Under wing inspectionplates

[DonMuncy]

My hangar elf needs access inside the wing behind an inspection panel  immediately behind the pitot tube. This is one of those that appears to be riveted in place. It looks like it is attached with Cherry max type rivets, and the panel looks like it was installed from inside the wing. That is, when free, the panel won't fall out, but will need to be pushed up and turned, to come out the hole. I assume the rivets could be drilled out, but replacing it would seem to require opening another removable panel to be able to get behind the non-removable one to re-rivet it, either with bucked rivets or Cherry maxs. Does anyone know the diameter of the rivets to be drilled, and have any tips on the easiest way to do it.

[orionflt]

you can put ancor nuts on the old plate and reinstall it

[jaylw314]

6 minutes ago, DonMuncy said:

My hangar elf needs access inside the wing behind an inspection panel  immediately behind the pitot tube. This is one of those that appears to be riveted in place. It looks like it is attached with Cherry max type rivets, and the panel looks like it was installed from inside the wing. That is, when free, the panel won't fall out, but will need to be pushed up and turned, to come out the hole. I assume the rivets could be drilled out, but replacing it would seem to require opening another removable panel to be able to get behind the non-removable one to re-rivet it, either with bucked rivets or Cherry maxs. Does anyone know the diameter of the rivets to be drilled, and have any tips on the easiest way to do it.

Cherrymax rivets are a pain to drill out, but not impossible.  Not sure the diameter, but I'd guess 1/8"--that's the smallest size Cherry rivet, and larger ones are typically only for structural members.

hit the steel core with a spring punch to make a tiny dent, then use that as a starting point for the drill.  You need to go slowly and angle the drill back in to the center if it starts getting offcenter, and check every few turns to make sure you're still centered, but eventually, you'll be able to pop out the head.  Don't knock in the tails, because you'll wind up with loose rivet tails in your wing.  Instead, just drill out all the heads, take out the panel, then knock out the tails once the panel is out with a 1/8" punch backed by a block of wood with a 1/4" hole drilled in it for the tail to come out.

On the other hand, CherryMax rivets are a breeze to install, and require no access to the backside.  The are structurally equivalent to solid rivets as acceptable replacements.

[jetdriven]

If they’re dome head Cherrys, grind them off with a sanding drum and a dremel. Reinstall wirh CR3213-4-10 or close. Get the cherry grip gauge to know the length for sure. 

Edited January 30, 2019 by jetdriven

[jetdriven]

I got a guy who has some. @cnoe you still have some for a bro ?

[jaylw314]

22 minutes ago, jetdriven said:

If they’re dome head Cherrys, grind them off with a sanding drum and a dremel. Reinstall wirh CR3213-4-10 or close. Get the cherry grip gauge to know the length for sure. 

I'd worry about grinding through to the wing panel using a dremel.  With drilling, while the steel mandrel makes it more challenging, you also have a clear guide to keep the drill centered!

+1 on the gauge, I forgot about that.

[jaylw314]

23 minutes ago, bluehighwayflyer said:

Or, even easier, buy a used inspection panel with nut plates already installed, on eBay.  I have purchased several over the years for $15 each, shipped.  

Jim

Aw c'mon, nutplates are fun to install!   "Nutplates" has to be one of my favorite words.  My wife didn't understand why I was giggling for days when I started the RV project...

[Andy95W]

Don, I'm pretty sure the pulled rivets that hold on the under wing inspection panels are easily drilled out aluminum that are barely one step above pop rivets.  Pretty sure 1/8" drill (actually a #30, but close enough).

@M20Doc will probably be along shortly with the actual part number to replace them when you're done, but they might be these:

https://www.aircraftspruce.com/catalog/hapages/cherrynrivet.php

"Cherry" rivets are like Aircraft quality pop rivets, the CherryMax are structural with the steel core.

Please let us know what you have!

[Guest]

Don

Your hangar elf’s will find that these rivets can be a pain to drill out.  A good sharp #30 drill bit will be required.  The steel stem is much harder than the steel stem so care must be taken that they don’t drill off centre.

I find that if you can reach in thru a neighbouring inspection hole you can place a bucking bar beside the rivet, then with a small pin punch you can drive the stem back making drilling easier.

