I am intending to start in a few days for a trip to the coast of North Carolina in the vicinity of Roanoke Island, for the purpose of making some experiments with a flying machine.  It is my belief that flight is possible and while I am taking up the investigation for pleasure rather than profit, I think there is a slight possibility of achieving fame and fortune from it.  It is almost the only great problem which has not been pursued by a multitude of investigators, and there carried to a point where further progress is very difficult.  I am certain I can reach a point much in advance of any previous workers in this field even if success is not attained just at present.  At any rate I shall have an outing of several weeks and see a part of the world I have never before visited.

Wilbur to his father, September 23, 1900

I have my machine nearly finished.  It is not to have a motor and is not expected to fly in any true sense of the word.  My idea is merely to experiment and practice with a view to solving the problem of equilibrium.  I have plans which I hope to find much in advance of the methods tried by previous experimenters.  When once a machine is under proper control under all conditions, the motor problem will be quickly solved.  A failure of motor will then mean simply a slow descent & safe landing instead of a disastrous fall.  In my experiments I do not expect to rise many feet from the ground, and in case I am upset there is nothing but soft sand to strike one.  I do not intend to take dangerous chances, both because I have no wish to get hurt and because a fall would stop my experimenting, which I would not like at all. . . .  My machine is more simple in construction and at the same time capable of greater adjustment and control than previous machines.

I have not taken up the problem with the expectation of financial profit.  Neither do I have any strong expectation of achieving the solution at the present time or possibly any time.  My trip would be no great disappointment if I accomplish practically nothing.  I look upon it as a pleasure trip pure and simple, and I know of no trip from which I could expect greater pleasure at the same cost.

Orville in Boy’s Life, September 1914, as told to Leslie W. Quirk

I suppose my brother and I always wanted to fly. Every youngster wants to, doesn’t he?  But it was not till we were out of school that the ambition took definite form.

We had read a good deal on the subject and we had studied [German experimenter Otto] Lilienthal’s tables of figures with awe.  Then one day, as it were, we said to each other:  “Why not?  Here are scientific calculations, based upon actual tests, to show us the sustaining powers of planes.  We can spare a few weeks each year.  Suppose, instead of going off somewhere to loaf, we put in our vacations building and flying gliders.”  I don’t believe we dared think beyond gliders at that time—not aloud, at least.

That year—it was 1900—we went down to North Carolina, near Kitty Hawk.  There were hills there in plenty, and not too many people about to scoff.  Building that first glider was the best fun we’d ever had, too, despite the fact that we put it together as accurately as a watchmaker assembles and adjusts his finest timepiece.  You see, we knew how to work because Lilienthal had made his table years before, and men like [engineer Octave] Chanute, for example, had verified them.

To our great disappointment, however, the glider was not the success we had expected.  It didn’t behave as the figures on which it was constructed vouched that it should.  Something was wrong.  We looked at each other silently, and at the machine, and at the mass of figures compiled by Lilienthal.  Then we proved up on them to see if we had slipped somewhere.  If we had, we couldn’t find the error; so we packed up and went home.  We were agreed that we hadn’t built our glider according to the scientific specifications.  But there was another year coming and we weren’t discouraged.  We had just begun.

Wilbur to Octave Chanute, November 16, 1900

My brother and myself spent a vacation of several weeks at Kitty Hawk, North Carolina, experimenting with a soaring machine. . .

The machine had neither horizontal nor vertical tail.  Longitudinal balancing and steering were effected by means of a horizontal rudder projecting in front of the planes [wings].  Lateral balancing and right and left steering were obtained by increasing the inclination of the wings at one end and decreasing their inclination at the other.  The short time at our disposal for practice prevented as thorough tests of these features as we desired, but the results obtained were very favorable and experiments will be continued along the same line next year.

