REFLECTOR: Fuel Filters

KMis178813 at aol.com KMis178813 at aol.com
Mon Apr 6 21:43:17 CDT 2009


Collective
    For the new builders (or the old builders with new  engine install) be 
careful not to save money on fuel filters!! Automotive  filters are typically 
paper elements and when introduced to fuel with water  trace's clog with a gel 
substance. Aircraft filters are usually metal screens  and will pass water but 
not debris. At least this gives you a fighting chance if  you have some water.
    The Factory vent line that Brian referred to went up the  firewall to the 
roof and then a foot forward before returning to the firewall  and then out 
the belly. The reason for this was from another factory plane with  full tanks 
and a much increased angle of attack (with high output engine) the  front of 
the strakes were higher than the vent line. Normally the fuel  would have just 
come out the vent but in the configuration that it was installed  the fuel 
came out the vent directly into the induction air stream and went to  way rich on 
the mixture. After the engine lost power the angle of attack  lessoned the 
mixture went correct and then repeated. Moving the vent forward on  the roof 
increases the vent height when the nose is high. FWIW
     Ken 
 
 
In a message dated 4/6/2009 1:12:45 P.M. Eastern Daylight Time,  
nmflyer1 at aol.com writes:

I have  several fuel filters. I have one of those glass jobs on each line 
that goes  from the tank into the sump. Once I run enough fuel through this 
thing, those  will come out. I also have another filter just before the pumps. This 
one is  cleanable and will stay in. 

Kurt 


-----Original  Message-----
From: aminetech at bluefrog.com
To: Velocity Aircraft Owners  and Builders list <reflector at tvbf.org>
Sent: Mon, 6 Apr 2009 11:04  am
Subject: Re: REFLECTOR: Engine failure causes


 


--- _michalk at awpi.com_ (mailto:michalk at awpi.com)  wrote:

From: Brian  Michalk <_michalk at awpi.com_ (mailto:michalk at awpi.com) >
To: Velocity  Aircraft Owners and Builders list <_reflector at tvbf.org_ 
(mailto:reflector at tvbf.org) >
Subject:  REFLECTOR: Engine failure causes
Date: Mon, 06 Apr 2009 11:10:59  -0500

I've been going through the possible theories as to why my engine  failure 
occurred.  I didn't want to post rampant speculation, but a week  has passed, 
and I need to bounce some ideas off the  collective.



More unlikely theory #4: Water in fuel
Even  though I did not check the sump before first flight, the tanks with 
caps on  are very tight, and the plane kept in a hangar.  Again, the high angle  
from takeoff might have injested the water.  There should be evidence of  
water in the main tanks if this theory is correct.  The dry fuel return  hose 
begins to rule this scenario out as a candidate.

I believe I had water in my fuel once.  I recieved fuel at a  class C airport 
after I had done my preflight and did not sample the gas after  fueling.  At 
about 300 ft agl the engine cut out and regained power about  3 times in rapid 
succession.  It's basically the same way a car runs with  water in the fuel.  
I then reduced climb to 500 ft/min and the engine ran  fine.  The control 
tower must have noticed as they instructed me to  maintain a good rate of climb.  
At 3000 ft I increased the climb to 1000  ft/min and experienced a few mild 
hesitations, so I went back to 500 ft/min  and proceeded with caution without 
further incident during my 3 hour  flight.  After landing I checked the 
carburator bowl and found no  water.  However avgas in the South is aromatic based 
and can dissolve 500  ppm of water, so I wasn't too surprised not to find any.
 
More unlikely theory #5: excessive vacuum on vent line
It might be  possible that the vent line exiting the plane is in a high 
vacuum area.   I'll try to simulate with a leaf blower.
 
Not sure this matters.  I have my fuel filter before both fuel  pumps and 
neither pump has any problem sucking the fuel through the  filter.

John



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