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ARRIVAL AND DEPARTURE DELAY CHARACTERISTICS IN NIGERIAN AIRLINES
(A CASE STUDY OF PORT HARCOURT AIRPORT)
G. N. Okeudo and E. A. Ejem
Department of Transport Management technology, Federal University of Technology, Owerri
The study analyses Departure and Arrival Delays from four (4) airlines in Port Harcourt International Airport (Nigeria) using the performance metric methodology. Several data fields for every aircraft departing from or arriving at the airport in a 14-day period were attached from the inbound and outbound flight strips from the control tower and the approach. Aggregate statistics were derived from the complete data set and presented as functions of the days of the week. The percentage of aircraft delayed more than the FAA standard of 15 minutes was shown in bar charts. A close consideration of the results of the research shows that a good measure of non-compliance with airline time schedule occurs in the Nigerian Aviation Industry by way of delay flight as a result of bad weather, technical fault of aircraft, malfunction of airport facilities, and traffic congestion in the airway and fuel scarcity.
Key words: Arrival, Departure, Aircraft, Traffic, Congestion
Air transport has in recent years become a basic and vital segment of Nigeria business and social life. Air transportation has some specific characteristics that give it natural advantages over other compelling transport mode. The ability of air transport to overcome natural obstacles of land and sea as well as its comparatively high speed, makes it a favoured mode for the accelerated movement of certain goods and persons. Delays in air transportation are prevalent and very costly. Delays occur in airline operations as a result, among others, of adverse weather conditions (Ohuegbe, 2005).
This study looked at aircraft delays as a result of bad weather condition, technical and logistic problem such as faults refueling, bird strike, scarcity of aviation fuel, passenger delay due to aircraft flight schedule delay. The aim of this study was to study delays experienced by the airline operators in the airport, know the causes of delays in the airport and then proffer solutions/recommendations on how to minimize delay in Nigerian Aviation Industry. However, it is appropriate to trace the history of air transport in Nigeria and identify the developmental changes that have occurred over the years in the industry.
Airport delay can be defined as the difference between the time it could take an aircraft or passenger to be served without interference from other aircrafts or passengers and the actual time it takes the aircraft or passengers to be served. Paul (2000) remarked that delay is defined in many different ways depending upon the context. Scheduled departure and arrival delay is how late a flight departs or arrives compared to an airlines schedule. Flight can incur delays while airborne or on the ground, for example as aircraft taxi between the runway and the gate. A late arrival of one flight may cause a late departure of the next flight on the itinerary of the aircrafts arrivals and departures.
Delay in the airport is a global issue. In the United States of America, Federal Aviation Administration, FAA (2000) reports from O Hare International Airport Chicago showed that in 2000, O Hare was ranked the third most delayed airport in the country. Overall, slightly more than six percent or all flight was delayed (i.e more than 15 minutes). Current capacity benchmark at OHare is 200-202 flights per hour in good weather. Current capacity decreases to 157-160 flights (or fewer) per hour in adverse weather conditions which may include poor visibility, unfavourable winds or heavy precipitation. On good weather days, scheduled traffic is at or above the capacity benchmark for 3 ½ hours of the day and about 2% of the flights are delayed significantly. Subsequently to the Airport capacity benchmark report 2001, the FAA (2001) ranked OHare as the most delayed airport in the U.S for calendar year 2002. The intensity of flight delays is exacerbated during peak traffic periods and during periods or poor weather and/or wet runway conditions. These delay periods impact the airports ability to provide a consistent level of air service to the traveling public and other airport users. In addition as aviation demand increases overtime, flight delays will continue to worsen, thus further deteriorating the airport operational reliability.
According to the F AA (FAA 2001), weather is a contributing factor in 74% of air carrier delays and 30% of all accident. Weather delays cost the airlines. Weather related flight delays are one to the interaction of two factors, one, how many planes can an airport accept during a give time period based on the weather (airport capacity). Two, how many planes are scheduled to arrive (airport demand) during the same given time period. The most significant and common weather variables that cause delays are low clouds and low visibility. Low visibility may be due to fog, haze, smoke and falling precipitation. When these conditions occur, planes may be spaced further apart thus resulting in fewer planes landing in any given hour. Strong cross-winds may make some runways unstable. Thunderstorms near the airport may limit the flight paths available into and out of the airport. Thunderstorms enroute may cause a reduction in the number of flight paths, causing delays. Heavy snow requires frequent plowing possibly making some runways unavailable. Freezing rain and snow usually necessitates the use of anti-icing and de-icing procedures. (Weather Depotstm 2005).
Aircraft Arrival and Departure Delay
According to Eric and Gano (2002), there are out, off, on and in times in aircraft operations. Out time refers to the time of push back (specifically when the parking brake is released). Off time refers to the take off time at which weight is no longer borne on the landing gear. On time is associated with the touchdown time, and the in time is related to the moment the parking brake is applied at the gate. These times are recorded and reported by the respective airlines, their definitions are used for delay and transit time computations.
