Jeppesen’s Airframe Oral & Practical (O&P) Practice Exam 2025 - Free Airframe Practice Questions and Study Guide

A thermocouple fire warning system operates based on the principle of measuring temperature changes through the combination of two different metal conductors. When these metals are subjected to heat, they produce a voltage that correlates to the temperature difference, effectively making thermocouples sensitive not just to a specific temperature but also to the rate at which the temperature changes. This characteristic allows thermocouples to detect rapid increases in temperature, which can be crucial in fire detection scenarios as it may indicate an imminent fire threat.

In contrast, thermal switches operate based on a predetermined temperature setpoint, triggering an electrical circuit when that setpoint is reached. They are not designed to provide information about how quickly the temperature is changing, making them less responsive to fast-rising temperature conditions compared to thermocouples. This fundamental difference underscores the unique operational characteristics of a thermocouple fire warning system, focusing on temperature change detection rather than solely on reaching a specific temperature threshold.