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FLIGHT INSTRUCTOR'S MANUAL      41

for a student's forming the habit of climbing slightly on right-hand turns and diving slightly on left-hand turns. This fault has many other causes, including the unequal rudder pressures required to the right and to the left when turning due to the torque effect, and usually is very difficult of analysis and correction.

The student will soon begin to notice that the bank almost always tends to increase and has to be held by the use of some opposite control. This tendency, present in all ships to some extent. although more pronounced

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Figure 3.—Showing paths followed by different parts of airplane. All three distances are covered in the same length of time, this the outer wing tip must go faster than the inner tip and due to its increased speed will have greater lift, resulting in an over-banking tendency.

in ships without dihedral, is due to the difference in the speed of the high and the low wings during a turn. The high wing, being farther away from the center of the turn, moves faster. This is obvious, for although both wings travel through the same arc in the same time, the radius of the arc is longer for the high wing which consequently must cover a greater distance. (See fig. 3.) This increased speed causes an increase of lift. The high wing tends to lift over the low one, thus increasing the bank. As the bank becomes steeper, this tendency becomes less until in a true vertical or 90° bank it vanishes altogether. This is one of the reasons for insisting that