BODY AXIS SYSTEM
Those points about which the aircraft will rotate (Figure 5).
Pitching Moment (IY)
Figure 5: BODY AXIS SYSTEM
MOMENT OF INERTIA
With respect to any given axis, the moment of inertia is a measure of the resistance of a body to angular
acceleration. Ix, Iy, and Iz are moments of inertia about the respective body axes (Figure 5).
EFFECTS OF MASS DISTRIBUTION
Mass distribution defines the way in which the mass of an aircraft is distributed between the fuselage and the
wings. Because aircraft are flattened into the XY plane, the maximum moment of inertia is invariably
around the yaw, or Z, axis (Iz). Depending on the aircrafts mass distribution, Ix is greater or less than Iy, as
illustrated in Figure 6. Mass distribution is usually expressed in terms of the inertia yawing moment param-
Ix - Iy
Where: Ix and Iy = Moments of inertia around the indicated axis
M = Mass of the aircraft
b = Wingspan