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Irregular Operations (IROPS)

Despite the rigorous planning that precedes a day of operation, there are innumerable factors that challenge the integrity of the schedule. Some disruptions are very minor in themselves, and can be absorbed and often isolated quite readily, with little or no ongoing effect to the greater schedule. More often than not, though, disruptions are not as neat and simple. Many times, they can be frustrating for Controllers as seemingly trivial issues (e.g., lost paperwork, flat aircraft torch battery, lack of crew meals) cause delays every day to every airline. But typically, problems tend to become quite complex, and frequently have far-reaching effects, both with regard to the day of operation, and often with roll-on effects into the next and subsequent days. For example, a significant problem with an international fleet operating long-haul may take four to five days for the schedules to be fully recovered and aircraft returned to their planned patterns. There may be immediate indications such as delays, diversions, threatened curfews, stranded passengers, aircraft out of position, crews both out of position and out of duty hours, and there may be an emerging series of consequences, largely unforeseen (as illustrated in this real case scenario).

What may begin seemingly as a simple issue (e.g., high-speed tape required for a cockpit window seal - a fairly straightforward maintenance issue), can translate into several consequential actions. In this example, the procedure required a sign-off from the aircraft manufacturer to approve the aircraft to operate. Due to the tight aircraft patterns (i.e., numerous flights with short ground or turn times) and to minimise a probable delay while this approval was being organised, a subsequent aircraft change was made to protect the schedule (using the same aircraft type), but resulting in a heavily fuelled aircraft (initially intended to operate a long-haul flight) being committed onto a short-haul sector. The Operating Captain of this short-haul sector advised that this aircraft was now overweight for landing due to the swap, necessitating either a defuel (involves recalling the fueller - if and when available, and then a lengthy process to defuel) or an offload of passengers and baggage (involves selecting passengers to offload based on class of travel, loyalty level, or some other method). Either way, a further delay resulted.

Not only may isolated disruptions propagate across a number of flights, but ironically several disruptions often tend to occur simultaneously, resulting in a vastly more significant network-wide effect. The IOC then becomes a hive of activity as the expertise is called upon to manage the situation. The approach by the IOC for managing the disruption is subject to the timing of problems, and likelihood of their emergence as threats to the schedule. These factors can be categorised according to risk; is there a likelihood of occurrence? If there is, what is expected to occur and when? What is happening right now? What has already happened that needs IOC attention? What resources are needed both now, and in the future? These and other issues are explored further below.

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