What could require a flight engineer's presence during operation?

The presence of a flight engineer during test flights and specific operational needs is critical due to their specialized role in monitoring and managing the aircraft systems. During a test flight, various parameters and systems may be evaluated for performance, safety, and functionality. Flight engineers are equipped with the knowledge and skills to handle complex systems, making their involvement essential for troubleshooting, providing oversight on equipment performance, and executing emergency procedures should the need arise.

Additionally, specific operational needs may include scenarios such as abnormal situations or the requirement for system analyses, which necessitate the expert guidance of a flight engineer. Their training allows them to interpret data, perform necessary calculations, and maintain situational awareness that is crucial in these scenarios.

While routine maintenance checks are typically the responsibility of ground personnel and not performed during flight operations, passenger comfort issues and weather-related evaluations may also be relevant but are not primary reasons for requiring a flight engineer's presence on board. These matters are usually handled by cabin crew and flight deck personnel, with the flight engineer focusing on the operational integrity of the aircraft systems.