The role of temperature probes in non-flight auxiliary power units

A non-flight auxiliary power unit (APU) is a device that provides energy for functions other than propulsion in various ground-based or non-aircraft applications. While traditional APUs are commonly associated with aircraft and provide power for electrical systems and air conditioning while the main engines are off, non-flight APUs are used in a wide range of industrial, commercial, and defence applications.

In non-flight APUs, temperature probes are critical components used to monitor and control the unit's operation. They are typically used in ground-based applications, such as in commercial or industrial settings, and are similar to those found on aircraft but operate under different conditions. Some of the applications where temperature probes are used include:

1. Monitoring Exhaust Gas Temperature (EGT): This is crucial for ensuring the combustion process within the APU is efficient and the unit is not overheating. EGT monitoring helps maintain optimal performance and can indicate potential problems, such as incomplete combustion or turbine wear, that need to be addressed to prevent damage.
2. Engine Oil Temperature Monitoring: Correct oil temperature is essential for lubrication and cooling of the engine's moving parts. Too high and it can lead to reduced lubrication efficiency and increased wear on engine components, too low and the oil may be too viscous, leading to inadequate lubrication and potential engine damage.
3. Coolant Temperature Control: In APUs that use liquid cooling systems, temperature probes monitor the coolant temperature to ensure that the engine remains within its optimal operating range and does not overheat.
4. Air Intake Temperature Measurement: Data on the temperature of the air entering the combustion chamber is used to adjust the fuel-air mixture for optimal combustion, especially in varying environmental conditions.
5. Safety and Shutdown Mechanisms: Temperature probes are integrated into the APU's safety systems to automatically shut down the unit if temperatures exceed safe operational limits. This is crucial for preventing catastrophic failures, such as fire, which could occur if the APU were allowed to overheat.
6. Diagnostics and Maintenance: By analysing temperature trends over time, operators can identify potential issues before they lead to failures, allowing for proactive maintenance and reducing downtime.

Temperature probes in non-flight auxiliary power units are vital for ensuring the safe, efficient and reliable operation of the unit. They provide real-time data that helps control combustion processes, manage cooling systems, and protect the APU from damage due to overheating.

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