Which of the following best describes the function of Fire Extinguisher secondary discharge?

The function of a fire extinguisher's secondary discharge is to release a fire suppression agent. This key function is critical for effectively combating an onboard fire. The secondary discharge provides an additional means of deploying the fire suppression agent, typically after initial activation, to ensure that the agent is properly distributed within the affected area.

Understanding the operational context, the secondary discharge might come into play in situations where the primary discharge does not fully extinguish the fire or when a more concentrated application of the fire suppression agent is required. This function enhances the aircraft's safety systems, ensuring that fire hazards are addressed as effectively as possible during operation.

The other options, while related to aircraft systems, do not directly pertain to the primary purpose of a fire extinguisher's secondary discharge. Activating auxiliary engines, connecting to ground service systems, and isolating fuel systems involve different operational protocols and are not part of the fire suppression mechanism itself.