Institute for Software Integrated SystemsVanderbilt University

MAPLANT

A Decision Support Tool for Aircraft Maintenance

Chris van Buskirk

June 28th, 2002

DARPA IXO ANTS - Complexity and Dynamics Workshop

Goals of the Presentation

2. Explain MAPLANT’s Scheduling Problem

c. set the stage for PM session to explore the possibilities for collaboration

b. scheduling techniques/algorithmsa. data formats for our repository of real-world

scheduling data

1. Quick introduction to the problem domain and the end-user application software

Goals of the Project• Develop efficient, distributed algorithms for

solving maintenance logistics problems– Localized concerns should be a key concept of the

software architecture

– Related concerns must communicate with one another during the problem-solving process

– Devise an architecture that, under run-time constraints, may not be able to satisfy all individual concerns, yet produces acceptable solutions--from a global perspective.

• Measure success based on performance of real systems in production environments

Architecture: Simplified

Decision Space

MAPLANT DomainEncoder

Scheduler

Test Bed Environment

• Marine Air Group 13– Marine Attack Squadron 513– Marine Attack Squadron 214– Marine Attack Squadron 311– Marine Attack Squadron 211– 11th Marine Expeditionary Unit– 31st Marine Expeditionary Unit

The Business

FlightOperations

AircraftMaintenance

FlightExecution

LegacyComputing

Systems

The CACE1 Toolset

SNAPISI / USC

MAPLANTISIS / Vandy

MSARISI / USC

LegacyComputing

Systems

DataWarehouse

& ReportingLLD

http://www.cacey.com

11010011000110010100 …

The Business

FlightOperations

AircraftMaintenance

FlightExecution

LegacyComputing

Systems

Maintenance Organization

Airframes PowerlineAvionics

Life Support

Ordnance

MaintAdmin

QA

ToolRoom

CorrosionControl

SeatShop

Maintenance/Material Control

Naval Regulation Commander’s Intent Domain Expertise

The Problem

• Long-Term Planning Tool:

Analysis of the effect of (a) operational tempo, (b) operator-defined guidance and (c) resource availability on the upcoming maintenance workload AND analysis of the ability to support various operational scenarios (~5 week planning horizon).

Inputs Considered

MAPLANTScheduler

5 WeekLook Ahead

Schedulew/i

10 minutes

Personnel Roster:

Full complement (+200 maintainers)

Ranks, quals by workcenter (10 WCs)

Aircraft Status: (~17 jets)

Maintenance Guidance: 4790/NAMP regulations, shift durations, holidays, spares strategy

desired aircraft utilization, fall-back margins, rules of thumb, …

Possible Maintenance Actions: All calendar-based, usage-based and phased maintenance inspections currently modeled plus a facility for defining any idiosyncratic inspection types.

Tools/GSE: Realistic O-level tool

inventory and GSE availability

Upcoming Aircraft Inspections:5 week planning horizon (thousands of maintenance actions)

Flight Schedule: based on squadron guidance for the upcoming planning period (from SNAP)

Operational Deviations:Extra [one-of]

workloads.

ROT: Example Strategies

1. When possible, stagger execution of those tasks having a resource consumption level that is unusually high.

2. Attempt to run concurrently those jobs that share work (e.g. remove wing on AC-03).

3. Retain 60% of day-shift mechanics for unexpected events.

4. Prefer to keep $X number of spare/backup jets which flying at tempo $Y

3. Risk analysis

5.Results

Architecture: Actual

1.Inputs2. Assignments & Projections

4. Maintenance Scheduler

DataWarehouse

GuidanceKnobs

A/C Status

CFSAProject

Flt HoursPFSA

UpcomingInspections

ProjectedMaint

CFSAView

OverlapMargins

ResourceMarginsScheduler

SNAP

Flt HoursAnalysis

MntPlanView

MaintManuals

RosterTools/SE

Guidance

ScheduleView Aircraft Availability

Maintenance Schedule

Encoder

Example MAPLANT Screens

Screen: A/C Status

Screen: Flight Schedule

Screen: Upcoming Inspections

Screen: Upcoming Inspections

Screen: Roster

Screen: Shift Guidance

Screen: Utilization Guidance

Screen: Maintenance Sched

Screen: Guidance Violated

Scheduler Slides Here

Gabor Szokoli …

Future Directions

• Shift-Change Decision Support: support unscheduled maintenance activities (requires many more manuals!)

