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SB inspect heads


jetjr
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From what I can see you (everybody) will have to remove all heads to inspect. That means ALL Jabiru motors, Thousands! .... It's about 4-6 hours re and re 6 heads...And who is going to put them straight back on without inspecting plus replace/reseat valves ( Fools and Angels?) I certainly wont.........Looks like "Its an ill wind that blows nobody good!" All the Lame's and L2's are going to have a busy few days, especially as it's before next flight! Jabiru parts staff on overtime...............Unless? it's only the Top Bolt ? Then it's really only an inspection, The picture shows a top bolt by the look of it. But the AWB does not say that, does it?

 

 

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The way I read it, it is an external crack and should be detected by just looking where indicated. Lots of alloy heads crack. Some require action and others require ongoing inspection. Darren is doing his job. This is aviation. Not lawn mowing. Nev

 

 

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You're right Nev but getting access to lower side is near impossible, inlet and exhaust ports there plus push rod and oil tubes.

 

Would appear either as indicated and heads will need removing or only considers top bolt in which case is poorly written

 

Other option I guess is half baked glance with a torch.

 

So on an engine with less than 100 hrs we are looking for cracks as seen on engine done 1900 hrs AND has to be done before next flight.

 

What issues are these cracks likely to lead to?

 

After rego renewals delays, claims that owners can no longer maintain Jabirus, rechecking of flight controls for only 19 reg. Im am having issues with competence from tech office. Not much flying going on this year.

 

 

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Can I borrow yours? Besides the Bulletin does not mention which bolt to check. You must assume it's all of them...Quote AB "cracks were discovered

 

between the cooling fins in and around the area of the hold down bolts" ie: check 'em all buddy"

 

 

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My OPINION is that the worst thing that could happen is a substantial compression leak. A leak could be checked with soapy water at the same time as the head is pressured for a leakdown check. Use a dentists mirror to see the hard to get to cracks better. A commonly occurring head crack typically goes from the spark plug hole to the exhaust port and can result in a valve seat insert falling out and considerable damage. This would be far worse than the crack we are talking about. The high hours mentioned makes the head replacement not so unlikely, It's probably the result of the heat treatment being nullified by the excess CHT it has been subject to many times, as well as the deformation of the head recessing into the cylinder at the contacting surface near the hot port, needing the retorqueing of the bolt(s).

 

Bex , I agree... If there has been only ONE instance of this it is an over reaction, especially at the number of hours done. Drawing user's attention to it is probably sufficient. Might be a bit touchy after a lot of CASA attention. Nev

 

 

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That's kind ne of what I thought. Wouldnt next major servic be adequate for inspection?

 

A compulsory, before next flight onspection based on one long hour engine seems excessive. I thought according to plenty here jabirus didnt go pver 400 hrs anyway so risk is low.

 

I bought a $40 USB one runs on laptop as webcam. its small enought to go down spark plug hole and might be good enough to do this.

 

 

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I believe you should check for gas leaks in that area every 100 hours. If the head face is leaking it will run a lot hotter, and I think they commonly do leak. The head metal closes in on the bolt too and requires easing after a while. Nev

 

 

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If it is an isolated case, It has little relevance as we don't know which type of head is and the variabilities of usage and the installation peculiarities mean we have far from a controlled situation to base anything on. There is no harm in being cautious. AS Deborah says it should be standard practice to inspect these areas, including exhaust joints and cabin heaters etc. Nev

 

 

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So I just inspected 3 of the spare heads I have in a box, done 600 hr's all are cracked. the cracks are happening where the bolt holes are counter sunk leaving a thin side wall ( top 3 head bolts) nothing sinister just a design flaw by the looks if the wall was machined out there would be no problem.

 

 

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Yeah sorry mate, long day sore eyes! exactly, wish I had a drawing, but it does appear to be insignificant if it can be stopped from propagating further. I'm just uploading some pic's to the computer and will post when done.

 

 

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Where did "compulsory" come from? I only saw "Advisory" as in "Advisory inspection before next flight".

 

So, if the problem had been reported to Darren and he did nothing with the information you'd all be OK with that? Or would people get the trots when they fall out of the sky and find out the Tech Manager knew about the issue but didn't tell anyone about it?

 

The big thing is to report all cracks found then Darren can work out if it is an isolated incidence or an epidemic.

 

My money is on the latter.

 

 

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Sorry the pic's are poor but you get the idea, yes I read it as an advisory only, however if it was the root cause of a failure the insurance company would be looking closely at it! It seems fairly benign however if the cracks propagate further than the radius of the bore..... well probably scrap! not sur what the fix will be, probably a SB with limits and monitoring every xx hours, long term will be the removal of the excess metal in the offending position.

 

 

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