Saken har vært omtalt tidligere, men er her bedre forklart. Dette vil kreve "station keeping" software, at flygerne er med på dette, og nye regler for lufttrafikktjenesten. Ubemannede fly utvikles nå som er ment å fly i formasjon med bemannet jagerfly; ref. Loyal Wingman prosjektet til Boeing. (Red.)
Why passenger jets could soon be flying in formation
Slutsken, CNN • Published 15th September 2020
(CNN) — Birds
are the undisputed masters of aerodynamics.
No
matter how many supercomputers and wind tunnels scientists throw at solving
flight's thorny calculations, they'll never match the perfection of airborne
avians.
A
focused peregrine falcon diving on its prey, a pair of feisty hummingbirds in a
territorial dogfight, or a huge albatross soaring effortlessly for days over
the ocean are the envy of aerodynamicists and pilots.
The airborne cacophony of a huge flock of geese, honking away while flying in a perfect "V" formation, is a wonder to see and hear.
Those
formations have also provided the inspiration for researchers at Airbus UpNext,
the aircraft manufacturer's future-flight demonstration and technology
incubator.
As
far back as a century ago, avian scientists began to understand that birds were
increasing aerodynamic efficiencies by flying in close formation, taking
advantage of the changed airflow in each bird's wake.
With
that in mind, the Airbus fello'fly flight demonstration project will fly two
large commercial aircraft in formation, looking to mimic the energy savings of
our feathered friends.
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Building
on test flights in 2016 with an Airbus A380 megajet and A350-900 wide-body
jetliner, fello'fly hopes to demonstrate and quantify the aerodynamic efficiencies
while developing in-flight operational procedures.
Initial
flight testing with two A350s began in March 2020. The program will be expanded
next year to include the involvement of Frenchbee and SAS airlines, along with
air traffic control and air navigation service providers from France, the UK,
and Europe.
"It's
very, very different from what the military would call formation flight. It's
really nothing to do with close formation," explained Dr. Sandra Bour
Schaeffer, CEO of Airbus UpNext, in an interview with CNN Travel.
Free Lift
Birds fly in a "V" formation to
increase aerodynamic efficencies.
PATRICK PLEUL/DPA/DPA/AFP via Getty
Images
An
aircraft in flight sheds a core of rotating air from the end of its wings,
known as a "wingtip vortex."
Extremely
powerful vortices -- especially those generated by a large aircraft -- have
been known to flip smaller planes that have encountered the horizontal tornado
of air streaming behind.
Avoiding wake turbulence is part of a student pilot's curriculum, as it will be in the fello'fly demonstration. "Pilots are trained to not fly into the vortex of a preceding aircraft," said Bour Schaeffer, an experienced flight-test engineer.
"They
will be 1 1/2 to 2 nautical miles away from the leading aircraft, and slightly
offset, which means they are on the side of the vortex. It's no longer the
vortex, it's the smooth current of rotating air which is next to the vortex,
and we use the updraft of this air."
Taking
advantage of the free lift in this updraft of air is called "wake-energy
retrieval." Bour Schaeffer says that upcoming flight trials using two A350s
could prove that on long-haul flights, fuel savings of between 5% and 10% may
be achieved, "which is an enormous number. This is the reason why we want
to accelerate it. It is not a product today, but it is something we strongly
believe in."
Millions of years
While
it may seem simple to just watch a flock of birds to figure out the
aerodynamics of their energy-saving flight, it really isn't.
"Birds
have been doing this for millions of years, but the disadvantage we have is
that we can't do controlled experiments very easily," said Dr. Charles
Bishop, of the School of Natural Sciences, Bangor University, in Gwynedd, Wales.
Airbus's fello'fly project tries to mimic
the energy savings of birds' "V" formation.
Airbus
However,
Bishop cited a landmark 2001
paper in weekly
international journal Nature by Henri Weimerskirch, where the researcher and
his team had access to tame pelicans -- known in the birding community as the
best at formation flight, even better than geese or swans.
"Their
study is technically the only one that shows direct evidence of energetic advantage
rather than theoretical calculations in aerodynamics."
Weimerskirch
was able to put heart rate monitors on the birds, and according to Bishop, the
trailing pelicans in the formation clearly saved energy.
"They
had a 14% drop in heart rate, and they also glided more. They were finding it
easy [to fly] with this aerodynamic advantage."
Talking about followers
: we are teaming up with @flyfrenchbee @SAS @DGAC #DSNA @NATS and @eurocontrol, to show how our #fellofly demonstrator can fly 2 aircraft safely together, reducing fuel burn to contribute to the industry’s #sustainability goals. fly.airbus.com/3k2iHAx
Check video here: https://tinyurl.com/y3yfe3w4
Practical challenges
And just like the pelicans, the pilots of
the trailing A350 in the fello'fly test will position the aircraft to optimize
the effect of the upwash -- but that points to one of the challenges facing the
research team.
"You
can't see the wake, so you just can't say 'Ah, I'm in the right spot,'"
said Bour Schaeffer. "We need to provide assistance to the pilot to
position the aircraft properly."
Once in the upwash, autoflight systems will be required to maintain the correct position, reducing the workload on the pilots and ensuring a smooth ride for passengers by avoiding the more turbulent components of the wake.
Procedures
to enable the two aircraft to coordinate their position will be tested -- much
like during an aerial refueling mission.
"We
need to make sure we can do the joining safely. We will have no compromise on
safety, whatsoever," said Bour Schaeffer.
Once
the wake energy retrieval concept is proven out, operational and financial
considerations will still have to be solved.
According
to Bour Schaeffer, air traffic service providers and government aviation
agencies will need to be convinced to change regulations to allow for much
closer aircraft separation standards than what are currently in place.
Flight
planning procedures will have to be developed for planes to match routes with other
aircraft, along with positions and altitudes to begin a formation flight.
And a
process to share the savings in fuel costs amongst airlines will be a priority.
"We
know there are questions. Our aim as a demonstrator is to find answers to those
questions."
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