With credit to Bob Avon:
Has anyone had to replace or repair a pitot line in the wing? I was blowing air from the instrument end to clear a possible obstruction (airspeed was showing 0 in flight), and I heard a lot air escaping in the wing root area. I pulled gently on the pitot line in the fuselage, and it came right out of the wing root. The end of the tubing did not look broken, but more like maybe it had slipped out of a fitting in the wing. I have tried to fish for the other end, but the hole to work through is about 1/2″. The only other option I can think of is to cut a new inspection hole in the bottom wing skin in the area of the fuel tank vent tube. Any other ideas or advice?
With credit to Jeff Bryant:
Last year I installed a new set of strobe lights. I had to remove the cover
inside the flap well to route the wires. I saw the pitot line and how it was
routed inside the wing and I believe that the only way to replace this line
would be to remove this cover again. The cover plate is on the trailing edge
of the wing, runs the width of the flap and is attached with about 250 #30
rivets. It will allow you access to the whole inside of the wing. I checked
my pitot line and fuel vent lines while I was in there.
With credit to Bob Steward:
As Jeff B. mentioned, removing the cover over the aft spar will give better
access to the area. And as he also mentioned, there are a LOT of rivets to
drill out.
I believe that your easiest route is to contact Raytheon/Beech support and
ask about an inspection plate kit. They will give (sell?) you a drawing and a part number for the inspection panel and mounting ring, and then you can do the work with a log book entry. This will only let you access the end of the line, and NOT give you enough room to access the whole line to replace it.
If you don’t get the data from Beech on acceptable locations for inspection
panels, then you will need a field approval to cut a hole in the bottom
surface of the wing.
Or you could just round up an RV-4/6/8 builder and get them to help with
the riveting in exchange for some flight time to and from pancake
breakfasts in the area. These guys have been slaving away in the basement or garage for years and many of them haven’t flown in quite a while. They will have driven and replaced many more rivets than your garden variety A&P, and can do much nicer metal work that most FBO guys. Check out his RV project before you let him drill on your plane…, but in most cases you’ll get someone that really knows how to set a rivet. Of course this requires an A&P’s supervision, no matter WHICH way you are repairing it, so line up the supervision and sign off FIRST, then go after the RV builder to help out.
EDITOR”S COMMENTS:
I cannot remember what this Pitot tube routing is like for its entire length, including where it may be tied off. I will make one suggestion that might be worth investigating before you concede to drilling rivets.
If there is an accessible section of the Pitot tubing out by the Pitot tube mast (through the wingtip opening), or perhaps further inboard through one of the large inspection holes, you can try one other technique. Gently see if the tubing seems to have any ability to slide in toward the fuselage. If it moves, see if someone can hear it sliding in the area where the fitting separated. If so, get a long enough piece of something like 1/8″ aluminum solid rod (or similar very thin rod), and see if you can slip it into the end of the separated fitting by “feel”. If you can get it into the end of the line, and you can disconnect and push on the other (outboard) end of the line, you may be able to get it to (and through) the grommet hole. Then you can reconnect it, and feed it back out into the wing. Even if the line is tied/clamped somewhere within the wing, it will be worth taking a look through all available holes (to see if you can readily free it up), before you start drilling out rivets.
I’m sure Bob has already had this thought go through his head, but it is worth repeating. The static lines and the Pitot lines, and their associated instruments, deal with very low pressures. You can destroy an airspeed indicator just by blowing into the Pitot tube. I’m sure that most folks know that they have to disconnect the instrument end before trying to clear any lines. What might not be readily obvious is that, since pressures are normally so low, all the connections in the system tend to be only moderately secure. They tend to be just tight enough to pass the mandated leak-down test, in part because most of the GA lines are plastic tubing. I’d think twice before using pressurized air to clear a line; use gentle mouth pressure first. If you find very low flow, or an obstruction, try to trace it back to its source, as opposed to trying to blow it out. If something like a mud-dauber wasp has made a nest in the Pitot tube, you’ll blow every connection off the line before you’ll blow out the nest. Even standing water can create enough resistance to pop connections loose, if you try to clear it with a blast of compressed air.
And last but not least, I do have a few of the Beech inspection plate kits for sale ($125), at far below the Beech List price ($208), while the supply lasts. Each kit provides all required parts and hardware for two inspection holes.