Both of these instruments provide turn information.  [Figure 6-12]  The turn coordinator provides both bank rate  and then turn rate once stabilized. The turn-and-slip indicator  provides only turn rate. As illustrated in  Figure 6-15,  power indicator instruments  include: The airspeed indicator provides an indication of power  best observed initially in level flight where the aircraft is in  balance and trim. If in level flight the airspeed is increasing,  it can generally be assumed that the power has increased,  necessitating the need to adjust power or re-trim the aircraft. Engine instruments, such as the manifold pressure (MP)  indicator, provide an indication of aircraft performance for a  given setting under stable conditions. If the power conditions  are changed, as reflected in the respective engine instrument  readings, there is an affect upon the aircraft performance,  either an increase or decrease of airspeed. When the propeller  rotational speed (revolutions per minute (RPM) as viewed  on a tachometer) is increased or decreased on fixed-pitch  propellers, the performance of the aircraft reflects a gain or  loss of airspeed as well.  Proper trim technique is essential for smooth and accurate  instrument flying and utilizes instrumentation illustrated in  Figure 6-16.  The aircraft should be properly trimmed while  executing a maneuver. The degree of flying skill, which  ultimately develops, depends largely upon how well the  aviator learns to keep the aircraft trimmed. A power change to adjust airspeed may cause movement  around some or all of the aircraft axes. The amount and  direction of movement depends on how much or how rapidly  the power is changed, whether single-engine or multiengine  airplane or helicopter. The effect on pitch attitude and  airspeed caused by power changes during level flight is  illustrated in  Figures 6-13  and  6-14 . During or immediately  after adjusting the power control(s), the power instruments  should be cross-checked to see if the power adjustment is  as desired. Whether or not the need for a power adjustment  is indicated by another instrument(s), adjustment is made  by cross-checking the power instruments. Aircraft are  powered by a variety of powerplants, each powerplant  having certain instruments that indicate the amount of power  being applied to operate the aircraft. During instrument  flight, these instruments must be used to make the required  power adjustments.  An airplane is correctly trimmed when it is maintaining a  desired attitude with all control pressures neutralized. By  relieving all control pressures, it is much easier to maintain the  Airplane Trim Power Control Trim Control Airspeed Indicator Engine Instruments • Airspeed indicator • Engine instruments Turn Coordinator/Turn-and-Slip Indicator Figure 6-12.  Turn coordinator and turn-and-slip indicator. DC ELEC  L R  Figure 6-13.  An increase in power—increasing airspeed accordingly in level flight. 6-8