Avoiding Vne

On Thu, 25 Mar 2004 08:53:00 GMT, "K.P. Termaat" wrote:

Yesterday evening I talked with a friend about avoiding excessive speed when
recovering from a spin in a modern low drag glider with the somewhat larger
span.
He came up with the idea of pulling the airbrakes when still recovering from
the rotating mode. I am not sure this can be done without disturbing the
recovering action or without hurting the glider.
Any comment will appreciated.

What has not been discussed so far in this thread is the acceleration
of the glider in a steep dive:

If you extend the airbrakes (far) below Vne, you have a lot more time
to pull out of the dive until your airspeed reaches Vne because the
acceleration of the glider is a lot slower.

Typical case: You extend your airbrakes once you exceed a certain
speed (for example Va or slightly higher).

Glider airbrakes are typically designed to keep the glider under Vne
at a dive angle of more or less 30 degrees, so if your nose-down
attitude is less than 30 degrees, the glider will decelerate while you
are still pulling out of the dive - this means that once you have
reached 30 degrees nose-down attitude, you are already safe and can
take all the time in the world to pull out the last 30 degrees till
level flight (...if you have enough height, of course) without
worrying about exceeding Vne.

You are probably going to loose more height during the recovery
(because of the "soft" pullout) this way, but the g-load will be kept
realtively low.



With retracted airbrakes the glider will accelerate quickly, therefore
you are going to need to pull higher g-load to get out of the dive
before you exceed Vne - and the glider will accelerate all the time
until it is nearly in level flight. And as others have already pointed
out in this thread, extending the airbrakes close to (or over) Vne at
high g-load is probably going to ruin your day...



Bye
Andreas