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jetjr

New Through Bolt SB JSB031-3

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Targeting Aircraft used for training

 

Private use exempted

 

Only briefly read but seems to say new 7/16 bolts, no loctite and 43lb torque

 

Must be done @500hrs bolt life

 

Needs to be read carefully as theres lots of info for 3/8 bolt users too.

 

 

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no loctite and 43lb torqueMust be done @500hrs bolt life.

Is this approaching industry standard practices for something new?

 

 

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But this won't get CASA off their back will it ? Another inconvenience foe flying schools. I am well and truly had enough of the BS involved with CASA and Jabiru.

 

 

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I believe we may have mentioned before, the CASA action could result in cost and problems for owners with little guaranteed result

 

jabirus in training now have to implement significant engine upgrade AND remain restricted

 

If it fixes the problems great, if not.....

 

 

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Camel, so you are unhappy when the Jab factory does something positive, and CASA is unhappy when they don't ?...

1. I complied with JSB031-1

 

2. Does JSB031-3 solve the problems ?

 

3. Will CASA accept this as the fix ?

 

4. Why is it directed at flying school aircraft only ?

 

5. Why bother doing the SB unless this is a fix and satisfies CASA ?

 

I'm happy to do through bolts and anything else, but not if it is still limited by CASA,

 

If CASA are allowed to continue this circus they will pick on anything they want.

 

I believe that Jabiru and CASA are being silly, if I do through bolts then what, what's going to finish this ?

 

I will wait and see and use my plane for my own pleasure until the final approved fix is agreed on.

 

Maj, what action do you support ? What is the the bigger problem Jabiru or CASA ? If CASA handled

 

this in an intelligent manner it could and would have been solved years ago. Doing it the way they did is

 

really strange !

 

 

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If CASA handledthis in an intelligent manner it could and would have been solved years ago. Doing it the way they did is

 

really strange !

Strange? It is completely outrageous, without proper foundation and completely lacking in actual evidence or valid reason. But then they are the regulator & can do what they like no matter what agenda they have.

 

 

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Hard to imagine that a 'school aeroplane" SB is any sort of long term fix, more likely to be a way to stop the failures (attempt to) while they sort the underlaying problems.

 

At least something is happening! Prey, the schools arent "testing' another idea tho, and they will apply it over the board IF it works..If thats the case, they can pay me as a test pilot !!

 

 

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1. I complied with JSB031-12. Does JSB031-3 solve the problems ?

 

3. Will CASA accept this as the fix ?

 

4. Why is it directed at flying school aircraft only ?

 

5. Why bother doing the SB unless this is a fix and satisfies CASA ?

 

I'm happy to do through bolts and anything else, but not if it is still limited by CASA,

 

If CASA are allowed to continue this circus they will pick on anything they want.

 

I believe that Jabiru and CASA are being silly, if I do through bolts then what, what's going to finish this ?

 

I will wait and see and use my plane for my own pleasure until the final approved fix is agreed on.

 

Maj, what action do you support ? What is the the bigger problem Jabiru or CASA ? If CASA handled

 

this in an intelligent manner it could and would have been solved years ago. Doing it the way they did is

 

really strange !

No doubt CASAs method was off the wall...I mean the Saturday after they had closed their offices for Xmas break..C'mon

 

However they have never been know for any style or class in the way they do things. What they have done I hope is put a red hot poker up RSs arse, so that he will finally have to look at the problems and do something about improving the reliability. He was not going to do anything any other way as I see it. Many of the reliability problems have been occurring now for at least 20+ years, ( overheating, sucking exhaust valves) wether the dedicated few want to admit it or not. I think at least CASA has got them moving, and I don't see any way out other than to improve the engine or replace it with another. My personal opinion only, not reflective of my role as a board member.

 

 

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What makes you think RS has changed his view from that he held 2 months ago.

 

This action and this SB hits owners not Jabiru.

 

They sell new aeroplanes, fixing old ones is just a legacy they could choose to ignore

 

Only thing that keeps them interested is value in the name and thats been damaged badly

 

 

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True, the name has been affected badly by poor reliability problems. Let's hope they are on the right track with these mods.

 

 

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What makes you think RS has changed his view from that he held 2 months ago.

This action and this SB hits owners not Jabiru.

 

They sell new aeroplanes, fixing old ones is just a legacy they could choose to ignore

 

Only thing that keeps them interested is value in the name and thats been damaged badly

Sue should send Rod overseas on a "fact-finding mission" (or lock him in a shed) and go talk with Ian Bent. They both have so much to gain- and everything to lose.

 

 

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So, if the engine has been built already and the mains gap is set won't more torque on the through bolts close the gap on the main bearings and cam tunnel?

 

 

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Id assume thats why theres direction to monitor this and check for it

 

 

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True, the name has been affected badly by poor reliability problems. Let's hope they are on the right track with these mods.

Let's hope indeed, but I suspect it's more a bandaid fix to show CASA that they're responding. Time will tell.

 

 

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The only way to control this is to evaluate the distortion due to clamping and allow for it in your original dimensions. There is "crush" built into all bearings or they would move in their tunnels and fret the surfaces. I doubt the extra torque on the bolts results in a large change of dimension. Be lucky to be a 1/4 of a thou of an inch but it is easily tested. Any time you press fit( as an example),a machined bush you have to allow for crush. Two halves of a case have dimensions that hold the bearings tightly. To do a good job you finally machine it in place. IF you want perfect roundness of the mainbearings you could do this, but it may not be necessary. Nev

 

 

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If you reduce the minimum running clearance you will have trouble. Any rapid wear situation is abnormal. In a clean normal environment there is very little actual wear occurring. If you have insufficient clearance the usual problem is overheating locally of the affected part and then lubrication failure and seizure (welding for want of a better term) Nev

 

 

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From memory ( which is not good) it was after a through bolt mod performed, the clamping force was too tight according to the independent investigation ( not jab).

 

 

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It would be possible for that to happen, but something would have to be wrong for it to be that critical, clearance wise. IF there is any fretting of the mating case surfaces it The stud,can't be replaced (or retensioned) without extensive work. When some Studs called Bolts break ,are they sometimes replaced without engine strip? Nev

 

 

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Id have to read it again but it talks about using spring gauge on prop whilst turning, measuring resistance before and after

 

Obviously with plugs removed

 

 

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You still have all the loads in the valve train and the piston rings to cause friction and make the determination difficult. It's pretty silly to use drag as an indicator, where practically no clearance must exist to cause some and a situation where a positive clearance of probably .002" is needed for the engine to run safely. Nev.

 

 

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I don't know that much in terms of Aero engine crankcase halves. But if fretting occurred I would suggest the crankcase may be a right-off unless the mating surfaces can be machined and the crankcase tunnel line bored.

 

Are you permitted to machine and then line bore aero crankcases?

 

Surely if the crankcase is correct in all dimensions, any minor increase in clamping pressure would have zero effect on bearing clearance. If it did have an impact on bearing clearance, I would suggest the crankcase dimensions are incorrect. The bearing clearances should be statically set by the machined surfaces of the crankcase relative to the symmetry of the main bearing tunnels.

 

Whats your thought on that Nev?

 

 

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