To conclude, you’ve learned about the various factors influencing aircraft efficiency and emissions, in particular the engines. In essence, a jet engine performs all the steps required to push the aircraft through the sky:

• It gathers air to use in its jet.
• It uses a fuel source, or energy carrier, to add energy to this air, causing it to exit the engine at a higher speed.
• As we know from Newton’s first law, action equals opposite and equal reaction. Therefore, the exiting air pushes the aircraft forward!

Engine development has been one of the most important drivers in new capabilities, higher efficiency, and reduced emissions of aircraft ever since aircraft were invented. A large part of the efficiency of modern aircraft is due to their amazing engines. However, these engines still require fuel, and burning this fuel still causes emissions. Next week, we will look in more detail at the elements of a propulsion system, and see what kind of energy carriers are available to reduce or eliminate these emissions.