On Fri, 3 Oct 2003 14:48:55 +0100, "W.J. \(Bill\) Dean \(U.K.\)."
wrote:



I know of three fatal accidents where it appears that the glider went
outside limits while recovering from what appeared to be an inadvertent
stall/spin recovery.

1. ASW20CL at Dunstable (I think more than 10years ago), the glider
reached a speed in the dive which made the dive irrecoverable; the C. of G.
may have been aft of limit.

2. Nimbus 4DM at Minden on 13th July 1999.

http://www.ntsb.gov/publictn/publictn.htm , then
http://www.ntsb.gov/publictn/2002/AAB0206.htm or
http://www.ntsb.gov/publictn/2002/AAB0206.pdf .

From the report it would appear that the glider departed into a stall/spin
while thermalling, and was overstressed in the subsequent dive while
recovering.

The brakes opened during the recovery, which reduced the 'g' limitations;
correspondence to Rec. Aviation Soaring indicates that some pilots have
experienced inadvertent deployment of the brakes on this type of glider.
There was also a suggestion that the pilots may have been incapacitated by a
problem with their oxygen system, thought there was no evidence to back
this.

3. Nimbus 4DM in Spain 1999.

Referred to in the report of the Minden accident above.

Quote: "the pilot stated they were in a turn when a heavy thermal caused the
glider to enter a steep descending spiral. The pilot could not recover the
aircraft from the spiral and the glider quickly exceeded Vne. The pilot
then reported that the right wing failed and he bailed out." The second
pilot was unable to bail out.
To which can be added the in flight breakup of a Blanik L13 at
Narromine NSW in about 1996 or 97 I think it was.
Two dead, instructor and student.

Intentional spin(Annual spin check!) which developed into a spiral and
the glider was overstressed in the recovery, bending the rear fuselage
and preventing recovery from the dive.
Neither pilot was wearing a parachute.

Just my opinion but intentional spinning is something that should be
treated with great caution. Brief the exercise properly, wear
parachutes and be prepared to use them. Best done in something like
Pitts S2 which is likely to hang together rather than a slippery
sailplane.

Mike Borgelt