Butt (or buttock) Line Zero. A line through the symmetrical center of an aircraft from nose to tail. It serves as the datum for measuring the arms used to determine the lateral CG. Lateral moments that cause the aircraft to rotate clockwise are positive (+) , and those that cause it to rotate counterclockwise are negative (-).
Calendar Month. A time period used by the FAA for certification and currency purposes. A calendar month extends from a given day until midnight of the last day of that month.
Civil Air Regulation (CAR). predecessor to the Federal Aviation Regulations.
CAMs. The manuals containing the certification rules under the Civil Air Regulations.