Four forces an aircraft should deal with: Thrust, drag, lift, and weight
Just as familiarity with a car’s engine and gear system helps a driver adjust their driving style and improve their car’s mileage, knowing how an aircraft operates and the forces that affect the aircraft’s flight will help you understand the strategies airlines use to improve their aircraft’s fuel efficiency. The four forces that influence the aircraft’s flight and its fuel consumptions are as follows.
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How these forces influence fuel consumption
At a given speed, the increase in the aircraft’s weight affects the drag and cruising altitude. A heavier aircraft flies at lower altitude, as it requires higher air density to provide the necessary lift. Higher air density increases the drag. Since the thrust should exceed the drag for the aircraft to accelerate, fuel consumption increases. The table above shows the fuel consumption for takeoff of an aircraft at different altitudes and gross weights. Fuel consumption increases as weight and altitude increase.
In the next article of this series, we’ll see how much United (UAL) lowers fuel consumption through weight reduction, engine modification, and winglets to reduce drag. All United’s peers, including Delta (DAL), American Airlines (AAL), Southwest (LUV), and JetBlue (JBLU), use standard winglets for fuel efficiency, but United is the first company to use the new Split Scimitar winglets.