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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. 

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. 

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 

of the two systems is applied and subjected to a high-stress sport jump, the capability of the harness may be exceeded. 

Both systems were tested using a 300-pound test dummy at 180 knots (207 MPH) Cat “B” TSO-C23c. 

System 1: 200 square foot canopy W/.8 C$_{d}$  produces a 1,304 pounds force on opening at test speeds. 

System 2: 100 square foot canopy W/.9 C$_{d}$ produces a 3,668 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. 

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] 

<img src='content_image/598948.jpg'>

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. 

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 

