were some 81 square feet of carrying
surface missing over that of last year's model. and some 25 pounds loss
of weight. Relatively, though, the 1909 model aeroplane, while actually
25 pounds lighter, is really some 150 pounds heavier in the air than the
1908 model, owing to the lesser square feet of carrying surface.

Some of the Results Obtained.

Reducing the carrying surfaces from 6 to 5 1/2 feet gave two
results--first, less carrying capacity; and, second, less head-on
resistance, owing to the fact that the extent of the parabolic curve
in the carrying surfaces was shortened. The "head-on" resistance is
the retardance the aeroplane meets in passing through the air, and is
counted in square feet. In the 1908 model the curve being one in twelve
and 6 feet deep, gave 6 inches of head-on resistance. The plane being
40 feet spread, gave 6 inches by 40 feet, or 20 square feet of head-on
resistance. Increasing this figure by a like amount for each plane, and
adding approximately 10 square feet for struts, skids and wiring, we
have a total of approximately, 50 square feet of surface for "head-on"
resistance.

In the 1909 aeroplane, shortening the curve 6 inches at the parabolic
end of the curve took off 1 inch of head-on resistance. Shortening the
spread of the planes took off between 3 and 4 square feet of head-on
resistance. Add to this the total of 7 square feet, less curve surface
and about 1 square foot, less wire and woodwork resistance, and we
have a grand total of, approximately, 12 square feet of less "head-on"
resistance over the 1908 model.

Changes in Engine Action.

The engine used in 1909 was the same one used in 1908, though some minor
changes were made as improvements; for instance, a make and break spark
was used, and a nine-tooth, instead of a ten-tooth magneto gear-wheel
was used. This increased the engine revolutions per minute from 1,200 to
1,400, and the propeller revolutions per minute from 350 to 371, giving
a propeller thrust of, approximately, 170 foot pounds instead of 153, as
was had last year.

More Speed and Same Capacity.

One unsatisfactory feature of the 1909 model over that of 1908,
apparently, was the lack of inherent lateral stability. This was caused
by the lesser surface and lesser extent of curvatures at the portions
of the aeroplane which were warped. This defect did not show so plainly
after Mr. Orville Wright had become fully proficient in the handling of
the new machine,