PIA Technical Standard 100  Parachute Industry Association Publications  March 27, 2015  Standardized Nomenclature for Ram-Air Parachutes  Introduction  Parachute Industry Association, Inc.  Definitions  Angle of  Area, This Technical Standard was adopted by the Parachute Industry Association (PIA) on March 27, 2015 Input concerning revisions and additions should be submitted to:  Attention: Technical Committee Chair  3833 West Oakton Street  Skokie, IL 60076  Telephone: 847-674-9472  Fax: 847-674-9743  Email: TechComChair@pia.com Airlock: On a canopy, a valve which permits air flow more easily in one direction, and restricts airflow in  the opposite direction. In most case, airlocks are installed in the nose of the canopy to permit air to enter  during deployment and flight, and restrict air from flowing out the nose to ensure better pressurization in  turbulent air. Trim: The angle formed between the horizontal reference line and the trim line. The Greek letter  theta ( θ ) is used to denote the angle of trim. Used instead of the somewhat analogous aircraft  term “angle of incidence.” See Figure 1b.  Attack: The angle formed between the flight path and the chord line. The Greek letter alpha ( α )  is used to denote the angle of attack. See Figure 3.  Airfoil Section: The finished cross sectional area of a given rib (airfoil) section. When ribs are  not identical, the specific rib must be identified. Used for calculations of pack volume and internal  volume of canopy. Planform: The product of the average chord times the average span of the canopy.  Projected: The area of an inflated canopy as viewed from above, perpendicular to the chord line  at the centerline of the parachute. Due to canopy curvature and cell inflation bulging the projected  area is always smaller than the planform area.  Aspect Ratio:  Span$^{2}$/Area, which for a rectangular planform reduces to Span/Chord. Page 1 of 8 A-3  $^{ }$ Change 1 (December 2015)