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Home GreeniacsArticles Automotive Airline Industry
Written by Rishi Das
Tuesday, 08 July 2014
Airline Industry
Every year, more than 732 million passengers take to the skies in the United States alone to
experience the miracles of flight.
1
Trafficking passengers at speeds in excess of 500 miles
per hour, modern air planes have made expedited travelling possible on a monumental scale.
Through the years, improvements in airline safety and technology have streamlined this
mode of transport, granting greater accessibility to millions around the world. While the
growth of the aviation industry is certainly improving connectivity and contributing to the
flattening of our world, the gargantuan scale of aircraft emissions certainly is not. On an
international flight, a Boeing 747 jumbo jet's four engines consume 1 gallon of fuel per
second,
2
amounting to a 36,000 gallon fuel use in a 10 hour flight. Therefore, just 1
international flight can amount to the release of 759,600 pounds of carbon dioxide
(CO
2
) into the atmosphere.
3
A sustainable environmental solution to flight is needed that
optimizes sustainable fuels with practical speed of travel, and several considerations are
needed in forwarding green aviation: management, design, alternative fuel, and propulsion.
i
Airline Industry Management
One of the best ways to reduce greenhouse gas emissions from aviation is to search
as far upstream as possible for preventative measures which minimize fossil fuel usage
in the first place. Improving information technology to prevent delays in landing is an example
of such a preventative measure because this decreases fuel usage. If an aircraft is forced to
standby in the air due to the lack of air traffic management, cumulatively there is a great deal
of fuel expenditure. A great way to improve aircraft management are technologies designated
as Required Navigation Performance (RNP), which include a wide range of navigational
equipment and data systems that help track aircraft position and optimize air traffic
management.
4
It is estimated that basic RNP implementation can save $5 - $10 billion dollars
in fuel costs annually.
5

Another management approach known as Continuous Decent Approach (CDA) may also
hold great prospects in minimizing unnecessary fuel loss during landing. Typically, a pilot's
descent profile involves losing altitude in gradual phases that involving descending,
maintaining altitude, and descending again. This stepwise approach tends to be wasteful in
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Turning off the tap when brushing
your teeth can save as much as 10
gallons a day per person.
ii
fuel since maintaining an altitude requires a moderate amount of engine power. CDA is a
strategy currently being investigated which aims to make use of information technology to
allow pilots to gain clearance for long and continuous descents that do not require altitude
plateaus. Studies conducted by Airbus have indicated a 10% increase in fuel efficiency
during landings if CDA is implemented.
6
Aircraft Design
Weight is the number one economic
concern of flying, so at least this factor is
in line with environmental considerations!
Many research ventures are seeking to
implement a lower weight design that
increases wing lift efficiency. Our previous
example of a 10 hour international flight
using 36,000 gallons of jet fuel needs to
carry 1,133 tons of fuel weight alone for its
journey.
7
Fuel literally weighs tons—this is
also the reason why hypermilers
choose to only fill up their car gas tanks
half way when they go to the gas station! Therefore, minimizing weight in order to maximize
fuel efficiency is a prime concern in aviation. Most modern aircraft today are made up of
aluminum alloys
8
that are fairly cheap, lightweight and strong. With the advent of even more
modern composite materials such as graphite-epoxy, which weigh even less while maintaining
the same strength of aluminum, there is a great push to build as much of the aircraft out of
composites as possible. A notable example of an aircraft making headway with composite
building is the Boeing 787, which makes use of a 50% composite fuselage structure.
9

Apart from the material, there is the design itself that maximizes lift efficiency of the wing while
minimizing drag. A very simple way of maximizing lift would be to increase the wing surface
area, and Boeing has managed to follow suite with the X-48B prototype that incorporates the
wing into the entire fuselage granting better fuel efficiency and load capacity.
10
The catch,
however, is a much lower airspeed due to a larger wing that is prone to being effected by air
resistance. The X-48B amazingly only has a top speed of 139 miles per hour, a speed
attainable by any roadway-using sports car. Airbus has also had a stab at revolutionizing
green transport with their current NACRE (New Aircraft Concepts Research) Pro green
aircraft featuring a large span upswept wing and a U-Shaped wing that also aims for greater
efficiency but with much slower speeds as well.
11
A prototype by MIT remarkably makes use
of a different approach to large wing spans and larger tails by using a design philosophy that
is completely opposite. Known as the double bubble,
12
the aircraft uses small wings and a
smaller tail than a commercial aircraft along with a fuselage that is composed of two partial
cylinders. Instead of a larger wing and tail, the double bubble makes use of a wide fuselage
to act as an additional wing, thereby increasing overall lift.
13
The concept not only
dramatically increases cabin space, but makes the passenger cabin functionally integral to
the aircraft.
On top of good ground-up design from the drawing pad, smart technology incorporated in an
aircraft could potentially work wonders in making air travel more environmentally sustainable.
One of the key requirements for flight is smooth, laminar airflow over the wing that makes
Bernoulli's principle
14
possible. The smoother the flow, the greater the lift that is generated
from the pressure differential created by differences in flow speed between the top and
bottom of the wing. NASA in conjunction with Boeing last year released a remarkable
technology known as Active Flow Control
15
which makes use of computer controlled
actuators to direct the airflow on the wing to be as efficient as possible. By blowing air over
the wing in a controlled fashion, Active Flow Control helps minimize turbulent air flows over
the wing, thereby maximizing lift efficiency on any wing design in which it is incorporated.
Type of Fuel
Fossil fuel based jet fuels such as Jet-A and Jet-B
16
that are compositionally similar to
kerosene are a major culprit in aerospace emissions. Therefore, alternative fuels are of
prime importance for the future of commercial aviation. One concept that is being thoroughly
investigated is plant or algal based aviation biofuels that are produced from the chemical
modification of non-food crop into combustible jet fuel. With the benefits of reducing carbon
dioxide emissions, aviation biofuels can be far more sustainable than non-renewable fossil
fuels, provided the proper land and crop management needed for such an undertaking. In a
study conducted by Boeing, scientists made use of a naturally oily and non-edible
jatropha,
17
native to Asia and Latin America, to manufacture biofuels for military aircraft.
Biofuels are a very practical option for promoting environmental sustainability for commercial
aviation because they can be blended with current aviation fuels, and no modifications to the
aircraft are needed to combust biofuels.

