4 Bolts

[RotorAndWing]

The thing to worry about is the 1 (one) single, only bolt on the end of the strut on many high wing airplanes. It's carrying all that load when you hit turbulence, pull, etc. And if that one bolt lets go, the whole wing folds up at the root.

Same with rotor blades on a helicopter, usually it's just one attach bolt on the grip. Then there is the Jesus nut on the rotor head.

 

[bnt83]

Start looking into Beechcraft wing bolts, spar bridges and spar strap. Get ahold of the ADs and maintenance manuals surrounding these bolts. The wing attach fittings can fail if the washers under the nuts or bolts are installed incorrectly.

 

[RotorAndWing]

Start looking into Beechcraft wing bolts, spar bridges and spar strap. Get ahold of the ADs and maintenance manuals surrounding these bolts. The wing attach fittings can fail if the washers under the nuts or bolts are installed incorrectly.

I thought Beech had so much "quality" built in their products this could never happen!

 

[Henning]

I thought Beech had so much "quality" built in their products this could never happen!

The design failure I see in this issue is that the bolt 'bathtubs' on the wings need regular cleaning because the drain hole is too small and gets clogged with typical scunge. Rain water sits in them and everything rusts and corrodes.

When I go look a Beech for someone the first thing I do is pop the tops off the tubs. I haven't kept track but I probably walk away from 30% of them at that point due to what I see. Those problems get really expensive really fast.

 

[Ted]

As I understand it, the Beech issue was more due to pilot stupidity than anything...

 

[weirdjim]

The B-727 pod engines (#1&3) are attached using 3 bolts.

Take a look at a Boeing or Airbus with under slung engines and the engine and pylon attach points as well.

And, as I remember from going through 3-holer maintenance school 50 some years ago, those bolts are machined down to provide positive failure and removal of the engine in flight from the airframe under extreme vibration rather than shake the tailfeathers off or toss blades through the structure when the engine lets go.

Yes?

Jim

 

[Henning]

Speaking of bimetallic issues I can't figure out why you can hardly find/buy Duralac in the US. It's specifically for these issues, when you put a steel or stainless steel fastener into aluminum you use this similar to how you would use anti seize and it insulates the interface against electrolysis. You should see the difference on a sailboat mast when you try to pull the stainless studs out of the aluminum threads.

 

[EdFred]

Take a single 1/2" bolt. It has a 150,000 psi strength and wouldn't shear below 17K lbs. of force. So nothing on a 4,000lb. airplane is going to break four of those unless you ram it into a concrete wall at 110 knots and probably not even then.

That's tensile, not shear.

A490 1/2" has about 17,000 psi of shear.

 

[BiffJ]

I think you all need to look up some hard to find info on actual AN bolts. Standard AN bolts are 125,000psi and the high strength stuff goes up much higher.
Here is a link to a chart. Of course there are safety factors involved but that doesn't involve derating bolts to grade 5 standards.....

I think Henning got it pretty much right on. You'll likely pull structure apart before breaking the bolts. Look at the seat belt retaining bolts and when you realize they're all number 10's (AN3) you may freak out. However with an ultimate shear (single) strength of just over 2100 lb each bolt can handle a 10 G load with the slightly overaverage weight flyer. There should be at least 2 holding the belts and 3 or 4 with shoulder belts. Look at what they're bolting the belts too and thats the place to cringe.....
This page has specs on the various bolts and fasteners

http://www.skybolt.com/Catalog-AN-MS-Hardware.pdf

Frank

 

[Henning]

I think you all need to look up some hard to find info on actual AN bolts. Standard AN bolts are 125,000psi and the high strength stuff goes up much higher.
Here is a link to a chart. Of course there are safety factors involved but that doesn't involve derating bolts to grade 5 standards.....

I think Henning got it pretty much right on. You'll likely pull structure apart before breaking the bolts. Look at the seat belt retaining bolts and when you realize they're all number 10's (AN3) you may freak out. However with an ultimate shear (single) strength of just over 2100 lb each bolt can handle a 10 G load with the slightly overaverage weight flyer. There should be at least 2 holding the belts and 3 or 4 with shoulder belts. Look at what they're bolting the belts too and thats the place to cringe.....
This page has specs on the various bolts and fasteners

http://www.skybolt.com/Catalog-AN-MS-Hardware.pdf

Frank

Yeah, the seat bolts don't carry the weight unless you're getting rear ended. They just have to hold the seat weight in a typical crash, the seat belt bolts/fittings take the occupant force.

 

[bnt83]

With 55WB's engine dismounted and at the engine shop, the club is taking advantage of the time to do some additional maintenance items, including an inspection and painting of the engine mount frame. Today I helped our club A&P remove it.

Amazing to me that all that's keeping that 6-cyl power plant mechanically connected to the air frame is just just 4 bolts.

But like 6PC, I'm easy amazed at many things in aviation. Like seeing a Cherokee's engine on my first lesson and marvelling how that small 4cyl engine was going to take me, the instructor, and the aircraft into the air and haul us around at 110 KIAS.

You should grab the horizontal stabilizer on a Beechjet, also known as Mitsubishi Diamond and Hawker 400XP, and shake it up & down. It looks like it could fall off at any moment.

 

[RotorAndWing]

And, as I remember from going through 3-holer maintenance school 50 some years ago, those bolts are machined down to provide positive failure and removal of the engine in flight from the airframe under extreme vibration rather than shake the tailfeathers off or toss blades through the structure when the engine lets go.

Yes?

Jim

Correct.

 

[jesse]

8 AN3 per wing is what keeps the Flybaby wings on. They don't look that strong but apparently plenty strong for a 1000 lb gross airplane.

 

[Arbiter419]

8 AN3 per wing is what keeps the Flybaby wings on. They don't look that strong but apparently plenty strong for a 1000 lb gross airplane.

2xAN5 bolts per wing on the super cub if I recall correctly...did not expect that first time I had the wings off that plane. Although that has the benefit of a strut, your flybaby has flying wires right?

 

[jesse]

2xAN5 bolts per wing on the super cub if I recall correctly...did not expect that first time I had the wings off that plane. Although that has the benefit of a strut, your flybaby has flying wires right?

Yeah. And the way it's built means the load isn't exactly even..so 4 of those will take more quite a bit more load than the other 4 I believe.