How Would Passengers Stay Lit During an Evacuation in a Nighttime Runway Incident?

Would passengers be left completely in the dark during an evacuation in the event of an aircraft incident, such as a double engine failure, during nighttime operations at a runway? This article discusses the role of onboard lights and emergency lighting systems, providing insights based on current aviation practices and standards.

The Incident Context

During a nighttime incident involving a runway, if both engines fail, the onboard lights need to be able to sustain the evacuation process. Let's explore the various scenarios and lighting conditions in such a situation.

Scenario 1: At a Larger Airport Without Immediate Evacuation Requirement

At a larger airport where the plane has successfully landed with intact wheels or has not taken off, the likelihood is that the plane will be towed to a conventional jet bridge or standard air stairs will be brought out. In this case, there is no immediate need for evacuation, thus the onboard lights will be sufficient to illuminate the plane.

The Role of the APU and Batteries

Depending on the condition of the Auxiliary Power Unit (APU), it can either power the entire electrical system. If the APU is not operational, the internal batteries will power the emergency lights within the cabin. Modern commercial aircraft typically have a battery-powered system for emergency lights, which are designed to last during cabin evacuation.

Scenario 2: The Severity of the Damage

The functioning of the emergency lights depends on the seriousness of the damage. If the APU is running, it will power the complete electrical system. If not, the internal batteries will power the emergency lights. However, the internal lights are usually turned off during night takeoffs and landings for safety reasons. After a crash, it is typically not a significant concern to turn on the lights, but the sudden turning on of lights could disrupt night vision.

Emergency lights in the aisle are designed to direct passengers to the exits. These lights are activated by either automatic mechanisms or switches. In some cases, passengers may need to manually turn them on.

Role of the APU and Other Systems

Modern commercial aircraft are equipped with an Airframe-mounted Power Unit (APU). This APU is a small jet engine that turns generators, allowing the aircraft to operate certain systems on the ground without running the engines. In the event of a double engine failure on a taxiway, the APU can provide power to the emergency lights. Moreover, the APU can even power utility hydraulic systems for a smooth deplaning process.

Battery Backup and Evacuation

If the APU fails, battery backup will provide power for essential systems, including supporting the emergency egress and lighting pathways. The emergency evacuation lights are battery-powered and specifically sized to operate during cabin evacuation. These batteries ensure that passengers can evacuate the plane safely, even in the event of a power failure.

Conclusion

In summary, during an emergency situation involving a double engine failure on a runway, onboard lights will be crucial for passenger safety during evacuation. The primary sources of power for these lights are the APU and internal batteries. Regardless of the severity of the damage, emergency lights are designed to last long enough to ensure a safe evacuation. This article highlights the critical role of emergency lighting systems in modern aviation to ensure passenger safety during night-time incidents.