What does the EMERGENCY lever position in the oxygen regulator indicate during normal operations?

The selection of "NORMAL" for the EMERGENCY lever position in the oxygen regulator during normal operations is accurate because this position ensures that the oxygen supply is delivered at a regulated flow rate appropriate for standard flying conditions. In the NORMAL setting, the oxygen system functions as intended for everyday operation, allowing for the efficient distribution of oxygen to the crew without the provision of excess that might occur if other settings were used.

The position labeled "EMERGENCY" is meant to be used in specific circumstances where immediate oxygen supply is critical, typically in situations involving high altitude or sudden cabin depressurization. Thus, maintaining the lever in the NORMAL position during routine flying ensures that aircrew members receive the necessary oxygen in a controlled manner.

The other options do not align with the protocol for normal operations. If the lever were set to ON, it could imply that the system is always providing oxygen, regardless of need, which is not efficient for regular use. Positioning it fixed at 100% would fail to allow for regulated oxygen flow, which could lead to waste or adverse physiological effects. The assertion that it is not used in normal operations disregards the importance of the NORMAL function for standard atmospheric conditions.