• Vertical Extensions: add new decision support tools targeted at higher levels in the command chain (requires interaction with new customers)

• Horizontal Extensions:add support for new equipment type/model/series (requires support from new customers; e.g. F-18 & C-130)

Future Directions

• System of Systems Negotiation Protocols:continue developing interaction protocols between related software systems in the CACE toolset– Maintenance vs. Aircraft Configuration &

Capabilities (MAPLANT-MSAR)– Maintenance vs. Operational Issues

(MAPLANT-SNAP)

Future Directions: CSP

• Unified flight & maintenance scheduler (distributed)

• Constraint Libraries:– Add more [reified] [domain-specific] soft constraints

• In the interest of safety, minimize the number of shift changes that a task must endure

• In general, start phase inspections in time to finish before the weekend (to avoid accumulating SCIR hours)

• Stateful/shareable resources• Multi-capability resources

– Explore intelligent constraints that adapt behavior based on the state of the search

Future Directions: CSP

• Optimizing Searches:– Make use of the branch and bound search

facility– GUIs/tools allowing for user-influenced

searches

• Labeling Heuristics:– Domain-specific heuristic strategies for

variable selection and value selection– Strategies for switching labeling mode

based on state of the search (e.g. time to deadline)

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Appendix A

Guidance

Each AC has:1. Min, Max, Pref for month2. Can/Cannot fly for each day of mo.3. Optional deadline with min, max,

and pref (takes precedence over month until it is satisfied)

Fleet Info

Gives AC types (day, night, radar)

FlightSchedule

FS with detailed sortie info

G AC

FS

Run until all AC’s have reached their minimum,or until no further sorties can be assigned.

Assign the AC’s to flights, by assigning to the most desperate AC’s first (based up Guidance info), using the FS for supporting information, and the Guidance for driving information.

1

Assign the AC’s to flights, but this time utilize the preference of the airplane, instead of a hard (min) constraint. Similarly, use the Guidance as driving info, and FS to collaborate.

2

Run until all sorties have beenassigned, or until no further Sorties can be assigned.

Run until all AC’s have reached their preference, or until no further Sorties can be assigned.

Now, use the FS as the driver, to make sure that all sorties are assigned, but utilize Guidance to make sure that max is not exceeded.

3

Aircraft Assignment

MAPLANT/IAM-1Operational scenario

1. Maintenance Control Tunes Parameters

• Aircraft Status Tweaks Intentionally remove jets from the pool

Mark downed jets with expected up times

Partial Flight Schedule Assignment (PFSA)

Define/Modify Guidance

2. Workload ProjectionComplete Flight Schedule Assignment (CFSA)

Day-By-Day Projection of Accumulated Flight Hours per A/C

Project Scheduled Maintenance Workload (dues windows)

MAPLANT/IAM-1Operational scenario (cont.)

3. Risk Analysis & Approval of Flight ScheduleCFSA Analysis (possibly override and re-iterate)

Resource Margins

Overlap MarginsPhase-Phase56-Phase (w/i and across a/c)Engine-PhaseEngine-56

Aircraft Utilization Rates

4. Schedule ComputationProduces

a.Maintenance Schedule

b.Aircraft Availability Projection

Consideringa.PFSA Constraints

b.Resource Availability

c.Resource Margins

d.Phase-Phase Overlaps

e.Engine-Phase Overlaps

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Appendix B

User-Influence Search Example

• CycleAgent.oz

Computes a plan of “operational flows” that conform to management’s desired flight-hour goals for the upcoming month, while simultaneously considering the risk of sortie cancellations due to committing to certain flow patterns given the projected status of the fleet throughout the month.

Definitions

• Turnaround Inspection:safety inspection required when plane lands and the pilot relinquishes control of the jet to its plane captain (requires a minimum two hour break before the plane can be assigned to subsequent sorties)

• Hot-Pit:less detailed procedure for turning the plane in preparation for its next sortie; requires that the same pilot fly the second sortie (i.e. a gas-and-go)

• Spare:backup aircraft to be used in the event of some unexpected problem with the primary side number

Definitions

• Operational Flow:A description of the sequence of pits and turns to be executed throughout some flyday.– 2p2t2 – 6t4p4– 2t2t2

The Scenario

• This code will compute a plan of operational flows, then measure its goodness in two dimensions:

– Agreement with the stated monthly flight hour goals

– Degree of risk of not carrying out the plan as stated