Final answer:
The PACK FLOW selector is part of an aircraft's environmental control system. The NORM setting is standard, LO is for low occupancy or energy saving, and HI is for high passenger load or hot conditions. Position should be based on operational needs and aircraft specifications.
Step-by-step explanation:
The PACK FLOW selector is commonly used in the aviation industry, specifically regarding aircraft environmental control systems (ECS). The PACK FLOW selector has three positions: LO, NORM, and HI. As a rule of thumb, the NORM setting is used for standard operations to maintain a comfortable cabin environment. The LO setting may be used when there is a low occupancy in the aircraft or to conserve energy. The HI setting is normally used when there is a high demand for air conditioning, such as when the aircraft is on the ground in a hot climate, or when there are more passengers on board than usual requiring increased air flow for comfort and safety.
The exact position should be determined based on the operational needs, passenger load, and ambient conditions. Aircraft manuals and company procedures often provide more detailed guidance specific to the aircraft model and operational preferences.