On 8/9/2020 11:30 AM, Dr. Feng Hsu via KRnet wrote:
Also, I wish to know what's the design error tolerance on the CG position
for KR (not KR2S)? Such tolerance is determined by the capacity (surface
area) of the stabilizer, correct? If there is any uncertainty about the CG
spot, or to put the last two ponds of extra luggage during loading, we
would much prefer to allow the tail heavier than otherwise, true or false?
+++++++++++++++++++++++
FALSE. Tail heavy is the worst possible condition for control and there
is no tolerance. In the case of the KR2, pilots advise to stay out of
the last two inches of the C.G. range. The 2S is longer so it may
tolerate the rear 2 inches.
Speaking of C.G. range, it is in the plans of which mine are at the
airport. I recall 8" to 16" referenced to a certain location but I
don't recall that location from memory. That range falls in the area of
15 to 30% of MAC (Mean Aerodynamic Cord is 48" in this case as it is
measured on the center section). Someone please post the range given in
the manual.
+++++++++++++++++++++++++++
Of course we can calculate the CG point if given design information, but I
suspect that the ultimate verification of CG is to use 3 weight scales (one
on each wheel) to find out the weight balance (empty or gross) point
perhaps. Am I correct?
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
That is the only way to determine C.G. location. Place the aircraft on
scales, perfectly level, select a datum point (a reference point to
measure from) , multiply the weight at each wheel times the distance
from the datum (arm) to determine the "moment" in inch pounds. Add all
the "moments" and divide by the total weight of all scales and that
gives you the c.g. location in inches from the datum. There are many
sites on the net that give the procedure. C.G range is, in my opinion,
equal to structural integrity in importance for safe flight. Do it
right or get your affairs in order for your survivors.
Larry Flesner
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