Fly with physics

Fly With Physics

The Physics of an Airplane’s Flight

By Marco Vitali, 10B Physics, May 28th 2009

Airplanes are an efficient way of traveling to places, especially if they’re far away. They are used every day by hundreds of thousands of people; more than 87,000 flights are in the skies in the United States every day and only one-third of those are commercial carriers, such as Iberia, American Airlines and Singapore Airlines. “At any given moment, roughly 5,000 planes are in the skies above the United States” (Air Traffic Control: By the Numbers). Even though they are used so much, still today, there are discussions on who invented the first working “flying machine” or airplane.

History

“Ever since [humans] first saw a bird fly, [humans have] wanted to fly. The first attempts were efforts to fly like a bird by attaching feathers to their arms and flapping. Those attempts were unsuccessful.”(History of Airplanes) The first recorded, successful flight was in 1783 but it was in a hot air balloon, which does not use any of the principles behind an airplane (History of Airplanes). Even though the former was the first successful recorded flight, many people believe that it was Leonardo Da Vinci who actually invented the first working flying machine and flew. According to the author of “Da Vinci Rising,” Jack Dann, “there is no clear hard-core evidence that specifically states [he did fly], however, if one goes over the material by Leonardo and his contemporaries one can cull out some rather interesting facts that attest to the fact that YES his machines did work and Leonardo did fly”(Dann).

Throughout the world there have been several possible candidates who may have invented the first airplane that flies using the principles that airplanes use today. According to ThinkQuest the first airplane was a non-motorized flying machine, invented by Sir George Cayel, called a glider. His first glider didn't have passengers or a pilot because it was too small for anyone to fit in it. Then, he made another one that flew his coachman across a small valley (History of Airplanes). While, according to WikiAnswer, it was “Richard Pearse, a New Zealander, [who] built and flew his plane in March 1903, 9 months before the Wright brothers [, the official inventors of the airplane]. His flight was over 350 yards, and ended with a crash landing in a bush.” (Who Invented the Plane).

Officially, though, the first patented airplane was developed by Wilbur and Orville Wright in 1903 (Airplane Patent). On Friday, December 17th, Orville made the first powered flight, which lasted 12 seconds, and flew 36.5 meters (Were Wright Brothers the First to Fly), (History of Airplanes). Wilbur made a second attempt which only lasted about 13 seconds. Orville’s 3rd attempt, though, covered 60 meters in 15 seconds. That same day, at noon, Wilbur made his fourth and most successful flight: “the Flyer covered 255,6 metres (852 ft) in 59 seconds. He landed safely, but a sudden gust of wind sent the plane tumbling, breaking the wings and damaging the motor. There would be no more flights in 1903” (Were Wright Brothers the first to fly). In 1908, the Wright Brothers finally built an aircraft that could fly for more than one hour and a half, allowing them to travel longer distances (History of Airplanes).

Airplanes have undergone continuous improvements since they were developed by the Wright Brothers. Now they travel thousands of miles at more than 7 miles of altitude, carrying up to 555 passengers in the case of the new airbus380 (airbus 380). Now passengers rest in comfortable seats, sleep and get lunches and dinner aboard, instead of having to lie on their stomachs like Orville did. Jet engines have replaced propellers and speeds of up to 4,520 mph have been reached by the X-15, the world’s fastest manned aircraft, or the X-43, a drone, which reaches around 7,000 mph (THE 100 FASTEST ...

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Physics

“The basic principles of why and how airplanes fly apply to all airplanes, from the Wright Brothers' first machine to a modern Stealth Bomber, and it's actually not difficult to understand how airplanes get, and stay, airborne.” (The Basic Principles of Flight)

Bernoulli’s Principle

The concept of airplanes and how they fly is based on Bernoulli’s principle. In 1738 a Swiss mathematician and physicist, Daniel Bernoulli, formulated a principle that relates fluid velocity to its internal pressure. Bernoulli’s principle states that the total energy in a steadily flowing fluid system is constant along the flow path. Therefore, if fluid speed increases, its pressure must decrease (Almeida). This can be simply exemplified in a flowing river; if the flow of water is continuous the water will speed up when it flows through a shallow or narrow part of the river because there is more pressure (Hewitt). Or, when you place your finger in front of a flowing hose: there is less space for the water to get out, so it will be expelled at a higher pressure and a greater speed.

