Just a heads up!

[facthunter]

Fretting rather than chattering marks. I think it has been under tensioned. Its the area that gets the hottest.

 

 

[jetjr]

Ill agree that the head wasnt tensioned up. surprised the problem wasnt heard or seen or felt in pre flight tests.

 

The newer thin finned heads are a big improvement in cooling and therefore recession and over temp problems in heads

 

In saying that, the rest of the older solid lifter engine should be better than newer variants.

 

 

[Scotty 1]

The owner of the engine had been in touch with the manufacturer and followed all relative AD's and their advice over a number of years! There was no indications of any problems during the preflight. The plane was on it's third test flight with an independent test pilot. The test pilot was doing circuits when he identified what he at first thought was an exhaust leak and immediately landed. After landing and finding the "exhaust leak" the bolts were found to be loose during the head removal.

 

Thank you all for your comments, especially the ones that made me laugh, and if there are any further developments or positive answers I will let you know but at this stage it looks like a flawed billet.

 

 

[gandalph]

ask me about the nightshift work I did changing Honda VFR 750 porous casings on the sly ...

Sly and Bex. Two words I wouldn't normally expect to see here!

 

 

[billwoodmason]

The head (or heads) on this engine may have been removed during the upgrades mentioned while engine was inhibited for all those years before finally being put in service. Just sayin.

 

 

[jetjr]

How loose were bolts? Has the head ever been off?

 

When it comes down to a choice between materials failure or human stuff up - maybe years ago - Ill back stuff up every time.

 

 

[Oscar]

Scotty, if all the AD's were done, were the through bolts replaced? I ask this because, if they were, with aged crankcase sealant it is very possible to get cracking of that when the tension on the through-bolts is released, which will lead to crankcase fretting.

 

That does in NO WAY explain the cylinder head situation - and I'll agree that an inclusion in the material may well have been the cause. BUT I'd - if it were my engine - be doing a full teardown at this point.

 

I also have an 'old' engine - though completely rebuilt and upgraded to CAE specs in most areas a couple of years ago, but only test run since then - so this is a very serious query and in no way a defence/excuse for Jabiru. I'd be most keen to know whatever you find.

 

 

[facthunter]

Rectify by replacing the head affected and check tension on all other bolts if there's no marks on the cylinder at all , or the piston and no erosion on the top face, you should just be able to replace the head. A factory rebuilt one should be fine if it's checked properly. Billet metal is rolled and is used to avoid faults. It's more reliable than a normal casting. I would be surprised if it had an inclusion. It has failed exactly as I would expect with loose bolts. Once there is a leak it's like a blowtorch and it just melts the metal away. Nev

 

 

[facthunter]

Why is that funny Ruff as ? Nev

 

 

[Oscar]

Billet is far more reliable in material spec. than cast; in fact, it was the extremely high rate of rejects from casting that steered Jabiru away from its first attempts at manufacturing (the 1600 engine). Cast and forged is reliabl;e - for a seriously volume manufacturer such as Lycontinental or even Rotax - but a small-volume manufacturer such as Jabiru has to balance the additional machining costs for billet manufacture against the waste costs of having to recycle defective castings.

 

For a manufacturer that can order tonnes of product, it's easy to return material supplied that by test is defective without penalty. A 'small' player, is forced to compromise.

 

Personally, I would not be at all prepared to scoff at the idea that this particular head had a material defect. It's the first one I have heard of with this type of failure, in what must have been around in excess of 7,000 heads produced. That's pretty small odds, but that's no relief to the poor owner who is sitting there with a broken engine.

 

There are very probably decent 'spare' heads out there, sitting in sheds, that may be of help with refurbishment - I have some, but they are REALLY early models.

 

For all its reputation on sites such as this, I have ALWAYS found Jabiru to be extremely helpful and informative if presented with a good explanation of the problem. They WILL go the extra yards to help you out.

 

 

[ruffasguts]

Why is that funny Ruff as ? Nev

Must be fat fingers

did not know that I had hit the funny button in fact don't know how to activate any of those add ons

 

Mick W

 

 

[gandalph]

For all its reputation on sites such as this, I have ALWAYS found Jabiru to be extremely helpful and informative if presented with a good explanation of the problem. They WILL go the extra yards to help you out.

That has been my experience as well. Although my ears did get singed by Rod over a query I made about the strength of some bonding on our aircraft that I thought wasn't too special, but it was sorted amicably and Jab have continued to provide me with excellent customer service whenever I've approached them.

 

 

[facthunter]

Vacuum diecasting is only for fairly mass produced stuff. It's NOT DIEMETAL. Metal multipiece dies are used, and are very accurate. Vaccuum casting eliminates porosity. That is how some of the good lawnmower V twin engines are made, and most mass produced motorcycle engines but again some of the metal used doesn't offer top of the metallurgy performance.

 

Forging has dimensional challenges. There is a limit to what you can reasonably forge shape wise. and there are stresses.

