Airline Fleet Readiness - George Mason Universitycatsr.ite.gmu.edu/SYST490/490_AFR.pdfSource: FAA –ATADS and BTS ... parts; an equal number of bolts, rivets and other fasteners;

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Airline Fleet Readiness:Trade-off Analysis of Alternate Maintenance Systems

1

Overview

1. Context

2. Problem and Need Statements

3. Scope

4. Stakeholder Analysis

5. Design Alternatives

6. Method of Analysis

7. Project Schedule

2

Overview

1. Context


3. Scope




7. Project Schedule

3

Unstable Demand, Fluctuating Prices

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Airline Profitability vs Time

Annual Profit

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Airline Profitability

: Recession (7/90-3/91, 3/01-11/01, 12/07-6/09)5

Source: BTS RITA Schedule 12 and NBER

Total Operating Expenses

6

Source: BTS

Direct Maintenance (≈10% of Total)

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Increasing Maintenance Costs

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Source: BTS RITA Schedule P-12

In Service: Producing Revenue

Out for Maintenance: Losing Revenue and

Incurring Costs

Indirect Cost of Maintenance

8

Fleet Readiness: The percentage of time that a given aircraft is in service

Low

erH

igh

er

Lower Higher

Maintenance Cost Gap

9

Co

st

Frequency of part replacement

Total Cost

Maintenance Costs (direct and indirect)

Other Operating Expenses

Current

Optimal

Goal:Reduce

Cost Gap

*Note: This figure is not drawn to scale.

Aircraft Complexity

10Source: FlightGlobal and Boeing

“*A Boeing 737 has+ 367,000 parts; an equal number of bolts, rivets and other fasteners; and

36 miles (58 kilometers) of electrical wire” - Boeing

Aircraft Complexity

11

System# of sub-systems

Navigation 182

Air Conditioning 145

Fire Protection 95

Fuel 93

Communications 75

Doors 73

Lights 63

Equipment/Furnishings 57

Flight Controls 52

Ice and Rain Protection 50

All Others 309

Total: 1194

Boeing 737 Family

Source: Boeing and FAA – Boeing 737 MMEL

Overview

1. Context


3. Scope




7. Project Schedule

12

Problem and Need Statements

13

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Direct Maintenance Cost

Problem: Maintenance costs are increasing over time.

Need: Airline companies need to reverse the current trend of increasing maintenance costs.

Indirect Maintenance Cost

Approach

14

Design and perform a tradeoff analysis of alternate maintenance systems to determine an effective method to reduce the number of parts replaced and increase fleet readiness

Mission Requirements

1. The system shall conform to all regulations imposed by governing bodies of the airline and safety industries.

2. The system shall reduce number of maintenance actions required by the aircraft.

3. The system shall reduce maintenance-related expenses.

15

Overview

1. Context


3. Scope




7. Project Schedule

16

Part Condition Tracking

Boeing 737 Family

Mx ActionsPerformed

Aircraft, Workshop and Enterprise

Levels

Part Replacement

Scope

17

Non- MxOperating Costs

Other Aircraft Makes and

Models

Mx = Maintenance

Time Spent on Each Mx Action

Outsourced Mx

Ticket Prices

FluctuatingDemand

Phased MxSchedules

Overview

1. Context


3. Scope




7. Project Schedule

18

System Operational Scenario

19Mx = Maintenance

Aircraft Workshop Enterprise

Primary StakeholdersSecondary Stakeholders

Affected by equipage changes and operational changes of personnel on each aircraft

Affected by changes in infrastructure, operations, and equipment that occur in the maintenance facility

Affected by changes in airline fleet management equipment and operations.

Aircraft Flight Crew X

Aircraft Passengers X X

Aircraft Manufacturer X X

Airline Fleet Operator X X X

Airline Fleet Owner X X X

Competing Airlines X X X

Federal Aviation Administration (FAA)

X X X

Federal Communications Commission (FCC)

X

Maintenance, Repair, and Overhaul (MRO) Personnel

X X X

Occupational Safety and Health Administration (OSHA)