Formula

A total energy, , as a steadily flowing fluid system, is constant along the flow path, k. Therefore . Apply the law of conservation of energy, PE+KE=k, and since and then . Divide both sides by volume, , and because V is a constant . Since Density, or P, equals then . Given that P, or pressure, equals pgh then which can be rewritten as (Nave), (Almeida).

and

Application to Airplanes

Airplane wings are shaped so that the top of the wing is longer than the bottom. Therefore, the airflow on the top of the wing will be faster and cause lower pressure on the top than the bottom, thus, this will cause lift. “The blade of the rotor of a helicopter is also shaped like an aircraft’s wing, thus creating the same effect.” The same concept is used in race car spoilers, only backwards so the cars won’t gain lift and flip in the air. They are shaped like up-side-down wings, making the airflow faster on the bottom, therefore since there will be lower pressure on the bottom the car will stick down to the ground creating a so-called “down force” (Almeida).

“The airflow striking the fixed wing airfoil of an aircraft or the aircraft itself is called the relative wind.” The angle at which the wings hit the relative wind is knows as angle of attack or alpha. The more you increase alpha the more pressure difference there will be, therefore greater lift (How Airplanes Fly). There is a limit on the lift, when alpha exceeds a certain angle, though, the so called critical angle of attack, around 15 degrees for a standard passenger. When a plane exceeds that limit it will stall, “the result of an alpha so great that the air can no longer flow smoothly over the curved top surface of the wing” (How Airplanes Fly), and the aircraft will start to drop (Kolano). Even though any pilot’s first instinct would be to pull the rudder up because of the feeling of dropping, that is the wrong thing to do since all he will be doing is increasing alpha even more, therefore increasing stall. What must actually be done is to pull the rudder down, to decrease the angle of attack, thus eliminating stall (How Airplanes Fly). Some military aircrafts such as the F-22 Raptor, though, virtually overcome stall, as they can reach angles up to 60 degrees without stalling because their engines and wings work differently (Peron).

The four main forces acting on a plane go in four opposite directions. The forward direction is called thrust, which creates the relative wind, and it is made by the motor or propeller. To go forward, the propellers use the same idea the wings use, Bernoulli’s principle, lower pressure is created in front of the propellers, and therefore the airplane is “sucked forward”. The backward direction, created by air resistance, is called drag. The upwards force is lift, created by the lower pressure above the wing which creates lift, or the Bernoulli’s principle. And the downward force is called gravity. When all these forces are balanced the airplane will be going straight and level at a constant speed (How Airplanes Fly).

Social Implications

Airplanes help people reach places more quickly and comfortably. Now-a-days you don’t need to ride on your stomach any longer, like the Wright brothers did. Today you get comfortable seats in which you can sleep, pillows and blankets, decent meals and all the assistance you need; it’s pleasant to fly. Airplanes are also much safer than cars, or most other common means of transportation, seeing that the odds of being killed on a single trip on an Airplane are 52.6 million to 1, while on a car there’re only 7.6 million to 1 (Are Airplanes Really Safer...). Statistically speaking, people should be more scared of riding a car than going on an airplane.

Even though new aircrafts are 70% more fuel efficient than 40 years ago and 20% more than 10 years ago, it’s still not enough seeing the petroleum crisis that is going on in the world and how much the prices of fuel have increased. Airlines are aiming for a further 25% fuel efficiency improvement by 2020, meaning about 3 liters per 100 passenger km, better than a compact car. Modern aircraft achieve fuel efficiencies of 3.5 litres per 100 passenger km (Fuel Efficiency). This would also help the prices of flights decrease since you have to pay less money for fuel.

