ion it may be
placed at from three to four times the area of a 20-foot glider. [3]

Some Practical Examples.

The Wrights used a biplane 41 feet in spread, and 6 1/2 ft. deep. This,
for the two planes, gives a total surface area of 538 square feet,
inclusive of auxiliary planes. This sustains the engine equipment,
operator, etc., a total weight officially announced at 1,070 pounds. It
shows a lifting capacity of about two pounds to the square foot of plane
surface, as against a lifting capacity of about 1/2 pound per square
foot of plane surface for the 20-foot glider. This same Wright machine
is also reported to have made a successful flight, carrying a total load
of 1,100 pounds, which would be over two pounds for each square foot of
surface area, which, with auxiliary planes, is 538 square feet.

To attain the same results in a monoplane, the single surface would
have to be 60 feet in spread and 9 feet deep. But, while this is the
mathematical rule, Bleriot has demonstrated that it does not always hold
good. On his record-breaking trip across the English channel, July 25th,
1909, the Frenchman was carried in a monoplane 24 1/2 feet in spread,
and with a total sustaining surface of 150 1/2 square feet. The total
weight of the outfit, including machine, operator and fuel sufficient
for a three-hour run, was only 660 pounds. With an engine of (nominally)
25 horsepower the distance of 21 miles was covered in 37 minutes.

Which is the Best?

Right here an established mathematical quantity is involved. A small
plane surface offers less resistance to the air than a large one and
consequently can attain a higher rate of speed. As explained further
on in this chapter speed is an important factor in the matter of
weight-sustaining capacity. A machine that travels one-third faster
than another can get along with one-half the surface area of the latter
without affecting the load. See the closing paragraph of this chapter on
this point. In theory the construction is also the simplest, but this is
not always found to be so in practice. The designing and carrying
into execution of plans for an extensive area like that of a monoplane
involves great skill and cleverness in getting a framework that will be
strong enough to furnish the requisite support without an undue excess
of weight. This proposition is greatly simplified in the biplane and,
while the speed attained by the latter may not be quite so great as that
of the monopl