The Science:

Forces: The Wrights' Larger Toy Helicopters Did Not Fly. Why Not?
What do forces have to do with the Wright brothers and their toy helicopter? You learned in the history section of this lesson that the Wright brothers received a rubber-powered toy "helicopter" from their father. They built larger copies of the toy. However, the larger versions of their toys did not fly very well. Based on the information you have learned about forces, their strength and direction, why do you think the larger models did not fly very well?

Let's look at the forces of our toy helicopter in flight. (Right now we will just look at the forces in general—just like we did with our example of the tug-of-war and the St. Bernard. However, in future science lessons we will examine each of these forces in great detail.)

The propeller's action is creating a force in the upward direction: "up." The weight of the toy is creating a force "down." In addition, the air rushing past the toy causes a resistance and acts to pull the toy down in this situation.

As you see there are two forces dragging the toy down and one force moving it up. If the one force moving the toy up is larger than the two forces acting down combined, the toy will lift up into the air. What happens if the size of the two forces acting down are almost the same as the one force going up? (Remember our tug-of-war example.) The toy will not lift up very much, or perhaps not at all.

Let's examine the direction and size of the arrows drawn on the diagrams below. In science and engineering, arrows are often used to depict the magnitude (size) and direction of different forces.

Look at the diagram of the toy helicopter below. In this case there is a long arrow, (signifying a large force) lifting the helicopter up and two smaller forces pushing it down. Each force has been colored with a different arrow: green for weight, red for air resistance, and the blue for the propeller's upward force.

Let's compare the magnitude of these arrows. In our example, the weight and the air resistance combined (added together) are about 2/3 the size of the force created by the propeller's blades.

Now look at the next example below. This time the two forces headed downwards, the helicopter's weight and the air resistance, are greater than the propeller's force upwards.

Recall our tug-of-war example. If there are more forces acting downward, which direction do you think the helicopter will travel?

With these examples in mind, can you answer these questions? The larger copies of the toy helicopter the Wright brothers made did not fly as well. What is a possible explanation using your knowledge of forces? (Hints: As they made the helicopter larger, did the weight change? As they made the helicopter larger, did the air resistance change?)

Orville Wright mentions that they did not understand why the larger toy machines did not fly as well. Subsequently, understanding, controlling, and overcoming the forces of flight were key to the Wrights successfully achieving the first powered flight in 1903. As we continue to study the Wrights work, we will continue to investigate the forces that act on "flying machines."