Air Traffic Control School Case Presentation – Dec. 2, 2010 Stephen Damian, Frank Trudo, Andrew Zuroski

Air Traffic Control School Training program for future air traffic controllers Must master scheduling processes to guarantee safe landing sequences for incoming flights Review given data for 8 incoming flights and determine the most cost effective landing order without crashing any planes Training program for future air traffic controllers Must master scheduling processes to guarantee safe landing sequences for incoming flights Review given data for 8 incoming flights and determine the most cost effective landing order without crashing any planes

Problem Statement Using feasible scheduling rules, determine which one is most cost effective Determine mean flow time, average number of planes, and mean lateness for each sequence Compare the trade-offs for each scheduling rule Maintain safety as the primary objective Using feasible scheduling rules, determine which one is most cost effective Determine mean flow time, average number of planes, and mean lateness for each sequence Compare the trade-offs for each scheduling rule Maintain safety as the primary objective

Data for Incoming Flights

Scheduling methods used in case MAIN OBJECTIVE: Land planes before flying time is finished causing a crash Shortest processing time (SPT)- job that has least processing time has highest priority Highest Cost per minute of flying time- order of sequence is dependent on the cost of a flight when it is flying (the highest cost has priority) Earliest Due Date (EDD)-job due earliest has top priority Critical Ratio (CR) -job with the smallest ratio of time remaining until due date to its processing time Slack Rule- flights landed in order of increasing slack time Could not use first come/first serve (FCFS), longest due date (LDD)or last come/first serve (LCFS) rules because planes would crash

Scheduling Definitions Lateness = completion time – due date (+ or -) Slack = due date – processing time Critical Ratio = time until due date/processing time Makespan = length of time to complete batch (land all planes) Flow time = time a job is complete –time job first available Lateness = completion time – due date (+ or -) Slack = due date – processing time Critical Ratio = time until due date/processing time Makespan = length of time to complete batch (land all planes) Flow time = time a job is complete –time job first available

Stick to the Schedule!

Earliest Due Date Landing Order EDD Cost per minute ($) Total Flying Time Limit (min) Processing Time (minutes)Flow Time (min)LatenessTotal Cost Flying ($) Total Landing Cost ($) Flight Flight Flight Flight Flight Flight Flight Flight Makespan (minutes)20.25 Total time (minutes)87 Mean flow time (minutes)10.88 Average # of Planes4.3 Total Lateness (minutes) -20 Mean Lateness (minutes) -2.5 Total Cost ($)

Earliest Due Date Process Time Total Flow Time

Shortest Processing Time Landing Order SPT Cost per minute ($) Total Flying Time Limit (min) Processing Time Minutes (shortest) Flow Time (minutes) Lateness (column D- column B) Cost Flying Total($) Total Landing Cost ($) Flight Flight Flight Flight Flight Flight Flight Flight Makespan (minutes)20.25 Total Minutes79.5 Mean Flow Time (minutes)9.94 Average # of planes3.93 Total Lateness (minutes) Average Lateness (minutes) Total Cost ($)

Shortest Processing Time (SPT) Process Time Total Flow Time

Analysis of SPT Method Advantages of using SPT Method Lowest Mean Flow time [9.94 minutes] Lowest average number of jobs [3.93 jobs ] Lowest Total Flow time [79.5 minutes] Minimizes WIP, Maximizes Customer Response Time Disadvantages of using SPT Method Can not achieve lowest cost Needs constant monitoring due to planes running out of flying time Increased job lateness compare to EDD [ minutes] Not as efficient as other methods

High Cost/Minute Landing High Cost/Min Cost per minute ($) Total Flying Time Limit (minutes) Processing Time (minutes) Flow Time (minutes) Late (minutes)Cost Flying Total ($) Total Landing Cost ($) Flight Flight Flight Flight Flight Flight Flight Flight Makespan (minutes) Total Minutes Mean Flow Time (minutes) Average # of Planes 4.09 Total Lateness (minutes) Average Lateness (minutes) Total Cost ($)

