Mailing List flyrotary@lancaironline.net Message #63738
From: Steven W. Boese <flyrotary@lancaironline.net>
Subject: fuel system
Date: Sun, 3 Sep 2017 15:34:51 +0000
To: Rotary motors in aircraft <flyrotary@lancaironline.net>

Todd,


The fuel filter and water separator that you specify has a max flow rate spec of 15 gph (data sheet is attached).  The fuel flow required by the engine would be more than that at times.  Since you are returning the regulator bypass to the inlet of the unit, the flow rate through it would always be more than the rating.  The unit must be capable of flowing more than the rating since it is working in your system.  It is possible that the flow limit is based on the unit's inability to separate water at higher flow rates.  The filter media is described as not allowing water to pass through it.  Does the media become impermeable to fuel if water is trapped on it due to the high flow rate?


The filter cartridge you specify has a 2 micron particle rating.  While this is appropriate for the diesel application that the unit was designed for, this seems much smaller than necessary for your application.  In subfreezing temperatures, I have observed fine suspended crystals when sumping the tanks. They are most likely ice since they disappear at warmer temperatures although no liquid water has been recovered when sumping the tanks.  Y'all who've never seen a snowflake would not run into this (sorry Charlie). The crystals have not caused any  problems in my system that I am aware of.  It is possible that they may be trapped by the fine filter media that you are using.  Whether or not this might be a problem remains to be seen.


The above concerns may be worth considering if you have not already resolved them to your satisfaction.


Dave,


Thank you for your explanation of the use of the fuel flow transducer in the fuel return line.  I have a single fuel flow transducer in the line leading to the dead headed fuel rail for fuel flow and fuel remaining purposes.  At the condition inspection, I temporarily attach a fuel line from the fuel rail to a tank filler opening allowing a check on the fuel system condition using that fuel flow transducer in conjunction with the fuel pressure reading.  Your system allows continuous monitoring while eliminating the need to install temporary plumbing to check the fuel system health.


Steve Boese 

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