If the APU is not operational, what is the maximum weight limit for shipments containing dry ice?

The correct selection for the maximum weight limit for shipments containing dry ice when the Auxiliary Power Unit (APU) is not operational is 50 pounds. This limitation is set due to the potential hazards associated with dry ice, which is solid carbon dioxide. In confined spaces, dry ice can sublimate and release carbon dioxide gas, which can lead to asphyxiation if there's insufficient ventilation.

When the APU is not operational, the aircraft may rely solely on cabin pressure systems and airflow, which could be affected. Restricting the weight of dry ice shipments to 50 pounds ensures that there is a manageable amount of dry ice in the cargo area, minimizing the risk of excessive carbon dioxide buildup in the cabin or cargo hold, particularly when the APU, which helps with air circulation, is not functioning.

This regulation helps ensure safety in flight operations where ventilation may be limited, striking a balance between operational needs and the safety of the crew and passengers.