• If You Are Having Trouble Logging In with Your Old Username and Password, Please use this Forgot Your Password link to get re-established.
  • Hey! Be sure to login or register!

Got Inspection Ports?

Lawn Dart

Registered User
Las Vegas, Nv
Stole this tip from MD and thought it was worth expounding on for my fellow newbies.

So??bought your new Cub and then discovered that some of the inspection ports are still covered over with fabric? Want to see what?s behind them? No problem, just get some inspection covers and an X-Acto knife and open them up!

Disclaimer:
This isn?t a direct quote from MD and I don?t condone nor endorse anything that I say on his behalf without his express written permission (and I?m sure he doesn?t either, but he did give me the idea so I want to give him the credit for that) This is my personal experience with a problem that I had. If you?re gonna go at your Cub with a knife and you?re a booger pickin moron, DON?T TRY THIS!. If on the other hand, you have reasonable mechanical skills and are so inclined, have at it, it?s a piece of cake, it just takes some nads.

With a new X-acto knife blade, cut about a 2 inch circle in the middle of the visible inspection ring. Then, working from the open hole towards the inspection ring, start a cut at about a 45 degree angle towards the inspection ring while GENTLY pulling down (or out as the case maybe) on the tail of the fabric that will result from the cut. Continue on until you get to the plastic ring.

But how will I know when I?ve reached the plastic ring?

Believe me mister, you?ll know! The fabric will make sort of a tearing sound (and feel) as you cut through it and the ring will be very smooth when you get to it. Now use your head. You don?t want to hack into the ring, but you?ve got to get all the way to it (see disclaimer above) Now that your at the ring, STOP, turn the knife blade away from the ring just enough so that it follows the inside circumference of the ring and continue cutting around the ring while GENTLY tugging on the tail (this part is easier then you?d think, the ring, the knife, and tugging, guide the knife). You?ll probably have to go back and trim a little, here and there, to get the hole just right (round) but then the scary part is over.

Now go back at the hole with a pencil tipped soldering iron and melt the edge of the fabric so that it doesn?t fray. While melting the edge (mind you, this part can go pretty quickly depending on the temperature of the soldering iron) feel the edge that you?re melting and get the iron at the appropriate angle so as to create a ramp on the fabric. Reach in with a finger and gauge how the job is going. You want the edge smooth enough so that the ?tangs? on the inspection plate ride over the edge of the fabric and don?t ?snag? as they ride in and out. That?s all there is to it. You?re done!

I had to open 18 holes! That?s a lot!. I don?t know why they were closed, but you better bet I wanted to know what was behind them.

Being a newbie, the first hole took me about 20 minutes to ?surgically? open, the last hole took me about 2 minutes to complete. Have at it!

I subscribe to the theory that ?there?s no such thing as denial? but in this case, you?ve got know what?s back there and opening the inspection holes really isn?t that tuff.

Hope this helps someone.
 
Got your PM Cavy, thanks.

By end of the compression ribs, I mean the compression struts in a Cub wing (compression rib is old-speek). These are the square members that go from fore to aft spar that the drag wires are attached to. One opening should be at the end of each of these. This area needs to be inspected each annual or 100 hr, if anything goes structurally wrong with a wing, the drag wires will either go slack, or break, or the compression rib will break loose from the spar. In a PA18 wing, one in each of these areas also cover all the pulleys, cables and attach points needed for inspection or service, except for some additional at the wing root below the flap bell crank, and fuel tank drain. I believe that makes 10 holes in each wing, no more, no less. Also, I use a normal round panel instead of the useual square one at the forward strut attachment, the square one is just a pain in the ass. This is all you need for routine maintenance and inspection of the wing. This does not apply to PA12/14 wings, which are entirely different. I swear, I've inspected wings where whoever did the covering just flipped the wing upside down, grapped a fist full of rings, closed their eyes and threw them at the wing. Where ever they landed, they got glued down. If you own one of these, you may not want to cut all the holes, or you may want to add some where they are really needed.
 
Tip: On a PA12 that has drag wires under the tank unlike a cub that has a tube through the tank--be particular where you put the rings so that you can adjust/tighten the wires if the jam nuts happen to be forgotten to be tightened. The attach bracket/ clevis clamp is really difficult to get to with an ignition wrench? I am still cussing the guy that covered my wings initially.

Also the Belcrank for the Ailerons/ flap is of particular concern for proper location of the inspection rings.

