And to reference the next article from the DG website
which rpeorts on actual Akaflieg flight testing:


'Add on after the soaring symposium Stuttgart 2000
and Braunschweig 2001:

Members of the Akaflieg Braunschweig have once again
focused on achieving an optimal center of gravity.
They have therefore completed a number of test flights
with two ASH-25 which had been carefully inspected,
set up and checked. Both planes were equipped with
highly complex measuring equipment due to the expected
marginal rate of differences between the two planes.
One was declared to be the reference plane, the other
was designed to allow altering the center of gravity
before every flight.

The test flights have been completed with various speeds
and flap settings. The results were later evaluated
by computer. The specific results are of no real interest
for us. A common pilot flies at various speeds with
a variety of flap settings during a normal long duration
flight. What was of interest to us was the average
result of the test flights. And even without the complete
set of results one thing can be noted:

The aft position of the center of gravity is not desirable
in order to achieve a really good result. The best
results were achieved about 30 - 35 % in front of the
aft limit of of the specifications for the center of
gravity. That is caused by the elevator since it is
not in a neutral (streamlined) position with a centered
C/G. Instead it has to produce lift (an up elevator
deflection) which it's not actually designed for resulting
in increased drag.

Some of our customers who want participate in competitions
ask us to carefully weigh the aircraft and set it up
at 98% aft center of gravity. Although we generally
fulfill all of our customers wishes this is one we
should not comply with. The sailplane will not fly
any better by achieving this extreme aft center of
gravity. It will simply react more nervously to pitch
and roll inputs. In fact, should the pilot loose 2
liters (1/2 gal) of water during a long flight (de-hydration!),
the sailplane has exceeded the specified limits of
C/G and control in all axes becomes very sensitive.



Please choose a center of gravity that is 30 to 35%

before the rearmost limit of the aircraft's specification.

This will grant an optimum in safety and performance.'

John Galloway



At 13:18 24 October 2003, Mark Stevens wrote:
this has been referenced before from the DG web site,
but it's not long so I'll post it here..