There are two approved methods of adding rear ballast to the K21 to move the
C. of G. aft.

It is possible to fit a lead ballast block in the rear fuselage just aft of
the fin spar, this is not intended to be fitted or removed between flights,
and of course the machine must be re-weighed..

It is also possible to have a hole through the fin to take a bar to carry
external ballast in the form of up to 10 x 1kg lead weights, which is
intended to be adjusted or removed between flights as required. See
"optional extras" on the specification sheet at
http://www.as-segelflugzeuge.de/englisch/e_main.htm , "Your Sailplane", "ASK
21", at the bottom of the page "Download Info:", "Specification ASK 21
(english)".

Both schemes are described in the owners' handbook. See also the
Schleicher AD and Technical notes
http://www.as-segelflugzeuge.de/englisch/e_main.htm "TN/LTA", "ASK 21" in
particular TN-No 4 &4a, see also "further TN/AD see overview (PDF)".

Note also that in common with all German gliders (as far as I know) the
minimum front cockpit weight is always shown as 70 kg (154 lbs). However
if the glider is carefully weighed it may be found that the minimum front
cockpit load calculated by moments when flown solo is less than this. Of
course the minimum front cockpit load calculated by moments will always be
reduced when there is a rear seat pilot, by an amount which increases as the
rear cockpit load is increased.

The importance of all this is that the glider will not hold a stable spin
unless the C. of G. is close to the aft limit (the numbers are in the
handbook), but you will be in trouble if you fly it with the C. of G. aft of
the aft limit.

Don't even think of trying for a full spin, or flying with the C. of G. well
aft unless you have read the pilots' manual AMENDED BY TN 23. The TN
itself is on the Schleicher web-site but the page amendments are not.

W.J. (Bill) Dean (U.K.).
Remove "ic" to reply.


"Markus Gayda" wrote in message
...

For the ASK-21 is a "spin-weight" available which can be installed on the
rudder. Of course you have to weigh the pilots before deciding which
weights to add to the glider.

But then you have a very nice trainer with which you can also train spins.

CU
Markus