## UNIT MAINTENANCE MC-4 RAM AIR FREE-FALL PERSONNEL PARACHUTE SYSTEM POROSITY PROCEDURES 

## THIS TASK COVERS: 

• Inspection 

## INITIAL SETUP: 

## Tools 

Porosity Machine (Item 33, WP 0063 00) 

## Equipment Condition 

Layout on packing table or other suitable area. 

## POROSITY INSPECTION CRITERIA 

## Personnel Required 

92R (10) Parachute Rigger 

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 year for land rigs, every five (5) jumps or one year for water rigs (whichever comes first), and when canopies exhibit poor performance characteristics during deployment, flight, and/or landing. When a canopy exhibits non-airworthy characteristics and a permeability-testing machine is not available, the canopy will be removed from service regardless of the remaining service life. 

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. 

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. 

## NOTE 

