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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 .
On aircraft with swept wings, wing tip stall also produces an undesirable nose-up pitching moment which hampers recovery from the stall. Washout may be accomplished by other means e.g. modified aerofoil section, vortex generators, leading edge wing fences, notches, or stall strips. This is referred to as aerodynamic washout.
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 RFB X-113 Aerofoil Boat was an experimental ground effect vehicle intended to work over water. It was one of three such aircraft designed by Alexander Lippisch in the 1960s and early 1970s. The X-113 first flew in 1970; only one was built.
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.
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. A fixed-wing aircraft increases or decreases the lift generated by the wings when it pitches nose up or down by increasing or decreasing the angle of attack (AOA).
A Boeing 737 uses an adjustable stabilizer, moved by a jackscrew, to provide the required pitch trim forces. Generic stabilizer illustrated. A horizontal stabilizer is used to maintain the aircraft in longitudinal balance, or trim: [3] it exerts a vertical force at a distance so the summation of pitch moments about the center of gravity is zero. [4]