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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