FAA AMT Airframe Practice Exam 2026 – Complete Exam Prep Guide

In a built-in fire extinguisher system, a thermal discharge is detected through the rupture of the red plastic disk in the thermal discharge line. This red plastic disk is designed to fail when exposed to a certain temperature, which triggers the release of the fire extinguishing agent. This method provides a reliable and visual indication of a thermal discharge, allowing maintenance personnel to identify the activation of the fire extinguisher system easily.

The other options are not typically used to detect a thermal discharge in a built-in fire extinguisher system:

A. While some fire extinguisher systems may have alarms as additional notifications, the primary method of detection is through the rupture disk.

B. Visual indicator lights are not commonly used as the main detection method but may be incorporated as a secondary alert.

D. Changes in pressure within the system can occur due to various factors and may not specifically indicate a thermal discharge, making it less reliable for this purpose.