My Mosquito has a long term phugoid. Try this. Get everything just
perfect. In trim, stable on airspeed, then let go of the stick for 10 minutes.
If it wanders off the trimmed speed, then corrects but overshoots, you
have a long term phugoid. If it eventually diminishes, it's damped. Most
pilots never notice a long term phugoid. The air is seldom smooth enough.

In article , Andreas Maurer
wrote:
On Sun, 04 Apr 2004 00:06:23 GMT, "Bill Daniels"
wrote:

No glider will stabilize itself at
the trimmed airspeed because the phugoid is undamped. It will oscillate
around the trimmed airspeed with ever increasing amplitude.

I think things are getting esoteric now.
I've flown about 40 kinds of gliders so far, an ALL of the stabilized
at the trimmed airspeed within a couple of oscillations. None was
showing the behaviour that you describe.
What am I doing wrong?




I have no trouble believing the stories about uncontrollable vertical dives.
The nose down pitching moment created by the airfoil is very likely
powerful enough on some gliders to completely overcome the up elevator
authority at some speed above Vne.

Well... it's simple: If you are flying faster than Vne, you become a
test pilot. But staying below Vne is extremely simple in a glider...



Take any glider and trim it for best L/D, then push it up to 10 Knots above
best L/D and release the stick. The pitch oscillations will increase in
amplitude until you take control again. This is true whether the stick is
free or fixed. To demonstrate the drag effect, just open the spoilers and
watch the phugoid damp out.

Hmmm... is it possible that you are flying with an extremely aft CG?


Bye
Andreas