REFLECTOR: Odd fuel stain?

Robert Wood slvegl99 at aol.com
Mon Nov 21 14:12:05 CST 2011


Ohh, OK. Mine is fine then.
Bob Wood



-----Original Message-----
From: Alex Balic <velocity_pilot at verizon.net>
To: 'Velocity Aircraft Owners and Builders list' <reflector at tvbf.org>
Sent: Mon, Nov 21, 2011 3:08 pm
Subject: Re: REFLECTOR: Odd fuel stain?


No- extend the loop on the vent system (which should currently go up the
irewall to the top of the roof, then back down through the belly )foreword
long the roof of the aircraft so when the aircraft is pitched up at say 45
egrees, the foreword most part of the loop will be at a higher elevation
han the front of the strakes where the fuel is located
-----Original Message-----
rom: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
ehalf Of Robert Wood
ent: Monday, November 21, 2011 1:36 PM
o: bobj at jaxtechllc.com; Velocity Aircraft Owners and Builders list
ubject: Re: REFLECTOR: Odd fuel stain?
I think when saying extend the vent forward they are saying during the
uilding process inside the tank. Am I wrong?
Bob Wood
On Nov 21, 2011, at 1:32 PM, "Bob Jackson \(Jax Tech\)"
bobj at jaxtechllc.com> wrote:
> John,
 
 Can you translate your 500 fpm climb limit to a number of degrees nose up?
> 
 Our normal full fuel, 160 KIAS climb to altitude (turbo IO-550N) is with
 1000 fpm and 7 degrees nose up.  We occasionally get a 'whiff' of fuel in
 the cockpit after takeoff or touch-n-goes, but I normally do those with a
 ~18 degrees nose up attitude (100 KIAS).  I assumed these were caused by
 occasional fuel sloshing, not by a steady state venting problem!
 
 Are you saying we need to either start climbing out at higher than 160
IAS,
 or a lower power setting, or extend our vent line a couple of feet along
he
 top of the fuselage?
 
 When this topic came up a while back, and I did rough calculations back
hen
 I figured that in climbouts the fuel was going to be very close to the top
 of our vent loop (which is as close to the top of the fuselage as we could
 make it), but not over.  
 
 I don't have the exact measurements here -- but the way I roughly figure
t
 is:  the top of the vent loop extends ~18" above the spar beam, and the
 tanks are full and there is fuel at the front of the strake (and the
trake
 front is about 48" forward of the vent line), and that it would take a
limb
 angle greater than ~ 20 degrees (arctan[18/48])before you started venting.
 I'll have to take some more accurate measurements.
 
 Bob Jackson
 Turbo IO-550N XL/RG
 
 
 -----Original Message-----
 From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
 Behalf Of John Abraham
 Sent: Monday, November 21, 2011 8:57 AM
 To: 'Velocity Aircraft Owners and Builders list'
 Subject: Re: REFLECTOR: Odd fuel stain?
 
 General rule of thumb I use is no more than 500fpm climb when above 75%
 tanks.  This helps prevent dumping fuel out your vent which you cannot
 calculate very easily.  The only solution to this would be to run your
ent
 1-2 feet forward so that your strake angle does not exceed the top of the
 vent.  
 
 IO-540 (260HP) RG should be climbing between 120-130kias, 300HP Lycoming's
 and Continentals should be 130-145KIAS.  *Note that the IO-550 RG's at 135
 will be above 500FPM so you may have to climb at a faster speed than 140.
 Turbo charged aircraft with RG systems are between 145-165KIAS in a climb.
> 
 FG aircraft, speeds in climb will vary about 10kts less.
 
 Also, make sure your vent is scarfed into the wind so that you continually
 pressurize your tanks and don't create a vacuum.  Vent lines in the back
 should be treated the same as your main feed lines.  You want a continual
 downhill slope into the tanks so that you don't have any low point in the
 vent lines otherwise you may get some fuel stuck in the vent that cant
 pressurize itself out very easily which will lead to uneven feeding.
 
 John
 
 -----Original Message-----
 From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
 Behalf Of Scott Baker
 Sent: Monday, November 21, 2011 7:47 AM
 To: Velocity Aircraft Owners and Builders list
 Subject: Re: REFLECTOR: Odd fuel stain?
 
 Maybe not the negative-G, but very likely the steep pitch up maneuver.  I
 have many times seen (from the ground) a vapor trail of fuel exiting the
 vent tube from Velocity aircraft doing high performance takeoffs at
 Sebastian.
 Scott B.
 
 ----- Original Message -----
 From: "Scott Derrick" <scott at tnstaafl.net>
 To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
 Sent: Sunday, November 20, 2011 7:18 PM
 Subject: REFLECTOR: Odd fuel stain?
 
 
> So after design/install of a new forward cabin heater system I took the 
> bird for a test flight.  I as also testing a new oil temperature sensor 
> which is working fabulously!
> 
> Played around to the north of GNT getting the plane setup for LOP at 9500
>> and playing with different settings of the heater controls, there is a 
> separate control for pilot and co-pilot positions, plus the oil flap 
> provides full or reduced air flow.
> 
> The problem occurred when I did a walk around in front of the hanger
fter
 
> the flight and saw a bit of a fuel(blue) stain on the rear cowl! Thats 
> really odd I thought!  It started about a foot to the rear of the fuel 
> vent and was kinda wispy looking, about a foot+ long.
> 
> I was pretty upset as I don't like fuel leaks, who does, and we are 
> planning on flying to Tahoe Tuesday morning. I was contemplating where it
>> could have come from, There is no way it cam from the engine compartment,
>> it would have pooled at the low point in the bottom cowl and come out the
>> drain holes, and this was nowhere near that. Plus the fact, is was 
> directly in line with the fuel vent, but why would it spit fuel in
light!
> 
> Then I had an idea.
> 
> When I came back to the pattern the airport crowd requested a low pass, 
> you know an altimeter/compass check, so I sucked the gear back up and did
>> a 185 knot 100 ft pass down the runway.  Turning about 2600 RPM, at mid 
> field I pulled up into a  steeper than usual climb, about 4,000+ ft per 
> minute, the speed rapidly unwinding, the altimeter doing the reverse. At 
> the top, about 1,000 agl and now at 120 knots I pushed over a little more
>> aggressive than I usually do, going just a bit negative G for 5 seconds
r
 
> so, leveled off and made a sedate pattern to landing.
> 
> My fuel tanks are almost full, about 26 gallons in 30 gallons tanks.
> 
> Now I wonder did the negative G maneuver cause the fuel to spit out the 
> vent?  Anybody else experience a similar thing?
> 
> Scott
> 
> -- 
> We are all here for a spell; get all the good laughs you can.
> Will Rogers
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