Text in force at 23-63: from 23-0, effective 1 Feb 1965.
The airplane must be longitudinally, directionally, and laterally stable under Secs. 23.173 through 23.181. In addition, the airplane must show suitable stability and control "feel" (static stability) in any condition normally encountered in service, if flight tests show it is necessary for safe operation.
29 FR 17955 · Source