The moment coefficient (Cm) in aircraft design represents the aerodynamic effectiveness of a control surface or an airfoil in generating or changing the pitching moment of an aircraft. Pitching moment refers to the rotational force that tends to pitch the nose of the aircraft up or down.
The formula for the moment coefficient (Cm) is typically defined as follows:
- Cm is the moment coefficient, a dimensionless quantity.
- ΔM is the change in pitching moment due to the control surface or airfoil, measured in Newton-meters (N·m).ρ is the air density, measured in kilograms per cubic meter (kg/m³).
- V is the velocity of the aircraft, measured in meters per second (m/s).
- S is the reference area of the control surface or airfoil, measured in square meters (m²).
- c is the average chord length of the control surface or airfoil, measured in meters (m).