Good look

Tim
 
Inspection Holes

Inspection Holes: All good advice, but a couple of things I might add. When cutting, I cut on the push and let off when pulling out. This is so that the fabric coating are not pulled away from the cut fabric edge by the knife blade when pulling out. Also I leave about 1/16" of the fabric around the inside edge of the ring. I have had fabric peel back and expose the ring if you cut out the bonded edge where the fabric comes together. This goes for all fabric rings and grommets. The rings and grommets are just sandwiched between the two layers of fabric. If you cut out the fabric all the way to the edge of the plastic and the fabric is not glued good enough, it will let go and curl back. Crash
 
Crash, try melting the edge of the fabric onto the ring, it really works quit well. I always cut the holes open right after the patch is put over the ring, then melt the wing and patch fabric onto the ring with the soldering iron, (I also burn the drain holes at this stage). Then all the build and finish coats seal the fabric to the ring, no loose edges to fray or snag. It is almost impossible for a ring or patch to come loose when done this way.
 
Just an observation, but I wouldn't open all of the unopened inspection rings just because they are there. Sometimes they get put on "just in case" or because there were a couple of extras laying around when the plane was recovered. Only the ones necessary for an inspection need to be opened.
 
My paper annual -- One of my wings was recovered last summer, the plane was annual-ed in March, yet no inspection holes have been cut yet. I suppose I'm gonna do this myself if I want my wings to stay attached :-? .
 
These are good points, it shows that there?s more than one way to skin a cat (or Cub).

Whoever did my fabric job was obviously a skilled craftsman. But the dope (of one sort or another) must have been getting to him when it came time to place the rings. It?s not as bad as MD?s ?ring toss game? scenario, you can see all of the key components (with a mirror) but an adjustment would be out of the question.

I looked at a Cub a couple of months ago that must of had 20 rings on each wing! Had the guy cut open all of those, there?d be more inspection covers then fabric.

The manual I looked at was pretty good about guiding you through the application of the fabric, but the chapter about where to place the inspection ports must have been missing from my copy. Too bad this part isn?t standardized by model, it seems to be a matter of personal choice. Given that, it doesn?t matter where you put them, someone?s bound to say ?why?d you do that?

Now if you?ll excuse me, I?m going to go find the guy that put the rings on my plane and kick his lily ass!
 
I remember seeing drawings (official blueprints from Piper) showing the locations of all the inspection rings for all the long wing Pipers -- if I can find them, I'll get them scanned and posted. It at least a good starting point. I know I used the drawing to buy parts for my PA-12 project: 54 rings total!!
 
The fabric manufacturers guide lines for placement of inspection rings needs to be general, because of so many different aircraft applications. AC43.13-1B chapter 2, section 1, paragraph 2-14 is the guide that should be used. It reads -

Inspection access is provided adjacent to or over every control bellcrank, drag-wire junction, cable guide, pulley, wing fitting, or any other component throughout the aircraft which will be inspected or serviced annually. They are installed only on the bottom side of the wings except where installed on the top surface by the original manufacturer.

Thats pretty simple, but some people just do not seem to understand it. Nothing will piss me off more than doing a annual on a plane for the first time and finding none of the inspection holes opened, and the owner saying that the mechanic who has done the annuals for the last 10 years did not see a need to open them. I guess he just paid for expensive preflights, then gets all teary eyed when I tell him I have to take a knife to his plane. THEN, I have to put up with a crying owner, do a lot of extra work to properly open the holes, buy a bunch of inspection plates and matching paint for the plates (and these are useually the planes with some "mystery" finish applied, and tough to match), prep, prime, and paint the plates, THEN find that the rings are not in the right place to begin with!, which means useing mirrors, THEN finding misaligned/worn cables, drag wires or whatever that should have been corrected long ago, and having to be triple jointed to get the job done. If you are recovering, make sure the holes are installed properly, and in the right locations (they should be opened before the wing is even reinstalled on the plane). Also, have some extra panels painted to match at the time of recover, in case you need to add holes someday, or loose a panel.

If you don't have a copy of AC43.13-1B/2A, get it. Any Cub owner wanting to know about the maintenance, repair of their machines should find it interesting. It is the Bible when fixing Cubs.
 
I can totally relate with MD on the issue of unopened inspection ports.

Guys, don't be the one he describes whining.

Dave Calkins.
 
Back
Top