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Know All the Angles

In July of 1901, the Wright Brothers were at Big Kill Devil Hill in North Carolina for more tests on their glider. On one day in particular, July 27 th , there were many unsuccessful launches. The glider did get into the air, but it would stall. The stall occurred under the same circumstances for each flight. It happened when the glider slowed its speed. When its speed slowed, the pilot would increase the wing angle to compensate and maintain lift. At a certain critical point when the angle was very steep, the airflow over the top of the wing would become turbulent. This meant that the wing stopped generating lift.

When the brothers returned to Dayton, Ohio, for the winter, they needed to perform some experiments on the angle of attack for the 1901 glider. They used their own wind tunnel to test airfoil shapes.

One day, the boy who lived down the road from the Wright Brothers, young Martin Northrop, brought in a glider he had made and asked if the brothers would test his model. Marty wanted some test data so he could fly his glider more efficiently, and even improve his glider design. Marty had these questions about his glider:

Which angle of attack would give the glider the gr eatest amount of lift?
What cruising angle would be the most efficient for flight?
What is the stall angle for his glider?

The Brothers agreed to help. They told Marty to return in a few days and they would have the data for him. When Marty returned, he received the results found on the data table on the next page. First, read the section "Understanding Wind Tunnel Test Results" carefully. Then, review the information found on the data table and the graphs. Finally, help Marty find the answers to his questions.