a simulation model for military aircraft maintenance and availability
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SYSTEMS ANALYSIS LABORATORYHELSINKI UNIVERSITY OF TECHNOLOGY
A Simulation Model for Military Aircraft Maintenance and Availability
Tuomas Raivio, Eemeli Kuumola,Ville A. Mattila,
Kai Virtanen and Raimo P. Hämäläinen
Systems Analysis Laboratory
Helsinki University of Technology
SYSTEMS ANALYSIS LABORATORYHELSINKI UNIVERSITY OF TECHNOLOGY
Outline
• Aim of the study• Aircraft fleet operations• Simulation model description• Model validation, results• Concluding remarks
SYSTEMS ANALYSIS LABORATORYHELSINKI UNIVERSITY OF TECHNOLOGY
Aim of The Study
• Development of a simulation model for a fleet of military aircraft– Here Bae Hawk Mk51 jet trainer
• Normal peacetime use– Training & patrol flights– Maintenance – Failure repair
• Performance measures– Flight and maintenance policy planning
– Determine the accuracy needed in modelling such a system
SYSTEMS ANALYSIS LABORATORYHELSINKI UNIVERSITY OF TECHNOLOGY
Operations of The Fleet
• Complex and dynamic logistic system• Need to understand functioning of the system as a whole
Maintenance Operations
Flight operations
SYSTEMS ANALYSIS LABORATORYHELSINKI UNIVERSITY OF TECHNOLOGY
Maintenance and Repair Organization
Maintenance levelsOrdinary (O) Intermediate (I) Depot (D)
Maintenance types
Pre-flight inspections, scheduled
maintenance, minor failure repair
Term maintenance, failure repair
Term maintenance, damage repair
Location Squadron Airbase Factory-level facility
Duration Minutes - hours Hours - weeks Weeks - months
Example tasksRefueling, minor
repairs, e.g. light bulb change
Component change/repair, e.g.
hydraulic pump change
Elaborate component or structure
changes/repairs, e.g. bird crash repair
SYSTEMS ANALYSIS LABORATORYHELSINKI UNIVERSITY OF TECHNOLOGY
The Simulation Model
• Discrete event simulation approach
• The model describes– The structure and interaction of the maintenance, repair and
flight processes
– The maintenance capacity in terms of manpower
• Outputs from the model– Performance measures (e.g. aircraft availability)
– Availability = #operatingAC / total #AC
SYSTEMS ANALYSIS LABORATORYHELSINKI UNIVERSITY OF TECHNOLOGY
Structure of The Model
I-Level Maintenance
O-Level Maintenance
Hangar
Depot-LevelMaintenance
Pre-Flight &TurnaroundInspections
FlightMission
MissionGeneration
Daily Flight Operations
FailureRepair
Regular Maintenance
SYSTEMS ANALYSIS LABORATORYHELSINKI UNIVERSITY OF TECHNOLOGY
Modeling Assumptions
• Three airbases are aggregated into one airbase • Model describes average operations• Maintenance operations are modeled in terms of
maintenance duration and manpower capacity – Other maintenance resources are assumed to be available all
the time
SYSTEMS ANALYSIS LABORATORYHELSINKI UNIVERSITY OF TECHNOLOGY
Input Parameters
• Most significant parameters– Maintenance durations and maintenance intervals
– Failure repair durations and failure intensities
– Maintenance manpower capacities – Flight mission durations and intensities
• Reference data collected by the FAF from several airbases– Point estimates and variances, or distributions estimated– Scaling to represent the aggregated base
SYSTEMS ANALYSIS LABORATORYHELSINKI UNIVERSITY OF TECHNOLOGY
Implementation
• ARENA simulation software– SIMAN based simulation engine
– Easy-to-use graphical interface
– Animation for easy demonstrating
– Possibility to create standalone models for nonexpert users
SYSTEMS ANALYSIS LABORATORYHELSINKI UNIVERSITY OF TECHNOLOGY
Screenshot from Arena
SYSTEMS ANALYSIS LABORATORYHELSINKI UNIVERSITY OF TECHNOLOGY
Model Validation
• Model structure is evaluated together with the maintenance and logistics staff of the FAF
• Quantitative validation:
– Aircraft availability Simulated average availability slightly larger than reference value
– Maintenance throughput timesSimulated throughput times are 0-30% shorter than reference values
SYSTEMS ANALYSIS LABORATORYHELSINKI UNIVERSITY OF TECHNOLOGY
30 %
40 %
50 %
60 %
70 %
80 %
90 %
100 %
1 2 3 4 5Time (years)
Dai
ly A
vail
abil
ity
Simulated Daily Availability
0 0,1 0,2 0,3
Frequency
SYSTEMS ANALYSIS LABORATORYHELSINKI UNIVERSITY OF TECHNOLOGY
Example Analysis
Maintenance Duration (percentage from the nominal maintenace duration)
30 %
40 %
50 %
60 %
70 %
80 %
90 %
100 %
50 % 60 % 70 % 80 % 90 % 100 % 110 % 120 % 130 %
Ave
rag
e A
vail
abil
ity
.
115 % 105 % 100 % 95 % 85 %
Capacity in The I-Level Maintenance(percentage from the nominal manpower capacity)
SYSTEMS ANALYSIS LABORATORYHELSINKI UNIVERSITY OF TECHNOLOGY
Conclusions
• ARENA based implementation – Easy what-if scenarios – Illustrative animation capabilities– Stand-alone applications for e.g. maintenance staff training
• Rapid estimates for relative effect on system performance in case of
– Major changes in maintenance capacity, flight intensity etc.– Aircraft modification programs
• Future modelling efforts– Insight to sensitive parts of the system– Easily upgradable platform
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