49 CFR § 831.51 - Definitions.

---
identifier: "/us/cfr/t49/s831.51"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "49 CFR § 831.51 - Definitions."
title_number: 49
title_name: "Transportation"
section_number: "831.51"
section_name: "Definitions."
chapter_name: "NATIONAL TRANSPORTATION SAFETY BOARD"
part_number: "831"
part_name: "INVESTIGATION PROCEDURES"
positive_law: false
currency: "2026-03-24"
last_updated: "2026-03-24"
format_version: "1.1.0"
generator: "[email protected]"
authority: "49 U.S.C. 1113(f)."
regulatory_source: "82 FR 29685, June 29, 2017, unless otherwise noted."
cfr_part: "831"
---


# 831.51 Definitions.

The following definitions apply throughout this subpart.

*IIC* means the NTSB investigator-in-charge.

*Investigative activity* means an activity performed by or under the direction of the NTSB during a casualty investigation led by the USCG.

*Major marine casualty* is defined in joint regulations of the NTSB and USCG at 49 CFR 850.5(e) and 46 CFR 4.40-5(d), respectively.

*Marine casualty* means—

(1) Any casualty, accident or event described in 46 CFR 4.03-1

(2) An occurrence that results in an abandonment of a vessel

(3) Other marine occurrences that the NTSB or USCG, or both, determine require investigation.