Wilbur’s diary, July 30, 1901

The good points as indicated by the experiments already made are these:—

1. The machine is strong.  It has suffered no injury although very severely used in some forty landings.
2. With less than an hour’s practice we succeeded in getting a free flight of over 300 feet at an angle of 1 in 6.  Many of our failures in other attempts were due only to the fact that the hill was not steep enough to really get a fair start.  The machine starting so close to the ground that the least undulation caused the rear ends of the ribs to touch the ground and thus prevent the machine turning up to sufficient angle to rise again.
3. We have experimented safely with a machine of over 300 square feet surface in winds as high as 18 miles per hour.  Previous experimenters had pronounced a machine of such size impracticable to construct and impossible to manage.  It is true that we have found this machine less manageable than our smaller machine of last year, but we are not sure that the increased size is responsible for it.  The trouble seems rather in the travel of the center of pressure.
4. The lateral balance of the machine seems all that could be desired.

Wilbur to his father, October 24, 1901

Since returning [from Kitty Hawk] we have been experimenting somewhat with [a wind tunnel] for measuring the pressure of air on variously curved surfaces at different angles, and have decided to prepare a table which we are certain will be much more accurate than that of Lilienthal.  Mr. Chanute has several times kindly offered to help bear the expense of these experiments but we have refused to accept money because we would be led to neglect our regular business too much.

Orville to George A. Spratt, June 7, 1903

Immediately after our return [from Kitty Hawk in 1901] we began the construction of [a wind tunnel] for measuring the effects of wind at various angles on surfaces.  After almost completing the machine we discovered that we would have to have a very large room in which to operate it, as the current in our tunnel would be stronger on one side and then on the other, according to the course taken by the air in returning to our fan.

Orville in Boy’s Life, September 1914

We wrote to a number of automobile manufacturers about an engine.  We demanded an eight-horse one of not over 200 pounds in weight.  This was allowing twenty-five pounds to each horsepower and did not seem to us prohibitive.

Several answers came.  Some of the manufacturers politely declined to consider the building of such an engine; the gasoline motor was comparatively new then, and they were having trouble enough with standard sizes.  Some said it couldn’t be built according to our specifications, which was amusing, because lighter engines of greater power had already been used.  Some seemed to think we were demented—“Building a flying machine, eh?”  But one concern, of which we had never heard, said it could turn out a motor such as we wanted, and forwarded us figures.  We were suspicious of figures by this time, and we doubted this concern’s ability to get the horsepower claimed, considering the bore of the cylinders, etc.  Later, I may add, we discovered that such an engine was capable of giving much greater horsepower.  But we didn’t know that at the time; we had to learn our A, B, C’s as we went along.

Finally, though, we had a motor built.  We had discovered that we could allow much more weight than we had planned at first, and in the end the getting of the engine became comparatively simple.  The next step was to figure out what we wanted in the way of a screw propeller.

Orville to George Spratt, June 7, 1903

During the time the engine was building we were engaged in some very heated discussions on the principles of screw propellers.  We had been unable to find anything of value in any of the works to which we had access, so that we worked out a theory of our own on the subject, and soon discovered, as we usually do, that all the propellers built heretofore are all wrong, and then built a pair of propellers 8 1/8 ft. in diameter, based on our theory, which are all right! (till we have a chance to test them down at Kitty Hawk and find out differently).  Isn’t it astonishing that all these secrets have been preserved for so many years just so that we could discover them!!  Well, our propellers are so different from any that have been used before that they will have to either be a good deal better, or a good deal worse.

We have also made some experiments on the best shapes for the uprights of our machine, and again found out that everybody but ourselves are very badly mistaken!!!

Wilbur to George A. Spratt, April 27, 1903

If a man is in too big a hurry to give up an error he is liable to give up some truth with it, and in accepting the arguments of the other man he is sure to get some error with it.  Honest argument is merely a process of mutually picking the beams and motes out of each others’ eyes so both can see clearly.  Men become wise just as they become rich, more by what they save than by what they receive.  After I get hold of a truth I hate to lose it again, and I like to sift all the truth out before I give up an error.