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“Are you going to be the next girls to become pilots?”—Amelia Earhart
Amelia Earhart in the cockpit of the Electra, ca. 1936.
Amelia, the latest film by Mira Nair (director of Mississippi Masala, and Vanity Fair), is the story of arguably the world’s most famous female pilot. A pioneer and promoter of aviation, Amelia Earhart was the first woman to fly solo across the Atlantic Ocean, and the first person to do so twice. She set a number of other aviation records, including the woman’s altitude record, being the first woman to fly non-stop across the United States, and the first person to fly solo from Honolulu, Hawaii, to Oakland, California. Although anyone would be remembered for these accomplishments, Earhart is most famous for the tragedy of her failed attempt to be the first woman to fly around the world. Earhart and her navigator, Fred Noonan, disappeared over the Pacific on July 2, 1937, on the way from Lae New Guinea to Howland Island. They had covered more than 75% of the 35,000 kilometer journey around the world. No wreckage of their plane has ever been found.
Amelia, based primarily on two biographies of Earhart (East With the Dawn, and The Sound of Wings), weaves her early flight adventures with scenes from the ill-fated round the world trip. In a 1930’s flying costume of leather helmet and jump suit, Hilary Swank looks almost identical to the familiar press and publicity images of Earhart. As a standard Hollywood biopic, romance is also an important storyline in the film, and we see Earhart’s relationship with her husband and publisher George Putnam (Richard Gere). The film also presents a relationship between Earhart and pilot Gene Vidal (Ewan McGregor), an early government official in aviation administration.
So what is there for a science teacher to sink his or her teeth into in Amelia? There is a lot of flying, and that means a lot of physics. Pilots are always negotiating the combination of lift (up), thrust (forward), weight (down), and drag (backward), not to mention rotation that can happen in any direction. I will omit rotation, a focus of my Fame review last month.
Amelia Earhart in the cockpit of the Electra, ca. 1936.
A plane generates lift primarily on the wings through a combination of the angle the wing makes with the air, and the curved top surface of the wing. The wing’s angle (angle of attack) means the wing pushes down on the air, and by Newton’s Third Law, the air pushes up on the wing. The curved top surface of a wing makes air going over the wing move a bit faster than air passing below. Fast air exerts less pressure than slow air, so there is less pressure on the top than the bottom of the wing, resulting in lift. (Another place to see this effect is in a soft-top convertible car—when driving on the highway, the closed roof bulges up because the air outside is moving faster than the air inside, and there is a net force up on the roof material.)
A dramatic depiction of this occurs early in the film during Earhart’s first flight across the Atlantic as a passenger while two men piloted and navigated the plane. They hit significant turbulence (more on that later) and the aircraft door pops open. By turns, Earhart and the navigator are nearly pulled out the door before they close it. Since the air outside is moving very fast, and the air inside is virtually still, there would be a large pressure difference tending to push objects out of the plane. There have been a few incidents of commercial aircraft losing a portion of the fuselage and passengers or crew have been ‘sucked out’ through the gap. The phenomenon that makes flight possible can have dangerous consequences as well.
If a plane is flying level, neither climbing nor descending, the lift up will exactly balance the weight of the plane. Occasionally, changes in the motion of air around the wing will cause a loss of lift or an extra push up, and passengers will be bounced around inside the plane. When this happens today, the captain turns on the ‘fasten seat belt’ sign. In particularly bad turbulence, flight attendants buckle up as well. Injury to passengers is rare, but most often affects those not wearing seat belts. Eyewitnesses often report people thrown up against the ceiling. While that is how it appears, Newton’s First Law of Motion tells us that isn’t what actually happened. This law tells us about inertia: in the absence of a net outside force, objects in motion continue in a straight line. When an airplane hits turbulence causing a sudden drop, people not wearing seatbelts do not drop with the plane. They continue to follow the path they were on before the turbulence. The plane around them moves down suddenly, in effect, hitting the passenger on the head. It is small wonder injuries occur this way. Just as in a car, the seatbelt in a plane keeps passengers moving along with the vehicle as much as possible, helping prevent injury.
Two major forces remain for pilots to manage: thrust and drag. In Earhart’s day thrust was provided by propellers using of aerodynamic lift (like the wings) and effectively pulling the plane through the air. They don’t work well at high altitudes where the air is thin and the maximum speed for propeller-driven aircraft is relatively low. Modern commercial aircraft use jet engines to create thrust. The engines pull air for combustion in the front and push exhaust out the back at high speed. Newton’s Third Law comes into play again: the engine pushing exhaust backward causes the exhaust to push the engine forward. Drag is the force of air pushing back on the plane: the wind resistance a cruising aircraft has to push against while maintaining speed. Trips west-to-east across the United States are usually faster than east-to-west because the jet stream provides a "tail wind" to push the eastbound planes. Going west, pilots try to avoid the jet stream which slows them down and causes greater fuel consumption.
Earhart worked throughout her life to advance women in aviation, a field that was and still is dominated by men. (Approximately 6% of U.S. pilots are women.) Amelia shows several examples of Earhart’s efforts to promote female pilots, including participation in women’s air races and leading The Ninety-Nines, an organization of female pilots. She is shown encouraging girls to imagine themselves as pilots in the future. Science teachers can use the story of Earhart’s life to inspire students to succeed in areas where hard work and dedication are required.
Jacob Clark Blickenstaff is Assistant Professor of Physics and Assistant Director of the Center for Science and Mathematics Education at the University of Southern Mississippi. He can be reached at email@example.com.
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