X

Tool and Part Manufacturers X X

Tool and Part Shipment Company X

Stakeholder Analysis

20

Stakeholder Interaction Diagram

21

Aircraft

Passengers

Aircraft

Manufacturer

Competing

Airlines

Aircraft Flight

Crew

FAAFCC

Tool and Part

Manufacturer

MRO

Tool and Part

Shipping

Company

Airline Fleet

Operator

Airline Fleet

Owner

Maintenance

System

OSHA

Regulation and Oversight

Supply ChainRevenue

Enterprise

Workshop Aircraft

RegulationsWorkshop

Mx System

Enterprise

Supply

Revenue

Aircraft

Overview

1. Context


3. Scope




7. Project Schedule

22

Design Alternatives

1. Hangar Transfer– Information is transferred in the

maintenance facility

– Preventative based

2. Flight Line Transfer– Information is transferred in

between each flight

– Condition based

3. Airborne Transfer– Information is transferred during

flight

– Condition based

23

B49

Maintenance Bay

Preventative Based Alternative (1)

• Preventative Based Maintenance

– Parts are replaced on a regular schedule, based on expected life of each part

– Parts may still be replaced if a scheduled inspection identifies a need

– Limited maintenance data is available through existing onboard sensors

• Hangar Transfer (1)

– Utilizes only existing maintenance sensors

24

Condition Based Alternatives (2 and 3)

• Condition Based Maintenance

– Parts are replaced with consideration for the overall condition of the part and the aircraft

– Additional sensors required

• Adds weight, complexity, and power needs

• Flight Line Transfer (2)

– May require additional terminal infrastructure

• Airborne Transfer (3)

– May require additional communications avionics and infrastructure

25

Alternative 1: Hangar Transfer

26Mx = Maintenance

Alternative 2: Flight Line Transfer

27Mx = Maintenance

Alternative 3: Airborne Transfer

28Mx = Maintenance

Assumptions

• A1. Effects of outsourcing are negligible

• A2. Emergencies, hijackings, crashes are not considered

• A3. Representative subsystems can generalize to the entire aircraft

• A4. A generic “aging effect” can be ignored

• A5. The implementation time for alternatives is negligible

29

Assumptions (cont’d.)

• A6. Only critical parts will be modeled

• A7. Only modeling part replacement

• A8. Time to replace a part will not be considered

• A9. Overall safety will be assured regardless of alternative

• A10. Maintenance personnel and facilities will be available when needed

• A11. The cost of a maintenance action will not change with respect to time

30

Overview

1. Context


3. Scope




7. Project Schedule

31

Model Design

32Mx = Maintenance

Green, Yellow, Red Assignments

33

Green

Yellow

Red

Replacement is not required

Replacement is required but immediate action is not necessary

Replacement is required at next landing

Model Variables

34

Aircraft

Part 1

Part 2

Part 3

Part 4

Part 5

• Expected Life of Part (Flight Hours)

• Current Age of Part (Flight Hours)

• Actual Condition (R,Y,G)

• Assigned Condition (R,Y,G)

• Reason for R/Y/G (Predicted Life, Fault Detection)

• Notification for Replacement (Y,N)

• Age of Aircraft (Flight Hours)

• Maintenance Trip Needed (Y,N)

Propellors/Propulsors

Navigation

Air Conditioning

Lights

Flight ControlsLanding Gear

Equipment/Furnishings

Powerplant

Stabilizers

Doors

Wings

Fuselage

Nacels/Pylons

0.00001

0.0001

0.001

0.01

0.1

1

0 10000 20000 30000 40000 50000 60000 70000

Fre

qu

en

cy o

f D

iffi

cult

y

Age of Airframe (In Flight Hours) at Time of Difficulty

Comparison of Reported Difficulties

Data Input: Part Life and Selection

35

Mo

re F

req

ue

nt

Older Airframes

Source: FAA – SDR Database (737 only) *Note: Part selection is not yet finalized

Data Input: Flight Length

36

––– Lognormal(2.05, 1.31)

Length of Flight (Hours)

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mb

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of

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hts

Source: BTS RITA:Form T-100 data, Average Ramp-To-Ramp Times,2008-2010

Logical System Model

37Mx = Maintenance

AlternativeProbability of Part Failure

Predicted Life of Parts

Maximum Allowable

Yellow Parts

Number of Maintenance

Stops

Number of Parts Replaced


WithNotification

Total Cost of Maintenance

Hangar Transfer (Preventative)

Low Estimate# hours (low) Infinity

# hours (high) Infinity

High Estimate# hours (low) Infinity

# hours (high) Infinity

Flight Line Transfer

(Condition)

Low EstimateInfinity # parts (low)

Infinity # parts (high)

High EstimateInfinity # parts (low)


