Institute for Software Integrated Systems Vanderbilt University MAPLANT A Decision Support Tool for Aircraft Maintenance Chris van Buskirk June 28 th, 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/algorithms a. 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 Domain Encoder Scheduler

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

The Business Flight Operations Aircraft Maintenance Flight Execution Legacy Computing Systems

The CACE 1 Toolset SNAP ISI / USC MAPLANT ISIS / Vandy MSAR ISI / USC Legacy Computing Systems Data Warehouse & Reporting LLD …

The Business Flight Operations Aircraft Maintenance Flight Execution Legacy Computing Systems

Maintenance Organization AirframesPowerlineAvionics Life Support Ordnance Maint Admin QA Tool Room Corrosion Control Seat Shop Maintenance/Material Control Naval RegulationCommander’s IntentDomain 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 MAPLANT Scheduler 5 Week Look Ahead Schedule w/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.Inputs 2. Assignments & Projections 4. Maintenance Scheduler Data Warehouse Guidance Knobs A/C Status CFSA Project Flt Hours PFSA Upcoming Inspections Projected Maint CFSA View Overlap Margins Resource Margins Scheduler SNAP Flt Hours Analysis MntPlan View Maint Manuals RosterTools/SE Guidance Schedule View Aircraft Availability Maintenance Schedule Encoder

Example MAPLANT Screens

Screen: A/C Status

Screen: Flight Schedule

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)

Appendix A

Guidance Each AC has: 1. Min, Max, Pref for month 2. 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) Flight Schedule FS with detailed sortie info GAC FS Run until all AC’s havereached their minimum,or until no furthersorties 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 been assigned, or until no further Sorties can be assigned. Run until all AC’s havereached their preference,or until no furtherSorties 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-1 Operational 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 Projection Complete Flight Schedule Assignment (CFSA) Day-By-Day Projection of Accumulated Flight Hours per A/C Project Scheduled Maintenance Workload (dues windows)

MAPLANT/IAM-1 Operational scenario (cont.) 3. Risk Analysis & Approval of Flight Schedule CFSA Analysis (possibly override and re-iterate) Resource Margins Overlap Margins Phase-Phase 56-Phase (w/i and across a/c) Engine-Phase Engine-56 Aircraft Utilization Rates 4. Schedule Computation Produces a. Maintenance Schedule b. Aircraft Availability Projection Considering a. PFSA Constraints b. Resource Availability c. Resource Margins d. Phase-Phase Overlaps e. Engine-Phase Overlaps

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