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Mark Rosenthal


Experimenting at the Threshold of Knowledge

‘The root cause of all problems is ignorance.’

Published: Tuesday, May 30, 2017 - 11:03

It was September 1901, in Dayton, Ohio, and Wilbur Wright was frustrated. The previous year, 1900, he had built and tested, with his brother Orville’s help, their first full-size glider. It was designed using the most up-to-date information about wing design available. His plan had been to “kite” the glider with himself as a pilot. He wanted to test his roll-control mechanism, and build practice hours “flying” and maintaining control of an aircraft.

But things had not gone as he expected. The Wrights were the first ones to actually measure the lift and drag forces generated by their plane’s wings, and in 1900, they were seeing only about one-third of the lift predicted by the equations they were using.

The picture below shows the 1900 glider being “kited.” Notice the angle of the line and the steep angle of attack required to fly, even in a stiff 20-knot breeze.  Although they could get some basic tests done, it was clear that this glider would not suit their purpose.

In 1901 they had returned with a new glider, essentially the same design only about 50-percent bigger. They predicted they would get enough lift to sustain flight with a human pilot. They did succeed in making glides and testing the principle of turning the aircraft by rolling the wing. But although it could lift more weight, the lift/drag ratio was no better.

What they thought they knew

Wilbur’s original assumptions are well-summarized in a talk he gave later that month at the invitation of his mentor and coach, Octave Chanute.

The following is excerpted from the published transcript of “Some Aeronautical Experiments” presented by Wilbur Wright on Sept 18, 1901, to the Western Society of Engineers in Chicago:

“The difficulties which obstruct the pathway to success in flying-machine construction are of three general classes:
• Those which relate to the construction of the sustaining wings
• Those which relate to the generation and application of the power required to drive the machine through the air
• Those relating to the balancing and steering of the machine after it is actually in flight

The Maxim Flying Machine

“Of these difficulties two are already to a certain extent solved. Men already know how to construct wings or aeroplanes which, when driven through the air at sufficient speed, will not only sustain the weight of the wings themselves, but also that of the engine and of the engineer as well. Men also know how to build engines and screws of sufficient lightness and power to drive these planes at sustaining speed. As long ago as 1884 a machine weighing 8,000 pounds [the “flying machine” built by Hiram Maxim] demonstrated its power both to lift itself from the ground and to maintain a speed of from 30 to 40 miles per hour, but failed of success owing to the inability to balance and steer it properly. This inability to balance and steer still confronts students of the flying problem, although nearly eight years have passed. When this one feature has been worked out, the age of flying machines will have arrived, for all other difficulties are of minor importance.”

What we have here is Wilbur’s high-level assessment of the current condition—what is known, and what is not known, about the problem of “powered, controlled flight.”

Summarized, he believed there were three problems to solve for powered, controlled flight:
1. Building a wing that can lift the weight of the aircraft and a pilot
2. Building a propulsion system to move it through the air
3. Controlling the flight—going where you want to

Based on their research, and the published experience of other experimenters, Wilbur had every reason to believe that problems Nos. 1 and 2 were solved, or easy to solve. He perceived that the gap was control and focused his attention there.

His first target condition had been to validate his concept of roll control based on “warping” (bending) the wings. In 1899, he built a kite and was able to roll, and thus turn it, at will.

At this point, he believed the current condition was that lift was understood, and that the basic concept of changing the direction by rolling the wing was valid. Thus, his next target condition was to scale his concept to full size and test it.

What happened

Wilbur had predicted that their wing would perform with the calculated amount of lift.

When they first tested it at Kitty Hawk in 1900, it didn’t.

However, at this point, Wilbur was not willing to challenge what was “known” about flight.

Instead the 1901 glider was a larger version of the 1900 one with one major exception: It was built so they could reconfigure the airfoil easily.

Impatient, Wilbur insisted on just trying it. But, to quote from Harry Combs’s excellent historical book, Kill Devil Hill (Ternstyle Pr Ltd., 1979, sixth reprint edition):

“The Wrights in their new design had also committed what to modern engineers would be an unforgivable sin.... They made two wing design changes simultaneously and without test.”

Without going into the details, they did manage to get some glides but were really no closer to understanding lift than they had been the previous year.

They had run past their threshold of knowledge and had assumed (with good reason) that they understood something that, in fact, they did not (nobody did). They almost gave up.

Deliberate learning

Being invited to speak in September actually gave Wilbur a chance to reflect and renewed his spirits. That fall and winter, he and his brother conducted empirical wind-tunnel experiments on 200 airfoil designs to learn what made a difference and what did not. In the process, as an “oh by the way,” they invented the “Wright Balance,” which was the gold standard for measuring lift and drag in wind-tunnel testing until electronics took over.

They went back to what was known, and experimented from there. They made no assumptions. Everything was tested so they could see for themselves and better understand.

The result of their experiments was the 1902 Wright Glider. You can see a full size replica in the ticketing area of the Charlotte, North Carolina, airport.

I’ll skip to the results:

Notice that the line is now nearly vertical, and the wing pointed nearly straight forward rather than steeply tipped back.

What do we need to learn?

Making process improvements is a process of research and development, just like Wilbur and Orville were going through. In 1901 they fell into the trap of “What do we need to do?” After they got back to Dayton, they recovered and asked, “What do we need to learn?” “What do we not understand?”

The coaching kata

What I have come to understand is that the main purpose of coaching is to help the learner (and the coach) find that boundary between what we know (and can confirm) and what we need to learn. Once that boundary is clear, then the next experiment is equally clear: What are we going to do in order to learn? Learning is the objective of any task, experiment, or action item because they are all built on a prediction even if you don’t think they are.

By helping the learner make the learning task explicit, rather than implicit, the coach advances learning and understanding—not only for the learner, but for the entire organization.

Where is your threshold of knowledge? How do you know?

First published April 26, 2017, on The Lean Thinker blog.


About The Author

Mark Rosenthal’s picture

Mark Rosenthal

Mark Rosenthal is an experienced lean manufacturing/quality director and manager with more than 20 years of experience implementing continuous improvement in diverse organizations. He brings deep understanding of the Toyota Production System and a proven ability to see any organization’s potential. Rosenthal is a change agent who facilitates the process of discovery to quickly make an impact on the way people think, enabling them to cut to the core issues and get things moving by engaging the entire team to develop solutions that affect the bottom line.


Where they went wrong

Interesting article on some of their errors:http://wrightstories.com/wrights-confused-over-calculation-of-lift/Most educators still get it wrong in claiming lift due to Bernoulli, 1738 rather than Coanda, 1936.