Physics

# That’s a Drag

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On December 14, 1903, Orville and Wilbur Wright invented the delayed flight, when Wilbur’s first attempt crashed. It was three days later and at 10:35 am on the day of the 17th, the brothers completed four successful flights. The Wright brothers had overcome the forces of gravity for an impressive 12 seconds. However, the purists debate whether flight is a byproduct of an excess of lift or an excess of thrust. No matter what side you take here are the four principals of flight, lift, weight, thrust and drag.

Thrust opposes drag – When an aircraft is stationary, there is equality in weight and lift. An aircraft is going to need thrust to get off the ground. The engine produces a force, when the force is greater than the drag the thrust propels the aircraft forward. When the thrust and drag are equal, there is no change in motion. In level flight, thrust equals drag.

Fun Fact: In 1929, the Dornier Do X had twelve engines.

Drag opposes thrust – If you held your hand out the window of your car the force of air on your hand is equal to the force your hand is placing on the air, Newton’s third law. A racecar may use a parachute to slow them after the race. When the drag and thrust are the same, the car is at a cruising speed. When the car deploys a parachute there is an excess of drag and the car slows down.

Fun Fact: The arresting wire system on an aircraft carrier can stop a 54,000-pound aircraft travelling 150 miles per hour in only two seconds. Now that is a drag!

Lift opposes weight – When there is an excess of thrust the plane moves forward. The quicker an aircraft moves forward the more lift it produces. When there is enough thrust generated, lift overcomes weight. When the thrust is equal to the drag the plane is in level flight. Back to holding your hand out the window, if you turn your hand from vertical to horizontal you can fly your hand.

Fun Fact: The F/A 18 Hornet have a rate of climb of 50,000 feet per minute!

Weight opposes lift – Heavier planes require more thrust to produce more lift to overcome weight. The heavier the aircraft the more thrust it needs. An aircraft carrying several tons of cargo is going to need more thrust than a small aircraft carrying a few people. Planes with less weight require less thrust. Therefore, we design planes to be as light as possible.

Fun fact – An ultralight weighs less than 254lbs.

Therefore, whether it is a cargo jet or glider the four principals of flight must be present.

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