Winter Instruments QM 3 Slip/Skid Indicator
Slip/Skid Size III, No. 1115 Winter Slip/Skid fits in a standard 57 mm (2 ¼") instrument hole.
Slip vs. Skid
Slipping turn An uncoordinated turn in which the aircraft is banked too much for the rate of turn, so the horizontal lift component is greater than the centrifugal force, pulling the aircraft toward the inside of the turn.
Skidding turn An uncoordinated turn in which the rate of turn is too great for the angle of bank, pulling the aircraft to the outside of the turn.
What is an inclinometer or slip / skid indicator?
A slip/skid indicator is also know as an inclinometer. Like the magnetic compass, this instrument requires no electrical power or input from other aircraft systems. The inclinometer is influenced by centrifugal force and gravity. Mounted in the bottom of a turn-and-bank indicator or mounted separately in the instrument panel, the inclinometer consists of a metal ball in an oil-filled, curved glass tube. When the glider is flying in coordinated fashion, the ball remains centered at the bottom of the glass tube. The inclinometer differs from the yaw string during uncoordinated flight. The ball moves to the inside of the turn to indicate a slip and to the outside of the turn to indicate a skid. Remember the phrase, “step on the ball” in reference to the inclinometer; it helps coordinate the turn using rudder inputs. The long glider wing tends to increase the adverse yaw effects from the ailerons and requires more rudder control than many aircraft. - Source: Glider Flying Handbook