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Prior to performing timed turns, the turn coordinator should be calibrated to determine the accuracy of its indications. To do this, establish a standard rate turn by referring to the turn-and-slip indicator. Then, as the sweep second hand of the clock passes a cardinal point (12, 3, 6, or 9), check the heading on the heading indicator. While holding the indicated rate of turn constant, note the heading changes at 10-second intervals. If the helicopter turns more or less than 30° in that interval, a smaller or larger deflection of the needle is necessary to produce a standard rate turn. After the turn- and-slip indicator has been calibrated during turns in each direction, note the corrected deflections, if any, and apply them during all timed turns. 

Use the same cross-check and contr ol technique in making timed turns that is used to make tu rns to a predetermined heading, but substitute the clock fo r the heading indicator. The needle of the turn-and-slip i ndicator is primary for bank control, the altimeter is primar y for pitch control, and the airspeed indicator is primary fo r power control. Begin the roll-in when the clock’s second  hand passes a cardinal point; hold the turn at the calibrated standard rate indication or half-standard rate for small ch anges in heading; then begin the roll-out when the compu ted number of seconds has elapsed. If the roll-in and roll-ou t rates are the same, the time taken during entry and recovery need not be considered in the time computation. 

If practicing timed turns with a full instrumen t pane l, check the heading indicator for the accuracy of the turns. If executing turns without the heading indicator, use t h e magnetic compass at the com pletion of the turn to check turn accuracy, taking compass deviation errors into consideration. 

## Change of Airspeed in Turns 

Changing airspeed in turns is an effective maneuver for increasing proficiency in all three basic instrument skills. Since the maneuver involves simultaneous changes in all components of control, pr oper execution requires a rapid cross-check and interpretation, as well as smooth control. Proficiency in the maneuve r also contributes to confidence in the instruments during attitude and power changes involved in more complex maneuvers. 

Pitch and power control techniques are the same as those used during airspeed cha nges in straight-and-level flight. As discussed previously, the angle of bank necessary for a given rate of turn is proportional to the true airspeed. Since the turns are executed at standard rate, the angle of bank must be varied in direct proportion to the airspeed change in order to maintain a constant rate of turn. During a reduction of airspeed, decrease the an gle of bank and increase the pitch attitude to maintain altitude and a standard rate turn. 

