. Every aircraft has an engine that may fail - every engine would have some history of a failure. You do your maintenance and pre flight checks and if there is a problem - you must be prepared for it and act accordingly. If you are not then take up golf.

 

 

[Dafydd Llewellyn]

POST DOES NOT ADD VALUE - MOD

 

 

[Derby]

Right on Dafydd. By the I have Had a Revolution 3 bladed prop made in Bundaberg for 350 hours it's carbon fibre and could not be happier with it.PS it's on a j400

 

 

[Oscar]

POST EDITED AS IT DOES NOT ADD VALUE - MOD

 

Not one single actual piece of reliable, researched solid information as to the actual CAUSE of the incidents has been produced. Assertions have been made, 'deductions' have been dogmatically proclaimed as 'fact', comments bordering on the actionably defamatory have been made. Entirely draconian proposals have been touted, up to 'ground the entire fleet', 'deny new registration' etc.

 

The rationale almost inevitably given for the vociferous attacks on Jabiru is 'safety', and usually couched with direct reference to 'saving lives'. All amazingly 'holy' in apparent intent, yet I see no equivalent zeal for improvements to 'safety' relating to other brands of aircraft, even when they are involved in accidents with fatal consequences. I don't need to list the types that have had accidents resulting in fatal consequences, even for just this year alone, most people know of them. Jabiru does not figure on that list.

 

The noisiest protagonists using this line to justify their statements are, I have noticed, quite often fond of using such terms as 'Nanny State' when it comes to denouncing, as they often do, other 'safety' initiatives not of their own confection, from CASA requirements to road rules and beyond. At the most polite, their concerns seem to be highly selective.

 

Has anyone actually asked the Jabiru owning / operating community what they want by way of 'action' on their behalf? Or is it simply a case that these protagonists have decided - for whatever underlying reasons they may have - that their intervention is required on behalf of all the Jabiru owning / operating community, abandoning their otherwise oft-held views that having other people make decisions about their 'safety' is an intrusion on their freedom to make their own decisions in the specific case of Jabiru?

 

 

[facthunter]

You have misquoted me Dafydd. Perhaps my post was not unambiguous. Apologies for that but some of my posts need to be read carefully. I don't work on Jabiru motors these days. It's too confused and getting to the stage where you are exposing yourself to litigation, potentially. The reference to pulling through of the tapers was in relating to the only failure mode I have experienced on ANY engine was that way. AS to dust wearing them out. I work on many motors that have the valve gear exposed fully (as many early aero engines did) and I have never seen the dust wear the collet retainers at the spring contact surface, out either, It does wear guides stems and rocker contact faces as you would expect.. Generally hard metals do not wear soft ones out in the presence of dust or grit. It is the other way around , as the dust gets into the softer metal and laps the harder one.

 

Like you I want concrete evidence of specific failures, to GET SOMEWHERE in a systematic process. that provides answers. I have some thoughts on the matter, but it's not relevant in the current hysterical??? environment. I have tried.. Nev

 

 

[Dafydd Llewellyn]

Nev, my apologies - I know well that you have similar views to myself.

 

POST EDITED AS IT DOES NOT ADD VALUE - MOD

 

I've never come across a wear problem with valve collet retainers, in the taper; really, there's no reason why the taper should wear, unless the valve springs are surging, because there should not be any relative movement between the outer faces of the collets and the bore of the taper. Normally, I have to tap the collet holder with something to release the collets, in fact. So I really want to see one of these failures with my own eyes.

 

 

[facthunter]

Thank you for the nice comment. I do appreciate that. The problem was deformation rather than wear. A few engines still wear the valve grooves and let the valve go. Once they don't clamp properly bad things happen. Even with nitrided stems. Nev

 

 

[Oscar]

Nev, I've seen several instance of exactly what you mention: valve stems grenading, they looked as if they'd been put in a chuck on a lathe and hit with an angle grinder. These were on the same engines I used to build for club-level racing: Toyota Corolla 3K's, heavily modified. (None of mine - but I restricted my engines to 8300 revs, and these had mostly been run to around 8700 before deciding to pursue a new career as scrap metal). Valve bounce and an aggressive cam. We used standard valves and collet retainers and the heaviest springs we could stuff in there in there; I've seen stripped/mangled/shattered collets but never a failed (though sometimes a seriously abused!) collet retainer.

 

I don't buy Jabiru's 'dust' explanation - but I do point out that Jabiru had accepted and identified the problem (nearly 23 or months ago) and recommended an inspection regime that IF FOLLOWED provided a response to that problem.

 

Let's get to some fact-finding here:

 

1.: How many documented cases are there since that Service Letter was released of collet retainers failing have there been?

 

2: How many instances of excessive wear have been found through inspection according to the Service Letter?

 

3: In the case(s) of excessive wear being found through inspection, has this been reported to RAA as a defect?

 

4: In the case(s) of excessive wear, has Jabiru been approached to provide a replacement collet retainer - and if so, has this been provided - and at what cost to the owner?

 

 

[Dafydd Llewellyn]

Well, Andy, you can get an answer to Q3, surely?

