## 5 Conclusions  
The problem associated with reliability analysis using a very small number of failure data has been solved in this paper. This research work provides a guide which can be used for reliability analysis of any repairable system and its subsystems when a very small sample size of failure data is available. Using CBH, the consistency of failure data of the system can be checked. Further to support the CBH test results, using meta-analysis the level of heterogeneity can be found out for systems and subsystems. After passing the above two tests, the very small failure data can be pooled. The pooled TBF data can be effectively further tested for trend analysis.  
By using the MLE method and PLP model reliability analysis can be carried out. The values of reliability and MTBF are estimated. The value of MTBF can be utilized in scheduling the maintenance of the engine. Additionally, the subsystem with the lowest reliability, i.e., self-starting subsystems should be taken extra care of during maintenance.  
The test values for all five subsystems falls between the lower (0.10) and upper value (5.99). Hence, the TBF data for each subsystem of three engines pass CBH suggesting pooling of TBF data for further analysis.  
The zero value for four subsystems and the low level of heterogeneity value for one subsystem indicated that there is no variability among the failure data of three engines for all the five subsystems. It suggests that all the samples came from the same underlying  
Figure 6: Reliability for five subsystems.  
Figure 7: MTBF for five subsystems.  
distribution, thereby supporting the result of CBH test which allows the pooling of failure data of three engines for each subsystem.  
The failure data of all five subsystems of the engine showed consistency by confirming the CBH test. Additionally, meta-analysis test supports the result of the CBH test which allows the pooling of failure data of three engines.  
The trend is seen for self-starting, fuel supply and cooling subsystems. No serial correlation is found for all five subsystems and thus, self-starting, fuel supply and cooling subsystems do not follow _iid_ characteristics whereas the air supply and lubrication subsystem follows it.  
The value of reliability is highest for fuel supply subsystems and lowest for self-starting subsystems. The lowest MTBF value is of the Self-starting subsystem which is 1186.47 h, and the highest is of the air supply subsystem which is 1525.50 h.  
Due to reliability analysis and a reliability-based maintenance schedule, the downtime and catastrophic failure of dumpers can be reduced.  
Conceptualization, B.K.D., A.K.M., S.C., S.S., F.A., J.M. methodology, B.K.D., A.K.M., S.C., S.S.; formal analysis, B.K.D., A.K.M., S.C., S.S., J.M.; investigation, B.K.D., A.K.M., S.C., S.S., F.A., J.M.; resources, B.K.D., A.K.M., S.C., S.S.; writing--original draft preparation, B.K.D., A.K.M., S.C., S.S.; writing--review and editing, B.K.D., A.K.M., S.C., S.S., F.A., J.M.; supervision, B.K.D., A.K.M., S.C., S.S.; funding acquisition, S.S., J.M. All authors have read and agreed to the published version of the manuscript.  
The authors are grateful to FCT--Fundacao para a Ciencia e Tecnologia who financially supported this work through the RD Units Project Scope: UIDP/04077/2020 and UIDB/04077/2020.  
Not applicable.  
The data presented in this study are available on request from the corresponding author.  
The authors declare no conflict of interest.