Wilbur Wright (1867–1912) and Orville Wright (1871–1948) grew up in Dayton, Ohio, in a family of seven children; their father was a bishop. Neither finished high school with a diploma. They ran a printing business, then from 1892 a bicycle shop, where they built and repaired bikes. In 1878 their father had brought home a toy helicopter driven by a twisted rubber band. They never forgot it.
Key idea
The problem
By the 1890s gliders had flown. In Germany, Otto Lilienthal made about 2,000 glides on wings he hung from, steering by swinging his body. In 1896 he lost control in a gust, crashed, and died. The Wrights read about his death and began studying flight seriously. In 1899 Wilbur wrote to the Smithsonian Institution asking for reading:
I am an enthusiast, but not a crank in the sense that I have some pet theories as to the proper construction of a flying machine. I wish to avail myself of all that is already known and then if possible add my mite to help on the future worker who will attain final success.
How the idea came: twisting a box
Watching birds, Wilbur saw that they balance by twisting the tips of their wings, so one side gets more lift than the other. How could a machine do that? In the shop, he idly twisted a long, thin cardboard box that had held a bicycle inner tube. The top and bottom twisted in opposite directions at each end, yet the box stayed strong. Two wings joined like that, a biplane, could be twisted with cords. They called it wing-warping. In 1899 they tested it on a five-foot kite. It worked.
What they tried, and what failed
They picked Kitty Hawk, on the Outer Banks of North Carolina, after asking the Weather Bureau where winds were strong and steady; the soft sand made landings safer. Their 1900 glider flew mostly as a kite. Their 1901 glider, bigger and built using the best published tables, gave only about a third of the lift the tables promised, and it was hard to control. They went home discouraged.
The wind tunnel, 1901
Instead of giving up, they tested the tables. In their shop they built a wooden box about 6 feet long with a fan driven by the shop's engine, and inside it a balance made from bicycle spokes and hacksaw blades. They tested about 200 small wing shapes at different angles, measuring lift and drag. They found that a number everyone had used for over a century, Smeaton's coefficient, was too large: about 0.0033 rather than 0.005. They also learned which wing shapes and proportions worked best: long, narrow wings with a gentle curve.
Key idea
Worked example: Using their numbers
- $L = 0.0033 \times 300 \times 20^2 \times 0.5$.
- $20^2 = 400$; $0.0033 \times 300 = 0.99$; $0.99 \times 400 = 396$; $396 \times 0.5 = 198$.
Answer: About 198 pounds.
Worked example: What the old number promised
- $0.005 \times 300 \times 400 \times 0.5 = 300$ pounds.
- That is about 1.5 times the true value: a big enough error to wreck a design.
Answer: 300 pounds, which they never got.
The 1902 glider: control in three directions
Their 1902 glider used the tunnel data, and it lifted as predicted. But in some turns it slid sideways and spun. They added a tail rudder, then made it movable and linked it to the wing-warping. Now they could control the machine in all three directions: nose up and down (pitch, with a front elevator), wings tipping (roll, by warping), and nose left and right (yaw, with the rudder). They made somewhere between 700 and 1,000 glides that fall. That three-axis control is still how airplanes are flown.
| When | What happened |
|---|---|
| 1867 | Wilbur born near Millville, Indiana |
| 1871 | Orville born in Dayton, Ohio |
| 1878 | Their father gives them a toy helicopter |
| 1892 | They open the Wright Cycle Company |
| 1896 | Otto Lilienthal dies in a glider crash |
| 1899 | Wilbur writes to the Smithsonian; the wing-warping kite |
| 1900 | First glider at Kitty Hawk |
| 1901 | Disappointing glider; Wilbur's talk to the Western Society of Engineers; the wind tunnel |
| 1902 | Glider with movable rudder: three-axis control |
Worked example: Lift and speed
- Lift goes with $V^2$.
- $2^2 = 4$.
Answer: It becomes 4 times larger.
What it led to
With control solved and reliable wing data, only power was missing. That is the next topic.
Common mistake
Read more: Wright brothers.