What should be buckled first to ensure proper harness fitting?

When considering proper harness fitting, the sternum strap should be buckled first because it plays a critical role in maintaining the overall position of the harness on the body. By securing the sternum strap, you create a stable structure that helps to align the shoulder straps properly across the chest, ensuring that they are snug but not overly tight.

Securing the sternum strap first helps to distribute forces evenly across the upper body in case of a fall, which enhances both comfort and safety. This initial step ensures that the shoulder straps remain in the correct position, as they tend to shift or slide off when not secured properly.

Once the sternum strap is secured, you can then proceed to buckle the leg straps, waist strap, and shoulder straps in a manner that maintains a consistent and safe fit throughout the harness system. This order of operation facilitates a more effective and secure harness fit, ultimately enhancing safety when conducting urban air operations.