Leak Checked Pitot System, Empennage Nutplates, Unusable Fuel and Firewall Passthroughs

I spent some time this morning working on the left wingtip lens before heading down to the hangar.  Since I reworked the pitot and AOA tubing yesterday, I wanted to leak check it today.  I disconnected the tubing at the new fitting in the wing inspection panel and attached some 1/4″ ID latex tubing.  I could roll up the other end of the tubing to increase the pressure in the pitot system and test for leaks.  AC 43.13 recommends increasing the pressure to an indicated airspeed of 150kts and then clamping the tubing for 1 minute to check for leaks.  As long as the leaks aren’t substantial enough to cause the indicated airspeed to drop more than 10kts, then everything is fine.  After 1 minute, I had a 3 kt drop, so I’m in great shape.

Next, I tackled installing the two Click Bond nutplates in the horizontal stabilizer.  I used some hemostats to scotchbrite and solvent wipe the inside of the horizontal stabilizer around the hole and then fished some 0.025″ safety wire up through the hole and out through the nose of the inboard end of the horizontal stabilizer.  I pushed the safety wire through the end of the silicone installation plug so that I will be able to pull it back through the hole.

The Click Bond adhesive I had had dried up, so I mixed up some epoxy with West System 404 structural adhesive filler.  I applied a little bit on the flange of the nutplate and then pulled it through the hole.

Here’s a picture taken through a mirror at the installed nutplate.  Once the adhesive cures, I can just pull out the silicone plug.

With the new fuel pump installed, I decided to determine the unusable fuel.  I rigged up the hose from the spider so I could capture any fuel pumped to the engine.  I dumped 16 oz into each wing and then ran the fuel pump until nothing came out.  Finally, I drained the fuel in each tank to see how much unusable fuel there was.  I drained almost 7 oz from the left tank and 6 oz from the right tank.  I then dumped the fuel back in the tanks so that it could be included in the weight and balance.

My buddy Greg noticed that the firewall pass-throughs didn’t grip these cables very securely.  I removed the eyeballs and wrapped a couple of layers of aluminum tape around each cable and then reinstalled them.  The cables are rock solid now.

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