Mis-located Pitot Tube Hole

snoopyflys · #1 06-25-2009, 07:27 AM

Greetings,

I drilled the 7/16" hole for my pitot tube at what I thought was the correct location as per plan page 15a of my -7a. After carefully measuring and checking, I discovered that I had drilled the hole outboard on the spar rather than inboard as shown in the plans. Will this cause me a problem beyond merely routing the plumbing lines around the aileron bell crank mechanism? Anyone have any suggestions on how to "fill" this hole in the spar and leading edge skin? (no dummy jokes, please

)

Thanks,

vlittle · #2 06-25-2009, 08:03 AM

As I recall, you can plug this holes with a countersunk screw/nut, and a washer sandwich made of back-to-back tinnerman washers and one or two AN960 flat washers that will sit in the hole:

screw-tinnerman-an960-an960-tinnerman-nut.

Many of times this has to be done to plug the standard pitot mounting hole in order to mount a pitot mast.

Vern

ArVeeNiner · #3 06-25-2009, 09:00 AM

I drilled mine in the right spot but I went with a pitot mast instead. I kept the old hole and put my temperature probe there instead.

N941WR · #4 06-25-2009, 09:03 AM

No big deal. Check out my wing page and scroll down to the 4/14/05 entry to see how I plugged the hole.

Birkelbach · #5 06-25-2009, 11:44 AM

Why not just leave it where it is? Running the tubing around the bellcrank shouldn't be a problem.

If you get any dummy jokes then somebody is hiding something. I'm glad nobody can see my crowning acheivement of drilling holes in the wrong place.

snoopyflys · #6 06-25-2009, 12:05 PM

Thanks for the replies. At least I know now there are options and that it's not a big deal. I get a little concerned when drilling holes in a critical structure (spar) and its in the wrong spot.

Kelly - good idea on the OAT solution. Do you have some pics to share?

Vern and Bill - thanks for the hole plugging solutions, both seem to be good alternatives.

Phil - leaving it where it is was my initial thought just not quite sure yet how to run the tubing so as not to interfer with the aileron bellcrank.
Thanks for the input.

Birkelbach · #7 06-25-2009, 12:19 PM

Don't worry about the stress. The spar is under less and less stress as you go outboard, so yours will be stronger than the design.

I would think that there'd be enough room to go above the bellcrank. There's probably enough room to go under it too but that may get in the way of final assembly and inspections. There are plenty of nuts and bolts right there that you could use to attach an Adel clamp to the spar to secure it.

I looked at an old picture of my spar and it looks like there may be enough room to go behind the bellcrank. It doesn't move that much once it's installed. You have plenty of options, and none of them are scary.

airguy · #8 06-26-2009, 09:54 AM

Quote:

Originally Posted by ArVeeNiner

I drilled mine in the right spot but I went with a pitot mast instead. I kept the old hole and put my temperature probe there instead.

Now THAT'S an excellent idea. I'm in the same boat, drilled my hole in the correct location, but decided to go with the Dynon AOA heated pitot and mast afterward. I've been thinking over in my head how to patch it, but now I'll reconsider.