0048 00  TM 10-1670-287-23&P  NOTE Personnel conducting permeability tests should be alert to  anomalies in the color of the canopy fabric. Localized discolorations  are evidence of exposure to environmental contaminants. A change  in color shade from one (1) canopy section/surface to another is an  indication that the canopy may have been manufactured from  different lots of fabric. In either case, a permeability check should  be made on these areas of concern.  0048 00-2  Change 1  CELL 1  CELL 5  CELL 4  CELL 3  CELL 2  CELL 6  CELL 7  CELL SPAN TOTAL TOP SURFACE SPAN TOTAL BOTTOM SURFACE SPAN (1) This procedure requires use of a tape measure. Lay the canopy out spanwise on a clean  surface. Using approximately two pounds of tension, measure the nose tape span of each  cell along the top surface of the canopy, from loaded rib to loaded rib (see illustration below). Loaded ribs are those which have V-tapes and line attachment points.  b.  Procedure number 2. Measurement of Top Surface Cell Widths:  (8) During the service life of a canopy, if the average permeability along the top surface nose is  12.0-cfm or greater, the canopy will be immediately and permanently removed from service.  (7) The maximum limit for a new, unused canopy is 6.0-cfm. Any new, unused canopy having a  permeability value of 6.0-cfm or greater will not be placed in service since its useful life can  be expected to be shorter than that of a properly manufactured canopy.  (6) The desired average permeability for a new canopy manufactured with PIA-C-44378 (1.1 oz.)  fabric should be in the range of 0-5 ft. 3 /min./ft. 2 (cfm). (5) Calculate the average permeability of all readings recorded along the top surface nose  section of the canopy. Record this value.  (4) If it is necessary to take a second reading within a cell, move to an untested area of fabric at  least 6-inches away (in any direction) from the location of the previous measurement.  (3) Take a permeability reading in each cell of the canopy on the top surface (i.e. the MC-4 is a  seven (7) cell canopy so seven readings will be taken). Readings can be taken from either  sub cell. Readings should be taken approximately 18-inches aft of the leading edge nose  tape and should be roughly centered within the sub cell.  (2) For best results, the canopy should lie in an unpacked, unstressed condition for 24-hours  prior to testing. Care should be taken not to physically stress the canopy fabric during  handling and testing. 