Accordion folding. The folding of the canopy for stacking in the container prior to closing.

Administrator. The Federal Aviation Administrator (FAA) or any person to whom he and/or she has delegated his and/ or her authority in the matter concerned.

Advisory circular (AC). The FAA issues advisory circulars (ACs) to provide guidance and information in a designated subject area or to show a method acceptable to the Administrator for complying with a related Title 14 of the Code of Federal Regulations (14 CFR). Each AC is issued with a number corresponding to the subject it addresses in the 14 CFR. Unless incorporated into a regulation by reference, the contents of an AC are not binding on the public.

Aerodynamics. The study of the behavior of moving air and the forces that it produces as it passes over or around certain shaped objects, such as wings, propellers, or parachute canopies.

AGL. Above ground level.

Airframe and powerplant mechanic (A&P). Any person certificated by the FAA to perform maintenance or inspections on an aircraft’s airframe or powerplant.

Airworthiness Directives (ADs). Issued by the FAA to notify owners and users of aeronautical products of unsafe conditions and the mandatory corrections under which the product may continue to be used. Each AD is an amendment to 14 CFR part 39, as such, it is part of the Federal Public Laws.

Airworthiness. A complete parachute assembly is considered airworthy when it conforms to its Technical Standard Order (TSO) and/or properly altered condition and is in condition for safe operation.

Alteration. A change to the original configuration or any other major change to any portion of the parachute from its original manufacture’s specifications.

Apex. The center and topmost point of a round parachute canopy.

Approved. An item, which in its present form, has received official certification from the FAA.

Assistor pocket. Air scoops at the top of a sleeve that provide drag and aid in anchoring the sleeve as the canopy is pulled out. Also, fabric pockets on the bridle of a free bag that aid in the deployment of the bag in the event of a horseshoetype malfunction.

Automatic activation device (AAD). A device for automatically releasing the reserve or emergency parachute; utilizes barometric and rate of descent sensors.

Auxiliary parachute. A reserve parachute.

Back parachute. A parachute that is worn on the back.

Backstitch. Used to anchor a row of stitching by turning the material and sewing over the stitching for a short distance.

Back strap. A part of the harness that extends across the wearer’s back. It may be diagonal, horizontal, or vertical and may or may not be adjustable.

Backpad. A foam-filled pad placed between the harness and the wearer that provides comfort and/or holds the harness in place.