On Fri, 28 Sep 2007 11:46:35 -0500, "Gig 601XL Builder"
wrDOTgiaconaATsuddenlink.net wrote in
:

The issues that Gyros have with negative G's make them less IFR capable than
a similar helicopter or fixed wing aircraft.

Is this claim a Mollerism?

http://www.cartercopters.com/
I have heard that two-bladed, teetering rotor systems have a
reputation for something called "mast bumping" in low-g flight.
What is mast bumping, and why is the CarterCopter not susceptible
to this problem?

Mast bumping is caused in helicopters by a lack of control of the
aircraft due to the rotor not producing much lift or negative
lift. During a zero-g maneuver, when the rotor is unloaded, it
does not create any lift force, so it does not have any force to
apply to the helicopter to control it. In this situation, if the
pilot moves the cyclic to try and control the aircraft, the rotor
will still tilt, but since it is producing no net lift, it will
not have a reaction on the rest of the aircraft. If the pilot
inputs more control because he does not feel the aircraft
responding, he makes the rotor tilt even more, until it hits the
mast. The tail rotor can aggravate this problem. Because it is
still producing a force, it pushes the aircraft to the side, and
if it's not directly on the centerline, causes the aircraft to
roll as well. The pilot feeling this movement will try to counter
it with the stick, causing the problem outlined above, with the
tail rotor pushing the fuselage in the opposite direction of the
rotor.

In the CarterCopter, because of the dual control system (airplane
as well as autogyro), the pilot always has control of the
aircraft, as long as he has sufficient airspeed. During a zero-g
maneuver, with the rotor unloaded and producing no lift, the
elevators and ailerons are still effective. When the pilot moves
the stick, the ailerons or elevator will control the fuselage,
keeping it in approximately the same relative position compared to
the rotor, so mast bumping is not a problem.