After more investigation I now have the answer. Elevator mass moment is the vertical line of force exerted to the aircraft (up or down) when the control surface is moved off of horizental plane. Vintage aircraft(before hydraulics) to ease the inputed control force needed to move the stablizer, there is a portion of the moving airfoil the is in front of the hinge. This forward surface catches the air flow and negates the force needed to displace the airstream by the control surface behind the hinge, The problem arises when the forward part of the stablizer is larger than needed and moves the vertice line of force in front of the hinge. What happens then is that the forward area catches the air stream and overpowers the control input. The pilot or servo than drives the surface in the other direction and again the forward surface catches the airflow and drives the elevator in the other direction. This condition is known as galloping. The solution is to reduce the forward hinged surface area, or increase the rear surface area, moving the moment to, or behind the hinge - behind is stable condition - ahead is unstable.
It looks like you're new here. If you want to get involved, click one of these buttons!
