# Research and Evaluation Method for Echelon Usage of Double-Life Equipment Considering Calendar Life
## 5 Examples and Results  
Take a double-life airborne item as an example. The units equipped with this type of equipment are Unit 1 to Unit 3. The estimated working life monthly usage (\(Ty^{\prime}\)) is 300 h, 150 h, and 150 h, respectively. The estimated number of units used each time is 7 (\(M=7\)). The equipment working life (\(Twl\)) and calendar life (\(Tcl\)) are shown in Table 1. The working life (\(Twl\)) is measured in hours, the calendar life (\(Tcl\)) is measured in months, and the initial working life value is 300 h, with an influence coefficient \(\omega=0.1\).  
The three units were evaluated according to the evaluation method. Calculate the slope of the optimal distribution curve (\(k\)), echelon uniformity (\(Q_{1}\)), life reserve (\(Q_{2}\)), echelon difference (\(Q_{3}\)), and reserve priority (\(Q_{4}\)) of each unit, as shown in Table 2.  
By analyzing the calculation results, it can be seen that the conclusion obtained by echelon difference (\(Q_{3}\)) is contrary to the conclusion of the echelon uniformity (\(Q_{1}\)). The controllable range recursive calculation method (1) (2) was used to check the equipment life of units 1-3, and the results are shown in Figure 6. The equipment in Unit 1 and Unit 3 is within the controllable range. Equipment No.1 and No.2 in Unit 2 is outside the controllable range, and the working life will be wasted in the future. The conclusion obtained using the echelon difference (\(Q_{3}\)) is more accurate.  
\begin{table}
\begin{tabular}{c c c c c c} \hline
**Item** & **Unit 1** & **Unit 2** & **Unit 3** \\ \hline slope of optimal distribution curve (\(k\)) & 12.63 & 12.63 & 12.63 \\ echelon uniformity (\(Q_{1}\)) & 90.15\% & 90.15\% & 70.45\% \\ life reserve (\(Q_{2}\)) & 54.72\% & 54.72\% & 54.72\% \\ echelon difference (\(Q_{3}\)) & 12.50 & 138.98 & 2.81 \\ reserve priority (\(Q_{4}\)) & 52.53\% & 105.07\% & 105.07\% \\ \hline \end{tabular}
\end{table}
Table 2: Calculation results.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline
**No.** & \multicolumn{2}{c}{**Unit 1**} & \multicolumn{2}{c}{**Unit 2**} & \multicolumn{2}{c}{**Unit 3**} \\
**Twl** & **_Tcl_ & _Twl_ & _Tcl_ & _Twl_ & _Tcl_ & _Twl_ & _Tcl_ \\ \hline
1 & 25 & 2 & 25 & 1 & 12.5 & 1 \\
2 & 50 & 4 & 50 & 2 & 25 & 2 \\
3 & 95 & 6 & 75 & 6 & 75 & 6 \\
4 & 100 & 8 & 100 & 7 & 87.5 & 7 \\
5 & 125 & 10 & 125 & 8 & 100 & 8 \\
6 & 150 & 12 & 150 & 9 & 112.5 & 9 \\
7 & 175 & 14 & 175 & 13 & 162.5 & 13 \\
8 & 200 & 16 & 200 & 20 & 250 & 20 \\
9 & 225 & 18 & 225 & 21 & 262.5 & 21 \\
10 & 250 & 20 & 270 & 22 & 295 & 22 \\
11 & 275 & 22 & 275 & 23 & 287.5 & 23 \\
12 & 300 & 24 & 300 & 24 & 300 & 24 \\ \hline \end{tabular}
\end{table}
Table 1: Equipment life information.  
Figure 6: Check of the controllable range of Units 1–3. (**a**) Check of Unit 1; (**b**) check of Unit 2; (**c**) check of Unit 3.  
The evaluation results of echelon uniformity for Unit 1 and Unit 2 are the same, and the difference in the life distribution cannot be distinguished. By evaluating Unit 1 and Unit 3 with the echelon difference, the difference of the optimal order of different life distribution can be clearly distinguished.  
Life reserve (\(Q_{2}\)) evaluation does not distinguish the evaluation under the condition of the same sum of working life, and has limited guidance on the degree of reserve life shortage and future equipment replenishment. According to the calculation result of the reserve priority (\(Q_{4}\)), it can be determined that the reserve priority (\(Q_{4}\)) of Unit 1's equipment working life is lower than that of Unit 2 and Unit 3. That is, if new equipment is not supplemented within 24 months, Unit 1 will experience an equipment shortage earlier than Unit 2 or Unit 3. Therefore, Unit 1 should be given priority when supplementing new equipment.