Plane 1Plane 2Plane 3Plane 4Plane 5Plane 6 Plane 7Plane 8 Flow Time4.25 min5.75 min8.5 min10.5 min14 min17 min20.25 min 2.5 min1.75 min1.5 min2.75 min2 min3.5 min3 min3.25 min Flight min Flight min Flight min Flight min Flight min Flight min Flight min Flight min $400/min$150/min$80/min$125/min$100/min$200/min$150/min$300/min Flight min $ Flight min $ Flight min $ Flight min $ min Flight min $100 2

Highest Cost/Minute Process Time Total Flow Time

Analysis of Highest Cost/Minute Method Advantages of Highest Cost per/minute Disadvantages of Highest Cost per/minute Longer mean flow time results in more WIP Increased total job flow time, and increased mean job flow time compared to SPT Increased average number of jobs compared to SPT minimized job lateness compared to SPT [ ] Most cost effective method [ $11, ]

Landing Order - CRStart Processing Time (min) Flow Time (min) Cost per Minute ($) Tota Land Cost ($) Total Cost of Flying ($) Time until due Lateness (min) Flight Flight Flight Flight Flight Flight Flight Flight Total Cost ($) Total Flow Time (min)91.25 TOTAL Mean Flow Time (min)11.4 Average Lateness Average # of Jobs Critical Ratio (Due Date/Processing Time)

Slack Time (mins) = EDD Landing Order - Slack (mins)Start Processing Time (min) Flow Time (min) Cost per Minute ($) Tota lLand Cost ($) Total Cost Flying ($) Time until due (mins) Lateness (mins) Flight Flight Flight Flight Flight Flight Flight Flight Total Cost ($) Totol Flow Time (min)87 TOTAL-20 Mean Flow Time (min) Average Lateness-2.5 Average # of jobs

Total Slack Cost Landing Order - Slack CostStart Processing Time (min) Flow Time (min) Cost Per Minute ($) Total Land Cost ($) Total Cost of Flying ($) Time until due (mins) Lateness (mins) Flight 24 - $ Flight $ Flight $ Flight $ Flight $ Flight $ Flight $ Flight $ Total Cost ($) Total Flow Time (min)82 TOTAL-25 Mean Flow Time (min)10.25 Average Lateness Average # of jobs

Flow Time Column1 Processing Time Flight 616Flight 894Flight 8076Flight 217Flight 101Flight 219Flight 118Flight 24 Due 16 minutes $5,625$2,587.50$280$656$800$1,700$1,800 Due 22 minDue 19 minDue 5 minDue 8 minDue 10 minDue 12 minDue 15 min Flow Time Processing Time Flight 616Flght 8076Flight 24Flight 217Flight 101Flight 219Flight 118 Due 15 minutes $5,625$280$5,400$656.25$800$1,700 Due 22 minDue 5 minDue 16 minDue 8 minDue 10 minDue 12 min Flow Time Processing Time Flight 616Flight 8076Flight 118Flight 217Flight 101 Due 10 min $5,625$280$1,800$656 Due 22 minDue 5 minDue 15 minDue 8 min Flow Time Processing Time Flight 616Flight 8076Flight 894Flight 217Flight 101Flight 219Flight 118Flight 24 Due 16 minutes $5,625$280$2,587.50$656$800$1,700$1,800 Due 22 minDue 5 minDue 19 minDue 8 minDue 10 minDue 12 minDue 15 min Total Slack Cost – Alternatives

Sequence for Slack Cost Process Time Total Flow Time

Conclusions Earliest Due Date – minimizes lateness, no adjustments to avoid crashes Shortest Processing Time – lowest mean flow time and average # of planes in process Slack Cost – modified sequence is the most cost effective in this case Earliest Due Date – minimizes lateness, no adjustments to avoid crashes Shortest Processing Time – lowest mean flow time and average # of planes in process Slack Cost – modified sequence is the most cost effective in this case

Thank you and have a safe flight!