Airborne Transfer

(Condition)

Low EstimateInfinity # parts (low)


High EstimateInfinity # parts (low)


Design of Experiment

38

Input Output

Utilities

39Mx = Maintenance *Note: Weights will be elicited by survey

Model Verification

• Compare total number of R/Y/G assignments with expectations

• Compare time to part failure with available data

• Check total number of maintenance trips for reasonableness

40

Overview

1. Context


3. Scope




7. Project Schedule

41

Project Schedule

42*Task is on Critical Path

Performance and Projected Cost

43

$37,875

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*Note: $50/hour (loaded rate)757.5 hours total

CPI and SPI

44CPI = Cost Performance IndexSPI = Schedule Performance Index

*Note: Index of 1.00 is performing as expected

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Risks

• Limited knowledge and experience with airline maintenance

– Mitigation: Sponsor in the aviation maintenance field

• Task saturation

– Mitigation: We now have an intern to assist with non-critical tasks

45

Questions?

?

46

Backup Slides

• Failure Patterns• Stakeholder Node Adjacency Matrix• Service Difficulty Reports

• Model Inputs and Outputs• Logical System Model (Expanded)

• Mx as a fraction of operating expenses• Quarterly Direct Mx Expenses

• Airworthiness Directives• Regulatory Pressure

48

Model

49

Discrete Event System Model

Probability of Part Failure

Maximum Allowed “Yellow” Parts

Predicted Life of Part

Inputs Outputs

Number of Maintenance Actions


Average Lead Time Before Repair

Total Cost of Maintenance

Failure Patterns

50

Failure Patterns

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

UAL Broberg MSP SUB

Bathtub

Exponential

Linear

Log

Flat

Decay

51

Aviation Naval

Stakeholder Node Adjacency Matrix

52

Node

Airline Fleet

Operator

Airline Fleet

Owner

Aircraft

Flight Crew

Aircraft

Manufacturer

Aircraft

Passengers

Maintenance

System

Competing

AirlinesFAA FCC MRO OSHA

Tool and Part

Manufacturer

Tool and Part

Shipping

Company

Airline Fleet

OperatorSchedules

Maintenance

Reports

Ticket Price

Competition

Airline Fleet

OwnerBudget

Cost of

Construction,

Capabilities

Budget

Aircraft Flight

CrewLabor Cost Labor cost

Aircraft

Manufacturer

Cost of

Construction

Aircraft

Passengers

Need for

Fewer

Delays

Revenue Ticket Sales

Procedures,

Airworthines

s Directives

Maintenance

System

Fleet

Operations

Down Time,

Schedule

CostSchedules,

Procedures

Trend

feedback,

Changes in

Equipment

DelaysDivergent

Practices

System

Interfaces,

Additional

Training,

Procedures

Inventory

Requirements

Need for Fast

Shipping

Competing

AirlinesTicket Prices

Price

Competition

FAA Regulations Regulations Regulations Regulations Regulations Certifications

FCC Regulations Regulations Regulations

MRO Labor Cost

Need for

Reliable

Shipping

OSHASafety

Regulations

Safety

Regulations

Tool and Part

Manufacturer

Tools and

Parts

Tool and Part

Shipping

Company

Shipping

Costs

Shipping

Costs

Tools and

Parts

To

Fro

m

Service Difficulty Reports

53

Model Inputs

• Probability of Part Failure: Expected percentage that a part will fail based on historical data

• Predicted Life of Parts: Mean Time Between Failure (MTBF)

• Maximum Allowable Yellow Parts: Number of parts nearing MTBF allowed before maintenance trip is required

• Fault Detection Accuracy: Estimated accuracy of the identification of a fault in the model

54

Model Outputs

• Number of Maintenance Stops: The total number of maintenance trips performed by the simulated aircraft during its service life

• Number of Parts Replaced: The total number of parts replaced during the simulated aircraft’s service life

• Total Cost of Maintenance: The monetary cost of maintenance over the service life of the simulated aircraft

• Average Lead Time Before Repair: Time in hours available for preparatory work by maintenance personnel

55

Logical System Model (Expanded)

56

System Model (Pseudo Code)

57

Action Formula

Initialize Initialize variables

Begin_flight

Age the aircraft and parts

Flight_length = lognormal(2.05,1)Aircraft_age = Aircraft_age + Flight_lengthP1_age = P1_age + Flight_length P1 = Part 1

Part degredation (Determine P1_actual)

