… / Smarter skies / Aircraft in free flight and formation along ‘express skyways’

Express skyways

In the future, highly intelligent aircraft would be able to “self-organise” and select the most efficient and environmentally friendly routes (“free flight”) - making the optimum use of prevailing weather and atmospheric conditions.

High-frequency routes would also allow aircraft to benefit from flying in formation like birds during cruise bringing efficiency improvements due to drag reduction and lower energy use.

Free-flying south for the future?

Take in the birds-eye view as your intelligent aircraft flocks in formation, mapping the best route along express flyways.  Welcome to a new skyway code.

Today, the term "direct flight" is something of a misnomer.  While borders have fallen at ground level, the same can’t be said for the skies above. As flights transit a patchwork quilt of international airspace they are passed between disparate air navigation service providers and diverted into sets of air corridors.

The result is circuitous, zig-zag flight patterns.  And the more time in the air, the greater the chance of delay, with both leading to unnecessary fuel burn and emissions.

However, what if the skies were stitched into one seamless blanket?

Aircraft could navigate more directly and thus more quickly, efficiently and safely from Point A to Point B through optimal gate-to-gate flight paths or express flyways. Huge efficiencies would come from flying less track miles through optimal "gate-to-gate" flight paths.  On an Airbus test flight from Brussels to Stockholm, a 20-minute gain meant fuel savings of 725 kg., in turn reducing CO2 emissions by 2,283 kg.

In addition, a generation of intelligent aircraft could use 4D navigation capability to self-select the most efficient route, making optimum use of prevailing weather, atmospheric conditions and each other. Just as birds heading south for the winter save energy by flocking together, formation flight can also boost the efficiency of commercial aircraft.

Trailing planes can effectively "surf" on the energy coming from the wing tip vortices of the preceding aircraft.  This reduces drag, which increases fuel efficiency and minimises engine emissions.

Flights to and from similar geographic areas could rendezvous in mid-air before continuing their journey.  For example, trans-Atlantic departures from San Francisco, Los Angeles and Las Vegas to the UK might meet over Utah and fly to England in formation. This also would offer the potential to streamline air traffic control workload by treating each flock as a single entity while in cruise.

It won’t take the wing-tip precision of the Red Arrows or Blue Angels either.  A safe flight separation of about 20 wingspans – far less than the four nautical miles that separates civil aircraft today but still over 1 nm – is sufficient to reap the benefits.

How will it work?

In a V formation of 25 birds, each can achieve a reduction of induced drag by up to 65 per cent and increase their range by 7 per cent.  While efficiencies for commercial aircraft are not as great, they remain significant.

Airbus is continuing to assess the feasibility for future operations, including studies in collaboration with Bristol, Cape Town and Stanford Universities. The study with Stanford was borne out of a proposal on the subject from its students that reached the final of the Airbus Fly Your Ideas challenge in 2009.  It employed simulation and aerodynamics analysis to explore the optimum number of aircraft in several configurations or geometries.

These included a two-aircraft formation, three-aircraft "skein" (the symmetric V-shaped formation associated with geese and ducks), an inverted-V and echelon formation.  The results suggest fuel burn savings of 10-12 per cent are possible, with emissions cut by up to 25 per cent.

Airbus already is looking into cooperative flight scheduling and conducting research into aircraft stability and control.  In parallel, a new breed of sensors able to detect the wake of the previous aircraft and rapid state changes must be developed. Avionic technologies already make this possible in principle.  Lightweight remote sensing equipment such as LIDAR (Light Detection and Ranging) and Infrared cameras allow aircraft to detect the wake vortex – which is the turbulence produced by an aircraft in flight – of those ahead.

For aircraft to autonomously keep station, they will need to communicate with each other.  High-speed, real-time computation, communication and coordination would take inputs from all sources in the air and on the ground.  High bandwidth telecommunications would cope with the increase in data being transferred around the network.

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Did you know?

"We surveyed over 10,000 people around the world who will be passengers in 2050 to ask what they want from the aviation industry in the future.

Their message was clear – we need to help as many people as possible share in the benefits that air transport brings, but we need to achieve this while looking after the environment."

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