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cffd(at)pgrb.com
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 Posted: Fri Nov 03, 2006 3:40 pm Post subject: Jab Service Bulletin JSB 012-1 Fly wheel bolts |
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According to Jab Service Bulletin JSB 012-1, it appears that almost all of
us will have to pull our alternators and check the fly wheel bolts after six
months or 50 hours which means now for most of us. It also says that if they
move at all, they must be removed cleaned and replaced with locktite 620
which is extremely strong. If used originally the 620 might keep them from
turning even if the tension on the flywheel is not enough, you may never
know.
Pete, Andy, Jim what is your take on this bulletin? Here is the link.
http://www.jabiru.net.au/Service%20Bulletins/Engine%20files/Jabiru%20Engine%
20Flywheel%20Attachment%20JSB012-1.pdf
Chuck D.
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Terminator
Joined: 15 Mar 2007
Posts: 4
Location: Cape Town
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| Posted: Sat Mar 17, 2007 1:48 am Post subject: Re: Jab Service Bulletin JSB 012-1 Fly wheel bolts |
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Hi Chuck, I have flown a short time in a Jab 400 with a total time of 250hrs, here in South Africa, with a good friend of mine. Three weeks ago we were in the air at 2000ft ASL and fortunatly 5 miles from an arifield, when we heard a lowd screech from the motor.
The noise stopped but we decided to land and inspect and gues what we saw ?!
Two sheared bolts!
I believe a Jab 80hp 2 seater had all 6 bolts sheer in Cape Town and now the preflight procedure is to hold the fly wheel and turn the prop.
You will have noticed that washers have been placed on the bolts. This is simply because the AMO was unable to tighten the bolts as they appeared to be too long, although they are stock standard.
I will send this thread to the AMO, as you may have a good tip in your post.
Mark
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rickpitcher
Joined: 27 Feb 2007
Posts: 76
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| Posted: Sat Mar 17, 2007 8:43 am Post subject: Re: Jab Service Bulletin JSB 012-1 Fly wheel bolts |
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| Terminator wrote: | Hi Chuck, I have flown a short time in a Jab 400 with a total time of 250hrs, here in South Africa, with a good friend of mine. Three weeks ago we were in the air at 2000ft ASL and fortunatly 5 miles from an arifield, when we heard a lowd screech from the motor.
The noise stopped but we decided to land and inspect and gues what we saw ?!
Two sheared bolts!
I believe a Jab 80hp 2 seater had all 6 bolts sheer in Cape Town and now the preflight procedure is to hold the fly wheel and turn the prop.
You will have noticed that washers have been placed on the bolts. This is simply because the AMO was unable to tighten the bolts as they appeared to be too long, although they are stock standard.
I will send this thread to the AMO, as you may have a good tip in your post.
Mark |
Looking at the photo, I have a couple of questions/comments?:
1) I see that the 2 bolts are NOT sheared, but appear to have backed out. The 2 are opposite each other as if the mecahanic was torquing in the standard "star pattern" where we torque opposite sides progressively to equally spread the tension, and the 2 opposite bolts were inadvertantly missed?
2) The pic shows some red stuff on the washer that your AME added. Is that loctite? Curious because the loctite 620 that is called for in the service bulletin is green, not red.
3) I don't see any evidence of loctite in the threads that are showing, my bolts had a residue of loctite along the shank that had to be cleaned off before replacing the bolts with a fresh coat of Loctite 620.
4) The washers under the heads bother seem odd. The new bolts were not the same length as the originals?
Curious.
Rick Pitcher
Jabiru 3300
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jetboy
Joined: 22 Jul 2006
Posts: 233
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| Posted: Sat Mar 17, 2007 1:58 pm Post subject: Re: Jab Service Bulletin JSB 012-1 Fly wheel bolts |
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Hi,
Re the failed bolts it would be hepful to know if the SB had been done or if they are original bolts at 250 hrs, and originally installed at the low torque, for which the SB was issued to correct?
From the photo I cannot tell if the bolts have sheared but this is likely as they will shear at the crankshaft flange which is 1" in from the head.
Mention is made about washers. Standard fitting includes six belleville washers. When I carried out the SB I hand threaded new bolts all the way without washers to test for possible bottoming, and had no problems.
As for the colour of threadlock, only the SB and new engines use green 620, earlier assembly would be red I expect - in my engine the old threadlock did not have much colour and was only evident around the thread ends.
Seems like doing the SB or more will be less troublesome than replacing the alternator.
Regards, Ralph
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Ralph - CH701 / 2200a |
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Terminator
Joined: 15 Mar 2007
Posts: 4
Location: Cape Town
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| Posted: Wed Mar 21, 2007 12:54 am Post subject: Re: Jab Service Bulletin JSB 012-1 Fly wheel bolts |
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Thanks Jetboy and Ric,
interesting info, I will pass this on as you may have some good points in your replies. Unfortunatly, this is not my aircraft and I do not have much knowlege of it so I am only able to comment on what I have seen.
Incidently, the engine was removed and brought to Cape Town for repairs. They found that 3 bolts had sheared and were doing the necessary upgrades re bolts and locktite.
Mark
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rickpitcher
Joined: 27 Feb 2007
Posts: 76
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| Posted: Wed Mar 21, 2007 10:59 am Post subject: Re: Jab Service Bulletin JSB 012-1 Fly wheel bolts |
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Hi Mark
I like your screen-name, it's the same name that our Governer goes by 
When I read your post a few days ago it prompted me to check with the RAANZ guys about an alternate method of compliance that their tech officer said had been approved (by himself) for compliance with the NZ CAA's flywheel bolt AD. The method that he described sounded a little "hinkey" to me, so I emailed RAANZ and NZ CAA to see how well the alternative method was proving out. Bad news.... seems the CAA didn't approve the modified fix after all. Any operator that has "modified" the AD
process will need to redo the AD in compliance with the published
instructions.
Just a "heads up" for your friend to pass along to the shop that is fixing his engine.
FWIW,
Rick Pitcher
Zenair Zodiac w/ Jab 3300
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