Under what conditions can an aircraft requiring flight engineer assistance operate?

An aircraft requiring flight engineer assistance is specifically tailored to operate in situations where specialized skills are necessary, often due to the complexity of the aircraft systems involved. In the context of test flights, these missions typically involve evaluating the aircraft's performance and systems under varying conditions, making the presence of a flight engineer essential for monitoring and managing intricate instrumentations and systems.

During test flights, the flight engineer plays a crucial role in ensuring that the aircraft operates within its safe parameters and that any anomalies are promptly addressed. This is especially relevant as test flights can involve non-standard operations and configurations that require close attention.

In contrast, operating in regular airline services, during maintenance checks, or on charter flights usually involves predefined procedures and operational staff who are trained to handle routine flight operations or maintenance tasks without the additional expertise of a flight engineer, unless specified by regulation or the aircraft's operational requirements.