Terrain Awareness and Warning System - TAWS Types

TAWS Types

Class A TAWS includes all the requirements of Class B TAWS, below, and adds the following additional three alerts and display requirements of:

• Excessive closure rate to terrain alert
• Flight into terrain when not in landing configuration alert
• Excessive downward deviation from an ILS glideslope alert
• Required: Class A TAWS installations shall provide a terrain awareness display that shows either the surrounding terrain or obstacles relative to the airplane, or both.

Class B TAWS is defined by the U.S. FAA as:

A class of equipment that is defined in TSO-C151b and RTCA DO-161A. As a minimum, it will provide alerts for the following circumstances:

• Reduced required terrain clearance.
• Imminent terrain impact.
• Premature descent.
• Excessive rates of descent.
• Negative climb rate or altitude loss after take-off.
• Descent of the airplane to 500 feet above the terrain or nearest runway elevation (voice callout "Five Hundred") during a non-precision approach.
• Optional: Class B TAWS installation may provide a terrain awareness display that shows either the surrounding terrain or obstacles relative to the airplane, or both.

Class C defines voluntary equipment intended for small general aviation airplanes that are not required to install Class B equipment. This includes minimum operational performance standards intended for piston-powered and turbine-powered airplanes, when configured with fewer than six passenger seats, excluding any pilot seats. Class C TAWS equipment shall meet all the requirements of a Class B TAWS with the small aircraft modifications described by the FAA. The FAA has developed Class C to make voluntary TAWS usage easier for small aircraft.