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The Pilots Desk
US-FAA14 CFR 135.154

Terrain awareness and warning system

Read the official rule

This regulation requires turbine-powered Part 135 aircraft to have terrain awareness and warning systems (TAWS), with requirements varying by aircraft size and manufacturing date.

Aircraft with 10 or more passenger seats need Class A TAWS equipment (the more capable system) plus a terrain situational awareness display. Aircraft with 6-9 passenger seats need at least Class B TAWS equipment. Both equipment classes must meet TSO-C151 standards.

For aircraft manufactured after March 29, 2002, these requirements apply immediately. For older aircraft manufactured on or before that date, operators had until March 29, 2005, to comply.

The aircraft's flight manual must include procedures for using the TAWS and explain how the flight crew should respond to terrain warnings. This equipment helps prevent controlled flight into terrain (CFIT) accidents by alerting pilots when they're dangerously close to ground or obstacles.

*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.