REFLECTOR: Interesting Angles -- Fuel Venting & Prop Strike

[Bob Jackson]

Scott,

 

I'm not sure, but I think the strake fore-aft length is about the same for
an XL and a STD, so all my numbers below should also be about the same.  If
not, and you want to give me the measurement from the engine bulkhead to the
front of your strakes (and also from the top of the spar to the inside
bottom of your fuselage), I will compute STD angles for you...

 

Bob

 

  _____  

From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Scott Derrick
Sent: Sunday, November 27, 2011 9:28 PM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Interesting Angles -- Fuel Venting & Prop Strike

 

Bob,

Great data for a XL, I wonder about the STD RG? 

Seems like the extended loop doesn't gain all that much at full tanks, when
it really matters?

Scott

-------- Original Message --------
Subject: REFLECTOR: Interesting Angles -- Fuel Venting & Prop Strike
From: Bob Jackson  <mailto:bobj at computer.org> <bobj at computer.org>
To: 'Velocity Aircraft Owners and Builders list'
<mailto:reflector at tvbf.org> <reflector at tvbf.org>
Date: 11/27/2011 07:18 PM



A little while back we were talking about how fuel is vented from the
Velocity in steep climb angles when the fuel in the front part of the strake
tank is higher than the vent loop normally routed to the top of the inside
of the engine bulkhead  I'm interested in this because we periodically do
smell a little fuel in the cockpit, and I think we are smelling wisps of the
vented fuel, coming back in the main gear leg holes.

 

So I made some measurements and computed a few angles (Velocity XL RG with
93 gal strake tanks and vent loop as high to the ceiling as possible, but
not routed forward -- which will allow steeper climb angle) that I thought
people might be interested in the summary:

 

            Fuel                  Max Angle of Climb (without venting)

       ------------------
--------------------------------------------------------------------

 

            FULL                            12 deg

             3/4                               18 deg

             1/2                               36 deg

 

and if you were to extend the vent loop forward about 12" along the inside
top of the fuselage:

 

            Fuel                  Max Angle of Climb (without venting,
extended loop)

       ------------------
----------------------------------------------------------------------------
--------------

 

            FULL                            14 deg

             3/4                               25 deg

             1/2                               63 deg

 

One other climb and rotation angle of interest is the maximum before your
prop strikes the ground -- which could conceivably occur on take-offs, but
more likely on a very slow, hard landing involving an over-rotated flare.
The GRT EFIS data from our flights indicates that our normal touchdown
fuselage angle is 9 to 10 degrees -- plenty of margin!!

 

            Prop Strike       =          > 11 degrees pitch attitude

 

Bob Jackson

N2XF

 

 
 
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