On which component are fire protection systems mandatory?

Fire protection systems are mandatory on the Auxiliary Power Unit (APU) because the APU is a critical component of an aircraft that provides power and cabin air conditioning while the aircraft is on the ground. Due to its combustion process and fuel usage, there is an inherent risk of fire. Implementing fire protection systems, such as fire detection and suppression mechanisms, is essential to ensure the safety of the aircraft and its occupants in the event of a fire.

While other components such as the main engine and fuel tanks also have safety measures, the regulation specifically mandates fire protection systems for APUs due to their unique operational role and the fire risk associated with their operation. Fire detection systems in APUs are designed to quickly identify and mitigate any potential fires, thus enhancing overall safety in aviation operations.