REFLECTOR: Interesting Angles -- Fuel Venting & Prop Strike

Sun Nov 27 22:57:13 CST 2011

According to our data dumps and my calculations, here are the various climb
(and Aircraft Data Line) angles, angles of attack, airspeeds and climb rates
for various climb angles (given a 2800 lb Velocity XL/RG weight with a
TNIO-550N generating 325 hp, 25 gal fuel, pilot and co-pilot onboard) :

            ADL Angle        Angle of Attack             Net Climb Angle
Airspeed           Rate of Climb

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

               19 deg                 10 deg                           9 deg
100 KIAS            1500 fpm

               13 deg                   7 deg                           6
deg                     120 KIAS            1200 fpm

                 7 deg                   3.5 deg                        3.5
deg                  160 KIAS            1000 fpm

As you can see, the effective climb angle is a lot lower than the actual
(ADL) angle WRT the horizon because of the high angle of attacks at low
airspeeds.  Your mileage will vary based on aircraft weight and engine
power.  As far as I can tell, we have the heaviest Velocity (and we're not
all that proud of it!).  After touch and go's we generally climb out at 100
KIAS.

Bob

  _____  

From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Brian Michalk
Sent: Sunday, November 27, 2011 11:12 PM
To: bobj at jaxtechllc.com; Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Interesting Angles -- Fuel Venting & Prop Strike

On my first flight, I climbed at full throttle, and used pitch to control
engine RPM until I reached 1000 feet AGL.  I had an engine failure at 900
feet, and using the altitude, and landmark, I calculated after the flight
that I was climbing at 19 deg.

That was purely for flight testing.  I may or may not have been venting
fuel, but that is a different issue.  For my current needs, I want to
reproduce the conditions of my first flight, so I've been looking at all of
the problems associated with doing that.

Due to the chatter here on the list about fuel venting, I went ahead and
made those changes ... it's just a sort of related sidebar.

Thanks for the confirmation on the climb angle.  I didn't know if that was
possible, seeing the plane in the hangar at such an angle, I can scarcely
believe it was at that attitude on first flight.  How many FPM do you see at
19 deg?

On 11/27/2011 09:08 PM, Bob Jackson (Jax Tech) wrote: 

Brian,

Your 19 deg climb out angle is correct (according to our GRT EFIS data
dumps) for a 100 KIAS climb.  For a more normal 120 KIAS climb, the angle is
about 13 degrees.  Our typical extended climb is at 160 KIAS (to help with
cooling), and it is about a 7 degree climb angle.

Why do you want to climb out at 19 degrees, Brian?  Unless you're unusual, I
think you're going to have cooling problems at that attitude, especially for
extended climbs (to 10 Kft or above).  For first flight, you will also
probably only have ~1/4 fuel, so you should be able to climb out at almost
any angle you want without venting fuel.

Bob

  _____  

From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Brian Michalk
Sent: Sunday, November 27, 2011 9:48 PM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Interesting Angles -- Fuel Venting & Prop Strike

How timely!

I am trying to figure out how to do some full power runs with the airplane
at 19 degrees.

I'm SE/FG with Franklin/IVO.  At 10 deg, the prop touches the floor.  To get
to 20 deg, I need to raise the wheels 23 inches, plus a bit for safety.

Why 19 degrees?  That's what I calculated to be my climbout on first flight.
Yesterday, I also added a vent loop that goes up along the ceiling.

On 11/27/2011 08:18 PM, Bob Jackson wrote: 

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.

  _____  

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