TM 10-1670-287-23&P
0048 00
UNIT MAINTENANCE
MC-4 RAM AIR FREE-FALL PERSONNEL PARACHUTE SYSTEM
POROSITY PROCEDURES
0048 00-1
THIS TASK COVERS:
Inspection
INITIAL SETUP:
Tools
Porosity Machine (Item 33, WP 0063 00)
Equipment Condition
Layout on packing table or other suitable area.
Personnel Required
92R (10) Parachute Rigger
POROSITY INSPECTION CRITERIA
1. The following techniques and standards have been provided to summarize and/or clarify the desired
design characteristics regarding factors deemed important to the inflation reliability of military ram air
canopies. These standards are intended to assist military riggers responsible for the inspection and
maintenance of ram air personnel parachutes in the identification of canopies, which possess
characteristics, which have been associated with non-airworthy canopies.
2. Where none had previously existed, tolerances are added to standards, which are intended to define
the maximum acceptable limits of deviation from these desired characteristics. A point system was
devised which will be used to determine the degree of compliance of a particular canopy to the
desired design characteristics. This point scoring system appropriately prioritizes and emphasizes
the issues affecting inflation reliability and general canopy airworthiness. Although a canopy may not
exceed any of the established tolerances, the cumulative effect of multiple minor deviations may also
condemn a canopy.
3. These procedures are intended to assist the inspecting rigger in identifying canopies, which may
exhibit non-airworthy characteristics. The below procedures will be added to the current standard
inspection criteria and be conducted during in-servicing, every 50 jumps or one (1) year period for
land rigs (whichever comes first), and every five (5) jumps or one year period for water rigs
(whichever comes first).
4. These procedures apply exclusively to the MC-4, however, the MTl-X, and MTl-S model canopies are
also considered within the family of Ram-Air Personnel Parachute Systems (RAPPS). The
procedures, techniques and parameters are as follows:
a. Procedure number 1. Fabric Permeability Test:
(1) This procedure requires use of a permeability-testing machine. The machine should be
calibrated and operated in accordance with the manufacturer’s specifications. Record
permeability measurements at a 0.5-inch (water) pressure head (vacuum) differential.
NOTE
Testing the fabric along the nose of the top surface is intended to
characterize a canopy’s ability to inflate in a reasonable period of
time. Users are encouraged to test other areas of the canopy to
identify sources of other flight performance problems. For example,
high permeability readings in the tail section may be indicative of a
reduction in flair maneuver performance. If certain sections have
unusually high readings, the rigger should use his/her judgment as
to what corrective action needs to be taken.
