Jabiru J170 Pre-Flight Checks - Wing Strut Mount Bolts

[Eric McCandless]

The Jabiru J170 POH says in the pre-flight inspection section 7.5

 

Wing Strut Mount Bolts.............................CHECK Security**

 

** - Wing strut bolts must not be tightened. Nut should just bear on washer.

 

The strut mount bolts appear to be obscured by covers, so I can't even see them. Surely I don't need to remove the covers for each preflight inspection? Maybe I have mis-interpreted the POH.

 

 

[old man emu]

When you are doing this check, you are looking for play in the wing mount. Just push the wing up and down to see if there is any play in it. If things are OK, when you push up, the plane should immediately lift on your side.

 

The covers are usually removed at periodic inspections. If you take them off too often, the screw holes wear and you will have to keep putting in thicker screws because you are ripping out the material the airframe is made from.

 

Once again, don't worry too much about the nuts coming off the bolts. The bolt is subject to Shear Forces, which want to cut the bolt into pieces across its length. If it was in Tension, it would be clamping the wing root and wing root mounting together, and the forces would act on the nut to try to slip it off the end of the bolt. (Poor explanation, but it is the best I can do at this time of night.) Actually, the nut on these bolts is acting mainly as a stopper to prevent the bolt sliding out of the holes it goes through.

 

Old Man Emu

 

 

[Eric McCandless]

Thanks OME. That's good advice about the screw holes too. I am trying to learn as much as I can about my toy, and I also want to be as safe as I can.

 

 

[old man emu]

Going by a lot of the responses to you various questions, I'd suggest that you work hard on developing a relation ship with your L2 or LAME and stick to their advice. They are the ones who have proved by examination that they know what they are talking about.

 

OME

 

 

[Herm]

If you have problems with your screw holes (no being rude!) LOL.... I use a small amount of 5 min epoxy in them to close the hole down again. It's better than using larger screws all the time. After a while you will end up using Coach Bolts...

 

Regards

 

Mardy

 

 

[J170 Owner]

Thanks OME. That's good advice about the screw holes too. I am trying to learn as much as I can about my toy, and I also want to be as safe as I can.

I have had my toy two and a half years and still learn new stuff!

 

 

[jetjr]

Jabiru now have a threaded insert which is glued into hole and allows proper threaded bolts/screws to be used instead of self tappers

 

Be VERY careful doing anything with the screws and holes on the fairing around upper strut mount onto wing, fuel tank is just mm away.

 

 

[brilin_air]

I am trying to learn as much as I can about my toy, and I also want to be as safe as I can.

Eric,

 

It is a good idea when you get your services done by your LAME/L2 to be there with him when he does it. Identifying and learning about the Jab, and how it operates, is one of the most rewarding things.

 

When Brian does services on either ours or other Jabs, I am always with him, and even though I don't fly I have become very familiar with how the servicing is done and what needs to be looked at when the certain hourlys come up.

 

-Linda

 

 

[ianboag]

Jabiru now have a threaded insert which is glued into hole and allows proper threaded bolts/screws to be used instead of self tappers.

Jabiru wanted about $3 each for them when I asked. Rivnuts/Nutserts (at 25c each) work the same. I went round my J200 with M4 Nutserts because I got tired of the self-tapper-hole-enlargement thing. It was a bit of a dog to do, but it was just the once ..

 

 

[jetjr]

Not sure they were that dear but were expensive, rivnuts can easily spin in the thinner material , leaving you a very difficult problem

 

Either way the self tapper thing is a problem long term

 

I lost a small fairing from over wheel strut - $100+ once it was painted etc. Makes these nutsert things look cheap

 

 

[ianboag]

Not sure they were that dear but were expensive, rivnuts can easily spin in the thinner material , leaving you a very difficult problem

I worked out that I needed 50-odd of the Jab thingos. That seemed like a non-trivial sum. I looked (with no joy) for the manufacturer or an agent - I very much doubt that Jab make them. All the 25c nutserts I put in were good - none spun. I was able to borrow the setting tool. Subsequent removal and replacement of covers was a breeze.

 

It worked for me. Your mileage may vary ....

 

 

[jetjr]

If they are done right and you can get a free tool then its probably OK I had them done while AC was there for other stuff, didnt form a major part of the significant other repairs.

 

I even had one of the nutserts with 2 pop rivets (on wheel spat) spin once, tore the rivets out without much effort. It was a xxxxxxxxxx job to get the spat off and fix

 

 

[ianboag]

I even had one of the nutserts with 2 pop rivets (on wheel spat) spin once, tore the rivets out without much effort. It was a xxxxxxxxxx job to get the spat off and fix

That's not a nutsert if I understand you right - those ones are called "captive nuts" or "receptacles". They are common in certified aircraft. The Rolls-Royce solution. Not supposed to ever let go. Jab use them to do things like hold the cowling on. Always seemed a bit of pain in the butt to me. Not cheap .... see http://www.aircraftspruce.com/catalog/hapages/recept.php

 

A nutsert is essentially the same as a rivnut. Kind of like a pop rivet with a threaded bolt in it - http://www.ebay.com.au/itm/200-PIECE-RIVET-NUT-KIT-M4-ALUMINIUM-RIVNUT-RIV-NUT-NUTSERT-RIVET-METRIC-/170873179141?pt=AU_Fasteners&hash=item27c8d5

 

YMMV .. the flexibilty of the ultralight world

 

 

[old man emu]

It's all well and good fitting metric hardware to your plane, but it's a bitch for maintenance people who are mainly tooled up for imperial sizes.

 

OME

 

 

[ianboag]

It's all well and good fitting metric hardware to your plane, but it's a bitch for maintenance people who are mainly tooled up for imperial sizes. OME

Fair comment. I can't buy 8-32 screws at Bunnings or 8-32 Rivnuts from my local engineering supplier. M4 is about the same size. To buy the imperial stuff I have to go to Spruce in the US - not that it's all that dear from them, just inconvenient. I'm not sure whether the PK's I replaced were metric or imperial :-)

 

 

[Wayne T Mathews]

Fair comment. I can't buy 8-32 screws at Bunnings or 8-32 Rivnuts from my local engineering supplier. M4 is about the same size. To buy the imperial stuff I have to go to Spruce in the US - not that it's all that dear from them, just inconvenient. I'm not sure whether the PK's I replaced were metric or imperial :-)

Try Aviaquip in Melbourne. They're pretty good at getting stuff to you fairly smartly...

 

 

[ianboag]

Try Aviaquip in Melbourne. They're pretty good at getting stuff to you fairly smartly...

Probably about the same as Spruce for someone here in NZ ... :-)

 

 

[old man emu]

How many 8-32 screws; how long; Pan head or countersunk; CAD lll plated steel or stainless?

 

You just gotta ask me.OME