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Slow Flight and Stalls

Slow Flight​

Objective​

Maintain coordinated airplane control at speeds slower than cruise speed.

Concepts​

Lift vs drag

  • Drag is minimum at best glide speed (best L/D).
    • To go faster than best L/D, we need more thrust to overcome parasite drag.
    • To go slower than best L/D, we need more thrust to overcome induced drag.
  • The goal of slow flight is to operate slower than best L/D, where additional power is required.

Operations​

  • Start with a reduction in power.
  • Put in flaps one notch at a time, anticipating the nose-up pitching movement when flaps are lowered.
  • Start pushing in power as we get slower.
  • Elevator controls pitch, power controls airspeed.
  • Controls become spongy.
  • Left-turning tendencies will increase:
    • Higher torque from higher power.
    • Higher slipstream from higher power.
    • Higher P-factor from higher power and AoA.
  • Turns should remain very shallow since most of our lift is being converted to drag.
  • Good to introduce after the 4 fundamental maneuvers.

Common Errors​

  • Failure to clear the area.
  • Inadequate elevator back-pressure.
  • Fixation on the airspeed indicator.
  • Inadequate compensation for left-turning tendencies.
  • Failure to anticipate changes in lift with changes in flaps.
  • Inability to divide attention between inside and outside the airplane.

Power-Off Stalls​

Objective​

Develop recognition of an impending stall in a landing configuration and apply proper recovery technique, avoiding a secondary stall.

Operations​

  • Slow the airplane as you would in slow flight.
  • Allow the airplane to descend as in a landing.
  • Slowly pitch up until a stall warning, then a stall.
  • Symptoms of a stall
    • Nose-high attitude
    • Low airspeed
    • Sloppy or mushy controls
    • Stall warning horn, light
    • Buffeting
    • Nose pitching down
  • Recovery
    • Move elevator forward just enough to eliminate the stall symptoms
    • Add full power, which will add left-turning tendency
    • Use enough rudder to stop wings from dropping (but not bringing the wing back up)
    • Bring wings level
  • Secondary stall
    • Being too abrupt when recovering pitch with the elevator can cause a secondary stall
  • Adding flaps can increase the likelihood of a wing drop

Common Errors​

  • Failure to clear the area
  • Inability to recognize impending stall condition
  • Premature recovery
  • Over-reliance on airspeed indicator
  • Inadequate rudder control
  • Inadvertent secondary stall
  • Excessive forward pressure during recovery
  • Excessive airspeed build-up during recovery

Power-On Stall​

Objective​

To develop recognition of an impending stall or stalled condition in the takeoff configuration, and initiated recovery.

Operation​

  • Reduce throttle, keep the airplane level, slow to rotation speed
  • At rotation speed apply full power and raise the nose to about 20 degrees
  • Stalls may occur more quickly
  • Recovery
    • Small reduction in elevator back pressure enough to eliminate the stall warnings
    • Use rudder to stop any wing from dropping
    • Raise any dropped wing with aileron during the climb

Spins​

A spin is caused by a stall aggravated by yaw.