Fuel System

We have included a description of how we installed our fuel system, because fuel system problems are one of the two most common owner built aircraft system failures (loss of control is number 2, so we will have a segment on that too). 

Vans provides two drawings:
-   DWG: 6A FUEL, BRAKE AND VENT
-   DWG: HIGH PRESSURE FUEL PUMP INSTALLATION (RV-7)
We also used:
-  FT-60 (Fuel Flow) Transducer Installation Instructions
-  Use Standard Aircraft Handbook

Strait fuel lines between selector and L/H and R/H tanks were easy, but we needed to remember to install fuel and vent system before rudder/brake system, and place bushings/grommets, sleeves and nuts on the aluminum tube before flaring the tube ends.  Fuel line is thick wall soft aluminum alloy tubing ( ATO-035X3/8) which is initially easy to bend, but it will work harden and will kink if shaped to anything more than a slight bend without a tubing bending tool such as the depicted which we used used for most bends:

The Parker flaring tool was used for all 37-degree  flares required for aircraft fuel systems :

Per the Standard Aircraft Handbook, bolt fitting or nut torque for aluminum alloy tubing is 75 to 125 inch-lbs. 
By far the most challenging component in the system was the electric high pressure auxiliary fuel pump installation (Airflow Performance P/N 3090050) and maintainable fuel filter (P/N 1090079) .  This is a cleanable 125 micron pleated stainless steel filter, with many advantages over paper which can restrict fuel flow due to susceptibility to absorb water.  This stainless steel filter will be very useful after first engine start to remove any debris which may not have been caught when lines are flushed.  Filter is readily removed for inspection and cleaning at regular intervals (after first 5 to 10 hours of operation and then during the annual condition inspection). 

To simplify and ease installation of the high pressure fuel pump installation, we installed an Andair FS20 type 3 fuel selector valve and to help route right fuel supply line clear of the manifold, we used a banjo fitting for the right fuel tank supply line.  Banjo fitting provides for a very compact 90-degree fitting as well as rotational adjustment and was the only way we were able to clear the manifold:

The Banjo fitting required safety wiring after final installation:

Final installation L/H view, with wiring for auxiliary pump and fuel flow transducer:

and R/H view:

We decided to supplemented Van's standard float type fuel gages with Flight Data System's FC-10 Fuel Computer.  Below is an image of the FT-60 Fuel Flow Transducer installed between the auxiliary electric fuel pump and the engine mechanical fuel pump. 

 

Modification of the Horizontal Stabilizer to Prevent Cracking (reference SB 14-01-31)

This process is noteworthy because it will prevent cracking in the forward spar of the horizontal stabilizer, originating at the stress relief notch at the inboard end of the spar flanges.  Basically, the modification makes the spar caps softer, by removing portions of the upper and lower caps and installs finger doublers to distribute the load  into the upper and lower spar straps.  We chose to incorporate the SB instead as preventive maintenance.    Installation of the mod kit is challenging as it requires removal and installation of rivets in very confined space between the upper the lower skins. Consistent good rivet removal technique is essential so we did a lot of studying and talked with  local airframe shop mechanics on how best to remove rivets: we used a punch to punctuate the dimple at the center of each rivet, used one-size-smaller drill to remove a portion of the center of each rivet, used a soft chisel to remove the factory head and used a punch and a pair of wire cutters to wiggle the rivet  shop head out of the hole. We made no changes to the design of the modification , but we made some process improvements:
-   we left the flush-heat rivets in the center of the forward spar,  i.e. we never completely separated the left half of the stabilizer from the right, which  made the stabilizer much easier to handle and maintained  alignment of the L/H and R/H halves of the stab
-   we using the rivet removal drill guide shown here; not sure why Vans does not mention this, made proper removal of rivets much easier.

 

 

 

Successful removal of the forward rib

and strap attachment rivets:

which will now include the finger doublers and new aft rib angle in the stackup. 

  

 

 

Here is what the installed SB looks like on the forward spar face,

and on the aft spar face (R/H side)

 and LH side:

and with ribs re-installed, awaiting touch-up prime and paint.