Accelerating/Decelerating Turns are practised to enhance attitude control during extreme speed changes.
At an operationally safe altitude, and after completing clearing turns, establish the aircraft at normal cruise speed, straight and level, and align with a prominent ground reference (preferably “the grid” based on the alignment of streets and avenues). Smoothly close the throttle; once the Vfe speed range is entered, smoothly deploy full flap, using care to keep the aircraft straight and at a constant altitude. Allow the aircraft to enter Vmc,1 at which point power is added sufficient to stabilize the slow flight condition and simultaneously initiate a 30°-banked turn through a heading change of 180°, making smooth pitch changes in conjunction with the required power changes to maintain Vmc. After completing the minimum radius turn, use aggressive but smooth power to accelerate quickly back to normal cruise speed, again with constant altitude and direction. Repeat with turns in alternating directions. Also, practice the same manoeuvre with speed during the turn slowing to 70 MPH, and using a 45° bank and clean flap.
This manoeuvre should only be practised at altitudes sufficient to recover from inadvertent spin entry, and the aircraft must therefore be operated in the utility category. Always check adjacent airspace for additional traffic prior to initiating the manoeuvre.
1 That is, the minimum speed at which the aircraft can be controlled.