FUEL SYSTEM PAGE 2

 

RH Fuel Fitting alignment Alignment after turning the fuel fitting around

On Saturday, 5-14-05, I continued on the fuel plumbing in the fuselage.  Before I began I was staring at the RH 90 degree fitting on the inside of the fuselage. It was not aimed at the center of the grommet hole in the F-782A-R cover (above left).  I had inadvertently put the custom made fuel fittings in backwards.  The nice thing about laying the holes in the fittings out symmetrically was that I was able to reverse the fitting without enlarging the holes.  The photo above right shows the 90 degree fitting in line with the hole after the fitting was reversed.

RH custom fuel fitting reversed LH fuel line from the custom fitting

The photo above left shows the custom fitting after I reversed it.  At right above I have started fuel line fabrication.  You can see that the grommet is in place and slipped on to the F-782D angle.

Modification to cover panel

RH cover panel in place

In order to install the F-782A cover over the grommet, I had to make some minor modifications to it.  The photo above left shows the area that had to be trimmed to install the cover (arrows).  The other photo shows the cover in place over the grommet.

Purge valve fitting Line from valve to purge fitting

In reading Dan Checkoway's web sight he describes a purge valve installation to help with hot starts.  I have allowed fuel injected Lycoming engines to pull me through the air for about 1500 hours and I can tell you that they do not like to be started when they are hot.  They will start when hot if you do exactly as Lycoming says.  Bottom line is that I may not put in a purge valve but I am putting the plumbing in the fuselage exactly as Dan suggests except that I will be pumping the purged fuel to the left tank instead of the right.  The photo above left shows the fitting that I built up for the purpose.  It consists of an AN917-2D tee with internal 1/4' pipe tap threads, two AN816-6D nipples, an AN912-1D reducer bushing (from 1/4" pipe to 1/8" pipe) and an AN822-4D elbow.  In both photos above the fuel line from the purge fitting to the fuel shut off valve is shown.  I am only guessing about the placement of this line at the inboard end because I do not have the valve yet.  I ordered a FS20f7F,3/8 Type 7 Fuel Selector Valve from Andair on March 21, 2005 and as of May 16, 2005 it had not arrived.

RH fuel line from custom fitting to shut off valve

View of both fuel lines to shut off valve

In the photo above left you can see that I made the RH fuel line is in two sections like the left.  I put an AN815-6D union between the two sections.  This was done to ease the making of the fuel lines.  The photo above right shows the fuselage portion of both main fuel lines installed.

1/4" line from purge fitting to cover bracket 1/4" line from firewall

Above left is a continuation of the purge line installation.  I put an AN 832-4D bulkhead union in the  F-7838-L cover support rib.  I fabricated a line from the purge fitting in the main fuel line to the bulkhead fitting.  Next I made a line from the firewall to the AN832-4D fitting (above right).  This line had multiple bends in it because I wanted to keep the body of it towards the left outboard edge of the cabin cover.

Fuel lines attached to bottom of the cabin cover

AN833-4D and -6D in firewall through doubler

Above left is a photo of the purge line and the main fuel line installed on the bottom of the cabin cover.  I re-manufactured the main fuel line because I thought it was a little crude.  The two fittings above right are installed in the firewall at the doubler that I made (see "Fuel System Page 1").  The one on the left is an AN 833-4D bulkhead elbow for the purge line and the one on the right is an AN833-6D bulkhead elbow for the main fuel line.

View of fittings from front Center cabin cover with lines and pump installed

Looking at the two fittings from the front of the firewall you can see that they each have a washer.  The arrow is pointing to the main fuel line washer.  It was Sunday and there was no way to buy these washers so I made them  It is good to have a mini-mill and a lathe.  Above right is a picture of the fuel pump assembly and the center cabin cover in place with the fuel lines.

Main fuel line and purge line attached to firewall First step of making spacers

Above left is a picture of the Purge line and the main fuel line connected to their respective fittings.  The next operation towards completing the cabin portion of the fuel system was to make spacers for the fuel vent fittings.  There was supposed to be a couple of spacers with the kit but either I used them on something else or I lost them.  At any rate because I have a mill and a lathe I decided to make some.  The first step was to lay some circles out on aluminum.  I put some masking tape on some scrap .040 2024T3 and using a compass I laid out 6 circles approximately 1.1" in diameter.

