REFLECTOR: FUEL FEED [heur]

[Jim Sower]

You're not venting into the engine compartment (at least I'm not).  I 
have a vent from my sump tank that goes to the top of the firewall and 
is capped off there.  On those rare occasions that the sump gets emptied 
(like for maintenance or heaven forbid I get into my last 5 gals of 
fuel) I have to open the vent long enough for the sump to fill up.  If I 
left the sump vented, there is the distinct possibility that the strakes 
wouldn't gravity feed fast enough to keep up with the engine (like a 
leaky fuel cap) and with the vent open the fuel pump couldn't "draw" 
fuel out of a strake that wasn't pressurizing.

In flight, sump tank should NEVER be vented ... Jim S.

Scott Derrick wrote:

>
> I think it is extremly dangerous to vent the fuel system into the 
> engine compartment!
>
> Why would anybody do that??? 
> Scott
>
> Ron Brown wrote:
>
>> Tom,
>>
>> I don't think it is a good idea to vent the fuel system into the 
>> engine compartment, especially if you happen to flip upside down 
>> during a crash landing.  You will have lots of fuel draining out the 
>> vent system into the hot engine compartment.
>>
>> With the factory designed fuel vent line routed up to the top of the 
>> firewall then back down to exit the bottom of the fuselage, fuel will 
>> not leak out of the vent system when the airplane is upside down.
>>
>> One other thought on uneven fuel flow, even if the vents are tied 
>> together and the plane is flying level/ball centered: there is a 
>> possibility that an air bubble trapped in the vent line with fuel on 
>> either side of the bubble can cause an uneven venting of the tanks.  
>> This wouldn't happen if the vent lines always slope upward to the 
>> manifold.  I think this may be the scenario that Jim Sower is seeing 
>> from time to time.  I have had it happen a couple of times on long 
>> trips after filling the tanks nearly full.  After landing and parking 
>> in my hanger, the fuel tanks were 5 or so gallons different and 
>> remained that way until I opened the fuel caps.  STRANGE!  Wings are 
>> level when parked in the hanger.  Another experiment - I placed a 2 x 
>> 6 under one main tire, simulating a wings down.  Guess what - the 
>> fuel level difference was MUCH LESS than I have seen in the air.
>>
>> But again, it could be fuel caps that are not always sealing 
>> perfectly for every flight.
>>
>> Ronnie
>>
>> ----- Original Message ----- From: "Tom Martino" 
>> <tmartino at troubleshooter.com>
>> To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
>> Sent: Tuesday, February 15, 2005 12:23 PM
>> Subject: RE: REFLECTOR: FUEL FEED [heur]
>>
>>
>> My plane flies perfectly.  Not my opinion, it is the assessment of my
>> test pilot.  The ball is in the center and the plane flies "hands off"
>> straight and level.
>>
>> I will keep looking.
>>
>> -----Original Message-----
>> From: Scott Derrick [mailto:scott at tnstaafl.net]
>> Sent: Tuesday, February 15, 2005 9:18 AM
>> To: Velocity Aircraft Owners and Builders list
>> Subject: Re: REFLECTOR: FUEL FEED [heur]
>>
>> A leaking gas cap can cause uneven fuel flow but is not the prime
>> culprit. A bit of fuel valve lube applied to the O ring once a year will
>>
>> insure this doesn't happen.
>>
>> A miss-rigged airplane is most likely the cause. Shim your rudders so
>> the ball is right in the middle and you will get perfect fuel flow.
>>
>> To test, be sure your turn and bank is installed correctly first,
>> garbage in garbage out. Then fly, this is the fun part.. Once you see an
>>
>> uneven condition, press on the rudder that will put the ball in the
>> middle. If you want to even up the tanks fast, press on the correct
>> rudder so the ball is on the other side for a couple minutes, you'll see
>>
>> the fuel even up and even go into the opposite imbalance if you keep the
>>
>> rudder depressed. Then hold the rudder so the ball is centered, fuel
>> will flow as it was designed to.
>>
>> Scott
>>
>> Tom Martino wrote:
>>
>>> Well, now that I'm in my test flying mode ... I will really be asking
>>> a lot of questions.
>>>
>>> Here are some of them, as they relate to my fuel system:
>>>
>>> 1. What makes the fuel tanks feed unevenly to the header tank/engine?
>>> (My right tank is feeding twice as fast as my right tank.)
>>>
>>> 2. Will that cause a problem when the fast-feeding tank runs out?
>>>
>>> 3. I used the larger vent lines for my tanks and tied them al together
>>
>>
>>
>>> with a manifold, then vented the entire system out through the top of
>>> my firewall in the engine compartment (about four inches below my naca
>>
>>
>>
>>> duct). Do you think the system gets enough venting there?
>>>
>>> 4. Is there a need for a "whistle" hole in any of the tank vents ...
>>> for additional venting (like we do with the crankcase breather?
>>>
>>> Any help is appreciated from my more experienced Velocitologists J
>>>
>>> Tom
>>>
>>> N173EX
>>>
>>> (A mere 6 hours)
>>>
>>> -----------------------------------------------------------------------
>>
>>
>> -
>>
>>>
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