Where must the flight engineer's quick donning oxygen equipment be located when operating above flight level two five zero?

The flight engineer's quick donning oxygen equipment must be located within immediate reach of the duty station when operating above flight level two five zero. This is crucial for safety, as it ensures that the flight engineer can quickly access the oxygen equipment in the event of cabin decompression or an emergency situation that requires supplemental oxygen.

At high altitudes, the atmosphere becomes less breathable, and a rapid response is necessary to maintain crew and passenger safety. Having the oxygen equipment within immediate reach allows the flight engineer to quickly put on the mask and ensure a continuous supply of oxygen without delay, which could be critical in preserving consciousness and ensuring effective operation of the aircraft.

Other locations mentioned, such as the overhead compartment or baggage area, would delay access to the equipment, which could significantly compromise safety during a rapid decompression or emergency situation. Additionally, while the cabin behind the cockpit might seem accessible, it is not as practical as having the equipment directly at the duty station, where the flight engineer can quickly respond to changing situations.