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In aerodynamics, the pitching moment on an airfoil is the moment (or torque) produced by the aerodynamic force with respect to the aerodynamic center on the airfoil . The pitching moment on the wing of an airplane is part of the total moment that must be balanced using the lift on the horizontal stabilizer. [1]: Section 5.3 More generally, a ...
The aerodynamic center is the point at which the pitching moment coefficient for the airfoil does not vary with lift coefficient (i.e. angle of attack), making analysis simpler. [ 1 ] d C m d C L = 0 {\displaystyle {dC_{m} \over dC_{L}}=0} where C L {\displaystyle C_{L}} is the aircraft lift coefficient .
This leverage is a product of moment arm from the center of gravity and surface area. Correctly balanced in this way, the partial derivative of pitching moment with respect to changes in angle of attack will be negative: a momentary pitch up to a larger angle of attack makes the resultant pitching moment tend to pitch the aircraft back down.
A stability derivative. This is an example of a common shorthand notation for stability derivatives. The "M" indicates it is a measure of pitching moment changes. The indicates the changes are in response to changes in angle of attack.
The aerodynamic center, which is the chord-wise location about which the pitching moment is independent of the lift coefficient and the angle of attack. The center of pressure, which is the chord-wise location about which the pitching moment is momentarily zero. On a cambered airfoil, the center of pressure is not a fixed location as it moves ...
The center of pressure of an aircraft is the point where all of the aerodynamic pressure field may be represented by a single force vector with no moment. [3] [4] A similar idea is the aerodynamic center which is the point on an airfoil where the pitching moment produced by the aerodynamic forces is constant with angle of attack. [5] [6] [7]
A control system includes control surfaces which, when deflected, generate a moment (or couple from ailerons) about the cg which rotates the aircraft in pitch, roll, and yaw. For example, a pitching moment comes from a force applied at a distance forward or aft of the cg, causing the aircraft to pitch up or down.
Mach tuck occurred at speeds above Mach 0.65; [3] the air flow over the wing center section became transonic, causing a loss of lift. The resultant change in downwash at the tail caused a nose-down pitching moment and the dive to steepen (Mach tuck). The aircraft was very stable in this condition [3] making recovery from the dive very difficult.