The (relatively simple) physics of flight

A Moment of Science

While the engineering behind modern aircraft is incredibly complicated, the basic concepts behind getting airborne is simpler than you might think. 

“So the fundamentals, the physics of flight, deal with 4 basic forces. You’ve got weight down, lift up, drag back, and thrust forwards,” says Nick Carden, a pilot who tests Boeing 787s coming off the line at the plant in North Charleston.

The four forces at work for a plane in flight.
Credit: Boeing South Carolina

Let’s go into a bit more detail about each of those forces.

Weight- the downward force of gravity

“Weight is just that. The mass of the aircraft or the mass of the object times gravity,” says Carden. “So you can imagine in the 787 to just give you an idea, is nearly 600,000 pounds”

And that’s light compared to other commercial aircraft thanks to the weight saving composite used in the Dreamliner! To overcome that weight, the plane’s wings do the heavy lifting.

Lift- the vertical force generated by a moving aircraft

They aren’t completely flat, rather slightly bulbous, designed that air flows faster over the top & slower underneath. This creates higher pressure underneath the wings that pushes the aircraft upwards! 

A lot of lift needs to be generated to get a 600,000 pound aircraft off the ground. This is where thrust comes in.

Thrust- the forwards force created by the engines

“Those engines create a push of airflow that pushes us forward and we increase speed. Now as we increase speed we increase airflow over the wing, which increases lift.”

However as speed increases, so does drag in the opposite direction of the plane’s forward motion- slowing it down & creating less lift.

Drag- the force opposite the plane’s motion as a result of air friction

Smart engineering with thoughtful attention to aerodynamics drastically reduces this drag, “That’s why if you look at most aircraft, the surface is smooth to decrease that friction, decrease that drag force,” explains Carden.

These 4 forces are constantly playing tug of war with one another: lift v. gravity, thrust v. drag. When all four are balanced, the plane flies steady at a constant speed. A pilot must consider when and how much to reduce or increase lift, thrust, or drag (a pilot isn’t going to reduce weight while airborne).

Storm Team 2 Meteorologist David Dickson

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