What are the main components of a typical fire protection system on a narrowbody, and what is the first action on a fire warning in a pertinent compartment?

• A. Fire detection sensors and extinguishing systems; on a fire warning, isolate the affected area by shutting off fuel, bleed air, and electrical sources, discharge extinguishing agent, and follow QRH.
• B. Fire protection is only extinguishing agent; no isolation.
• C. Shut off oxygen supply and evacuate; do not discharge agent.
• D. Disconnect the battery and ignore other systems.

Answer: (A)

Fire protection on a narrowbody centers on rapid detection paired with a controlled suppression sequence that quickly isolates the fire from its fuel and energy sources. The main components are fire detection sensors that sense flames or smoke and the extinguishing systems that physically release agent to suppress the fire. When a fire warning sounds in a pertinent compartment, the first action is to isolate that area by shutting off the fuel supply, the bleed air feeding the system, and electrical sources in the affected zone. This combination removes the fuel and ignition energy, helping to prevent the fire from reigniting or spreading. After isolation, the extinguishing agent is discharged to suppress the flames, and the crew follows the QRH for subsequent steps and checks. This approach is essential because it limits damage, protects other systems, and provides a standardized, safe response.

The other options don’t fit because they skip or underestimate the critical isolation step, or propose actions that aren’t aligned with standard aircraft fire protection practices (such as shutting off the oxygen supply or evacuating without using the extinguishing agent, or ignoring other essential systems).