REFLECTOR:CG Test
Jim Sower
reflector@tvbf.org
Sat, 24 Jan 2004 14:49:01 -0600
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John,
What I was talking about is suspicions around where the factory
puts the CG of the pilot. I've heard repeated stories about
guys doing W-B with the empty plane and again with them in the
pilot's seat, backing up the results and discovering that their
(pilot) CG was an inch or two from where the factory said it
would be. IIRC the discrepancies in where pilot CG is are
larger and more common with bigger heavier pilots, but if you're
checking for aft limits, I think you'd do well to know from
actual measurement where your personal CG falls in the airplane.
Just a theory .... Jim S.
John Dibble wrote:
> Jim,
> I appreciate your comments. I suspect a weight/balance would
> confirm an aft cg loading according to the numbers that
> Velocity provides. What I am trying to do here is establish a
> limit specific to my plane which may be different from the
> standard assuming there are small differences in how each
> plane is built. Scott S told me that, for a standard
> Velocity, typically 170 lbs in the front seat is enough to put
> you within the aft cg limit. So perhaps my plane is
> different, or maybe the original cg measurements are off. In
> any case I think an actual flying stall test is more
> meaningful than measurements on the ground. Of course with
> flying there is risk involved and the weight/balance
> measurement is essential before first flight when you know
> nothing about how it will fly. My plane has 280 hours (75 of
> which are mine), so I know it flies ok and I'm looking to fine
> tune (determine with more certainty) my aft cg limit and
> hopefully avoid adding weight to the nose. From recent
> reflector discussions I felt I understood the causes and onset
> indicators of a deep stall as well as how to recover from it
> (altitude, prop pitched for power, moveable weights) and felt
> sufficiently comfortable to stall the canard near the aft cg
> limit. I think doing a weight and balance measurement now is
> like measuring the length of the bungee cord after having
> already jumped off the bridge. If anyone disagrees, please
> tell me.
>
> John
>
> Jim Sower wrote:
>
>> Having done what you have done, I would be inclined to
>> muster up some friends and do a
>> weight/balance with the fuel load you tested with, you
>> *personally* sitting in the
>> pilot's seat, and the weights you used just as close as you
>> can place them to where
>> they were in the back seat.
>> Just to be sure .... Jim S.
>>
>> John Dibble wrote:
>>
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John,
<br>What I was talking about is suspicions around where the factory puts
the CG of the <i>pilot</i>. I've heard repeated stories about guys
doing W-B with the empty plane and again with them in the pilot's seat,
backing up the results and discovering that their (pilot) CG was an inch
or two from where the factory said it would be. IIRC the discrepancies
in where pilot CG is are larger and more common with bigger heavier pilots,
but if you're checking for aft limits, I think you'd do well to know from
actual measurement where your personal CG falls in the airplane.
<br>Just a theory .... Jim S.
<p>John Dibble wrote:
<blockquote TYPE=CITE>Jim,
<br>I appreciate your comments. I suspect a weight/balance would
confirm an aft cg loading according to the numbers that Velocity provides.
What I am trying to do here is establish a limit specific to my plane which
may be different from the standard assuming there are small differences
in how each plane is built. Scott S told me that, for a standard
Velocity, typically 170 lbs in the front seat is enough to put you within
the aft cg limit. So perhaps my plane is different, or maybe the
original cg measurements are off. In any case I think an actual flying
stall test is more meaningful than measurements on the ground. Of
course with flying there is risk involved and the weight/balance
measurement is essential before first flight when you know nothing about
how it will fly. My plane has 280 hours (75 of which are mine), so
I know it flies ok and I'm looking to fine tune (determine with more certainty)
my aft cg limit and hopefully avoid adding weight to the nose.
>From recent reflector discussions I felt I understood the causes and onset
indicators of a deep stall as well as how to recover from it (altitude,
prop pitched for power, moveable weights) and felt sufficiently comfortable
to stall the canard near the aft cg limit. I think doing a weight
and balance measurement now is like measuring the length of the bungee
cord after having already jumped off the bridge. If anyone disagrees,
please tell me.
<p>John
<p>Jim Sower wrote:
<blockquote type="cite" cite="mid4011F9AF.FCFC2173@frontiernet.net">
<div wrap="">Having done what you have done, I would be inclined to muster
up some friends and do a<br>
weight/balance with the fuel load you tested with, you *personally* sitting
in the<br>
pilot's seat, and the weights you used just as close as you can place them
to where<br>
they were in the back seat.<br>
Just to be sure .... Jim S.<br>
<br>
John Dibble wrote:<br>
<br>
</div>
</blockquote>
</blockquote>
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