Navigating highways in the sky

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Good preparation is half the battle won. Nowhere is this more true than in flight planning. 

To the average passenger, flying might seem like a straightforward journey across the sky from point A to point B. Behind the scenes, however, countless variables must be taken into account to ensure that each flight is operated safely, economically and in compliance with complex rules and regulations.

The process begins with route planning, which is completed months before launch in response to commercial demand. Most flights operate along airways, or invisible corridors in the sky, which consist of a series of waypoints along the route.

“Airways can be bi-directional or unidirectional, and there may be altitude restrictions. Some are available only at given hours of the days, and some have specific communication or navigation requirements. This means there are plenty of optimization opportunities for airlines,” explains Antti Koskiniemi, who oversees Finnair’s flight planning. His job is to ensure that “every Finnair flight, every day” operates as efficiently as possible.

“We normally plan the most economical available route that keeps flights on schedule. Often the shortest flight time means the lowest fuel consumption and is thus the most economical. Not always, though, because overflight navigation charges vary in different countries,” he adds.

Each sovereign state has authority of the airspace over its territory and can freely determine its navigation charges. The state in question may furthermore require overflight permits. Obtaining such permits is often a laborious, time-consuming task that cannot be accomplished at short notice.

Music of the runways

The amount of care and forethought invested in route planning also goes into preparing each individual flight plan, which is normally completed about two hours before take-off. This is a standardized job for which airlines have a dedicated staff called flight dispatchers. Finnair flight dispatcher training is much like that of pilots, taking between six and nine months.

“Some people describe flight dispatchers as an extra crew member on the ground. I prefer to think of them as the music-writers and the pilots as the musicians,” describes Koskiniemi.

The flight dispatchers ensure that take-off is possible for the particular aircraft in question, at its specific weight and in the prevailing weather conditions – which involves highly complex computerized calculations.  The pilots then repeat the same calculations just before take-off, taking into account any last-minute changes in runway conditions.

“We can prepare for a thunderstorm that is forecast to break in a few hours, but we cannot be sure it will occur at the exact time it is predicted. There is always a gap between forecast and actual conditions. It all depends on the readings from the air traffic control tower and the actual conditions on the runway during taxiing. Last-minute adjustments are always possible, and these are normally done by the flight crew.”

Gross weight at take-off is a critical factor, notes Koskiniemi.  Acceleration is slower if the aircraft is heavier, which means it needs a longer runway to accelerate to flying speed. Safe take-off depends on a combination of variables such as runway length, aircraft technical status, wind, temperature, air pressure and contaminants on the runway.

“We have to prepare for every eventuality. If, say, a bird collides with the aircraft and we lose an engine, we have to ensure that we can safely abort and stop on the remaining distance of runway, or alternatively continue take-off with one engine out.”

Cargo never complains

Planning a cargo flight is more flexible than a passenger flight, reveals Koskiniemi. “With cargo, you can make technical stops to refuel. But with passengers, time is of the essence because of connecting flights. The convenience of the travel experience is paramount but cargo doesn’t complain about minor delays.”

With cargo flights, the chief objective is maximizing payload. “A wet runway after a thunderstorm limits the aircraft’s take-off weight. It doesn’t reduce acceleration, but it does reduce braking action in the event of an aborted take-off, hence you need to reduce weight. With a passenger flight, offloading cargo might be needed to lighten the weight just to stay on schedule, but with a cargo flight, it is possible to wait for the runway to dry.”

Text by Silja Kudel

Published May 20, 2013

Category: Finnair Cargo

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