The relationship between the aircraft’s speed and bank angle  to the rate and radius of turns is important for instrument  pilots to understand. The pilot can use this knowledge to  properly estimate bank angles needed for certain rates of turn,  or to determine how much to lead when intercepting a course. The rate of turn, normally measured in degrees per second,  is based upon a set bank angle at a set speed. If either one  of these elements changes, the rate of turn changes. If the  aircraft increases its speed without changing the bank angle,  the rate of turn decreases. Likewise, if the speed decreases  without changing the bank angle, the rate of turn increases. Changing the bank angle without changing speed also causes  the rate of turn to change. Increasing the bank angle without  changing speed increases the rate of turn, while decreasing  the bank angle reduces the rate of turn. The standard rate of turn, 3° per second, is used as the main  reference for bank angle. Therefore, the pilot must understand  how the angle of bank varies with speed changes, such  as slowing down for holding or an instrument approach.  Figure 4-15  shows the turn relationship with reference to a  constant bank angle or a constant airspeed, and the effects on  rate of turn and radius of turn. A rule of thumb for determining  the standard rate turn is to divide the airspeed by ten and  add 7. An aircraft with an airspeed of 90 knots takes a bank  angle of 16° to maintain a standard rate turn (90 divided by  10 plus 7 equals 16°). The radius of turn varies with changes in either speed or  bank. If the speed is increased without changing the bank  angle, the radius of turn increases, and vice versa. If the speed  is constant, increasing the bank angle reduces the radius of  In a slipping turn, the aircraft is not turning at the rate  appropriate to the bank being used, and the aircraft falls to  the inside of the turn. The aircraft is banked too much for the  rate of turn, so the horizontal lift component is greater than  the centrifugal force. A skidding turn results from excess of  turn, while decreasing the bank angle increases the radius of  turn. This means that intercepting a course at a higher speed  requires more distance, and therefore, requires a longer lead.  If the speed is slowed considerably in preparation for holding  or an approach, a shorter lead is needed than that required for  cruise flight. Any time ailerons are used, adverse yaw is produced. Adverse  yaw is caused when the ailerons are deflected as a roll motion  (as in turn) is initiated. In a right turn, the right aileron is  deflected upward while the left is deflected downward. Lift is  increased on the left side and reduced on the right, resulting  in a bank to the right. However, as a result of producing lift  on the left, induced drag is also increased on the left side.  The drag causes the left wing to slow down, in turn causing  the nose of the aircraft to initially move (left) in the direction  opposite of the turn. Correcting for this yaw with rudder, when  entering and exiting turns, is necessary for precise control of  the airplane when flying on instruments. The pilot can tell if  the turn is coordinated by checking the ball in the turn-and- slip indicator or the turn coordinator.  [Figure 4-16] As the aircraft banks to enter a turn, a portion of the wing’s  vertical lift becomes the horizontal component; therefore,  without an increase in back pressure, the aircraft loses altitude  during the turn. The loss of vertical lift can be offset by  increasing the pitch in one-half bar width increments. Trim  may be used to relieve the control pressures; however, if used,  it has to be removed once the turn is complete. Coordination of Rudder and Aileron Controls Rate of Turn Radius of Turn Radius≈1,500  Radius≈3,500  Radius≈6,500  Radius≈8,000  Radius≈3,500  Radius≈2,000  Figure 4-15.  Turns. 4-11