On Thu, 27 Sep 2007 21:21:13 +0200, virtuPIC
wrote in :

UFO HeliThruster

Apparently this auto-gyro is incapable of recovering from negative G
forces. It is unclear what method is used to prevent encountering
meteorologically generated negative G force in the case of turbulence
for instance.


http://www.ufo-helithruster.com/safe...yrocopter.html
First PPO "Power Push Over", by far the most dangerous of the
three scenarios discussed here. What happens here is the gyro is
deliberately forced nose down creating "Negative G". Negative G is
almost always non recoverable. Gyros are NOT designed to do this
maneuver. PPO is a flight maneuver (deliberate) at the top of a
climb or a nose-down dive from level flight.

Further, an “innocent” POWER ON can bring about PPO! Innocent in
that it should be a safe thing to do, that is, putting power on.
If the design of the gyro has some fundamentals wrong with it, or
a combination of them; high profile C of G, poor stability,
insufficient tail profile, then when power is applied vigorously
the propeller in such a craft can push the "top" of the Gyro
forward while the "bottom" lags (drags) behind, thus inducing PPO.
Technically what has happened in PPO is that the ROTOR has (in
effect) been uncoupled from the aircraft. Therefore, if you unload
the rotor (by making a zero-g maneuver) the rotor drag almost
vanishes and the thrust of the engine will make the aircraft
nose-down.

Power Push Over are done by people who are stupid, maybe to
impress a crowd they will dive at high speed, pull out at the
bottom which loads up the G forces (the rotor revs will
automatically increase), they do a spectacular zoom upwards and
when they reach the position when they stop climbing, we are in
zero-g, for a second there is no incoming air to turn the blades,
even worse the airflow is reversed, and this has a dramatic effect
on stopping rotor revs. With decreased rotor revs a pilot pushes
the stick forward, but it is too late; it is impossible to recover
lost revs.

This sounds scary stuff and it is. We hope you aren't stupid
enough to see if PPO is unrecoverable. But let's put this in
perspective, when you fly an airplane you know you can't land it
up side down, so you don't do it; with gyros you can't fly in
zero-g so you don't do it.