The FAA (2002) categorizes delays into gate delay, taxi-out delay, enroute (in-flight) delay, terminal delay and taxi-in delay. This is also validated by Bjorn Syren (2002). Each category of delay arises when the aircraft requires more time than was scheduled. According to the Bureau of Transportation Statistics (BTS) (2002) defined a delayed flight as one in which the aircraft fails to release its parking brake less than 15 minutes after the scheduled departure time. Surface movement inefficiencies, according to the Department of Transportation (DOT), are not the only reason for delays on the ground. Ground delay programs, enroute capacity constraints, aircraft maintenance issues, ground services (fuel, baggage and catering), customer service issues, late aircraft crew arrival, and poor weather conditions elsewhere all contribute to surface delays.
According to FAA (2001), Flight delay is separated into reportable, non-reportable and international delays. Delays recorded in the Air Traffic Operations Network (OPSNET) database are only 15 minutes or more, in other words reportable. Non-reportable delays are caused by pilot initiated enroute deviations around adverse weather; delay caused by mechanical or other aircraft operation/company problems; and delay for taxi time controlled by non-FAA entities. International delays are caused by initiatives imposed by facilities outside the United States.
Data used in this study were obtained from primary and secondary sources. Primary source include basically field work in monitoring various flight behaviours of the four Airlines used as sampling airlines in the airport. This method is therefore based on personal judgment. Secondary source includes data survey from existing documents such as inbound strips, outbound flight, strips, from the control tower (the air traffic control tower and the approach), personal contacts with FAAN and airport staffs, and publications from books, journals and articles.
To realize the aims of this study, four (4) Airlines in Port Harcourt International Airport were selected for the study of departure and arrival delay in airline passenger service delivery. The data needed for the analysis were extracted from strips from the control tower and approach for a period of 14 days. The two-week duration was chosen to have enough data for statistically meaningful results and to make possible analysis of the data as a function of days of the week. The strip (outbound and inbound) is a tool used by the Air Traffic Controllers and the Approach to store information about each flight of any aircraft. It shows detailed information about any aircrafts that arrives and departs the airport.
Data extracted are information on Aircraft destination, Aircraft origin, Scheduled time of departure or estimated time of departure (ETD), Actual time departure (ATD), Scheduled time of Arrival or estimated time of Arrival (ETA) and Actual time of Arrival (ATA).
The Analytical Tool used in this study is the performance metric parameters (Analysis). The delay metrics were generated for a typical day by day first averaging the result over 14 days. The average number of operations for any day is determined as:
F1 = Sni (1)
Where ni is the number of department or arrival on the 1st day, where m is the number of days. The average delay for a day operation of a particular airline is:
▲i = Sπj,i (2)
1 <j <ni
With delay defines as:
πj, i = (ta-ts) j, i (3)
Here ni is the number of departures or arrivals on the ith day. Ts are the scheduled departure. Ta is the actual departure time of the jth aircraft on the ith day.
Secondly, the average over the m number of days can be computed as:
F2 = S▲i (4)
1 <j <m
F2 is the average delay over the number of aircraft and the number of days at a specific airline.
A third measure, F3 is the percentage of aircraft departing/arriving late is defined as follows:
F3 = Sdi (5)
1 <j <m
Where the percentage of aircraft departing late on a single day is
di = 100 (S[πj, i>o]) .. (6)
1 <j <ni
The percentage of aircraft departing early can be determined by subtracting F3 from 100.
The fourth measure F4 that is the average amount of delay for each aircraft delayed fifteen (15) minutes or more is defined as the F4 measure:
F4 = Sgi (7)
with gi = S πj, i[πj, i> 15]
S πj, i> 15]
The fifth measure F5 is the percentage of aircraft that has always greater than 15 minutes.
F5 = Sci
where ci = 100 S[πj, i> 5]
1 <j <ni .(10)
The metrics F1 through F5 were computed for the arrivals and departures of the 4 airlines in the airport. Short definitions of each metrics are listed below(see appendices for tables 1 8):
Table 9 Summary of Delay Metric definitions
Source: Federal Airports Authority of Nigeria
Table 10: Basic metrics for all Aircraft that arrived at the Airport by the 4-airelines Arrivals
Source: Federal Airports Authority of Nigeria
Table 11: Basic Metrics for All Aircrafts That Departed the Airport by the 4 Airlines.
Source: Federal Airports Authority of Nigeria
derived from the complete data set, which includes all the traffic from the 4 airlines over a 14 day period. Fig 1 shows the percentage of aircraft as a function of departure and arrival delays. For instance, the first flight coloured bar shows the percentage of arrivals that had more than 10 minutes of delay. The first solid bar shows the percentage of arrivals that had more than 10 minutes of delay. The second set of bars shows the percentage of aircraft that had more than 15 minutes of delay.
