Bill Daniels wrote:
"Eric Greenwell" wrote in message
...

Mark Navarre wrote:


As speed increases, the nose will come up (away from vertical) even if

you

don't want it to, and even with full forward trim, it would still

require an

honest push on the stick to maintain that attitude.


Not true with all gliders. Several modern racing ships will, when

trimmed

within CG limits for best climb performance, "tuck" or pitch down with
increasing airspeed, resulting in a large outside loop or exceeding VNE

without

pilot input. The crossover speed for this in my own ship is about 115

kts,

above which slight back pressure is needed to maintain speed.

Which glider is that? I thought a pitch-up tendency with increasing
speed was a certification requirement? And what is the CG position for
this to happen? Is this "feature" mentioned in the flight manaul? Sounds
kind of scary.

Though it was certainly not a "modern racing ship" my old Lark IS28 would go
neutral pitch stability at about 90 knots and become very nose heavy above
that even with negative flaps.

Was that a common experience, or just your particular IS28? I'm
wondering if there might be a rigging error. None of the gliders I've
owned has exhibited that; in fact, all of them ran out (or required
nearly full) of forward trim nearing Vne. THese gliders are the Ka-6E,
Std Cirrus, Libelle H301, ASW 20 C, ASH 26 E, Blanik. The Cirrus had a
particularly noticeable concave under section on the elevator to induce
this behavior.

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Eric Greenwell
Washington State
USA