MS/NAS Gurus please come hither. 1

[uGlay]

Greetings fellow Eng-Tippers. Today I bring a query that regards hardware substitution in an aircraft manufactured by McDonnell-Douglas. (DC-9-50)

I need to find a bolt similar to HL11VAZ-6 but WITHOUT flush head and WITH either a hex or phillips slot. I know it's a long shot but maybe one of you has used something like this recently.

Background: We are installing antenna structure that utilizes 0.071" thick doubler on belly section of fuselage, around STA1050. Problem is that the Hi-Lok's collar is falling under the Longeron flanges and as a result we cannot tighten collars properly. We can fit a wrench alright, but it would be to install a simple nut such as MS21043 not a double-height HL collar.

Any help is greatly appreciated. I am also looking through SRM's substitutions section in hopes of finding something compatible. I attached a quick sketch of the section in order to give you guys a better visual of my problem.

Cheers,

uGLay.

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[rb1957]

then why don't you use a standard nut in lieu of the Hi-Lok collar ? (like lots of people do)

but hush, i can "feel" Will Talyor approaching ...

 

[uGlay]

yes. that's an option. but it's really up to the on-site DER and he wants us to find a replacement pin instead of just using a nut on there.

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[rb1957]

we have names for people think that ...

 

[uGlay]

i think theyre just playing difficult and at the end theyre just gonna put a nut on there.

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[uGlay]

OK just spoke to engineer on site and the problem with using regular nut is that the pin spins in place hence why they need a hex or phillips head.

im making a special tool in solidworks, we'll see how fast the machine shop can bang it out.

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[Dan320]

Have you tried a PIC239-x pin/screw?
They are best described as a c/s Hi-Lok pin with a Phillips recessed head.
They are used on the DC9-MD80.

 

[uGlay]

Dan:

thanks for the recommendation. where can i find full spec of such part? who made this PIC part, just curious.

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[Dan320]

I have a specification drawing (pdf) that says it's made by Phillips. Our DB says we buy them from Boeing.

 

[uGlay]

Dan: we are not supposed to post our email addresses on the site and i can get banned from eng-tips for doing so. can you please upload to third party website such as engineering.com uploader.

thanks a lot for your help and sorry for the inconvenience.

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[Dan320]

Let's save some time here, tell me how to do it. Can't find anywhere to upload on that site.

 

[uGlay]

Step 3 of the post reply gives you option to upload file
I am testing it out with HL11 PDF specs.

http://files.engineering.com/upload.aspx?referrer=http://www.eng-tips.com

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[Dan320]

Ahhh... It is now done. I hope.

 

[uGlay]

WOW that's an old drawing. August 16th, 1966

DAMN. Thanks a lot Dan!

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[Dan320]

Hope it works ok.
I know from past experience about the e-address rules.
Didn't mean to break them.

 

[KirbyWan]

problem with using regular nut is that the pin spins in place hence why they need a hex or phillips head.

How is this different from a Hi-Lok collar? You need to keep the Hi-lok pin from spinning by using the hex head on the threaded side of the pin with an allen key weather you are tightening a collar or a nut. Although there is usually enough friction from a proper interference fit on the pin so that the clamping friction will catch without the pin being held, sometimes you need to hold the pin.

-Kirby

Kirby Wilkerson

Remember, first define the problem, then solve it.

 

[uGlay]

KirbyWan: you are correct. the problem is that the allen key cannot be inserted in the hex aperture due to the longeron flange being in the way.

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[berkshire]

uGlay (Mechanical)
This may be an obvious question, however I am going to ask it anyway.
Did you try cutting off the short end of the key, until it just fitted between the top of the pin and the stringer?
From your original sketch, it looked as if you had enough room to do that.
B.E.

 

[KirbyWan]

In a couple of cases we cut a piece off an allen key and welded it through a hole in a plate and then ground all the excess off the back for a minimum height allen key. Your next option is to do an analysis to see if you can drill a hole through the longeron directly above the pin and use a T-handle allen key. I've done this on a duct casting when I had no other choice. You could also gain some height by using a shorter pin as long as the threads are not in bearing. Those are my ideas, but using a hex head counter-sink bolt should work, I'm just not familiar with the P/N's

-Kirby

Kirby Wilkerson

Remember, first define the problem, then solve it.

 

[uGlay]

Kirby: those are good suggestions. one thing to keep in mind is that the install has 64 hi-loks per a/c and fleet is of 80+ a/c so that would be a lot of work. not discounting your advice though, im sure under the right circumstances they would be life savers. thanks a lot for the help.

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