SYSTEMS ANALYSIS LABORATORY HELSINKI UNIVERSITY OF TECHNOLOGY A Simulation Model for Military...

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


Outline

• Aim of the study• Aircraft fleet operations• Simulation model description• Model validation, results• Concluding remarks


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


Operations of The Fleet

• Complex and dynamic logistic system• Need to understand functioning of the system as a whole

Maintenance Operations

Flight operations


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


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


Structure of The Model

I-Level Maintenance

O-Level Maintenance

Hangar

Depot-LevelMaintenance

Pre-Flight &TurnaroundInspections

FlightMission

MissionGeneration

Daily Flight Operations

FailureRepair

Regular Maintenance


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


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


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


Screenshot from Arena


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


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


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)


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

SYSTEMS ANALYSIS LABORATORY HELSINKI UNIVERSITY OF TECHNOLOGY A Simulation Model for Military...

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