PROPELLERS WITH VARYING PITCH.—It is growing more apparent each day, that a new type of propeller must be devised which will enable the pilot to change the pitch, as the speed increases, and to give a greater pitch, when alighting, so as to make the power output conform to the conditions.
Such propellers, while they may be dangerous, and much heavier than the rigid type, will, no doubt, appear in time, and the real improvement would be in the direction of having the blades capable of automatic adjustment, dependent on the wind pressure, or the turning speed, and thus not impose this additional duty on the pilot.
CHAPTER XI
FLYING MACHINE ACCESSORIES
THE ANEMOMETER.—It requires an expert to judge the force or the speed of a wind, and even they will go astray in their calculations. It is an easy matter to make a little apparatus which will accurately indicate the speed. A device of this kind is called an Anemometer.
Two other instruments have grown out of this, one to indicate the pressure, and the other the direction of the moving air current.
THE ANEMOGRAPH.—While these instruments indicate, they are also made so they will record the speed, the pressure and the direction, and the device for recording the speed and pressure is called a Anemograph.
All these instruments may be attached to the same case, and thus make a handy little device, which will give all the information at a glance.
THE ANEMOMETROGRAPH.—This device for recording, as well as indicating the speed, pressure and direction, is called an Anemometrograph, The two important parts of the combined apparatus, for the speed and pressure, are illustrated, to show the principle involved. While the speed will give the pressure, it is necessary to make a calculation to get the result while the machine does this for you.
Fig. 61. Speed Indicator.