NTSB Investigation Process
Authority
The NTSB is required per 49 CFR 831.2(a) to investigate all civil aviation accidents and select incidents. The purpose of these investigations, as stated in 49 CFR 831.4(a), is to determine the facts, conditions, and circumstances relating to an accident. The NTSB uses these results to determine one or more probable causes of an accident, and to issue safety recommendations to prevent or mitigate the effects of a similar accident. The NTSB is required to report on the facts and circumstances of accidents it investigates.
NTSB investigations are fact-finding proceedings with no adverse parties. The investigative proceedings are not conducted for the purpose of determining the rights, liabilities or blame of any person or entity.
Classification
The NTSB has a classification system for investigation depth and final report for each event (accident or incident). Part 137 events are virtually all either Class 3 or Class 4. See the table below for further details. When NTSB issues a preliminary report, NAAA will differentiate between Class 3 and Class 4 investigations due to the fact that a Class 4 preliminary report contains no detailed event information.
| Investigation | Class 3 | Class 4 |
|---|---|---|
| Seek to identify: | safety issues that reveal underlying cause(s) of the accident | the cause of the accident |
| Led by: | investigator-in-charge, may be assisted by other NTSB subject matter experts | investigator-in-charge |
| In-Person/Remote: | may travel to scene of accident, or conducted entirely remotely | generally conducted remotely |
| Final Report: | Following a final technical review of the gathered facts and analysis of those facts, a final report will be made available to the public following Board approval that identifies the probable cause(s) of the accident and factors that contributed to the outcome of the accident, if any. | Class 4 investigations are limited in scope and of the shortest duration. A final report will be made available to the public that identifies probable cause(s) following Board approval and within 6 months. The report only examines the actions and conditions directly relating to the accident, and the documented sequence of events and probable cause reached is simple and straightforward. |
Data
NAAA aggregates data from NTSB’s Case Analysis and Reporting Online (CAROL) tool for accidents wherein the flight was conducted under 14 CFR Part 137. This data is only periodically retrieved by NAAA for informational purposes. Visit the CAROL Aviation Investigation Search for the most up-to-date info.