What parameter is monitored to prevent the APU from overheating during operation?

What parameter is monitored to prevent the APU from overheating during operation?

• A. Cabin humidity
• B. External temperature
• C. EGT limit is monitored to prevent overheating during operation
• D. Wing load factor

Answer: (C)

Monitoring exhaust gas temperature (EGT) is how the APU prevents overheating. EGT directly shows how hot the turbine exhaust is, which reflects the thermal load on the turbine. The APU control uses an EGT limit so that, if the exhaust temperature approaches the maximum safe value, it reduces fuel flow or shuts the unit down to avoid damage to turbine blades, bearings, and other components. Other factors like cabin humidity, external temperature, or wing load factor don’t indicate the APU’s thermal state or directly control its temperature, so they aren’t used to prevent APU overheating.

Monitoring exhaust gas temperature (EGT) is how the APU prevents overheating. EGT directly shows how hot the turbine exhaust is, which reflects the thermal load on the turbine. The APU control uses an EGT limit so that, if the exhaust temperature approaches the maximum safe value, it reduces fuel flow or shuts the unit down to avoid damage to turbine blades, bearings, and other components. Other factors like cabin humidity, external temperature, or wing load factor don’t indicate the APU’s thermal state or directly control its temperature, so they aren’t used to prevent APU overheating.