 

The CNC'd heads Jabiru produce are quite impressive, particularly the port work. Higher spec metal might make the valve seats more firmly located. Higher tensile. Nev

 

 

[facthunter]

Must be fat fingersdid not know that I had hit the funny button in fact don't know how to activate any of those add ons

Mick W

Think that happens a few times. Thanks for telling me. Nev

 

 

[Scotty 1]

 

 

 

 

 

[IanR]

The pictures are interesting - for a motor that has only done 5 hours seems like quite a lot of vertical scuffing and the deposits on the cylinder walls look like rust ? Is the scuffing normal for this type of motor ?

 

 

[facthunter]

I would pull that cylinder. There's a couple of marks in the higher ring travel area where it's been hottest and you will need to clean the mating surface accurately. I've seen them hotter and looks like there has been rust.. Was the motor ever started before being installed in the plane? Nev

 

 

[jetjr]

supposed to be regularly inhibited even in storage, 60 days rings a bell.

 

What are the hoses running below cylinders? thats a very hot pathway to take. and suspect it will maybe hinder cooling a bit

 

 

[Oscar]

If it's a fuel hose, it should NOT have aluminium (as it appears to have) or brass fittings fittings anywhere in front of the firewall (and yes, I know that both the mechanical pump and the carby have, usually, brass fittings - a naughty according to FAA installation requirements... ) It looks to me as if it is an oil cooler hose to a rear-mount ( i.e. not Jab normal practice) oil cooler? Is it installed in a Jab?

 

Personally, I suspect that barrel is cactus. It appears that there is considerable heat/flame erosion around quite an area and the contact between the entire head and barrel mating surface area is quite critical for effective heat transfer; if 'skimming' the top land on the barrel to restore the surface, you'd need to get the recess in the head to be a factory-tolerance match. However - and I am not a metallurgist, but the owner might want to talk to someone with the appropriate expertise - a localised heat exposure to combustion-temp heat MAY change the molecular distribution within the metal and make that barrel very likely to warping / embrittlement or other nasty consequences.

 

One further point: the last set of piccies ( especially Piccy #3) show an obvious amount of Loctite (POSSIBLY 515 - the crankcase sealant grade - but one can't tell from the colour) having been applied to the head prior to installing. It's been some time since I built my own Jab. engine at CAMit, under the watchful eye and mentorship of the CAMit engine assembly guys , but I certainly don't remember using any Loctite when seating the heads, and it certainly is NOT mentioned in the Jabiru 2200/3300 Engine Overhaul Manual JEM0001-2. (available from the Jab. web-site) - p.126.

 

IF - as it appears - that engine ( or that head, anyway) was assembled using any Loctite as a sealant between the head and the barrel join, I personally would have it as No. #1 SUSPECT for the loosening of the head bolt tension. CAMit would have done the original engine assembly, and Ian Bent can almost certainly tell you what assembly techniques were used for that specific engine. If it was supplied as a 'factory-fresh' engine from Jabiru and has definitely never had a spanner on it since, there are many questions to be answered. If it has had SBs undertaken locally since it was made, then I suggest there is a real case for digging into who did those, and how they did them.

 

 

[Scotty 1]

One further point: the last set of piccies ( especially Piccy #3) show an obvious amount of Loctite

 

obvious amount of Loctite??????

 

 

[Oscar]

One further point: the last set of piccies ( especially Piccy #3) show an obvious amount of Loctiteobvious amount of Loctite??????

Scotty: in Piccy #3 of Post #40m, there is an obvious ring of red-brown Loctite at the base of the head/barrel join. Seriously, trust me on this - I've spent HOURS trying to remove the last vestiges of Loctite 515 from the crankcase join of a Jabiru (actually, two, to be accurate).

 

The problem with Loctite 515, is it sets like cement in about 5 minutes at around 20C. Read the Jab engine maintenance manual and you will see that Jab. mandates an assembly at high speed. I've watched the CAMit assembly guys putting a Jab. engine together, and it's a Pas de Deux for two highly-experienced operatives working in a controlled environment. If you saw a video of the crankcase assembly , you'd think it was fast-forwarded - but it is most definitely NOT.

 

If Loctite 515 sets before the adjoining components are torqued up, it is like resorcinal glue: brittle as glass, and with no adhesion to the mating surfaces which it was supposed to join. Under the forces of expansion and contraction at 180C plus, it will crack and be blown out of the joint under pressure. THEN - you have no torque on the securing bolts.

 

 

[01rmb]

Oscar - are you talking about the silver between 3 o'clock and 7 o'clock? It looks to me to be molten aluminium from the head. And my guess is the head was not properly tensioned to the cylinder face causing the hole and the burning across the face of the head cooling fin.

 

 

[Oscar]

No, the radial scouring at the face of the barrel/head join land. It's fairly close to the finish you get with a CNC oxy-cut - not even as fine as a water-jet cut.

 

 

[jetjr]

If the throughbolts have been done, then one side heads have been off

 

Actually looks like they have NOT been changed

 

 

[Scotty 1]

Sorry Oscar, but there is no other way to put this. You are totally wrong. Others have seen, it appears, what you can not. Same as in your post#12 your post #46 may have been in haste. There was no Loctite used on the heads. Anywhere. Bolts or mateing surfaces.