of the two systems is applied and subjected to a high-stress  sport jump, the capability of the harness may be exceeded.  changes the X$_{1}$  factor by fractional amounts and only affects  the outcome minimally as described earlier.  National Aerospace Standards (NAS) 804 has the best  requirements for structural integrity of any standard written  to date. This is because it has a strength requirement: 3,000  pounds for the Low Speed Category and 5,000 pounds for  the Standard Category. Other standards (AS8015) use a  performance requirement (weight versus speed) for structural  integrity verification. This would be acceptable except for one  small problem. AC 105-2, Sport Parachute Jumping, allows  for mixing and matching of approved components. This is  a problem because different canopies open with different  opening characteristics at the same weights and speeds. This  is defined and accounted for by the C$_{x}$ value. Therefore, if a  harness is built and tested using a canopy with a low C$_{x}$ and  matched with a canopy (under the provisions of AC 105-2)  with a high C$_{x}$ , the results could be disastrous.  Both systems were tested using a 300-pound test dummy at  180 knots (207 MPH) Cat “B” TSO-C23c. System 2: 100 square foot canopy W/.9 C$_{d}$ produces a 3,668  pounds force on opening at test speeds. System 1: 200 square foot canopy W/.8 C$_{d}$  produces a 1,304  pounds force on opening at test speeds. The ratio of opening force differential is 2.8 to one or System  2 opens with 2.8 times greater force than System 1. Let’s say a harness is built for System 1 using 1,500 pounds  capable hardware. It passes the structural drops, as it only  sees 1,304 pounds. NAS 804 systems need no further consideration other than  originally called for. The Low Speed designation is limited to  use in aircraft under 150 MPH at any weight. Likewise, the  Standard Category of 5,000 pounds has no weight or speed  limitations. This is an unlimited category. One reason for this  is because of the limited effect of weight on opening forces.  Speed is what kills. If a human body were to reach a 5,000  pound shock load, it would come apart before the harness  or canopy. At less than 150 MPH, even at a high weight, it  will not exceed 3,000 pounds.  Another harness is built for System 2 that has a canopy with  desirable flight characteristics but that tends to open hard. The jumper wants the canopy with desirable flight  characteristics in his new System 1 rig. If compatibility  is derived from performance standards, then these are  compatible since they were both tested using a 300-pound  drop test dummy at 180 knots. It is entirely possible that a  sport opening under extreme conditions could produce an  opening of 1,600 pounds, which exceeds the capability of  the 1,500 pound hardware.  [Figure 4-53] It may be evident now that there is a flaw in our structural  requirements due to the mixing and matching of approved  components under the performance standard versus a  structural standard. This came about as a result of the change  from a Structural Standard (NAS-804) to a Performance  Standard (AS 8015b). Now we have no way to determine  compatibility for TSO-C23c (AS8015b).  It may not be possible to have compatibility using  performance standards alone. That is why we added placards  for the “weight tested to” for harnesses and the “force  generated” for canopies to TSO-C23d. There is no way  to determine compatibility from one parachute system to  another within the same category of the same standard if  they are judged using a performance standard. Just because  they were tested at the same weight and speed does not mean  they saw the same opening forces. Different canopies open  with different characteristics. Listed below is a hypothetical  comparison of the opening characteristics of two different  systems tested to the same performance standard. The math  is the same as previously discussed. The two canopies have  very different opening characteristics, and they produce very  different results when tested at the same levels. When a mix  The current regulation for placarding (AS8015c/TSO C-23d)  calls for “Average Peak Force.” Under AS8015b/TSO-C23c  (the previous version), there is no way for a rigger to make the  necessary determinations without help from the manufacturer  TSO-C23b does not really have any limitations except for  speeds below 150 for “Low Speed” category with no weight  limit. That standard is good for all skydiving scenarios. The  3,000 pounds test load is strong enough for anything and  force is a good base line for compatibility.  4-15 Canopy Characteristics Variable System 1 System 2 System 2  with 100-foot canopy C$_{d}$ S$_{o}$ Q Subtotal X$_{1}$ C$_{x}$ Force = 0.8 200 108.7 17,392 0.15 0.5 1,304.4 0.9 100 108.7 9,783 0.25 1.5 3,668.625 (Ratio 2.8125) 0.9 100 50 4,500 0.20 1.5 1,620 pounds Figure 4-53.  Canopy characteristics.