longitudinal magnetization. A method of magnetizing a part for magnetic particle inspection. Current flows through a solenoid, or coil, that encircles the part so the lines of magnetic flux pass lengthwise through it. Longitudinal magnetism makes it possible to detect faults that extend across the part.
longitudinal separation (air traffic control). The longitudinal spacing of aircraft at the same altitude by a minimum distance expressed in units of time or miles.
longitudinal stability (aircraft stability). The tendency of an airplane to remain level about its lateral axis. (The lateral axis passes through the center of gravity and extends outward parallel to the span of the wing.) Longitudinal stability, also called pitch stability, is provided by a downward aerodynamic load on the horizontal tail surface. The center of gravity, which does not change with airspeed, causes the airplane to rotate nose-down about its lateral axis. The tail load, which does change with airspeed, is located behind the center of gravity, and it causes the airplane to rotate nose-up about its lateral axis.
If the nose pitches down, the airspeed builds up, and the downward tail load increases. This brings the nose back to a level flight attitude. If the nose pitches up, the airspeed slows down, and the tail load decreases. The center of gravity causes the nose to return to a level flight attitude.