# Disposal and Recycle Economic Assessment for Aircraft and Engine End of Life Solution Evaluation
## 6 Analysis and Result Discussion
### Averaged Data Set and Economic Indicators
#### 6.1.2 Sensitivity Analysis for Averaged Data Set  
General sensitivity measures are calculated for the averaged data set. The impact of the model inputs on the economic indicator is obtained. Those model inputs are tightly related to their respective cost drivers. This also motivates further inspections of their interactions [50]. Tornado diagrams for the D&R economic indicators \(I_{D\&R}\) and the NPV measure \(I_{D\&R\_NPV}\) are generated by applying \(\pm\Delta x_{i}\) for the model inputs, viz., residual value, D&R cost, and salvage value. Three ranges of \(\Delta x_{i}=0.1x_{i}\), \(0.5x_{i}\), and \(0.99x_{i}\) are applied. We mainly focus on the sensitivities of the economically efficient D&R cases. Therefore, the general tornado diagram for an engine for narrow body aircraft is exemplified in Figure 4. \begin{table}
\begin{tabular}{c c c c} \hline \hline \(I_{D\&R}\) & **Narrow Body** & **Wide Body** & **Regional Jet** \\ \hline Aircraft & \(-\)30.6 & \(-\)106.7 & \(-\)4.1 \\ Engine & 70.8 & 51.5 & 52.2 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Average values of the disposal and recycle economic indicator (\(I_{D\&R}\)). \begin{table}
\begin{tabular}{c c c c} \hline \hline \(I_{D\&R\_NPV}\) (\(\$1\times 10^{6}\)) & **Narrow Body** & **Wide Body** & **Regional Jet** \\ \hline Aircraft & \(-\)2.01 & \(-\)9.43 & \(-\)0.22 \\ Engine & 1.44 & 1.43 & 1.01 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Disposal and recycle NPV based on average aircraft value (\(I_{D\&R\_NPV}\)) (\(n_{D\&R}=3\), \(i=8\%\)) (2014 USD). According to the general sensitivity analysis for **I\({}_{\textbf{D\&R}}\)** (Figure 4a,c,e) \(\phi_{D\&R}(i)^{+}\) and \(\phi_{D\&R}(i)^{-}\), the **individual effect** of the salvage value is shown to be the most sensitive for \(\Delta x_{i}=0.1x_{i}^{+}\), \(\Delta x_{i}=0.5x_{i}^{+}\), and \(\Delta x_{i}=0.99x_{i}^{+}\) (relating to positive input changes). The second influential factor is the D&R cost in all three \(\Delta x_{i}^{+}\) cases. The increase of the D&R cost and residual value introduces negative effects, while the increase of the salvage value introduces a positive impact on the change of \(I_{D\&R}\) (all \(\Delta x_{i}^{+}\) cases). Considering the negative input changes \(\Delta x_{i}^{-}\), the individual effect of salvage value is the most sensitive when \(\Delta x_{i}=0.1x_{i}^{-}\), while the D&R cost is the most sensitive model input when \(\Delta x_{i}=0.5x_{i}^{-}\) and \(\Delta x_{i}=0.99x_{i}^{-}\). The second influential factor is the D&R cost when \(\Delta x_{i}=0.1x_{i}^{-}\), and it is the salvage  
Figure 4: General sensitivity diagram–Engine (Narrow body). value when \(\Delta x_{i}=0.5x_{i}{{}^{-}}\) and \(\Delta x_{i}=0.99x_{i}{{}^{-}}\). The decrease of the D&R cost and residual value introduces positive effects on \(I_{D\&R}\), while the decrease of the salvage value has a negative effect on \(\text{I}_{\text{D\&R}}\) for all \(\Delta x_{i}{{}^{-}}\) cases. From the perspective of \(I_{D\&R\_NPV}\) (Figure 4b,d,f) \(\phi_{D\&R\_NPV}(i)^{+}\) and \(\phi_{D\&R\_NPV}(i)^{-}\), the individual effect of the salvage value is consistently the most sensitive factor in all \(\Delta x_{i}{{}^{+}}\) cases. The second-most influential factor is the residual value (all \(\Delta x_{i}{{}^{+}}\) cases). The increase of the D&R cost and residual value introduces negative changes of \(\text{I}_{\text{D\&R\_NPV}}\), while the increase of the salvage value has a positive impact on \(I_{D\&R\_NPV}\) (all \(\Delta x_{i}{{}^{+}}\) cases). With the negative input changes \(\Delta x_{i}{{}^{-}}\), the individual sensitivity shows a symmetrical performance: The salvage value is the most sensitive (all \(\Delta x_{i}{{}^{-}}\) cases), while the residual value is the second influential factor (all \(\Delta x_{i}{{}^{-}}\) cases). The decrease of the D&R cost and residual value introduces positive effects on \(I_{D\&R\_NPV}\), while the decrease of the salvage value has a negative effect on \(I_{D\&R\_NPV}\) for all \(\Delta x_{i}{{}^{-}}\) cases.