P1_actual = compare rand() to probability of failure (POF) graph at P1_age: if(rand()>POF(P1_age), "G") else if(rand()>0.8*POF(P1_age),"Y"), else "R"

Determine P1_assigned for Part 1

if(P1_age>P1_exp, P1_reason = "PL“ and R=R+1), else if(P1_age>0.8*P1_exp, P1_reason = "PL“ and Y = Y+1),else if (P1_actual="R", P1_reason = "FD“ and R = R+1), else if (P1_actual="Y", P1_reason = "FD“ and Y = Y+1), else "G"

"PL" = Predicted Life"FD" = Fault Detection

Count "R","Y" if( R > 0 or Y > Max_allowable, goto Mx_trip), else P1_notify="true" and goto Begin_flightMax_allowable = 2 for 5-part systems

Mx_trip

Count notifictions total_notifications = sum(Px_reason = "PL") + sum(Px_reason = “FD" and Px_notify="true") total_notifications

Count replaced parts total_replaced = Sum(Px_assigned ="Y") + Sum(Px_assigned = "R") total_replaced

Replace parts Initialize variables for all Px_assigned = "Y" or "R"

End Mx_trip goto Begin_flight

Mx as a fraction of operating expenses

58

Operating Expenses

59

SYS_FIELD FIELD_DESC Description

FLYING_OPS51000 - Flying Operations

Expenses incurred directly in the in-flight operation of aircraft and expenses related to the holding of aircraft and aircraft operational personnel in readiness for assignment for an in-flight status. ( Air Carrier Financial Reports (Form 41 Financial Data) )

MAINTENANCE 54000 - Maintenance All expenses, both direct and indirect, specifically identifiable with the repair and upkeep of property and equipment. ( Air Carrier Financial Reports (Form 41 Financial Data) )

PAX_SERVICE55000 - Passenger Service

Cost of activities contributing to the comfort, safety, and convenience of passengers while in flight or when flights are interrupted. Includes salaries and expenses of flight attendants and passenger food expenses. ( Air Carrier Financial Reports (Form 41 Financial Data) )

AIRCFT_SERVICES64000 - Aircraft And Traffic Servicing

Compensation of ground personnel, in-flight expenses for handling and protecting all non-passenger traffic including passenger baggage, and other expenses incurred on the ground to (1) protect and control the in-flight movement of the aircraft, (2) schedule and prepare aircraft operational crew for flight assignment, (3) handle and service aircraft while in line operation, and (4) service and handle traffic on the ground after issuance of documents establishing the air carrier's responsibility to provide air transportation. ( Air Carrier Financial Reports (Form 41 Financial Data) )

PROMOTION_SALES67000 - Promotion And Sales

Cost incurred in promoting the use of air transportation generally and creating a public preference for the services of particular air carriers. Includes the functions of selling, advertising, and publicity, space reservations, and developing tarrifs and flight schedules for publication. ( Air Carrier Financial Reports (Form 41 Financial Data) )

GENERAL_ADMIN68000 - General And Administrative

GENERAL_SERVICES69000 - General And Administrative

DEPREC_AMORT70000 - Depreciation And Amortization

TRANS_EXPENSES71000 - Transport Related Expenses

All expense items applicable to the generation of transport-related revenues. ( Air Carrier Financial Reports (Form 41 Financial Data) )

Quarterly Direct Mx Expenses

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Direct Mx Flight Equipment (Adjusted for inflation)Direct Mx Flight EquipmentDirect Maintenance cost per flight hour (adjusted for inflation)

Airworthiness Directives

61

0

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2000 2001 2002 2003 2004 2005 2006 2007 2008 2009

Annual Count of Airworthiness Directives Issued

MEL Systems

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182145

95 93 75 73 63 57 52 50 49 44 39 24 23 23 21 14 12 12 12 9 9 6 4 4 2 2

1194

0

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Quantity of parts under under main systems ( number)

Cumulative

Regulatory Pressure

$3.9 Million: total of civil penalties for maintenance issues in the last year$24.2 Million: FAA-proposed penalty for Airworthiness Directive noncompliance.

63

FAA – Quarterly Enforcement Reports

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Total penalties assessed per quarter

Documents

Airline Fleet Readiness - George Mason Universitycatsr.ite.gmu.edu/SYST490/490_AFR.pdfSource: FAA –ATADS and BTS ... parts; an equal number of bolts, rivets and other fasteners;