Radial seam.  A seam extending from the skirt to the apex,  joining two gores. A portion of the suspension lines may be  concealed in the tube formed by the radial seam.  Pocket ripcord handle.  Elastic or spring-edged pocket that  holds ripcord handle in an accessible position on the harness.  The chest-type pocket consists of a piece of straight elastic  webbing serving the same purpose. Porosity.  The ratio of void or interstitial area to total area of a  cloth expressed in percent. The ratio of open space to covered  area of a drag surface. Used for ring slot, ribbon, ring sail,  and rotafoil canopies. Not to be confused with permeability. Ram-air parachute.  Generally, a rectangular, double- surface canopy with airfoil shaped ribs inflated by the air  flowing into the front openings to produce an airfoil shape. Rate of descent.  The vertical velocity, in feet per second, of  a fully-opened parachute. Premature opening.  Any accidental opening of the  parachute prior to the intended time.  Rating.  A statement that, as a part of a certificate, sets forth  special conditions, privileges, or limitations. Ravel (unravel).  To separate, untwist, or unwind, leaving a  frayed or ragged edge. “Unravel” is often used with the same  meaning, although grammatically incorrect. Prepack inspection.  The inspection made on the parachute  prior to its packing. Presser foot.  The part of the sewing machine above the feed  dog that holds the fabric in place. Raw edge.  The unfinished edge of the material; liable  to raveling. R Preventative maintenance (PM).  The systematic care,  servicing, and inspection of equipment and facilities for the  purpose of maintaining them in a serviceable condition and  detecting and correcting incipient failures. Simple or minor  preservation operations and the replacement of small standard  parts not involving complex assembly operations. Reefing.  A temporary restriction of the skirt of a parachute  to a diameter less than the fully inflated diameter. Reefing is  used to decrease drag area and/or to obtain stability. Reinforcements.  Commonly strong tape or webbing used to  strengthen parts of the canopy, container, or harness. Proof load.  The testing of an item for conformance with  strength requirements. Relative humidity.  Ratio of the amount of water vapor  present in the air to that which the air would hold at saturation  at the same temperature. Proper layout.  Process by which the canopy and suspension  lines are arranged on the packing table for inspection  and packing. Repack cycle.  The time that a certificated parachute is  considered to be airworthy before being inspected and  repacked. The current U.S. repack cycle is 180 days. Pull the dot.  A particular type of snap fastener that can only  be opened or closed by pulling in one direction designated  by an indented dot on the button. Pull-up cords.  Nylon cords of varying length used to pull up  the sides and ends of the container flaps over the container  cones and to pull the cones through the grommets.They are  also used to pull the suspension lines into place in some  types of containers. Reserve parachute.  The second or “auxiliary” parachute  worn by a person making a premeditated jump. Reserve static line (RSL). A backup device for activating  the reserve after a cutaway. Usually a line, webbing, or  cable that connects the main risers with the ripcord handle,  housing, or cable. Restitching.  The process of sewing directly over base or  broken stitching. Quality control.  A method of describing the inspection  and test procedures necessary to ensure that each article  produced conforms to the type design and is in a condition  for safe operation. Quick connector snap.  A large hook-shaped, spring-loaded  snap, two of which are used to quickly attach the chest-type parachute to the two D-rings on the harness. Retainer band.  A rubber band used to hold folded suspension  lines or static lines to the parachute pack. Q G-9