Definitions and Acronyms  Section 9  9.1_SMSM_201904  Originally published April 2019  Uncontrolled copy when downloaded  11 5  NAS Change. A modification to any element of the NAS that pertains to, or could affect the  provision of air traffic management, communication, navigation, or surveillance services.  Near Mid-Air Collision Categories. FAA Order 8900.1,  Flight Standards Information  Management System , Volume 7, Chapter 4, identifies the following definitions of Critical,  Potential, and Low categories:  Objective Evidence. Documented proof; the evidence must not be circumstantial and must be  obtained through observation, measurement, test, or other means.  Observation. The process of witnessing an organization’s process. It differs from a physical  examination in that the auditor only observes the process; no physical evidence is obtained.  Operational Assessments. An assessment to address the effectiveness and efficiency of the  organization. The objective of an operational assessment is to determine the organization’s  ability to achieve its goals and accomplish its mission.  Oversight. Regulatory supervision to validate the development of a defined system and verify  compliance to a pre-defined set of standards.  Physical Examination. The act of gathering physical evidence. It is a substantive test  involving the counting, inspecting, gathering, and inventorying of physical and tangible assets,  such as cash, plants, equipment, and parameters.  Preconditions. The system states or variables that must exist for a hazard or an accident to  occur in an error-tolerant system.  Predicted Residual Risk. The risk that is estimated to exist after the safety requirements are  implemented, or after all avenues of risk mitigation have been explored. 3) “C” – Low Potential. A situation in which a collision is unlikely, however, one or both pilots was  surprised  by the proximity of the other; one in which the course of the aircraft bring them closer than required standard separation; a situation where whether or not the pilot took evasive action a collision probably would not occur; or a situation in which there is ample time to take action to avoid a collision. A TIS alert or TCAS traffic advisory may cause the pilot to take action after sighting the traffic either with or without the aid of an electronic alert system; situations of encounters of 500 feet or greater; slowly converging flightpaths may be considered low potential collision risks. 2) “B” – Potential. A situation which would probably have resulted in a collision if no action had been  taken  by the pilot; a situation in which a Traffic Alert and Collision Avoidance System (TCAS) Resolution Advisory (RA) was received and followed; or where a Traffic Information Services (TIS) alert or  the  pilot sighting the traffic without electronic aid caused pilot evasive action. A “potential” risk is a situation in which a collision would probably occur eventually if no action is taken by either pilot. Situations of encounters of less than 500 feet separation may be considered potential risk. 1) “A” – Critical. A situation in which collision avoidance was due to chance, rather than a pilot’s evasive act or action. Situations where large evasive maneuvers are necessary to avoid collision and/or situations where little or no time is available to recognize the threat and react appropriately. Encounters of less than 100 feet separation are considered to be critical risk.