Business Rules

NMACS System Level Business Rules

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1. The data provided by ASIAS has been collected by people not directly associated with ASIAS. ASIAS does not certify the accuracy of the data.

2. The NMACS data are maintained by the Air Traffic Quality Assurance (ATQA) program, formally known as the National Airspace Incidents Monitoring System (NAIMS). ATQA is under the jurisdiction of Air Traffic Organization, ATO-A.

3. A NMAC is defined as an incident associated with the operation of an aircraft in which a possibility of collision occurs as a result of proximity of less than 500 feet to another aircraft, or a report is received from a pilot or a flight crewmember stating that a collision hazard existed between two or more aircraft.

4. The initial NMAC data are recorded from FAA Form 8020-21, Preliminary Near Midair Collision Report.

5. The final NMAC data are recorded from FAA Form 8020-15, Investigation of a Near Midair Collision Incident. The investigator should complete FAA Form 8020-15 within 90 days after the actual NMAC.

6. Elements that are not completed in FAA Form 8020-21or FAA Form 8020-15 appear blank in the NMAC database.

7. NMACs are reported on a voluntary basis, not in accordance with a regulatory requirement. Any studies based on NMAC reports should consider that the data could be subjective and that the number of NMAC reports filed does not represent the total universe of such events. Therefore, the use of this data to calculate NMAC rates by individual airline is unlikely to result in a metric that is a valid indicator of safety performance.

8. The NMACS database contains reports regarding civilian and military aircraft. For a NMAC report in include a military aircraft, the event must have involved military and civilian aircraft.

9. Some fields in the database are blank because of changes made to the data collection forms. Examples of elements added in January 1992 are EVENT_LCL_DATE and LOC_OCEANIC_FLAG.

10. NMAC reports are often filed if someone senses danger or an aircraft is deemed to be within an unsafe proximity. For this reason, NMAC reports are not always the result of the operation of an aircraft in which a possibility of collision occurs as a result of proximity of less than 500 feet to another aircraft. A "surprise" factor influences the initiation of NMAC reports.

11. A pilot or other flight crewmember is responsible to determine whether a NMAC occurred and to initial a NMAC report.

12. The data collection forms are filled out by hand and the forms are entered by hand. As a result, there is always the potential for typographical errors and misinterpretation of instructions.

13. The submission of a NMAC report can be influenced by a number of factors. Pilot experience and the operational airspace they operate in can influence reporting. (For example, pilots who routinely fly in heavily used airspace, and are used to flying in relatively close to other aircraft, may be less likely to file a report than a pilot who usually flies in sparsely populated airspace.) The accuracy of the reporting individual's perception of a NMAC can vary considerably among the flight crewmember population. Factors include experience, visibility conditions, the proximity of aircraft involved, relative angle of approach, size of the aircraft involved, and the trauma experienced by the pilot or flight crew.

14. Some NMACs are not reported because the flightcrews do not observe the other aircraft or determine that a collision hazard did not exist between the aircraft.

15. If a NMAC occurs outside of air traffic control radar coverage, the pursuant investigation may not determine the distance between the aircraft.

16. ASIAS standardizes the following fields: operator, state, airport and aircraft make/model.