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 Simulation of flight and maintenance operations of the aircraft fleet of the Finnish Air Force (FiAF) Importance for maintenance designers –Predicting supportability requirements –Evaluating performance of operating policies Special interest in operations of crisis situations –Uncertainty due to limited knowledge of such circumstances

3 S ystems Analysis Laboratory Helsinki University of Technology Flight and maintenance operations A complex logistic system –Overall performance greatly influences the fleet’s operational capability Flight policy Periodic maintenance Failure and damage repairs Equipment reliability Personnel resources Supply of materials Operating conditions Crisis situations

4 S ystems Analysis Laboratory Helsinki University of Technology Operational environment The fleet operates under a threat of an enemy –Limited knowledge of actual encounters  Uncertainty of operating conditions  Uncertainty of model parameters and model form

5 S ystems Analysis Laboratory Helsinki University of Technology Flight operations in crisis situations Increased and uneven flight intensity –Reacting to enemy’s actions Engagements –Battle damages

6 S ystems Analysis Laboratory Helsinki University of Technology Maintenance operations in crisis situations Changed maintenance requirements –Emphasis on battle damage repairs –Varying intensity Decentralization of airbases –Maintenance facilities threatened by the enemy Specialized maintenance personnel Uncertain supply of materials

7 S ystems Analysis Laboratory Helsinki University of Technology Uncertainty in model construction Construction based on incomplete information –Emphasis of expert knowledge –Experience of normal operations –Live exercises and contingency plans Ambiguity in defining the model  User is allowed the flexibility to describe a variety of operating policies and conditions

8 S ystems Analysis Laboratory Helsinki University of Technology The simulation model Discrete-event approach Features –3 squadrons operating from own airbases –Central depot-level maintenance facility –Periodic maintenance, failure, and damage repairs –Personnel and material resources Implemented with Arena- software

9 S ystems Analysis Laboratory Helsinki University of Technology Structure of the model

10 S ystems Analysis Laboratory Helsinki University of Technology Model validation Evaluation by subject matter experts –Assumptions, results –Various groups of FiAF personnel –In different phases of the modeling effort Comparison of results –To reference data from normal operations –To results of an earlier tentative simulation study

11 S ystems Analysis Laboratory Helsinki University of Technology Example analysis Changing maintenance policy during a crisis –Periodic maintenance is discarded to release resources to other activities – How does the change affect aircraft availability? A scenario with 4 phases 1Increased flight intensity 2Further increase in the amount of flights, decentralization of airbases 3Aerial battles 4Decreased flight intensity due to losses

12 S ystems Analysis Laboratory Helsinki University of Technology Results Change in policy is necessary to sustain operational capability

13 S ystems Analysis Laboratory Helsinki University of Technology Conclusions A model for fleet operations in an uncertain operational environment –Quantitative assessment of maintenance policies in crisis situations Implementation with a graphical simulation software –Easily manageable simulation analyses for maintenance designers –A tool for training of maintenance personnel