When donning the helmet with the aircrew eye respiratory protection (AERP) system, which locking position is the bayonet inserted?

When donning the helmet with the aircrew eye respiratory protection (AERP) system, the bayonet is inserted into the 2nd position. This is the correct locking position because it ensures a secure fit and proper alignment of the AERP system with the helmet. The design of the helmet and AERP system relies on this specific alignment to maximize visibility and functionality, while also ensuring that the respiratory components are adequately sealed.

Using the 2nd position allows for the necessary configuration that supports both the protective and operational aspects of the equipment. It also helps maintain comfort for the aircrew member while providing critical protection against environmental hazards encountered during flight operations. Inappropriate positions may lead to compromised fit, reduced effectiveness of the respiratory protection system, or discomfort during prolonged use.