Power Off Stalls


Objective: The objective of this lesson is to develop a student’s ability to perform and knowledge of the maneuver. To develop the students ability to perform the maneuver with proficiency according to the standards set forth in the PTS. To develop an understanding of the factors involved in a Power-Off stall.

Mechanics: A stall is a condition where the wings of the aircraft will cease creating lift. This is due to the aircraft exceeding the critical angle of attack. The Critical angle of Attack is a very relative term. Let us first look at what an Angle of Attack is. An angle of attack is the difference between the Chord line and the relative wind. The chord line is an imaginary line that extends from the rear edge of the wing through the front of the wing and into space. The relative wind can be thought of as the airflow past the aircraft. So the difference between these two is considered the Angle of Attack, AOA. This angle becomes critical at the point where the aircraft stalls, but since we have no Critical of Attack meter in the aircraft we use airspeed as a gauge. For example we know that the aircraft will stall at 56 kts when we have full flaps out and gear extended. That is to say we know that we can not hold the aircraft at an angle that will keep altitude without stalling in this configuration because to keep altitude it would take to great an Angle of Attack, nose up attitude.

Steps:

  1. Clearing Turn
  2. Carburetor heat on and power back to 1700 rpm
  3. 10 degrees flaps and stabilize, while maintaining altitude
  4. 20 degrees flaps and stabilize, while maintaining altitude
  5. 30 degrees flaps, while maintaining altitude
  6. Reduce power to idle, while maintaining altitude
  7. Add 10 degrees bank if turning in the stall
  8. Raise nose to stall horn/buffet/break

Recovery:
To recover from a stall we want to decrease our angle of Attack, get our speed high, and decrease the drag of the aircraft. To that effect the steps or recovery are as follows.

  1. Lower nose slightly below horizon
  2. Apply full power and carburetor heat off
  3. 20 degrees flaps and stabilize
  4. 10 degrees flaps and stabilize
  5. Flaps up
  6. Accelerate to normal cruise speed
  7. Straight and level
  8. Power back to cruise

Common Errors:

  1. Secondary stall – once we have created airflow over the wings again (out of a stall) we must not be to hasty to pull up and regain our altitude because we are flying at a low airspeed and it will be easy to exceed our critical angle of attack.
  2. Not pushing forward enough to break the stall initially

Completion Standards:

  1. The student will be considered proficient when he or she understands the aerodynamic concepts of this maneuver and can perform the maneuver according to the standards set forth in the PTS.

PTS Standards of completion

  1. Exhibits knowledge of the elements related to power-off stalls.
  2. Plans and enters the maneuver at appropriate altitude, no less than 1,500 AGL.
  3. Establishes a stabilized approach in correct landing configuration as determined by the examiner.
  4. Transitions smoothly from the approach or landing attitude to the attitude that will induce the stall.
  5. Maintains specific heading + 10 degrees, in straight flight; maintains a specific angle of bank not to exceed 20 degrees + 10 degrees in turning flight while inducing stall.
  6. Recognizes and recovers promptly after the stall occurs by simultaneously reducing the angle of attack, increasing power as appropriate, and leveling the wings to return to straight and level flight attitude with a minimal loss of altitude appropriate for the airplane.
  7. Retract flaps to the recommended setting; retracts the landing gear if retractable after a positive rate of climb is established.
  8. Accelerates to Vx or Vy speed before the final flap retraction; returns to the altitude, heading, and airspeed determined by the examiner.