Page 185 - Airplane Flying Handbook

Figure 9-14. Forward slip.

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Some pilots try to avoid using forward slips. An approach with flaps allows for coordinated and more familiar flight orientation, while
the sideways force on the occupants of the aircraft during a forward slip may seem uncomfortable. However, in a real emergency that
involves engine failure, the ability to use a forward slip provides a pilot with a technique contributing to a better outcome. In that
situation, a pilot may initiate a descent using a forward slip much more quickly than by deploying flaps. To reduce the descent, the pilot
can remove the slip without penalty. On the other hand, retracting flaps on an approach could lead to an unwanted loss of altitude. Even
with full rudder displacement during a forward slip, the pilot can adjust to the left and right of the intended ground track by increasing
and decreasing aileron deflection. The value of the maneuver explains its inclusion as a task in the Private Pilot Airman Certification
Standards (ACS).

9-14