*3.3. Determination of the Theoretical Load Capacity of Separate Configurations*

Once the ratio of the redistribution of the total applied force to the individual structural elements is known, it is possible to calculate the load capacity of the individual components. For this operation, it is important to know the strength of each component declared by the manufacturer [12–14]. In Table 2, these values for single parts are listed. For clarity, Figure 17 shows the position of the items marked in the table. The mark C indicates the carabiner (buckle) and mark S indicates the strap (webbing). Its number corresponds to the specific designation of the measuring element.


**Table 2.** Declared strength of the elements.

With this knowledge, it is possible to use Equations (2)–(3) to determine the limiting force during the canopy activation stage, at which the maximum allowable component load is reached. The given force calculation will thus show not only the critical element but also the strength margin for the other components. This makes the uniformity or non-uniformity of the strength margin of each element visible at first sight. As an example, test case one is analyzed according to the mentioned procedure. With the use of Equations (2)–(3), the results defining the critical applied force to reach the limit force in separate construction elements for test one are as stated in Table 3. The calculations shown in Equations (2)–(3) are demonstrated on the critical element for test case one.

b1 = percentage value of the force carried by the element, relative to the loading force. Fc1 = force at a particular position C1.

Fresultant = total loading force that represents the opening load of the parachute. Flimit = the manufacturer's declared element limit force.

Fcrit = loading force at which the maximum permitted force value is reached.

$$b\_{1(C1)} = \frac{F\_{c1}}{F\_{resulant1}} \cdot 100 = \frac{1910}{7665} \cdot 100 = 24.9 \text{ [\%]} \tag{2}$$

$$F\_{\text{crit\\_1(C1)}} = \frac{F\_{\text{limit\\_C1}}}{\left(\frac{b\_{1(\text{C1})} \cdot F\_{\text{resultant1}}}{100}\right)} \cdot F\_{\text{resultant1}1} = \frac{F\_{\text{limit\\_C1}}}{b\_{1(\text{C1})}} \cdot 100 = \frac{2224.91}{24.92} \cdot 100 = 8928.3 \text{ [N]} \tag{3}$$

**Figure 17.** The highlighted position of the evaluated elements.

**Table 3.** Recalculation of critical force for test case one.


The results show that while the theoretical strength of element C1 is achieved at 8.928 kN, element S2 can withstand a value more than ten times higher. By evaluating all the remaining tests, it was found that C1 is a critical element for all configurations. The other elements indicate a significant difference in the safety margin compared to element C1.

Table 4 summarized the critical force calculated according to Equation 1 for all the test setups. This procedure also highlights the most vulnerable position of the dummy, where the limit load of element C1 first appeared.

**Table 4.** Extracting the limit force at the weakest point of the harness for all test configurations.


It is evident from the results that the asymmetric load is the first case in which the limit load is exceeded. In other words, test configuration two. However, the differences in the strengths of individual cases are not so significant. It varies up to 14.8% for tests one-five.

The evaluation of element C1 brings another important piece of information related to the influence of chest strap tightening. This can be achieved based on the comparison of the results from test one, where the chest strap was tightened, and test six, where it was loose. The difference in maximum value to reach the limit load is about 107% higher in the case of a loosening chest strap.