 

I'd observe that "valve bounce" is in fact what happens when the valve springs reach their critical surge frequency - i.e. normally an RPM well above what the engine was designed for. This causes the spring to momentarily lose its pressure. That would definitely cause mischief in the valve collet area - but I'd not expect this to be a likely cause in a Jab engine in an aircraft. See

 

 

 

[Russ]

This thread just might get interesting........." Facts" .......gimey the facts.

 

 

[facthunter]

About time we dealt in them.

 

Once things start to shed metal it gets all through the engine. I recall a BMW engine years ago that wouldn't hold valve clearances. The rockers were steel on steel and eventually the entire engine was history. Not a lot of metal but you don't need much.. Nev

 

 

[AVOCET]

Question ,

 

Have these retaining washers been failing in "from new " heads , or are the failing in overhawled top end heads ,

 

Mike

 

 

[facthunter]

I have no idea, but it would not rate as a real problem in the big scheme of things if logical steps were made to correct it. It's rarely a problem. This is NOT a race engine. It just shouldn't happen. So that is the easy fix.

 

Exhaust valve failures Yes. Why not? They are a critical part and if they overheat and warp or don't have the correct running clearance, I would expect failures. IF you run manually adjusted tappets and keep a record of what is happening to the settings on each ex valve, you have a chance to anticipate the problem and rectify it before it fails. The timing was set to a more retarded figure sometime ago together with a compression reduction. The more retarded ignition timing would tend to make the exhaust temp increase, also. Nev

 

 

[Dafydd Llewellyn]

Question ,Have these retaining washers been failing in "from new " heads , or are the failing in overhawled top end heads ,

Mike

Let's go back a step:

1. Have these retaining washers actually been failing?

 

2. If so, what is the failure mode?

 

3. If we have an answer to Q2, who has the failed part?

 

4. Was the failed part analysed to determine its metallurgy & heat treatment condition?

 

5. If not, why not?

 

 

[jetjr]

POST EDITED AS IT DOES NOT ADD VALUE - MOD

 

Yep likely some valves have failed/dropped/whatever.

 

did they have washer problems? or it that just what people assume because of SB.

 

The valves can give problems for plenty of reasons, crook valve, excess leakage, burnt stem, most likely is sticky guides. A long term known problem. Detailed in manuals as long as Ive owned one.

 

Ive had a few of these, have sent back 2 heads on new rebuild to be looked at. tolerances are very fine. This is what daily pull through is looking for.

 

Was taught to look VERY closely for burnt oil in rocker boxes at service as this escaping gas gums up guide. Ironically maybe they are tight from new, loosen a little, then begin to gum up all maybe in 300-400hrs???

 

Theres some link to overheating too but cant think of it

 

Jabiru are aware of it and are doing things to make this type of failure less catastropic, recessed pistons is a recent one. Roller rockers and Camit rockers are to help side loading and guide wear???

 

Can valve problems be linked to detonation in any way?

 

 

[Oscar]

jj - the new CAMit rocker geometry is a better than 50% improvement in reducing side load on the valve stem over the original ones: http://camitaeroengines.net/collections/engine-components/products/2200-rocker-arm-kit-solid-lifter. They, plus the CAMit bushes, are rather cleverly grooved to get oil down to the guide no matter what the attitude of the aircraft (in normal flight conditions!) is.

 

You're exactly on the money re obvious signs of overheating being a wake-up call to look for 'collateral damage' - as it were - that may not be intuitively obvious, nor immediately present itself as a problem. Fukl engine monitoring with data recording that can be examined, say, at each service would help a lot in providing guidance for maintainers as to what they should particularly check.

 

Perhaps one day someone will contact some of the FTF's that have good service history from their Jabs. - I believe that Lilydale, Echuca and Gawler (I think it is) are amongst those who do - and seek to get a profile of how they manage their aircraft, both in terms of maintenance and operation.

 

 

[Dafydd Llewellyn]

A good example of the oversimplification of the issues by othersYep likely some valves have failed/dropped/whatever.

did they have washer problems? or it that just what people assume because of SB.

 

The valves can give problems for plenty of reasons, crook valve, excess leakage, burnt stem, most likely is sticky guides. A long term known problem. Detailed in manuals as long as Ive owned one.

 

Ive had a few of these, have sent back 2 heads on new rebuild to be looked at. tolerances are very fine. This is what daily pull through is looking for.

 

Was taught to look VERY closely for burnt oil in rocker boxes at service as this escaping gas gums up guide. Ironically maybe they are tight from new, loosen a little, then begin to gum up all maybe in 300-400hrs???

 

Theres some link to overheating too but cant think of it

 

Jabiru are aware of it and are doing things to make this type of failure less catastropic, recessed pistons is a recent one. Roller rockers and Camit rockers are to help side loading and guide wear???

 

Can valve problems be linked to detonation in any way?

Thanks for that; I can't at this point do more than surmise that all these things indicate excess valve temperatures. The link to overheating is likely to be that the valve guides are "growing" inwards - bronze does that, and provided it's not excessive, it's useful in maintaining the guide to valve clearance. The stellite valve seats are poor conductors of heat, so the valve has to shed its heat via the guide - and obviously the guide clearances are critical to that. If the valve head gets too hot, it acts as a trigger for detonation, as Ian Bent has identified, and detonation drives the exhaust valve temperature even higher, so it's a vicious circle. The whole thing seems to go over the edge when the CHT gets up around 200 C (but Ian has first-hand info on that, not I).