A major problem in modern aviation, though, is terrorism. Now-a-days there is the danger of onboard terrorists, like in the case of September 11th 2001, that there wasn’t in the past. Because of this there is much more airplane and airport security thus the process of check in, security and boarding takes much longer. According to CNN, “[Professor,] Bruce Hoffman [said], we should anticipate that terrorists are constantly searching for new vulnerabilities and adapting and adjusting to our countermeasures” (Explosions led to Russia crashes). Today, in any airport, there are metal detectors, x-ray tunnels, cameras, a large security staff and many more means of security to fight terrorism. This usually protects us from the danger of a hijack, but sadly, in some cases there is nothing we can do.

Today they even make furniture out of airplanes. According to Adam Frucci, “MotoArt builds custom out of old airplane parts, turning a B-25 wing into a desk or a DC-3 propeller into a martini table.” Even though they are really expensive, around $10,000, it’s an interesting and original way to recycle old airplane parts that would be otherwise left to rust (Frucci).

Works Cited

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<http://www.airliners.net/aircraft-data/stats.main?id=29>.

"Air Traffic Control: By the Numbers ." NATCA. 15 May 2009.

<http://www.natca.org/mediacenter/bythenumbers.msp#4>.

"Airplane Patent." Virtualology. 15 May 2009.

<http://virtualology.com/virtualpubliclibrary/hallofthehistoricarchives/AIRPLANEPATENT.COM/>.

Almeida, Benedict. "Bernoulli's Principle." YouTube. 10 23 2006. Youtube. 16 May 2009.

<http://www.youtube.com/watch?v=kXBXtaf2TTg>.

"Are Airplanes Really Safer Than cars" Fact Check . 26 10 2007. 3 May 2009.

<http://factcheck.gullible.info/discussion/81/are-airplanes-really-safer-than-cars/>.

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<http://library.thinkquest.org/2819/bernoull.htm>.

Dann, Jack. "DID LEONARDO DA VINCI FLY?." 15 May 2009.

<http://sped2work.tripod.com/davinci.html>.

“Explosions led to Russia crashes.” CNN World Edition, August 30, 2004. 16 May 2009.

<>.

Frucci, Adam . "Furniture Made From Airplanes Lets Your Social Life Take Off." Gizmodo. 03 14 2007. 16 May 2009.

<http://gizmodo.com/gadgets/gadgets/furniture-made-from-airplanes-lets-your-social-life-take-off-244119.php>.

"Fuel Efficiency." Environment. 2009. IATA. 16 May 2009.

<http://www.iata.org/whatwedo/environment/fuel_efficiency.htm>.

Gordon. "CONCORDE." Concorde History June 2000 Web.28 Apr 2009.

<http://www.concordesst.com/index.html>.

Hewitt, Paul. Conceptual Physics. 3rd. Scott Foresman Addison Wesley, 1999. Print.

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<http://library.thinkquest.org/J0112389/airplanes.htm>.

"How Airplanes Fly." Public Resource . 03 24 2008. Merit Film. 16 May 2009.

<http://www.youtube.com/watch?v=ocni_Whz5EA&NR=1>.

Kolano, Ed. "What Is Angle of Attack?." Ithacanet. 2 May 2009.

<http://www.ithacanet.org/Orgs/EHFC/AngleOfAttack.pdf>.

Nave, R.. "Bernoulli Equation ." hyperphysics. 16 May 2009.

<http://hyperphysics.phy-astr.gsu.edu/Hbase/pber.html>.

Peron, Lee. "-22 INITIAL HIGH ANGLE-OF-ATTACK FLIGHT TEST RESULTS." sfte-ec. 2 May 2009.

<http://www.sfte-ec.se/data/Abstract/A2000-II-02.pdf>.

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"Wiki: Stall (flight)." Wapedia. Wapeia. 16 May 2009.

<http://wapedia.mobi/en/Stall_(flight)>.

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