ii
Several long term options still in development may hold the answer to future requirements for
greener aviation. Solar energy has made great headway in powering homes and
automobiles, and similarly solar energy may be used to power tomorrow's commercial
aircraft.
18
Instead of powering a car engine, solar cells could be designed to power electric
turbines in aircraft engines for indefinite periods of time as long as there is abundant sunlight
in the upper atmosphere. As it stands now, however, solar cells could probably power a
single seater aircraft at unremarkably slow speeds. Much research is needed in creating
efficient solar cells that can provide very high power outputs for commercial aviation.
Propulsion
Another approach to reducing fossil fuel emissions from commercial aircraft involves making
the beating heart of the aircraft—the engine—more efficient. Most commercial aircraft in our
skies today run on turbofan engines, a type of gas turbine engine that uses a system of
compression blades to compress air and ignite fuel in order to create a propulsive jet stream
in the back of the engine.
19
The bypass ratio of a turbofan engine is a simple metric that
compares the ratio of air flowing around the fans and into the fans themselves. While the
mechanics of a turbofan are quite complicated, overall a high bypass engine can significantly
increase fuel efficiency on a commercial airliner.
NASA, in conjunction with engine manufacturers, are currently investigating ultra high bypass
engines
20
that could increase fuel efficiency as much as 30% based on several design
guidelines being investigated. There are also several other approaches being investigated to
improve turbofan technologies. GE Aviation is currently developing a fuel saving engine
making use of specialized valves to direct a third stream of air through the engine.
21
The
intricate system of valves is claimed to increase fuel efficiency as much as 25 percent. Pratt
and Whitney, another notable engine manufacturer, has developed a geared turbofan
engine that seeks to increase fuels savings by 9 percent.
22
A typical turbofan engine runs
optimally when the fan blades are spinning slower than the compressor blades.
23
The
geared turbofan succeeds in achieving this feat to a greater degree with the use of a system
of gears.
Airplanes are continuing to become a major source of transport related emitters, and
numerous future technologies are showing promise in making flight a far more sustainable
enterprise. A significant improvement in the environmental friendliness of aviation, however,
will rely upon the cooperation and open communication of both the private and public sector
in prioritizing environmental considerations for future implementation. As more of the world
turns to aviation for connectivity and transport, the drive for fuel efficiency will continue to be
a powerful driver to address the environmental and economical considerations of flight.
Browse all Greeniacs Articles
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1
http://www.faa.gov/news/press_releases/news_story.cfm?newsId=13394
2
http://science.howstuffworks.com/transport/flight/modern/question192.htm
3
http://www.eia.gov/environment/emissions/co2_vol_mass.cfm
4
http://www.strategyand.pwc.com/media/file/Future_of_Green_Aviation.pdf
5
Id.
6
Id.
7
http://www.convertunits.com/from/36000+gallon+[U.S.]+of+aviation+gasoline/to/ton
8
https://howthingsfly.si.edu/structures-materials/materials
9
http://www.boeing.com/commercial/aeromagazine/articles/qtr_4_06/article_04_2.html
10
http://www.boeing.com/news/frontiers/archive/2012/december/index.html#/20/
11
http://www.airbus.com/innovation/eco-efficiency/design/future-concepts/
12
http://www.gizmag.com/mit-double-bubble-green-aircraft/15142/
13
http://www.nasa.gov/content/the-double-bubble-d8-0/#.U6DYZfldU74
14
https://www.princeton.edu/~achaney/tmve/wiki100k/docs/Bernoulli_s_principle.html
15
http://www.networkworld.com/article/2225826/wireless/nasa--boeing-flaunt-high-tech-
wing-that-could-alter-future-aircraft-design.html
16
http://www.alglas.com/jet_fuel.htm
17
http://www.boeing.com/aboutus/environment/environment_report_11/3_biofuels_pg_2.html
18
http://science.howstuffworks.com/environmental/green-tech/sustainable/solar-aircraft.htm
19
http://www.grc.nasa.gov/WWW/k-12/airplane/Animation/turbtyp/etfr.html
20
http://www.aeronautics.nasa.gov/pdf/asm_presentations_promise_and_challenges1.pdf
21
http://www.gizmag.com/ge-aviation-develop-advent-variable-cycle-jet-engine/25556/
22
http://www.sae.org/aeromag/techinnovations/1298t10.htm
23
Id.
i

http://airchive.com/html/airplanes-and-airports/sao-paulo-congonhas-airport/so-paulo-
congonhas-airport-flight-information-monitors-so-paulo-brazil-2013-/27056
i i

http://www.seattlepi.com/business/boeing/article/Boeing-s-S-C-plant-finishes-first-787-
Dreamliner-3515805.php#photo-2865372
i i i

https://www.youtube.com/watch?v=uHjC7X7d8Fg
i v

http://www.freeimages.com/photo/1193546 - Icon
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Last Updated ( Tuesday, 08 July 2014 )
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