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The Pilots Desk
US-FAA14 CFR 135.151

Cockpit voice recorders

Read the official rule

This regulation requires Part 135 operators to install and use cockpit voice recorders (CVRs) in certain aircraft. The requirements vary based on aircraft size and manufacturing date:

Basic requirements: Multiengine turbine aircraft requiring two pilots and having 6+ passenger seats must have a CVR. Aircraft with 20+ seats have additional specifications. The CVR must run continuously from the pre-flight checklist through the final checklist.

Recording duration: Older recorders must retain at least 2 hours of audio. Newer aircraft (manufactured after specific dates between 2025-2029, depending on size) must retain 25 hours using modern TSO-C123c standards.

Microphone use: On equipped aircraft, pilots must use boom microphones below 18,000 feet MSL.

After accidents: Operators must preserve recordings for at least 60 days following accidents or reportable occurrences. The FAA cannot use CVR recordings for enforcement actions against pilots—they're solely for safety investigations.

The regulation includes specific technical installation standards referenced in Part 23, 25, 27, and 29 of the FARs.

*This is a plain-English summary for study only. The official 14 CFR text on this page is controlling — always read the current regulation and consult a CFI.*

This is an original plain-English explanation for training and reference, not legal advice and not for navigation. Always rely on the current official rule linked above. Last reviewed June 20, 2026.