Fuel system changes, and second test flight.

It's been 9 days since the first flight.  Been working to understand the header tank issue so I can fix it.

First was to essentially redo the fuel flow test to understand if the vents are working properly and fuel / air can move where they need to move.

For the first flight the header tank venting system went like so:

• From the header tank, two vent lines come out of the top and run horizontally towards each wing.
• Make a 90 and head aft and go up the door frame.  From there they go along the top of the door to the wing hinge just forward of the aft spar.
• Then they make 180 and go forward and are attached to the root rib.  They transition around the forward spar and then into a conduit along the leading edge of the wing.
• They exit the leading edge at the tip and are T'ed into the vents from the main and aux tanks.  
• Then into a Andair checkvalve, then to the JD airparts vent under the wing.

The problem with this... the big U from the door back to the leading edge could be a P trap.  I did it this way so you can still easily fold the wings.

So I changed all this.  The vent now exits the fuselage at the leading edge of the wing and goes straight down the leading edge.  It is now always uphill to the wingtip.  All of this was accomplished in a couple hours.

Then to test...

Ran many, many tests.  The summary of what I found.  

1. The fuel flow with the original and new vent configuration is the same.  
2. The right wing was transferring fuel averaging 30% slower than the left.
3. I separated the vents at every point possible and redid the test.  Was always within a couple percent of each other.

The focus then became why is the right wing transfering fuel slower?  It wasnt the vent.

• Folded the wings (again).  Took out the finger strainers.  Strainers were clean, but there was construction debris (what my friend Geoff calls 'sworf').  Cleaned.  Tested again, no change.
• Focused on the areas between the wing root and fuel selector.  Drained the lines, took every fitting apart and checked.  Found some shitty pipe ends that needed some filing.  
• Removed the fuel valve.  Tested from the wing to the input of the fuel valve.  Both sides where identical.
• Did a flow test on the fuel selector.  Same on both sides.
• The lines from the wing to the fuel selector are 3/8".  The output of the fuel selector to the header tank was also 3/8".  No bueno.  I had the right fittings to change that to 1/2".  Header tank removed.  Drilled and retapped the tank (luckily the boss was HUGE).  New 1/2" fitting on the header tank.
• Reassembled EVERYTHING and tested.  Now the flow is within 5% of each other.  On BOTH the fuel flow is considerably faster.

I tried to find fittings for the header vent at the wing / fuselage intersection.  Everything I tried leaked.  Finally just put in a short hose coupler with some clamps.  No leak.

Slept... tested again in the morning.  Still good.  Put the rest of the interior back in, wingtips back on, cowlings on.  Time to fly.

So I repeated the first flight.  Overhead the airport.

On the first test flight the header tank warning went off 26 min into the flight running at 13 GPH, 1500 feet.  So i did that again, but for 45 minutes.  Rock solid.  For the next 15 minutes I played with different power settings from 5 GPH to 15 GPH.  Still solid.  Landed without incident.  Airplane and pilot reusable.  Success!

No crowds this time.  No fanfare.  Just me and the Sportsman.

I put 40 lbs of stuff in the back and tied it down.  Move the CofG aft a bit.

Takeoff was great.  Climbed very quickly.  Setup an orbit at 1500 ft.  No alarms... only green LED's.

So that was flight test #1 repeat.  No audio issues.  My landing still sucked :-).