Putting 7/16" holes in center of circles Separating the circles on the band saw

I drilled a 3/16" hole in each circle on the mini-mill and using a Unibit I enlarged the holes to 7/16" which is the size a #4 bulkhead fitting needs.  I then cut the circles out of the aluminum with the band saw.  I made no attempt to trim them to size yet. 

Preparing to cut the spaces on the lathe Four spacers made two rough cut still

I stacked four of the rough cut spacers on to the fittings that will be used for the lower fuselage vent and chucked them up in the lathe.  I removed the tape and the protective plastic first.  I turned them down to 1.050".  IN the photo above left you can see 4 completed spacers, two that are still rough cut and the fitting that I used to chuck the spacers up in the lathe.

Preparation to make two thicker spacers 3/16" spacer on the fitting the other is in the background

The spacers that I made did not look like they would be thick enough to let the vent line around the lower "L" angle on the fuselage.  I checked out Dan Checkoway's web site and he put both of the kit supplied spacers on the inside of the airplane for this very reason.  I had a piece of 3/16" scrap left over from another part of the project (rear spar carry through, I think) so I decided to make two 3/16" spacers.  I used the same technique as I did on the thinner spacers.  The completed spacers are shown above. 

Placement of the hole for the fitting Fitting installed

Now I had to figure out where to put the holes for the fittings.  That should be simple, just consult the plans.  Here is a direct quote from page 8-15 of the plans, in the first bullet under the heading of "Installing Cabin Systems;" "The routings and fitting details are so well depicted on DWG 36/36A that step by step instructions would be redundant."  Drawing #36 is where the fuel vent system is shown.  There were no directions or dimensions given there and none given in the plans.  Well, I looked at Dan's site again and I came up with a set of dimensions of my own.  These dimensions for the hole are an educated guess and I won't know if they will work for several months.  Anyway, I drew a line through the rivets in the lower angle (F-713) and another line through the rivets on the vertical angle (F-902 Bulkhead) that the fuel tank attach bracket will ultimately be bolted to.  I made the center of the hole for the fitting 1.65" down from the horizontal line and 1.1" forward of the vertical line.  I drilled a pilot hole and using a Unibit to enlarge it to 7/16".  See the two pictures above.  (It is obvious that I had already drilled the holes before I remembered to take a picture.)

 

Bending the vent line The RH line finally fits

At this point the easy part of the vent line installation was complete.  Now I had to fabricate the lines.  What a pain this was.  Trial and error, fit and check, the task went on all day on Saturday.  At the end of the day I had the RH line shaped and basically contoured to fit the fuselage per the plans.  The lower arrow points to a hole in the floor that I enlarged from an existing pilot hole to a 7/16" hole for the vent fitting.  As it turned out I was not done shaping.  I made the line to lay next to the flange of the F-902 and then to go around the middle angle (F-719, upper arrow).  The Adel clamps would not fit between the flange and the screw holes in the F-902. 

Final shape of the RH fuel vent line at the F-902 Initial shaping of the LH fuel vent line

A check of the drawing revealed that the line needed to lay next to the inboard edge of the F-902.  I re-shaped the line one last time.  The photo above left shows the final shape of the line from the fitting past the hole for the rudder cable.  Notice that it is now the next day.  Shaping and fitting these lines is a long and tedious process.  After the RH line was completed I started the left vent line.  This time I had already been through it once.  I shaped the line from the fitting past the rudder cable hole first. 

Close-up of the left fuel vent fitting Left fuel vent line complete

Above left is a close up of the left fuel vent line from the fitting past the F-713 auxiliary longeron.  At right is a photo of the installed vent line.  I have installed three of the four clamps with clecos instead of screws because I intend to remove the line to paint the interior later on.

Lower forward clamp External vent fitting installed

The arrow above points to a potential problem.  The gap between the F-684 gusset and the outside skin is not wide enough for the #8 screws supplied with the kit.  The screw will dig in to the outside skin if you don't realize this.  I cut three threads from the screw and it was OK.  Above right is a photo of the external vent fitting installed temporarily.  I still have to install a screen on it per the drawing.