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Greening Aviation – Not as Simple as it Sounds

According to recent research conducted by the University of Reading in the UK, many tonnes of fuel could be saved by airlines, (and therefore many tonnes of greenhouse gases) if they planned to always fly in favourable winds whilst crossing the Atlantic.

The study found that commercial flights between New York and London last winter could have used up to 16% less fuel if they had made better use of the fast-moving winds at altitude.

New satellites will soon allow transatlantic flights to be tracked more accurately while remaining a safe distance apart. This opportunity could allow aircraft to be more flexible in their flight paths, in order to more accurately follow favourable tailwinds and avoid headwinds, offering the aviation sector a cheaper and more immediate way of cutting emissions than through advances in technology.

The report stated: “Current transatlantic flight paths mean aircraft are burning more fuel and emitting more carbon dioxide than they need to”.

“Although winds are taken into account to some degree when planning routes, considerations such as reducing the total cost of operating the flight are currently given a higher priority than minimising the fuel burn and pollution.”

Boeing 747-400 pulling Contrails at high altitude. This fabulous photo was taken by Sergey Kustov

This needs to be put into context.

Way back in time, I used to create flight plans professionally. This was done by hand and was sometimes quite time consuming, and required careful study of aeronautical charts, upper air weather, including icing levels, and any forecast areas of turbulence.

A Transatlantic Chart showing the Entry and exit waypoints for the North Atlantic Track System

The charts would also be checked to see the locations of forecast Jetstream activity.

A quick explanation here about Jetstreams.  Jetstreams are caused by two factors. Firstly, solar heating, which causes massive air movements, combined with the effects of the earth’s rotation (The Coriolis Effect).

Image courtesy of NASA

At lower levels, these air movements are known as Trade Winds, and two hundred years ago, clipper sailing ships used them very effectively to transport goods relatively quickly around the globe, hence the name.

Most weather phenomena is generated in the troposphere, which extends from the surface up to high altitude (30’000 feet at the poles, and 56,000 feet at the equator), and it is at these upper levels that we find the jetstreams.

Jetstreams are defined as winds with a minimum speed of more than 70 knots (80 mph), and often they may exceed 220 knots (250 mph) and so it makes economic sense to make use of them.

This has been recognised by the aviation airspace regulators, and specific routings that take advantage of the jetstreams have been in place for many years.

Typical Jetstream activity over Euope.

Each night, weather data for trans-oceanic flights is analysed, and tracks are optimised to use the flows sensibly.

Flights crossing the Atlantic use a system known as NATS (North Atlantic Track System). In simple terms, a number of tracks are generated for both easterly and westerly traffic that will enable aircraft to benefit from a tailwind, or at least a reduced headwind.

These tracks will move north and south over the Atlantic according to the weather and the predicted positions of jetstreams; sometimes tracks will start to the north of Scotland, and terminate in the far north east of Canada.

On other occasions tracks will run to the south of the UK, and cross the southern part of the north Atlantic joining the continental air route systems as far south as the Canadian/US Border.

Typical NAT Tracks. Westerly tracks, showing available flight levels for each alphabetically-identified track.

So, flights across the Atlantic already have some basic fuel saving principles built in advance. The same system operates for flight crossing the Pacific Ocean, known as PACOT tracks.  They run between the western seaboard of the USA and Japan and Asian destinations.

However, times move on, and grey-haired aviation expertise has been replaced in almost every arena with technology.

Modern computer-based flight planning systems are extremely sophisticated, and use some advanced algorithms to plan with even better accuracy.

Consider this.

Every nation has the right to charge a fee to every aircraft that uses its airspace. Airspace charges may be based on the time that the flight remains within that state’s territory.

So, modern flight planning systems will look at every aspect of the flight. It will perform calculations that compare fuel burn with overflight charges.

Sometimes, whilst flying in a Jetstream will burn less fuel, it may mean that the flight will pass through airspace with relatively expensive overflight charges. If the overflight charges amount to more than the cost of fuel, then the system will plan to use the cheaper route, and therefore save money overall.

Airlines also use a system known as Cost Index to further optimise the flight costs.

This is basically a system that compares the direct operating costs of the flight, with the cost of the fuel being used. If the direct operating costs (crew wages, navigation charges, cost of galleys and airframe hours – affecting the amount of maintenance required) are more than the cost of fuel, the system will plan to fly faster, burning more fuel in order to get on the ground faster. Conversely, if the fuel is more expensive than the direct operating costs it makes sense to fly slower, burning less fuel.

Airlines are extremely cost conscious, and low-cost carriers will do everything they can to reduce and eliminate costs wherever possible. For example, Ryanair removed paper safety cards as they wear out and need replacing. Now, their safety information is riveted to each seatback.

Ryanair Boeing 737 – and Safety Cards riveted to the seatbacks!

Some carriers do not serve peanuts, as if they drop into the seat mounting rails, they take time to remove, and time is money.

So, persuading airlines to always optimise their routes and use high speed Jetstreams to the fullest extent may take some time.

Stay Safe…