center-of-pressure coefficient[′sen·tər əv ′presh·ər ‚kō·ə′fish·ənt]
The ratio of the distance of a center of pressure from the leading edge of an airfoil to its chord length.
i. The linear distance the center of pressure travels along a chord over the entire range of angles of attack, ignoring the effects of compressibility and subsonic flow. The center of pressure moves forward as the angle of attack increases until the stalling angle is reached. At this point, the center of pressure generally moves backward along the chord.
ii. The linear distance the center of pressure travels over the operating range of Mach numbers in supersonic aircraft. The center of pressure tends to move backward as the aircraft's speed increases from low subsonic to high subsonic. It moves forward rapidly as soon as the airflow over the aircraft becomes sonic. Once the free-stream Mach number is above M = 1, the C of P (center of pressure) moves backward and settles down at about 50% of the chord at supersonic speeds.