Fuel Lines

Here's the path of the fuel system...

The fuel system begins with two 25 gallon aluminum tanks in each wing.  Four solid 3/8" aluminum fuel lines, two from each tank, make their way to the fuel selector that lives on the cockpit floor between the two front seats, just above the flaps handle.  Before reaching the fuel selector, the lines are reduced 2 to1 through a 3/8" Tee.  We now have one 3/8" line coming from each side, left and right.  

The left and right lines are routed into the fuel selector which offers Left, Right, Both & Off.  

After the fuel selector, one 3/8" line carries either the left, right or both selected lines to the Gascolator.  The Gascolator is also known as the main line strainer, settlement bowl, or fuel strainer and should be placed at the lowest point of the fuel system as a point for water and sentiment.  A quick drain is installed on the bottom of the Gascolator that will be used for pulling fuel samples during pre-flight to examine using a see through plastic cup for water and debris.

My Bearhawk will be powered by the Lycoming YIO-540-EXP Thunderbolt engine.  This is a fuel injected engine and will require an auxiliary fuel pump to be installed behind the firewall.  The specific YIO-540-EXP I selected will use the AirFlow Performance Fuel Injection system.  I visited with AirFlow Performance owner, Don Rivera, at his shop in Spartanburg, SC a few weeks ago.  Don really helped me understand how his fuel injection system works and after looking at my plans and fuel system configuration diagram, he suggested the addition of an inline fuel filter to be installed after the Gascolator and before the aux fuel pump.  Don felt that the screen in the Gascolator was too course and not fine enough for the FI system.  Here is a link to the AirFlow Performance website:  http://airflowperformance.com/

  Continuing with the fuel line... the 3/8" line exits the Gascolator and is routed to the inline filter.  From the inline filter it goes to the aux pump, then exits the aux pump and routes through the station B bulkhead and finally up to the bottom right of the firewall. 

Here are the tools I used to cut, bend and flair the lines.  It's important to note that aircraft fuel lines are flared at 37 degrees, not 45 degrees like automotive lines.  

Picked up this inexpensive pipe cutter at Northern Tool

Flexzion makes a really good Tube Bender that can be purchased through Amazon:  https://www.amazon.com/gp/product/B077ZQLC4V/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

Most importantly, don't use a cheap flaring tool.  Get a good one like this Rigid 37 degree flaring tool.  https://www.amazon.com/gp/product/B001HWNS40/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

I used all AN type aluminum fittings from Aircraft Spruce.  These fittings do not require a great amount of tensioning.  Run them on finger tight, then about a 1/4 turn with a tool to snug them up. 

I used aluminum AN fitting wrenches.  These wrenches create a soft grip and will slip off occasionally.  This is ok and will prevent over tightening.  In tight areas where I had to use a steel wrench, I was very delicate with my torque on the fitting.