Tank Calibration and Transfer Pump (Aux to Main tanks)

I had not calibrated my tanks in a level attitude.  As a stop gap I put the same cal values from a tail low attitide into the level attitude column.  I needed to find a way to have the aircraft stable while doing the calibration... it takes awhile.

Qty 3 2x4's, and a cheap boat winch.

Calibration done, except the right aux tank.  The transfer pump died.  New one ordered (plus a spare).

This is when everything went wrong.  I took the pump out, verified it was dead and went to put it back in so I could fly.  Somehow I cross threaded the Swagelok fittings.  I tried to repair the threads, and was successful EXCEPT on the fuel line side.  Can't get it off.  So had to change out the right wing to flex hose.  Now everything is just standard AN fittings.

Now I have to do the left wing one day... not a hard change when required.

Header tank, venting, flow, low fuel levels

The header tank - and more specifically the header tank level indication - have been giving me problems.

On the first flight, the header tank warning went off.  Landed quickly, and tore the entire system apart and made it better.  

4 hours of trouble free flying after that.

Then the low fuel header warning started going off again - but it always cleared, usually within 30 to 60 seconds.

I am not going to live with this, so investigation into why.

I know the fuel system can keep up with the demands of the engine.

Through a bunch of smart fellas on the forum and fellow UL builders, we have been scratching our heads.

The suggestion came up to look for something on the suction side that is tight enough to not leak, but not tight enough to not let air into the pump / injectors.  He also suggested del rings (available at spruce) that provide a better seal on AN fittings.  But then I found it.

On the input to the pumps, the clamps were not tight.  And the hose barb fittings on the other side of the hose had no clamps.

Before

After:

Time will tell if this solves the problem... but the current working theory is air was coming in through the return line into the header.  The air would build up, and it would take time for there to be enough pressure for the air to make its way up the vent and 'burp' the tank.  Then everything would be fine for awhile.

Header tanks are a real head scratcher in their design, specifically the vents (in high wing aircraft).  I think I am slowly ironing out the kinks.

Update:  This did not solve the problem, and now the problem is worse.  I started putting some pieces of the puzzle together a few days ago.

I started of running ethanol free 89 octane fuel, and used boostane to bring it up to 94 octane.  Around hour 5, I switched to ethanol 94 octane, which I can get locally (have to go to Blaine, WA for ethanol free).  The problems started (again) when I switched fuels.  I did not put these two things together until about hour 19.

So the problem started again after switching to ethanol fuel, and it has been getting worse the as the outside air temps have risen.

I started googling 'ethanol fuel', 'injection systems', and 'header tank'.

And then add this (below) from the UL installation manual.

What I make from all this.

• I had 5 trouble free hours running non-ethanol fuel
• My header tank design had a flaw, in that my return was on the top of the tank.
• Ethanol fuel is more prone to frothing
• I've been having more problems since the weather started warming.

I now have a tube / stand pipe for the return that is 5" below the top of the tank.

This should fix or at least help the frothing problem.  I may be dealing with vapour as well.

The vents are capable of clearing the air... it's been doing that for 14 hours of issues.

I have replaced a section of the vent line on the A pillar with translucent tubing.

The hope is I will be able to see bubbles.  I plan on having a camera face the vent tube to capture what is going on.

I am going to go back to ethanol free fuel.  I may start off with a 2/3'rds mix as I have to get rid of the ethanol 94.  1 part ethanol, 2 parts non ethanol.

Cameras on the panel and the vent tube.

Ground run first to shake out any issues.  If that is successful, will stay over the airport for at least an hour to shake it out more. 

So fast forward months... 

I've upgraded the vent line to a 6 mm ID all the way out to the wing tips.

I moved the header vent line to be AFTER the check valve (not before).

The problem is virtually gone... it will happen every once in awhile, and you need to drop a wing and go into uncoordinated flight for 30 seconds to get the bubbles moving from the header up to the tips.  Seems to happen about every 2 hours of flight.

