FUEL SYSTEM PAGE 1

 

Since I have decided on the fuel injected Lycoming engine for my power plant I ordered the high pressure Airflow Performance, Inc. fuel pump that Van's sells.  I ordered the entire installation kit knowing in advance that I probably wasn't going to use most of the parts in it.  The pump arrived in late December.

Contents of the kit Fuel pump on the platform in the kit

The kit is complete (above left) and when assembled it looks very professional (above right) but I decided not to use the installation kit since my Center Cabin Cover was modified substantially from the plans.  I will get back to this later in the narrative.

Making the fuel fittings on the lathe Fuel fittings

Another thing I decided to try was to separate the fuel lines on the outside of the fuselage from the fuel lines on the inside of the cabin.  I would do that by machining a fitting to go into the side of the fuselage on each side.  Above left is a picture of one of the fittings in the lathe.  I actually did most of the machining for these two parts on the big lathe at the hangar but I finished them on my new home lathe.  Above right is a picture of both fittings prior to drilling the holes for the fittings and the rivets.

Drilling the fitting holes Tapping the holes with a 1/4" pipe tap

The next step was to drill the holes in the center for the 1/4" pipe tap.  I step drilled the hole to a final size of 7/16".  Next I tapped the fitting with aforementioned tap (above right).  Note: Do not use a tap purchased from Home Depot or even Lowe's.  They will not cut new threads at all well.  They may be OK for cleaning up previously installed threads.  I had to borrow a good tap from one of the guys at work to complete this step.

The fittings are ready to install on the fuselage Fuel vent fittings

We'll put that project aside for a while.  Being the hopeless fanatic about details that don't really matter that I can be, I decided that the vent fittings should be modified so that the exterior is round instead of hexagonal.  (Actually, I was just looking for stuff to make with my new lathe.)  At right above is one of the two vent fittings chucked up in the lathe.

Making the wrench area round Finished fittings

The photo at left above shows a fitting being turned in the lathe to remove the wrench flats.  At right are the completed fittings.  You are wondering how I intend to hold them to keep them from turning when I install them.  I will show you when I get that far.

Rivet pattern Template Installed on the fuel fittings

Now to lay out the rivet patterns I decided to use my AutoCAD program to make a pattern.  If I only have to drill up two fittings, why did I make patters for 4?  Well the answer is simple.  It is very easy in AutoCAD to make copies of what you have just drawn and since these patterns are on typing paper, I could have easily destroyed one cutting it out.  I didn't though and the photo above right shows the patterns on the fittings. 

Drilling one of the fittings 3/4" hole in the side of fuselage

 Here you see a drill pattern on a fitting (above left).  I am drilling pilot holes on the mini-mill.  Next, I had to enlarge the holes in the side of the fuselage to 3/4" which is the size that I made the center fitting to (above right).

Fitting cleco'd to side of fuselage View from the inside

After the holes were enlarged to 3/4" I put a fitting in each side and transferred the pilot holes to the fuselage skin (above left).  I then enlarged the pilot holes to #30 (not shown).  The photo above right shows a fitting from the inside with a 90 degree elbow installed.  Now I'll put this part of the fuel system away for awhile.

Center cabin cover Fuel pump mounting

The next part of the project was to mount the fuel pump/filter assembly to the center cabin cover.  First I decided it was time to add two more attach holes on each side (above left).  Notice the date in the photos above.  It has been almost four months since I last worked on the fuel pump.  In the mean time I ordered 2 each MS21919-WDG 26 Adel clamps and 2 each MS21919-WDG28 Adel clamps.  The larger ones were used to hold the fuel pump to the center cabin cover (above right).  Notice that I had to cut the rubber off of the outside of the aft clamp to get it under the relief valve.

Nutplates for clamp bolts Fuel filter installed next

I put K1000-3 nutplates on the cover so that the cover did not have to be removed to remove the pump (above left).  At the right above you can see the installation of the filter using the MS21919-WDG 26 Adel clamps.  The line that came with the kit is installed at this point, plus one line that I made.

Fuel pump in place in its new home Upper cover installed

Here are two pictures of the fuel pump installation in the airplane.  I think it looks good.  I hope it works OK.

Side of fuselage prior to fuel fitting installation Fuel fitting installed

I waited to install the fuel fittings until they were primed.  I primed them along with the canopy slide and some other parts.  I then primed the side of the fuselage where they go with a brush (cotton swab actually) and riveted them in place with AN470AD 4-4 rivets (photos above).

Fuel line snap bushings Fuel line installed and clamped

It was finally time for the main fuel line installation.  I did not particularly care for the idea of sandwiching the fuel line between the cover and the outside skin in foam per the plans.  I drilled the two stiffeners for 3/8" ID snap bushings, a 1/2" hole.  I made the fuel line and flared the aft end.  I put a ferrule and a "B" nut on it and slid it through the snap bushings.  I then installed two MS21919-WDG6 Adel clamps on the line (above right).  Why did I install only two?  That is all that was in the kit.  I will have to order more because I do not know what these two were intended for. 

Fuel line with 90 degree bend at the front Fuel line ready to be attached to a 90 degree fitting

I put another "B" nut and another ferrule on the forward end of the fuel line.  I then flared it and bent it 90 degrees (above left).  The right picture above shows the fuel line ready to have a 90 degree fitting installed in the firewall to attach it to.

Doubler Pattern Scrap metal, .050

To add a fitting to the firewall I wanted a doubler similar to the one for the brake lines (see "Firewall and Bulkheads).  I made it from a scrap piece of .050 2024T3 that I used for an assembly fixture on the aft fuselage lower skin.  Above left is a drawing that I made in AutoCAD.   It could have been done with paper and pencil or even laid out directly on the part but I have AutoCAD so that was easier.  Why three you ask.  It was easy to cut and paste so I made three before I printed the pattern in case I messed one up.

Elmer's spray adhesive and pattern Cutting the doubler

I cut one pattern out of the paper and glued it to the aluminum with Elmer's Spray adhesive.  I then took it to the band saw and cut it out.  These two steps are shown in the two photos above.

Doubler cleco'd in place Finished doubler

Before I removed the center cover, I put a 90 degree bulkhead fitting on the fuel line so that I could lay out a pilot hole for the center of it.  If you look at the picture above left you will see a piece of masking tape peeking out from under the doubler.  That is what I drew the center line for the pilot hole on since it is hard to write on stainless steel.   Above right is a picture of the completed doubler.  The second hole is for a 1/4" bulkhead fitting in case I decide to install a purge valve for easier engine starting.  I haven't decided whether to do it yet but I am going to add most of the plumbing now, just in case.  Dan Checkoway gave a really good description of his purge valve installation and he also did a nice job of explaining why having one is a good idea.  

Please select "Fuel System Page 2" for the continuation of the Fuel System narrative.