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are as follows: Speed in horizontal flight, 55 miles per hour; useful load, 600 pounds; weight of machine empty, 1,200 pounds; fuel and oil for six hours' flight, 200 pounds; total weight in flight order, 2,000 pounds; climbing speed, 250 feet per minute; seating capacity for three arranges so as to permit of the largest possible view, control to be in triplicate; gliding angle, one in six.

For east of transportation the Breguet type of biplane is adopted as this machine possesses the feature of demountability in a very large degree. To land and start from a ploughed field it is necessary to use large wheels in the landing gear, and such a combination of engine and propeller that will give a high ground thrust.

In order to determine the most suitable wing section it is necessary to approximate the weight of the machine without passengers or supplies. By comparing the different machines that competed in the recent French military trials it has been determined that the average weight of a biplane capable of carrying two passengers and an aviator will be something less than 1,200 pounds when fitted with a motor of from 80 to 90-horsepower.

Assuming 1,200 pounds as the weight of the empty machine and a rate of fuel consumption based on the use of an 80-horsepower motor, at a rate of 10 gallons of fuel and oil per hour, the weight of the necessary supplies for a run of six hours will be about 200 pounds, making the total weight of the machine in order of flight 2,000 pounds.

The efficiency curve of the wing section adopted is shown at the right of the design chart. This curve shows the same general slope from two to eight degrees, indicating that the efficiency of this type of wing will be the same within these

*"How to Design a Modern Aeroplane," AERO, Vol. III, Nos. 15