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FLIGHT INSTRUCTOR'S MANUAL                                                          55

a race with an airplane during which the airplane and the pilot alternately chased each other until a crack-up called a halt to the proceedings.

                                 USE OF THE THROTTLE
 The student should learn in his training that the throttle or "power control" is a control to be used and coordinated the same as the stick ot the rudder. With the exception of vertical banks, maneuvers executed in the same  horizontal plane will not require its use, but all others should have the power coordinated properly in applying the proper amount of power at the proper instant will, of course, be developed during the practice of advanced maneuvers. However, the student should be taught the fundamentals of throttle operation as early as is consistent with his aptitude and progress.
 The throttle should never be used abtuptly, even when necessity requires quick application of full power. The student should be impressed that the throttle must always be used smoothly and deliberately even though the action required may be immediate. The difference between fast smooth operation and abrupt operation is difficult to explain, but can easily be demonstrated. This difference is very much akin to similar use of the stick or the rudder. In many cases the engine will not respond as quickly to the abrupt action as to the smooth use due to the design or some slight operating maladjustment of the carburetor, the setting of the mixture control, or some mechanical feature in the design of the partucylar engine.
 Another reason, common to engines of higher hoesepower, is the torque effect on some aircraft. In these, the sudden application of power will impart a violent rolling moment to the airplane which may result disastrously if it happens in a glide close to the ground or as the result of throttle use necessitated by  a bad landing. It also will cause an uncontrollable ground loop during the initial period of the take-off or while taxiing because the rudder is too ineffective to overcome this tendency at such low soeeds.
 The main reason for smooth operatin of the throttle, however, is the mechanical abuse which attends abrupt and sharp use of the throttle. This is more or less true of all engines but is particularly  true of supercharged engines or engines equipped with rotary induction systems. Many engines habe these "blowers" geared from 10 to 15 times crankshaft speed. Taking for example an engine with top speed of 2,000 r.p.m. and a blower geared 10 to 1, the sudden opening of the throttle from idling position of say 800 r.p.m. to full throttle of 2,000 r.p.m., causes thecrankshaft to accelerate almost instantly 1,200 r.p.m. This places severe loads on all the moving parts while overcoming their inertia during this rapid aceleration. However, this is increased many fold on the much lighter and more delicate parts of the impller system, since in the same length of time they must accelerate 10 times as much as the crankshaft or from 8,000 r.p.m. to 20,000 r.p.m. Since the stresses and inertias increase in more that direct proportion to the increased speed and more particularly to the relative rapidity of this increase, it can easily be seen that sever strains are imposed in parts that are