Side Slip

Side-Slip

Slipping is a manoeuvre in which the aircraft is placed in a banked attitude but its tendency to turn is either reduced or prevented by the use of rudder.

Objectives

  • Entry, practical use and recovery from different slips.
  • Safety considerations.

Why ?

  • This technique it’s important for landing with crosswind.

Link

Review Questions

  • How do you maintain a coordinated flight ?
  • What is the main difference from a spin and spiral?
  • If you apply left rudder, which way would the nose of the aircraft point ?

Type of slipping

  • Side-Slip (regular slip): used for crosswind landings.
  • Forward slip: used to lose extra height. (Needed during flap failure for instance).
  • Slipping Turn: used to lose extra height while in a descending turn.

Side-Slip

  • Side-slip purpose is to counteract the effect of drift when landing in a cross-wind.
  • In a sideslip, the airplane’s longitudinal axis remains parallel to the original flight path.
  • The steeper the bank—the greater the degree of slip.
  • As bank angle is increased, additional opposite rudder is required to prevent turning.

Side-slip: Entry

  • Use ailerons to bank the airplane in the direction of the wind.
  • At the same time use opposite rudder to maintain the airplane’s longitudinal axis parallel to the original flight path.
  • Use elevator to control approach speed.
  • Use power to control rate of descent while on approach to landing.
  • The drift is controlled with aileron, and the heading with rudder.
  • Anticipate control pressure when maintaining a slip. If full rudder is used, considerable aileron pressure may be needed to maintain the bank.

Side-slip: Recovery

Simultaneously :
  • Releasing rudder pressure.
  • Leveling the wings.
  • Adjusting pitch to resume normal descend and attitude.

Forward-slip

  • The forward slip will change the heading (longitudinal axis) of the aircraft away from the down wing, while retaining the original track (flight path over the ground) of the aircraft.
  • A forward-slip is useful when a pilot has set up for a landing approach with excessive height or must descend steeply beyond a tree line to touchdown near the start of a short runway.
  • Assuming that the runway is properly lined up, the forward slip will allow the aircraft track to be maintained while steepening the descent without adding excessive airspeed.
  • Since the heading (or longitudinal axis) is not aligned with the runway, the slip must be removed before touchdown to avoid excessive side loading on the landing gear.

Forward-slip Entry

  • Power to idle to increase the rate of descent.
  • Roll into a gentle bank into the wind
  • At the same time, apply opposite rudder to keep the plane from turning on the lowered wing.
  • Pitch: To prevent the airspeed from increasing, raise the nose slightly above the normal gliding position.

Forward-slip Recovery

  • Raising the low wing
  • In the same time release rudder pressure.
  • Level the wing and adjust the pitch attitude.

Slipping Turn

  • A slipping turn uses the same procedure as forward slip (increased the rate of descent without increasing airspeed) but does this in turn.
  • The turn is slowed, but not prevented, by the use of opposite rudder.
  • The slipping turn can be useful during a turn to final approach, especially in the case of a forced landing in which excess altitude must be lost.
  • Recovery procedure is identical to forward slip

Instruments

  • Turn Coordinator:
    • Wings slightly inclined
    • Ball indicates opposite to rudder position
  • Altimeter and Vertical Speed Indicator:
    • High rate of descent
  • Attitude indicator:
    • Bank in the direction of control column deflection.

*Because of the location of the pitot tube and static vents, airspeed indicators in some airplanes may have considerable error when the airplane is in a slip.

Review Questions

  • What’s the procedure for entry and recovery from a side-slip?
  • What are the 3 types of slip ?
  • In a sideslip, does the airspeed indicator over-read or under-read ?