Observation from the figure shows that a slightly greater percentage of aircraft encounter arrival delay between 10 minutes and 30 minutes than experience departure delay. This may be due to those aircrafts that experience departure delays, which propagated through to become arrival delays. I should be noted that the difference between the percentages of delayed departures and arrivals is seven implying that some of the delay originates before departure.
Fig 1: Percentage of Aircraft as a Function of Departure and Arrival Delays
Fig 2 shows the average number of departures out of the air-port by the 4 airlines as a function of the day of the week. To create the bar chart, the number of departures from the airport by the air lines were summed up for one day of the week (for instance Tuesday) and divided by the number of such days (number of Tuesdays in the 14 days data set).
The bar chart shows that traffic is less on Thursdays and Saturdays. It should however be noted that the difference between the minimum traffic on Thursday and Saturday and the minimum traffic on Tuesday is only 4.0%.
Fig. 2: Average Number Of Departures Out Of The Air-Port By The 4 Airlines As A Function Of The Day Of The Week
In fig 3, it shows for each day of the week in the 14-days data set, all departures from the airports by the 4 airlines that were delayed by more than 15 minutes. The average percentage of aircraft delayed by more than 15 minutes was found to be 5.1% observe that although the traffic volume is low on Thursday (fig 2), the percentage of delayed aircraft in fig 3 is high on Thursday.
Fig. 3: Departures from the Airports Delayed By More Than 15 Minutes
From the performance metric parameter it was observed that aircraft for airline A, 13.4 minutes for airline B, 15.5 minutes for airline C and 8.4 minutes for airlines D. These delays occurred before arriving at their scheduled destinations. These delays were as a result of unfavourable conditions, such as heavy rains, winds, low visibility, haze, fog, etc.
There is also have take off delay, which is caused by tower by not giving clearance on time for engine start. While arrival delay can also occur enroute to the port destinations as a result of low and thick clouds, which makes the pilot to take right of course or left of course, descend or ascend. Before the pilot can do any of these things, clearance has to be gotten from the tower. If there are other aircrafts waiting, the pilot has to stand by. Eventually, time is lost as a result of all these little things, causing arrival delay.
On the other hand, from the parameters it was observed that the percentage of aircraft departing alter than 15 minutes were 25%, 30%, 50% and 5% for airlines A, B,C and D respectively. Wherever an airline experiences arrival delay, automatically there would be departure delay. Departure delay can also occur when the pilot in command intentionally delays in order to carry a full load. In a situation like this, he wants to make more money for the airline and in turn get an increased salary. Also the tower, he might be delayed as well. On the runway, there can be a situation whereby 4 or 5 aircrafts want to take off. Taking off has to be done one after the other. In this case delay occurs. Traffic congestion comes into a play.
Conclusion and Recommendation
It has been found out that delays actually occur to aircraft due to deviations actual aircraft arrival and departure time from the scheduled flight time.
To reduce the level of airport delays due in Nigeria, the efficiency of the airport system must be improved which should be a joint venture between the airport authorities and individual airlines.
With the contribution and co-operations of the airport authorities and the airline operators, transport managers and planners and the government, optimistic belief that if all the recommendations suggested above are strictly implemented, it would help in solving the airport delays, at the airport.
Bjorn Syren (2003), Delays report over ACARS; published in SAS data-link system
Bureau of Transportation Statistics (BTS) (2002)
FAA (2001), Aviation Delays in 2000; a publication of Federal Aviation Administration, USA. January 31.
FAA (2001), Air delays will continue; published in weather COM of Federal Aviation Administration, USA, February 3.
FAA (2001), OBNET database; a publication of Federal Aviation Administration
FAA (2002), Monthly Summary of Air Traffic activity and Delays in the National Airspace System; a publication of Federal Aviation Administration, USA.
FAA (2002), Domestic Airline Operation in Nigeria; published in the Newsletter of Federal Airport Authority of Nigeria, May 16.
Ohuegbe, S.C. (2005), Delay study in airline passenger service delivery; undergraduate project submitted to the Department of Transport Management technology, FUTO, Nigeria.
Paul, T.R , Lisa A.S. and Leonard, A.W (2001), Flight connections and their impacts on delay propagation; MITRE Corporation, Mclean, VA22102.
Rebecca, B. James, B., Melissa, M.C. and Chris, R. (2001), Transportation is the major source of noise impact; the major stationary noise sources are the diesel power; modeling airline economics: airline decision making in a hub and spoke environment.
Weather Depotstm (2005) Airport Delay forecast information.
Table 1: Arrival Statistics For Airline A
Table 2: Departure Statistics for Airline A
Table 3: Arrival Statistics For Airline B
Table 4: Departure Statistics For Airline B
Table 5: Arrival Statistics For Airline C