Jon Meyer wrote:

Yes, as has already been mentioned the ASW20 has a
problem, where exceeding Vd can result in wing twist
that results in a terminal dive even with the stick
fully back. Not to mention what flutter can do anyway.

According to Bill Dean "I gather that the investigators
contacted Schleichers about the accident, and the information that the
glider would be unrecoverable at some speed below 200 knots,"

NO mention of Vd (about 160 knots), so it is speculation to say
exceeding Vd can result wing twist. It might be 170, 180, 190,... we
don't know.

In most modern gliders you should be able to pull
6g+ without breaking any bits
off them.

Not at VNE !!!


Yes, I think Ed is probably right. Although the glider
will probably be a write-off after you land, because
the material will yield in highly stressed areas. Glider
wings are bloody strong, and are unlikely to snap,
but the reason you dont want to exceed the G-limits
every day is because bits will start to creep, and
your glider's structure will gradually deteriorate
and eventually fail, but as a One-off it is unlikely
to result in failure, particularly as the stalling
angle of the wing will limit the maximum g you can
pull below VNE. It will be pretty high, but is unlikely
to be more than 10g, and you shouldnt need to pull
this hard anyway.

At Vne, my ASH 26 can pull 2.2 times the flight limits of 5.3 G. And if
you hit a gust at the same time, or have some aileron or rudder input...

To be honest if it was a choice between
flutter, where bits like ailerons and elevator might
come off, and exceeding the G-limits where the wing
might be a write off but the plane will remain flyable
and be safe to land (or at least bail out of), I know
which I would choose.

Who wouldn't choose a plane that was safe to land instead of one where
bits have fallen off? What we are discussing is if the choice is "and
exceeding the G-limits where the wings might break off".


The drag rise is not enough to avoid overspeeds. The
rise in drag
provided by *airbrakes* (not pulling too hard) is the
*only* way to
avoid either flutter (above VNE) or breaking the wings
(by overloading).


I believe that with the airbrakes open your safe positive
G-limit reduces to +2.5G.

For my ASH 26 E at Vne: 4 G load factor (down from 5.3 at Va); 3.5 G
load factor airbrakes extended. It looks like the G limits at Vne are
fairly close together. I am curious about why they decrease.

snip

Ask an aerobatic pilot if you don't want to take my
word for it, but I believe their rule of thumb is that
it is always better to exceed the g-limits than to
exceed VNE, and that you should NEVER open the airbrakes
in an attempt to limit speed, because it has such a
small effect on drag and such a huge effect on the
g-limits.

Are they talking specifically about gliders designed for aerobatic use?
Quite a different bird than what most of us fly, with very high G and
Vne ratings. Perhaps their rule of thumb applies just to them? And, I am
very skeptical of the "small effect on drag" remark, since at Vne, the
air brake drag will be greatest drag of all the sources. Or maybe not,
if you mean gliders designed for aerobatic use.


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Eric Greenwell
Washington State
USA