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The Gantt Chart

The main device used in IOCs has been and still is the Gantt chart, named after its founder, Henry Gantt (1861-1919) who created the tool to assist in planning major infrastructure projects.1 Numerous vendor suppliers have created and developed aviation-related operations tools, mostly based upon the Gantt chart as its clear displays and copious amount of critical information benefit the viewing, interpretation and manipulation of the flight schedules in a dynamic environment. Information contained within them varies considerably, subject to the airline’s specifications and the vendor’s capabilities, and there is usually a series of parameters that can be modified by the users such as adapting time scales to suit own preferences, colours and levels of detail, zoom capability, data filtering and

Representative Gantt chart sorting, and several other navigation features

Figure 4.1 Representative Gantt chart sorting, and several other navigation features. Control and functionality over the Gantt chart normally resides within the IOC, but viewing ability is extended to numerous departments to enable greater awareness of the day of operations. Figure 4.1 presents a representative Gantt chart. In Part II of the text, the Gantt charts will appear larger and in more detail, to support the description of each scenario and enable ready inspection.

Understanding the Gantt chart

The purpose of the chart for operational use is to provide a comprehensive means for displaying the airline’s fleet and schedules across a time period. To do this, a matrix structure depicting the airline’s flight schedules is built. The schedules are represented by a series of individual blocks (sometimes known as ‘PUKs’), which are organised according to departure and arrival times. The fleet of aircraft is displayed on a vertical axis (usually sorted primarily by aircraft type, then further sorted by aircraft registration or tail number). The larger the fleet, the greater the scrolling required to view all of the aircraft. One or more time scales (e.g., UTC/Zulu time or local time as preferred by the user) are sequenced across the horizontal axis. For some airlines, displaying the flights according to the time zone of the IOC’s location (e.g., London, Melbourne, Toronto) may be more useful to Controllers within the IOC as they can relate timing of events anywhere in the network to their own location and circumstances. In this case, the flight blocks display local departure and arrival times, but may be positioned according to the time zone of the IOC’s location, as shown in Figure 4.2. Note that for the sake of clarity, the times shown on all Gantt charts throughout the text are rounded to the nearest five minutes. In practice, the scheduled times are subject to (and therefore shown as) specific minutes (e.g., 0738) based on slot or other agreed times.

In contrast, flag or international operators conventionally display flights according to UTC times, as shown in Figure 4.3. An advantage of this standardised approach helps to alleviate any confusion across the network or when communicating with other personnel around the world.

Some systems enable both UTC and local times to be displayed, for ready recognition and mentally adapting communication as appropriate. The ability for individuals to set their own preference emphasises the flexibility needs for designing the software. The series of blocks over a chosen time period (e.g., from a few days to a few weeks) will form each aircraft’s line of flight schedules. The schedules will be grouped by aircraft type and then chronologically positioned according to the desired time scale.

Flight blocks positioned according to IOC time zone

Figure 4.2 Flight blocks positioned according to IOC time zone

Flight blocks positioned according to UTC time zone

Figure 4.3 Flight blocks positioned according to UTC time zone

The advantage of positioning flights according to departure and arrival time informs Controllers’ awareness of the status of flights and assists in their ability to readily identify common operating times, common ground times and other features, any of which may facilitate disruption management. The length of each flight block (horizontal measurement) on the display is governed by the duration of the scheduled flight. For example, a one-hour, short-haul flight between two ports will be represented by a relatively small block. In relation to a predominantly short-haul operator, several such blocks will form each flight pattern usually within a day of operation or extending overnight for ‘red-eye’ (or ‘back of the clock’) flights. Examination of the patterns reveals the high number of flights located in a tightly knit sequence, reflecting the levels of complexity common to domestic or short-haul carriers. Figure 4.4 presents an example of a short-haul operation on a Gantt chart.

In contrast, a block representing, say, a 16-hour long-haul flight will span extensively across the display. In the case of a predominantly long- haul operator, several of these types of operations will traverse a number of days on the display. Figure 4.5 presents an example of a long-haul operation on a Gantt chart. Note the compressed time scale.

On most Gantt displays, identifiers denoting the aircraft registrations/ tail numbers and blocks representing the line of flying per aircraft are similarly colour coded to facilitate easy identification for the user. So, for example, the registrations/tail numbers and flight blocks of one type of aircraft may be coloured blue, another type coloured green, and another perhaps coloured grey (in this text, shading differentiates the aircraft types).

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