The availability of weapon systems such as fighter aircraft, battle tanks and warships during high intensity conflicts becomes low. In this paper the availability of fighter aircraft with five major subsystems (structures, engine, avionics, electrical and environmental) are considered. This depends mainly on attrition factors (failure due to unreliability and failure due to battle damage) and logistic delays, which affect repair process. We develop a simulation model considering the fighter aircraft as the weapon system for arriving at transient solutions for availability with logistic delays. The methodology is based on discrete event simulation using Monte Carlo techniques. The failure time distribution (Weibull) for different subsystems, repair time distribution (exponential) and logistic delay time distribution (lognormal) were chosen with suitable parameters. The results indicate the pronounced decrease in availability (to as low as 20% in some cases) due to logistic delays. The results are however sensitive to the reliability, maintainability and logistic delay parameters.
During air-attack operations, i.e., air-to-air and land-air operations in battles, maintaining a high level of availability of weapon systems (aircraft and weapons) becomes important from the point of view of winning the battle. Availability may depend on severity of combat operations, attrition factors (battle damage failures and reliability related failures), and logistic delays in weapons deployment and in the repair process. In this paper, a simulation model is developed for availability of weapon systems considering air-to-air and land-air combat operations, multiple failures causing aircraft failure and logistic delays in weapons deployment, and in the repair process. The availability of aircraft and the availability of weapons are separately derived from simulation and the product of them is denoted as combined availability for analysis. The results are analyzed in terms of fluctuations in availability on specified days of battle such as 1, 7, 14, and 21 days from the graphical output. The simulation procedure employs discrete event simulation technique using Monte Carlo methods. The time to failure distribution and the time to repair distribution for the major subsystems of the aircraft and helicopters is considered to be Weibull and exponential respectively. The logistic delay time distribution for weapons replenishment and for logistic factors, spares, crew, and equipment, is considered to be lognormal. Assuming a certain range of values for air-attack missions and for the number of sorties to be generated and a set of reliability and maintainability parameters for the considered major subsystems of the aircraft, the simulation for availability is analyzed. The number of aircraft (both fixed wing and rotary wing) for different missions is varied. The possible reduction in availability due to changes in logistic factors, considering two extreme cases noted as optimistic and pessimistic is specifically examined through simulation runs. The results obtained indicate the pronounced decrease in availability of weapon systems and their fluctuations due to multiple failures and logistic delays in weapons replenishment and in the repair process. The results are, however, highly sensitive to a combination of reliability, maintainability, and logistic delay parameters.
PurposeAvailability of military systems is of major concern for military planners at both tactical (battle) level and at strategic level (long‐term national planning). Availability factors critically affect the operational effectiveness during military operations. Military systems are complex and lend themselves to simulation approach for availability estimation as analytical solutions are extremely difficult. The purpose of this paper is to discuss the method of systems modeling to approach the simulation for availability estimation of military systems.Design/methodology/approachAvailability measures are needed for two main domains of application: peacetime operations and battlefield situations. Availability measures include not only inherent availability of interest to designers/manufacturers, but also operational availability and field/service availability. The simulation approach adopted here involves discrete event simulation (DES) techniques using Monte Carlo methods since a network of events can be included in the model. A system engineering approach is emphasized, starting with system representation and characterisation, and using system aggregation techniques.FindingsModeling involves hierarchical models and network diagrams for events. First the system is described by a hierarchical model; the events and transitions are represented with state transition diagrams (STD). The simulation scheme would be based on initial resources or inventory as military operations proceed, with random variates for event times or rates. The availability as a function of time A(t) is arrived at. The reliability and maintainability models are simulated with probability distributions or using empirical distributions. The methods of data collection and analysis, and sensitivity analysis are mentioned. The methodology is explained with two case studies from the authors' work. The approaches of other workers in recent years are summarised.Originality/valueThe paper shows that the simulation models can suitably be modified to include their applications for army and navy military operations. Also, with proper data on all major subsystems of interest for the weapon platform and accurate past war data, it is possible to fine‐tune the models for online use during military campaigns. The availability figures thus obtained may also be used for procurement decisions for long‐term and strategic planning.
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