REFLECTOR: Testing forward CG

via Reflector reflector at tvbf.org
Thu Sep 25 07:44:46 CDT 2014


Brian,

Start with measuring your elevator throw.  If you are achieving less than 26 degrees work on that.  You want between 26-28.  On the opposing side to that if you are over 28 degrees you will stall the elevator.  What is your empty weight and empty nose weight? Normal nose empty weight should be around 80-85.  If you start to break 100lbs this will highly affect your stall speed.  Then the other obvious question, is your airspeed indicator correct? Double check on a calm day with ground speed in 3 directions.

Most SE's should see around 60-67KIAS for canard stall assuming standard weight.
173's should be the same, with VG's installed downward of 55KIAS
XL's will be 67-75 pending how heavy they are.

VG installation.  You can put VG's on the main wing AND canard or just the main wing.  I strongly recommend you DO NOT put them on the canard only unless you speak to Scott Swing.  If you are losing the canard at 80KIAS then it could be elevator throw, wing incidence, weight related.  You don't want to delay the stall of the canard unless you do the same to the main wing.  

If you do deep stall testing would it work out?  Well maybe but if we dont have to do this to any others something else is not right.

Fly Safe,

John Abraham
Executive V.P. Sales and Marketing, Chief Pilot


-----Original Message----- 
> From: "John Dibble via Reflector" <reflector at tvbf.org> 
> To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org> 
> Date: 09/25/14 08:33 
> Subject: Re: REFLECTOR: Testing forward CG 
> 
> On 9/24/2014 10:28 PM, Kurt Winker via Reflector wrote:
> > What CG value and gross weight?
> >
> > Only have 9 hrs on mine...
> > Canard up at 73...rotate smoothly at 80.
> > Final at 85... Touchdown at 83.  If I let it slow below 80.   Feels like I do not have enough reserve elevator.
> Do you have the elevator trimmed for "hands off"?  The trim spring 
> creates artificial travel limits.  You may have more available travel 
> than it appears.
> 
> John
> 
> >   This is right at the lower end of the first flight envelope for the 173.
> >
> > Hope to be back in the air this week. Wondering when I should put the wheel pants on?
> >
> >
> > Kurt.
> >
> > Sent from my iPad
> >
> >> On Sep 24, 2014, at 21:00, Brian Michalk via Reflector <reflector at tvbf.org> wrote:
> >>
> >> In my flight tests, as I move the CG farther forward, I notice that I am unable to get the airplane to stall in straight flight. Instead if stalling, the Vm begins to increase.  Vm is the minimum speed to maintain altitude, and is something I check on each flight, because it's the speed below which I am unable to flare for a landing.
> >>
> >> I don't have a specific CG in mind, but when I have 380 lbs in the front seats, I run out of elevator authority for landing at normal air speeds.  I really need to carry more speed on final than I'm comfortable with.  With this weight in the front, I'm flying approach at 95kts.  My Vm is 80kts.
> >>
> >> My next check is to see the actual elevator travel from the neutral position.  I believe I'm very close to the book values, but maybe I need more elevator travel.  If my problem is not elevator travel, I'm thinking about testing VG's on the canard, starting out with only one VG per side to see if this helps.  I know VG's on the canard only are verboten, but if one does deep stall testing, and clears the aft CG regime, then is this still forbidden?
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