## 5 Conclusions  
The purpose of this paper is to propose an efficient driving plan (i.e., new driving mechanism) of emergence extension for aircraft nose landing gear (NLG) through reliability sensitivity analyses with a mixture of models, to address the emergence extension fault of the landing gear for the initial driving mechanism. Through the reliability sensitivity analyses of the initial driving mechanism and the validation of the proposed new driving mechanism, some major conclusions and findings are summarized as follows:  
1. Through the reliability analysis of emergence extension, it is illustrated that the start reliability has the most failure probability in five reliability modes (starting reliability, continuous movement reliability, movement precision reliability, and static strength reliability), indicating that the event X\({}_{1}\) (excessive resistance torque on strut rotation axis) seriously influences the reliability of NLG emergence extension.
2. From the sensitivity analysis of NLG emergence extension, the effect levels of nine torques (M\({}_{1}\), M\({}_{2}\),..., M\({}_{9}\), explained in Table 2) on the failure probability of NLG emergence extension are determined, and the sensitivity degrees of the torques M\({}_{5}\), M\({}_{8}\) and M\({}_{7}\) are the top three by the order by sensitivity degree for nine torques. The conclusion is promising guidance for the driving plan design of NLG emergence extension.
3. Two driving plans of NLG emergence extension are designed in this paper. One is to adjust the damping coefficients of the actuating cylinder, and the other is to the aerodynamics of forward door. Through the comparison and validation of the two plans, the second driving plan is acceptable, because this plan can reduce the adverse torque of emergence extension by about 24.8%, increase the transmission ratio of the driving mechanism, and address the emergence extension fault problem and reliably realize the emergence extension of aircraft NLG besides the  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Driving Mechanisms**} & \multirow{2}{*}{**Flight Speed /Kts**} & \multicolumn{2}{c}{**Lowering Time of NLG/s**} \\ \cline{3-4}  & & **Emergency Extension** & **Normal Extension** \\ \hline \multirow{4}{*}{Initial driving mechanism} & 270 & Failed lowering and lock & 10.69 \\  & 250 & Failed lowering and lock & 10.81 \\  & 220 & Failed lowering and lock & 11.02 \\  & 180 & Failed lowering and lock & 11.38 \\ \hline \multirow{4}{*}{New driving mechanism} & 270 & 14.66 & 11.09 \\  & 250 & 15.24 & 11.25 \\ \cline{1-1}  & 220 & 15.95 & 11.28 \\ \cline{1-1}  & 180 & 17.17 & 11.61 \\ \hline \hline \end{tabular}
\end{table}
Table 5: The lowering time of the initial and new driving mechanism.  
normal extension system. The proposed new driving mechanism is illustrated to be a promising feasible driving plan with high reliability. The developed driving mechanism is promising in the application of civil and military aircrafts, which supports the safety and airworthiness in flight.  
Conceptualization, C.-W.F.; Data curation, C.L.; Formal analysis, Z.-Z.Z.; Funding acquisition, Y.-W.F.; Investigation, C.L.; Methodology, Z.-Z.Z., C.L. and C.-W.F.; Project administration, Y.-W.F.; Resources, C.-W.F.; Software, Z.-Z.Z. and C.L.; Supervision, Y.-W.F. and C.-W.F.; Writing--original draft, Z.-Z.Z.; Writing--review & editing, C.-W.F.  
This research was funded by [National Natural Science Foundation of China] grant number [51875465, 51605016 and 51975124], [Special Science and Technology Program of Civil Aircraft of China] grant number [MJZ-Y-2018-92], and [Research Start-up Funding of Fudan University] grant number [FDU38341]. The APC was funded by [FDU38341].  
The authors declare that there is no conflict of interests regarding the publication of this article.