A Federal Aviation Administration Senior Rigger recently inspected a United Parachute Technologies Sigma tandem harness that had seen many years of use and discovered that the lower lateral snap would not spring back to position. Detailed inspection showed that the torsion spring, which keeps the gate closed, had broken in one place and was about to break entirely. This could have resulted in the snap staying in the open position and become disengaged in the plane or upon exit.
The lower laterals keep the student tight against the body of the instructor, aid in stability during opening shock and keep the center of mass at the pair’s arch position during freefall. The locking lever should lay flat against the snap body, and there should be a positive “click” when it’s put in the locked position.
In addition to normal maintenance inspections by a rigger, instructors should inspect all the harness fittings prior to each jump. Additionally, a pat-down of the attachment points in the plane prior to exit will ensure these feel locked in, since they are often out of sight.