The shoulder harness take-up, inertia-lock reel is intended as a safety device for seat occupants to restrain torso and head/neck movement during a crash, deceleration, or violent flight motion of an aircraft.

Each specific application of the QPL inertia reel shall require the inertia reel be subjected to "as installed" system testing tailored to evaluate the suitability of the QPL inertia reel for the intended application. Such evaluation cannot occur without the inertia reel being either oil a QPL or satisfactorily completing the qualification testing required herein prior to the evaluation. Qualification of an inertia reel to I type of designation shall not be construed as qualification to any other type designation contained in this specification. Nor shall the approval of all inertia reel for a particular application be construed as approval for any other application not specifically identified in that approval.

Approval of an inertia reel for a specific aircraft application requires review and approval of the service tests (see 4.2.2) by both the Government Qualifying Activity for inertia reels and the Cognizant Engineering Activity or Configuration Manager for the aircraft.