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Schedule Delay
Initial Delay
Crews
Gate Space
Aircraft
Passengers
Propagates into Large Delay
Non-linear Response to Capacity Reduction
Reducing the airport capacity to 50%, generates over 65,000 minutes of delay at the airport and 139,000 minutes system wide.
System delay
0
50000
100000
150000
200000
250000
300000
100 96 92 88 83 80 75 72 67 63 58 55 50 47 42
Available Airport Capacity (Percentage)
Del
ay
Airport delay
Current CDM GDP Process
FAA/Airline Evaluation Demand Vs.
Capacity
GDP ModelingSend Proposed GDP
Advisory
Airline Response(cancellations)
Is GDP still required?
Issue GDP Airline Response(Substitutions & Cancellations)
CompressionGDP Revision/Extension
Yes
End
No
Exit loop when program expires or is cancelled.
(Ration by schedule)
TFM Dependencies
Although, the capacity at an airport is reduced and ATC delay has been applied, users may cancel and delay flights as well as notify the FAA of earliest feasible departure times of flights.
FAA Actions
Cancellations
Airline Delays beyond ATC delay
Earliest Departure/Arrival Time updates
Airline Actions
Issue ATC delay
Generate Demand
Reduce ATC delay
Passengers
60
116
93
87
87
Total 443
P-DELAY = #PSGR X min DLYD
P-Delay min = 26580
P-Delay min =3600
Original P-Delay is
738% greater than revised
Passengers
0 CNX
176 (60 late)
93
87
87
Airline and FAA Actions can Reduce Delays
What Do We Measure?
• Event Predictability (also referred to as compliance) ETA predictability– Departure Compliance– ETE Fluctuation– Arrival Compliance
• Arrival rate delivery• Rate Control Index (RCI)
• What could have been done to improve?• What are the impacts of new changes
(e.g., +_5 minute window)?
What Do We Measure?• Departure Compliance
What Do We Measure?• ETE Fluctuation
What Do We Measure?
• Arrival Compliance
What Do We Measure?Arrival Rate Delivery
• Rate Control Index (RCI)– Used to quantify the deviations in the actual hourly
arrival counts from the planned hourly arrival counts– Can be used to compare one program to any other – Perfect score = 100%
• Aggregate RCI– Looks only at total number of flights in each hour
• Nominal RCI– Looks at which flights arrived in each hour– Nominal RCI < Aggregate RCI
What Could Have Been Done to Improve?
• More frequent revisions• Tighter enforcement of departure times• Higher standards for data quality to remove:
– Time-Out cancellations– Time-Out delays– Cancel but flew
• Re-evaluated treatment of Pop Up flights
What Do We Measure?+/- 5 minute Compliance Test
• Controlled flights departing to a GDP are required to depart within +/- 5 minutes of their Expected Departure Clearance Time (EDCT)
• Flights that fail to meet the compliance window must request a new EDCT from the ATCSCC.
• Miles In Trail restrictions are lifted for flights destined for 7 airports; ATL, DFW, ORD, EWR, STL, SFO, PHL.
• Goal of improved departure compliance.
Impact of New Changes• Departure
Standard DeviationBefore test = 32.14During test = 15.90
Impact of New Changes• En Route
Standard DeviationBefore test = 12.85During test = 10.00
Impact of New Changes• Arrivals
Standard DeviationBefore test = 33.32During test = 38.12
Impact of New Changes• RCI
Average Aggregate RCI 1/1/01-4/2/02: 87.94
Average Aggregate RCI 4/3/02-4/21/02: 96.75
RCI has improved by: 10%
The Need for Revision
• As the demand changes, the need for revisions increases.
• The arrival demand would have been smoothed out if a revision had been run at 1758Z during this PHL program.
• Solid bars = current demand
• Hashed bars = revised demand
The Fallacy of Binning
• Measuring demand in one-hour bins does not describe how that demand is distributed throughout the hour.
• Each hour bin below has the same total demand. However, the demand distributions vary dramatically.
=19.4 =8.66 =0
Solution to Binning:Arrival Flow Rates
Viewing the demand in one-hour bins does not show the underlying fluctuations that exist.
Viewing the demand as a Flow Rate shows the actual demand fluctuations,forecasting the potential for airborne holding – viewed as a moving window average
Images from the Flow Rate Analysis Tool
Equity Measures
• Affected Average Delay
• Proportions from carrier statistics
• EMF/EMA from power run
Equity Measures• Affected Average Delay
Equity Measures• Proportion of Flights Affected by Carrier
Equity Metric for Airlines (EMA) and Equity Metric for Flights (EMF):
• EMA/EMF: Compares the amount of imposed ground delay to the baseline of airborne holding
• 2-8: Good Equity
• 9-16: Significant deviations from good equity
• 16+: Poor equity
The Many Facets of Equity
• Long haul Vs. Short haul flights• GA Vs. Scheduled Carriers• Regional Vs. Majors• Overhead stream Vs. Departures• Equity across flights, carriers, ARTCCs,
airports,...
• No single vantage point serves for all occasions
Distance-based GDPs• Set inclusion for ground
delay based on distance from GDP airport
• As GDP radius is increased, delay per flight goes down but (risk of) unrecoverable delay goes up
• Find optimal tradeoff
Delay Graphic
Air HoldOuch
220
200
180
160
140
120
100
80
60
40
20
Minutes
Unrecoverable Delay
Average Delay
200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 2800
Miles
Air HoldUnrecov DelayAverage DelayMax Delay
160
58
37
What Do Airlines Measure?
• Air En Route Times
• Fuel Burn
• Diversions
• Taxi-Out Times
• Passenger Load Factor
As the time of the event approaches, certainty goes up but possible options are reduced.
Time Before Event
OptionsCertainty
Time Before event
There is Always a Trade-off in Delaying Actions
Options Decrease While Knowledge Increases
• Objective – increase knowledge while options remain open.• Essential to explore tactical relationships
Op
tion
s
Certainty
Increase knowledge earlier
Keep options open longer
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