1 S ystems Analysis Laboratory Helsinki University of Technology A Simulation Model for Aircraft Maintenance in an Uncertain Operational Environment Ville Mattila, Kai Virtanen and Tuomas Raivio Systems Analysis Laboratory Helsinki University of Technology

2 S ystems Analysis Laboratory Helsinki University of Technology Objective Modeling and simulation of flight and maintenance operations of the aircraft fleet of the Finnish Air Force (FiAF) Prediction of supportability requirements and fleet performance –Effect of operating conditions –Effect of operating policies and supposed system improvements Special interest in conflict operations –Uncertainty involved in the operational environment

3 S ystems Analysis Laboratory Helsinki University of Technology Development Early considerations in FiAF, static failure models Initiative for simulation of aircraft maintenance, joint project between FiAF and Systems analysis laboratory Discrete-event simulation as approach, Arena software as tool Simulation model of one airbase Model with multiple airbases, normal and conflict operations A simulation tool for FiAF Simulation of helicopter maintenance Introduction in FiAF Scheduling of aircraft maintenance

4 S ystems Analysis Laboratory Helsinki University of Technology Discrete-event simulation Widely applied in analyzing logistic systems –Conceptually simple approach –Intuitive consideration of uncertainty –Allows the inclusion of highly complex processes and interactions in a model –Possibilities for visualization –Powerful software tools for model construction and analysis, flowchart modeling

5 S ystems Analysis Laboratory Helsinki University of Technology Aircraft availability Maintenance resources operating policies environment Flight activities modes of flying intensity selection of aircraft Battle damages threat scenarios tactics Reliability Deterioration Preventive measures

6 S ystems Analysis Laboratory Helsinki University of Technology Conflict operations Limited knowledge on how the presence of the enemy affects the fleet’s operations –Unpredictable flight pattern –Battle damage rates –Changed maintenance requirements –Decentralization of airbases –Material supply –Assaults on airbases

7 S ystems Analysis Laboratory Helsinki University of Technology The simulation model Aircraft availability

8 S ystems Analysis Laboratory Helsinki University of Technology Construction and validation of the model Based on incomplete information Emphasis on expert knowledge –Conversations with FiAF representatives –Presentations to maintenance professionals –Available data on normal operations, exercises and contingency plans Affects the way the model can be used –Definition of input data –Interpretation of results –Sensitivity analyses

9 S ystems Analysis Laboratory Helsinki University of Technology Utilization of the model Implemented with Arena -software Appears as a stand-alone tool to the user –Customized user interface and simulation reports Simulation analyses for maintenance designers –Allocation of maintenance personnel, spare parts and equipment –Comparison of flight and maintenance policies –Effect of reliability improvements... Applicable for training of maintenance personnel –Demonstrates the significance of maintenance and support logistics to performance of the fleet

10 S ystems Analysis Laboratory Helsinki University of Technology Example analysis Change of maintenance policy during a dynamically evolving conflict –Periodic maintenance is suspended to release aircraft to flight activities At what time should this occur? A scenario with 4 phases 1Increased flight intensity 2Further increase in flight intensity, decentralization of airbases 3Aerial battles 4Decreased flight intensity due to losses

11 S ystems Analysis Laboratory Helsinki University of Technology Example analysis: results

12 S ystems Analysis Laboratory Helsinki University of Technology Conclusions A simulation model for the aircraft fleet of FiAF Quantitative assessment of supportability requirements and fleet performance –Diverse operating policies and conditions A tool for maintenance designers and training of maintenance personnel –Introduced to Air Force units