The rivet is an Avex countersunk from Spruce or a Cherry CR9162 series.  Don’t use a Cherry Max rivet.

Clarence

[kortopates]

Mooney didn't use Cherrymax structural rivets on inspection panels only Avex non structural which are easy to remove once your hangar ferry learns from someone with experience. I suggest the latter so you don't end up making the holes any larger.


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[DonMuncy]

Thanks to all who contributed. Just the kind of responses I needed.

[jaylw314]

1 hour ago, kortopates said:

Mooney didn't use Cherrymax structural rivets on inspection panels only Avex non structural which are easy to remove once your hangar ferry learns from someone with experience. I suggest the latter so you don't end up making the holes any larger.

I thought that was a little strange for an inspection panel, and I remember the rivets on mine not looking like Cherrymax rivets, but I supposed it was possible somebody went in later and replaced them with Cherrymax's.  That would be an unpleasant surprise

 

[MikeOH]

1 hour ago, DonMuncy said:

Thanks to all who contributed. Just the kind of responses I needed.

I’m pretty sure you meant, “Just the kind of responses my hangar fairy needed.”

[kortopates]

I thought that was a little strange for an inspection panel, and I remember the rivets on mine not looking like Cherrymax rivets, but I supposed it was possible somebody went in later and replaced them with Cherrymax's.  That would be an unpleasant surprise
 

I really doubt an A&P would do such a thing - plus Cherrymax are $$. There are lots of Cherrymax rivets under the wing so I am sure the hangar fairy was just going by inaccurate memory.


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[Flymac]

For learning, why would any inspection panel be secured with rivets in the first place?  This also makes me think of every annual (that I aim to do everything possible my mechanic allows me/has taught me/inspects for me) and looking at the sea of what feels like a hundred panels under each wing...what do most limit their removal/inspection to, just where there are any bellcranks or such?   Sorry if thats alittle bit of thread creep!

[carusoam]

Might be important to know why it was riveted in place...?

When doing owner assist... I removed every panel that wasn’t glued in place... (not the Fuel tank panels)

in the Long Body There is some instrumentation in the wing that is hiding behind a riveted panel... electric compass device...

Best regards,

-a-

[kortopates]

For learning, why would any inspection panel be secured with rivets in the first place?  This also makes me think of every annual (that I aim to do everything possible my mechanic allows me/has taught me/inspects for me) and looking at the sea of what feels like a hundred panels under each wing...what do most limit their removal/inspection to, just where there are any bellcranks or such?   Sorry if thats alittle bit of thread creep!

Not all are called out in the maintenance manual and thus not all are ordinarily removed at annual. The manual calls out very specifically what needs to be done at each panel that is to be removed. There is the occasional task or deeper inspection that might have you removing such a panel e.g, such as perhaps pulling a new wire etc.


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[Steve W]

Annoyingly the hangar elves on my M20J found that the OAT probe plate was riveted in when it was time to put in the JPI probe. Best match appeared to be these:     AVEX NON-STR BLD RVT 1604-0412 https://www.aircraftspruce.com/catalog/hapages/avexblindriv.php Although until the A&P inspects the elves work they haven't been reinstalled. 

 

[jetdriven]

thats your standard Avex non-structural pop rivet. Use the flush ones of the proper length.

 

[Steve W]

5 minutes ago, jetdriven said:

thats your standard Avex non-structural pop rivet. Use the flush ones of the proper length. 

 

Which is why I included the part number too. (1/8 dia up to 0.250 grip length) And if it gets really screwed up, my A&P can go up a size and curse at the elves.

[kortopates]

You can confirm looking it up in your IPC


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[jetdriven]

Thats the P/N in the IPC

[cnoe]

@jetdriven has a good memory of what’s in my hangar. Let me know if you need a replacement cover. I have some extras indeed and you’ve helped me out in the past. They have nutplates; no need for rivets. None on my J are riveted. 

[DonMuncy]

Thanks, I'll tell my hangar elf keep that in mind.

[jetdriven]

You can put the panel in with brass screws. Non-magnetic. The nit plates are steel but a very minimal impact to the local magnetic field around the flux valve. However they do make stainless nut plates also.