Study of a Ground Delay Program (GDP) (2015)Trabajo Inglés
In this work, we show a study of a Ground Delay Program enforcement at a random airport. A set of different tasks are done in order to analyze the GDP from the Air Traffic Management point of view. The file time and the radius of exemption, among other parameters, are to be examined to understand the effect that falls on the GDP and the delays obtained by using this ATFM initiative. We will also plot different figures to appreciate, at a glance, the traffic situation before and after enforcing the GDP.
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Study of a Ground Delay Program
Mart´ı Esteve Pascuala , Sergio Fern´andez Sanzb
Telecommunication and Aerospace Engineering School of Castelldefels
Technical University of Catalonia - BarcelonaTech
In this work, we show a study of a Ground Delay Program enforcement at a
random airport. A set of different tasks are done in order to analyze the GDP
from the Air Traffic Management point of view. The file time and the radius of
exemption, among other parameters, are to be examined to understand the effect
that falls on the GDP and the delays obtained by using this ATFM initiative.
We will also plot different figures to appreciate, at a glance, the traffic situation before and after enforcing the GDP.
Keywords: Ground Delay Program, ATFM, Delay.
1. Introduction Passenger and freight demand for air transportation has been growing over the last years and is forecast to keep growing for several years. The additional capacity at big airports has not solved the congestion problems. That is why ATFM initiatives have been used to sort out daily demand-capacity imbalance. In particular, the Ground Delay Program has been used to collaborate with airlines to manage scheduled arrival flow into airports according with actual arrival capacity.
It is a popular initiave since enables the airlines to reduce the cost of delays by holding on ground instead of airborne.  A GDP is an air traffic procedure where aircraft are delayed at their departure airport in order to reconcile demand with capacity at their arrival airport. GDP will usually be implemented at airports where capacity has been reduced because of meteorological conditions or when demand exceeds capacity for a sustained period. They are implemented to ensure the arrival demand at an airport is kept at a manageable level and to prevent aircraft from having to divert to other airports. GDP affect all flights within the defined scope of the program. The program’s scope can be defined as distance, as tier or as time.  Preprint submitted to GEAIO May 22, 2015 2. GDP characteristic features A Ground Delay Program is defined by a set of parameters, the change of these parameters will alter the results obtained.
• File time: Time at which we decide to implement the GDP. It is usually decided up to 5 hours prior the enforcement.
• Start time (Hstart): Time at which the GDP for a given airport starts.
• End time (Hend): Time at which the GDP for a given airport ends.
• No regulated time (HNoReg): Time at which the airport recovers its nominal capacity.
• Reduced capacity: Capacity at which the airport works while the GDP is enforced.
• Nominal capacity: Capacity at which the airport works usually in standard conditions.
• Radius of action: All aircraft arriving to an airport where a GDP is enforced and meet the requirements of the selected scope.
The following plot (Fig.1), shows the aggregate demand curve and the reduced capacity in the period of time that the GDP is active, the nominal capacity is plotted from the end time till the no regulation hour. For a reduced capacity at an arrival airport, the amount of delay depends only on the airport acceptance rates (AAR) and the flight demand at the airport.
Aggregate Demand Plot Demand (number of aircraft) 700 Aggregate Demand Reduced Capacity Nominal Capacity 600 500 400 300 200 100 0 0 2 4 6 8 10 12 14 16 18 Time of the day (Hour) Figure 1: Aggregate Demand for the given GDP 2 20 22 24 3. GDP analysis GDP planning can be best conceptualized as a task of adjusting the arrival times of flights. A GDP is run when the number of flights scheduled to arrive at an airport exceeds the number of arrival slots available over a certain period of time.
To correct this imbalance, some flights are assigned to later arrival time slots.
The ground delay assigned to a flight is simply the difference between the flights assigned arrival time slot (CTA) and the time slot it originally was scheduled to use (ETA).
