Peter,
R is radius. i.e where the mass is relative to the C of G.
If you have the situation of a light pilot and no
tail ballast the C of G may be in certain position.
Put a heavy pilot in and ballast the tail to get
the C of G in the same position. THIS IS NOT THE SAME SITUATION.
The Moment of Inertia ( m*r*r) of the glider
around the yaw and pitch axes will be increased.
It will require more force to get the aircraft to
rotate around those axes but once rotating, more force to stop the rotation.
As the story illustrated, relatively small
changes noticeably altered the spin and recovery
characteristics of the aircraft.
Casual spinning in gliders is something few of
the experienced soaring pilots of my acquaintance
will do. It simply isn't part of a normal cross
country soaring flight. I've certainly NEVER spun
a glider while it was water ballasted and only
once in late 1968 have I spun "accidently". It
was my first flight in the ES57 Kingfisher (*the*
one hanging up in the Bullsbrook RAAF museum) and
I was pushing the envelope in a steep turn to see
how tight I could turn and it was not entirely a
surprise when the ground started rotating in front of me.
Did it twice more to confirm. Then did a fair bit
of flying in the thing over the next year or so
and never came anywhere near spinning it.
Mike
At 08:15 PM 26/01/2015, you wrote:
Thanks Mike,
I read you reference.
M is Mass. What is R?
On Fri, Jan 23, 2015 at 10:14 PM, Mike Borgelt
<<mailto:[email protected]>[email protected]>
wrote:
<http://www.avweb.com/news/features/A-Test-Pilot-Spins223410-1.html>http://www.avweb.com/news/features/A-Test-Pilot-Spins223410-1.html
I've always had my doubts about sticking lead on
the tail to make glider more spin prone.
C of G is M * R
Moment of inertia is M * R * R
Mike
Borgelt Instruments - design & manufacture of
quality soaring instrumentation since 1978
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