REFLECTOR:Determining AFT CG Limit

[Scott]

Good description Scott...

Thats how I tested my AFT CG limit after removing the elevator cuffs and 
installing the VG's.

Scott

At 10:53 AM 12/6/2003, you wrote:
>Lack of pitch stability is certainly a clue.
>Set out a detailed, conservative flight test program to determine the aft 
>cg limit of your aircraft.
>Step 1. would be to calculate the loading conditions to achieve a 
>rear-most cg (as shown in the POH).
>Step 2. would be to load the aircraft so that the cg of the aircraft is 
>... say 2" forward of the rear most suggested limit and go fly the 
>aircraft.  At a safe altitude and at a safe location - enter slow flight 
>(75-80 knots) and raise the nose (about 7-10 degrees pitch up attitude) 
>into a low power climb (about 16" map or around 1800 rpm) and wait for the 
>onset of the canard stall.  Try to hold the pitch attitude during the 
>stall.  If the nose is dropping and (in order to maintain the constant 
>climb attitude) you are pulling "nose up" stick force, this is 
>good.  Land, calculate what it will take to shift the cg aft another 0.5" 
>and go do it again.
>VERY IMPORTANT NOTE>  If, on the other hand, at the onset of the stall you 
>find the canard rising - and you are pushing on the stick to maintain the 
>constant climb attitude - you are in the dreaded "too far aft" cg range 
>... immediately apply full forward elevator and full power, lean forward, 
>and take thyself back to the airport and (while adding 5 knots to your 
>normal approach speed) ... land and shift some weight forward ... and then 
>go do it again.
>SB
>----- Original Message -----
>From: <mailto:romott@adelphia.net>Ronnie Brown
>To: <mailto:reflector@tvbf.org>reflector@tvbf.org
>Sent: Saturday, December 06, 2003 8:34 AM
>Subject: REFLECTOR:Determining AFT CG Limit
>
>There's been a lot of discussion the last couple of months about flat 
>stall on Velocities and it has even come up in the more recent VG 
>conversations.
>
>But I don't recall any discussions on how to determine where the aft CG 
>limit is.  Just what phenomenon are we looking for when we are on the 
>ragged edge of AFT CG other than the dreaded Flat Stall???
>
>On a conventional airplane, the aft CG is determined by the lack of pitch 
>stability as the CG is moved rearward.
>
>Danny Maher ran a bunch of "trailer" tests and there were accidents but 
>beyond that, just how do you determine what the aft CG is (other than use 
>the numbers the factory provides).
>
>Ronnie Brown