High wing aircraft are more stable laterally, which in some cases is countered by anhedral. It is not due to a pendulum effect though. Think about it. You have one lifting force, acting perpendicular to the wing through the centre of gravity. How could that roll the aircraft?
In the case above there is no desire for a roll - the lifting force acting acting perpendicular to the wing through the centre of gravity
indicates wings level. However following a disturbance in roll pendulum effects DO
come into play and will attempt to restore a high-wing aircraft to level flight (lateral stability).
Imagine a 172 viewed from behind is disturbed by a gust, lifting the port wing. This results in the CoG being displaced towards the high-wing side
and creates a moment about the CL
opposite to the direction of the disturbance - ie: a restoring moment. So you could imagine in the case above with a 60 ton tank in the belly of the C-17 and any significant vertical distance between the CoG and CL
the result will be quite a large moment opposite to the direction of the desired turn - hence the use of anhedral.
Given the same disturbance in a warrior - this time however the CoG (being above the CL
) will be displaced towards the low-wing side
, creating a moment about the CL in the direction of the original disturbance
- ie: strengthening the roll towards the lower wing. Hence the use of larger angles of dihedral on low-wing aircraft.
It's harder to explain without diagrams but pendulum effects definitely increase the lateral stability of high-wing aircraft. Sometimes so much so that desired levels of controllability are lost. Fred?