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Alternative Fuel

The U.S. Department of Energy’s Energy Policy Act of 1992 defines alternative fuels as those that are currently, or have been, commercially viable for vehicles:

  • • Biodiesel
  • • Electricity
  • • Ethanol
  • • Hydrogen
  • • Methanol
  • • Natural Gas
  • • Item
  • • Propane


The International Air Transport Association (IATA) has two classifications for biofuel:

First Generation biofuels are produced from sugars, starches, oils or fats of agricultural products using conventional technologies. These fuels have traditionally been developed on the same land used for food production and/or water. According to IATA, most First Generation biofuels do not meet all specifications for aviation fuel.

Second Generation biojet fuels are made from sustainable sources that are not widely used, including forest, industry and agricultural residue (e.g. sawdust, black liquor from the paper industry and corn stover), and municipal waste. Or, those biofuels made out of non-food biomass sources such as algae, switch grass, jatropha, babassu and halophytes.

Bypass Ratio

Bypass ratio refers to how much air goes through a jet engine’s propulsor versus how much air goes through its core.

A jet engine works by taking in a large volume of air at its front that is then heated, compressed and slowed down. The air is forced through several spinning blades, which, when mixed with jet fuel, release hot air. The power of this air is used to turn the blades. The faster the blades spin, the noisier the blades and hotter the air, which is less efficient. When a propulsor and fan are added to this process, the air forced through the blades is cooler and therefore more efficient.

Carbon Dioxide

Carbon Dioxide (CO2) is a colorless, odorless gas that is exhaled by animals and engines and “inhaled” by plants.

Carbon Dioxide Emissions

Carbon Dioxide (CO2) is emitted in a variety of ways, including through human activity. According the U.S. Environmental Protection Agency, human activities have increased CO2 concentrations in the atmosphere.

Climate Change

A change in climate that can be identified through statistical testing and measurement of its properties. It must persist for an extended period, typically decades or longer. Climate change may be due to natural internal processes or external forces, or to human-induced changes in land use or the atmosphere.

Coal Gasification

A process that converts coal into electricity, hydrogen or other energy products through gasification. Gasification is a thermo-chemical process used to break down coal into its basic chemical components. The gasifier is typically exposed to steam and controlled amounts of air or oxygen under high temperatures or pressures. Some industry experts predict that coal gasification will be a viable part of clean coal technology plants.

Engine Wash

In terms of aircraft engine maintenance, “washing” is literally cleaning the dirt off an engine’s airfoils, which can improve fuel efficiency by approximately 1 percent.

Legacy technologies use harsh detergents or abrasives. Pratt & Whitney's EcoPower® engine wash service uses a closed-loop system with pure, atomized water to wash aircraft engines, which avoids potential contaminant runoff.

Fischer-Tropsch Fuel

The Fischer-Tropsch (F-T) process was discovered by Franz Fischer and Hans Tropsch and used to make fuels during World War II. Liquid fuel is produced through a Fischer-Tropsch reaction that converts a mixture of hydrogen and carbon monoxide - derived from coal, methane or biomass - into liquid fuels. According to the U.S. Department of Defense (DOD), F-T fuels reduce the number of different fuels required and their environmental impact because they burn cleaner than other liquid fuels. The U.S. Department of Energy advocates F-T fuels because they have a high energy content, and powering capabilities, comparable to traditional jet fuel. They also do not require technology redesign or component development.

Geared Turbofan

Geared Turbofan technology is a result of more than 20 years of development at Pratt & Whitney and is a unique part of the PurePower PW1000G engine. The unique gear system allows the engine’s fan to operate independent of the low-pressure compressor and turbine, resulting in greater fuel efficiency and a slower fan speed for much less noise. The geared architecture allows the fan to complete only one revolution for every three rotations of the turbine.


Geothermal energy is heat from the Earth. Geothermal resources can come from shallow ground, and hot water and rock found beneath the Earth's surface. Resources can also be found in high temperatures of molten rock (or magma).

Greenhouse Gas Emissions

Greenhouses gases (GHGs) are generally considered gases that trap heat in the atmosphere. GHGs that enter the atmosphere because of human activity include Carbon Dioxide (CO2), Methane (CH4), Nitrous Oxide (N2O), Fluorinated Gases and ozone depleting substances (e.g. CFCs, HCFCs and halons).

LEED Green Building Rating System

The Leadership in Energy and Environmental Design (LEED®) Green Building Rating System was first published in 1999 by the U.S. Green Building Council. It helps professionals across the U.S. improve the quality of the country's buildings and their impact on the environment.

Material of Concern

A material that has the potential to adversely impact the health or safety of individuals exposed to it, or have an adverse impact on the environment during the life-cycle of a product containing the material.

Nitrogen Oxides

Nitrogen oxide (NOx) is the generic term for a group of colorless and odorless highly reactive gases. They contribute to smog formation and are regulated by the U.S. Environmental Protection Agency.

Other Fuels

Pratt & Whitney is working with the aerospace industry to develop and approve jet fuels made from sustainable biomass materials such as jatropha, camolina and algae.


R.E.A.C.H. (Registration, Evaluation and Authorization of Chemicals) is a European Union regulation that requires businesses to show the chemicals it uses are safe (on an annual basis) by providing environmental testing and safety information for all substances manufactured or imported, in quantities of one metric ton or more, in the EU.


Pratt & Whitney's Technology for Advanced Low Oxides of Nitrogen (TALON) low-emissions combustor is an evolution of an earlier NASA (Rich/Quench/Lean technology and Float Wall) combustor designed to control nitrogen oxide (NOx) emissions.

In partnership with NASA, Pratt & Whitney developed the TALON family of combustors that reduce NOx, unburned hydrocarbons (UHC) and carbon monoxide (CO), which are several regulated pollutants that impact local air quality, and in the case of NOx, can also impact climate change.