Can the Wright Flyer Handle It?

Teachers Guide  

Introduction:

*For background information on the four forces and angle of attack click here.  

            The four forces of aeronautics are lift, weight, thrust, and drag.  Lift is the force that must overcome the weight of the aircraft.  Weight is the pull of gravity on an object.   In order to fly, an object must overcome the force of weight.  Lift and weight work in opposite directions.  To achieve flight, lift has to be greater than or equal to weight.  Thrust is the force produced by the engines of an airplane.  As thrust moves the plane forward, air flows over the wings to create lift.  Drag is a force that resists the movements of objects in fluids such as air.

 

 

 

Angle of attack is the angle between the wing and the airflow.  As you increase the angle of attack, lift is increased.  Changing the angle of attack can control the lift of the plane.

There is an upper limit to the amount of lift that a wing can produce. At a certain angle of attack, the flow over the wing is suddenly disrupted and the lift is reduced. This condition (when the air no longer flows smoothly over the upper surface of the wing) is called "stall".

 

Velocity is speed with direction; it is the rate of change of distance over time in the same direction.

Data:

            Here is data from a Wright Flyer replica tested in NASA’s 40 x 80 windtunnel.  Make graphs for the following data. 

For this data set, plot the points and connect them.
The velocity of the plane is measured in knots.

Table 1: Lift vs. Velocity

 

Table 2: Lift vs. Angle of Attack (at 24.6 knots)

  

 

*There is repeated data in this graph because the data is not all at exactly 24.6 knots, and there is measurement error. With older kids it may be a better idea to have them draw a best fit line with the given data.

Problem:

            Say the Wright Flyer travels at a speed of 24.6 knots and it weighs 750 pounds with Orville on board.  Use on of your graphs to decide the angle of attack that the plane should fly in order to generate enough lift?

Angle of Attack = 1.398° ≈ 1.4°

            *Use the Lift vs. Angle of Attack graph.  Draw a constant line for total weight at y=750, then find the intersection point of the two lines.

 

 

Hypothetically speaking, if the Wright brothers wanted to carry 150 pounds of mail on this flight, how fast would the plane need to fly in order to carry this extra weight if the angle of attack is held constant? (Hint: use one of the graphs and remember to include the original total weight of the plane and pilot)

 

New Total Weight = 750 + 150 = 900 pounds

*Use the Lift vs. Velocity graph.  Draw a constant line for New Total Weight at y=900, then find the intersection of the two lines.

 

The structure of the Wright flyer is fragile and limits the plane from flying at speeds greater than 27 knots, so the plane continues to travel at 24.6 knots.  Then what would have to be increased so the plane will be able to carry the additional weight (new total weight = 900 pounds)? And by how much?

 

Angle of attack will have to be increased to 3.477° ≈ 3.5°

            *Use the Lift vs. Angle of Attack graph.  Draw a constant line for New Total Weight at y=900 and find the intersection point between the two lines.

 

Extended Thinking

In advanced engineering drag must be taken into consideration. In order to achieve flight lift thrust must overcome drag. The Wright Flyer barely created enough thrust to overcome the drag and to produce lift.

*Lesson plan created by Shilpi Verma, SHARP 2002 Summer Intern, with the help of NASA Engineers Craig Hange and Steve Smith, and Eloret Engineer Peter Gage.