The "Hammerhead" is also called a "Stall Turn". The simplest version of this maneuver starts when the airplane leaves horizontal flight and does a quarter loop to a vertical up line. At the top, the plane stops, pivots on its center of gravity and establishes a vertical down line. At the bottom of the down line, the aircraft flies a second quarter loop to return to horizontal flight.
According to the AMA Competition regulations, the following situations cause deductions:
The entry and the exit radius of the quarter loops do not match. The number of points deducted is at the discretion of the judge.