I think I have a bit of a P trap in a climb... but it doesnt always happen in a climb.  So I dont know.  Its FAR FAR FAR better than it was.

Prop - Pitch Motor Change

On the first few flights the prop controller would go into current limit.  I contacted Airmaster and they had me check everything... blades off, every connection, brushes, slip ring, etc.  The only thing I found that was suspect is one brush was angled and had been wearing unevenly.  So those were changed.  Flew again, same problem.

The prop would go into current limit only during large changes (mode changes) in the course direction.  IE going from Takeoff to Climb, or Climb to Cruise.

Then we increased the current limit from 4 amps to 5.5 amps.  That fixed the problem.  However, Airmaster sent me a new motor with higher gearing, plus a new motor cap to accomodate the larger motor.

Tested on the ground... all good.  Fine, course and feather pitch stops all work fine.

Next is flight test...

All is AOK.  Have had zero problems since changing the motor.  Thank you Airmaster!

Flying!

Have been slowly expanding the flight envelope.

After the first few problems, kept really close to the airport or farmers fields.  Once the confidence grew, started expanding out.

Stalled the sportsman on Tuesday.  Very benign.  Just like Jake's Glastar.

Configured the AOA.  That was fun.  Turned off the voice notifications.

Did the climb test, as required by Transport Canada.  Piece of cake (except their graphs do not take into account a close to sea level airport, and a high pressure day - resulting in a negative pressure altitude.

From takeoff, climbed 2580 feet in 3 min.

And that was at max gross... all tanks filled, 2 crew, and almost 200 lbs in the back.

Started increasing the altitude and testing cruise.  Worked my way up to 8500 ft.

It's not a screamer, but its quick and can haul a lot and is very comfy.

Some other pics from that day...

First Maintenance

Flying requires maintenance.  And that's where I am... well have been, because its almost done.

UL Power requires the following at 15 hours

• Change oil and filter
• Check valve lash
• Torque cylinder heads
• Clean course (pre filters), change fine filter.
• And check everything else.

Good chance to go through everything.

To get to the head bolts you have to lift the plenum... and I thought "DAMN".  I thought I had built them not removeable... alas no.  6 bolts / screws and they lifted off (plus the plenum tops).

Everything has gone swimmingly.  All the valves needed some tweaking, and I got a nudge out of around half the head bolts.

All the spark plugs look good.

No chaffing or other badness.

Ran the engine today after everything to check for leaks.  Nothing.  Cowls back on and ready to go flying again.

One of my facet transfer pumps (between the aux and main tanks) decided to pack it in.  Two new ones ordered.

Flying!

It's kinda surreal... after over 9 years of building I now have an airplane.  That was always the goal... but when you consider the project 1000 little projects, you lose sight of that.

Not that I don't have bugs to work out.  But honestly there are few.

The header tank gave me some issues... now 7 hours of flying in with the changes and no issues.  That is a good feeling.

Aileron cables were either not tight enough or stretched.  Regardless, they are now back where they should be.

Airmate maps installed on my panel.  That is very cool.

No leaks... that is nice.

Tweaking my forward cylinder cooling.  The fronts are a bit cold, the middles are a bit hot, and the aft are just right.

Engine runs great... just burns a lot of fuel.  10 gph is normal.

Flight testing continues.  Next is to configure the AOA.  Needs some help with that one (2nd pair of hands).

Some pics from a friend on the ground last week.

7 hours and counting.  18 to go.

Minor prop issues... the controller would go into current limit when switching modes in the course direction (from TAKEOFF to CLIMB, or CLIMB to CRUISE).  Checked everything, and all I could find was one brush that was not wearing evenly.  Changed that, problem continued.

Airmaster had me increase the current limit from 4A to 5.5A.  That solved it, but they are sending me a new motor that is stronger and has higher gearing.

Need to do climb test, but that will not be a problem.

Lots of comments about the sound... does not sound 'normal', like a lycoming.  And the 4 blade prop has a distinct sound.

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 :-).