Figure 2: Basic GDP parameters  The basic GDP parameters are shown in Fig.2. The variables that affect the most on the GDP results are the file time and the radius of exemption. In the following analysis, we will vary this parameters and the results will be analyzed.
i File time variation: is a key decision parameter, since all the flights airborne at the time of filing cannot be delayed. This is why the variation of this parameter will drastically change the results obtained.
ii Radius of exemption variation: it is tipically set to exclude from having to realize ground delay aircraft departing from greater distances than the selected radius of distance.  A trade-off exists when defining this radius: big radius distribute the required delay among more aircraft and reduced the airborne holding delay close to the destination airport, while the probability to realize unnecessary delay increases if the GDP is canceled before planned.
In the following analysis we show four cases performing different changes on the parameters and comparing what is happening in every case. The common parameters for every case are the following: Table 1: Given GDP parameters.
Parameter Value Hstart 10:00 PAAR 45 Parameter Value Hend 13:00 AAR 90 3 We have plotted the histogram of aircraft considering the non-regulated traffic and the regulated traffic by the GDP. In the regulated case, we can see that from 10:00 to 13:00 the capacity is reduced, given by the PAAR, and all the delayed traffic is allocated in slots after 13:00 where the nominal capacity is fully used.
100 80 60 40 20 0 Arrivals regulated traffic Arrivals (number of aircraft) Arrivals (number of aircraft) Arrivals non-regulated traffic 0 5 10 15 20 Time (Hours) 25 100 80 60 40 20 0 0 5 10 15 20 Time (Hours) Figure 3: Histograms of arrivals.
Another thing to be studied is the delay and holding delay evolution as the file time is defined with less hours in advance before the GDP initialization. In this figure we show the average and the maximum delay (and holding delay) against the file time (Hdef). We considered that radius=1500.
Maximum delay Average delay 120 Delay (minutes) Delay (minutes) 40 30 20 10 100 Delay Holding Delay 80 60 40 20 0 6 7 8 9 10 File Time (Hdef) 0 6 7 8 9 10 File Time (Hdef) Figure 4: Delay values against file time.
As we can see the delay is greater than the holding delay for each case. This is logical since the flights delayed on ground (those controlled by the GDP), are more delayed than those flights that have to hold airborne, it is basically what GDP bases on. Moreover, the delay increases as the file time approaches to the start hour since there are more excluded aircraft to allocate with preference.
4 25 By variating the radius of exemption the results on the average and maximum delay are the following (note that we considered Hdef=[7 00]): Average delay Maximum delay 250 100 Delay (minutes) Delay (minutes) 120 80 60 40 20 0 200 150 100 50 0 500 1,000 1,500 2,000 2,500 Radius of exemption Delay Holding Delay 500 1,000 1,500 2,000 2,500 Radius of exemption Figure 5: Delay values against radius of exemption.
We can see that the closest the radius of exemption is from our studied airport, the most the delay generated by the GDP. This is why big radius distribute the required delay among more aircraft and reduce the delay close to the destination airport. However, the effect on enlargening the radius of exemption may produce other disadvantages if no cautions are contemplated .
4. Conclusions As expected, holding flights on ground is more economic and safer than airborne. The ground delay program is such a really useful initiative to regulate inbound traffic at an affected airport. We can state that it is preferred to active the GDP in short intervals of time, e.g., three hours, since it allows the airport to recover its nominal capacity in a short period of time. Nevertheless, it is important to know how to manage the file time and the radius, because as we saw, they can affect on the GDP behavior.
References  B. Manley and L. Sherry ”The impact of Ground Delay Program (GDP) Rationing Rules on Passenger and Airline Equity” 3rd International Conference on Research and Airline Transportation, Fairfax, VA, 2008.
 M. Ball and G. Lulli ”Ground Delay Programs: Optimizing over the Included Flight Set Based on Distance” Traffic Control Quaterly, Vol. 12, 2004.
 L. Delgado and X. Prats ”Effect of Radii of Exemption on Ground Delay Programs with Operating Cost Based Cruise Speed Reduction” Tenth USA/Europe Air Traffic Management Research and Development Seminar, ATM2013.