POWER OFF STALLS
Power Off Stalls Lesson by wifiCFI
Objective
To determine that the applicant exhibits satisfactory knowledge, risk management, and skills associated with power off stalls.
Knowledge
The applicant demonstrates understanding of:
Aerodynamics associated with stalls in various aircraft configurations, to include the relationship between angle of attack, airspeed, load factor, power setting, aircraft weight and center of gravity, aircraft attitude, and yaw effects.
Stall characteristics and impending stall and full stall indications.
Factors and situations that can lead to a power-off stall and actions that can be taken to prevent it.
Fundamentals of stall recovery.
Risk Management
The applicant demonstrates the ability to identify, assess and mitigate risks, encompassing:
Factors and situations that could lead to inadvertent power-off stall, spin, and loss of control.
Range and limitations of stall warning indicators.
Failure to recognize and recover at the stall warning during normal operations.
Improper stall recovery procedure.
Secondary stalls, accelerated stalls, and cross-control stalls.
Effect of environmental elements on aircraft performance related to power-off stalls.
Collision hazards, to include aircraft, terrain, obstacles, and wires.
Distractions, loss of situational awareness, and/or improper task management.
Stalls (AFH C4)
A stall is an aerodynamic condition which occurs when smooth airflow over the airplane’s wings is disrupted, resulting in loss of lift.
Specifically, a stall occurs when the AOA, the angle between the chord line of the wing and the relative wind, exceeds the wing’s critical AOA.
It is possible to exceed the critical AOA at any airspeed, at any attitude, and at any power setting.
Impending Stall
An impending stall occurs when the AOA causes a stall warning, but has not yet reached the critical AOA.
Indications of an impending stall can include buffeting, stick shaker, or aural warning.
Full Stall
A full stall occurs when the critical AOA is exceeded.
Indications of a full stall are typically that an uncommanded nose-down pitch cannot be readily arrested, and this may be accompanied by an uncommanded rolling motion.
Stall Recovery
Depending on the complexity of the airplane, stall recovery could consist of as many as six steps.
Even so, the pilot should remember the most important action to an impending stall or a full stall is to reduce the AOA.
However, a pilot should always follow the aircraft-specific manufacturer’s recommended procedures if published and current.
Disconnect the wing leveler or autopilot (if equipped).
Pitch nose-down control.
Trim nose-down pitch.
Roll wings level.
Add thrust/power.
Retract speedbrakes/spoilers (if equipped).
Return to the desired flightpath.
Power Off Stalls (AFH C4)
The practice of power-off stalls is usually performed with normal landing approach conditions to simulate an accidental stall occurring during approach to landing.
However, power off stalls should be practiced at all flap settings to ensure familiarity with handling arising from mechanical failures, icing, or other abnormal situations.
Airspeed in excess of the normal approach speed should not be carried into a stall entry since it could result in an abnormally nose-high attitude.
Performing the Maneuver
To set up the entry for a straight-ahead power-off stall, airplanes equipped with flaps or retractable landing gear should be in the landing configuration.
Extend the landing gear
Apply carburetor heat (if applicable),
Retarding the throttle to idle (or normal approach power)
Hold the airplane at a constant altitude in level flight until the airspeed decelerates to normal approach speed.
The airplane should then be smoothly pitched down to a normal approach attitude to maintain that airspeed.
Wing flaps should be extended and pitch attitude adjusted to maintain the airspeed.
Private Pilot ACS Standards
Clear the area.
Select an entry altitude that will allow the task to be completed no lower than 1,500 feet AGL (ASEL) or 3,000 feet AGL (AMEL).
Configure the airplane in the approach or landing configuration, as specified by the evaluator, and maintain coordinated flight throughout the maneuver.
Establish a stabilized descent.
Transition smoothly from the approach or landing attitude to a pitch attitude that will induce a stall.
Maintain a specified heading, ±10 if in straight flight; maintain a specified angle of bank not to exceed 20°, +/-10°, if in turning flight, while inducing the stall.
Acknowledge cues of the impending stall and then recover promptly after a full stall has occurred.
Execute a stall recovery in accordance with procedures set forth in the POH/AFM.
Retract the flaps to the recommended setting; retract the landing gear, if retractable, after a positive rate of climb is established.
Accelerate to VX or VY speed before the final flap retraction; return to the altitude, heading, and airspeed specified by the evaluator.
Commercial Pilot ACS Standards
Clear the area.
Select an entry altitude that will allow the task to be completed no lower than 1,500 feet AGL (ASEL) or 3,000 feet AGL (AMEL).
Configure the airplane in the approach or landing configuration, as specified by the evaluator, and maintain coordinated flight throughout the maneuver.
Establish a stabilized descent.
Transition smoothly from the approach or landing attitude to a pitch attitude that will induce a stall.
Maintain a specified heading, ±10 if in straight flight; maintain a specified angle of bank not to exceed 20°, ±5°, if in turning flight, while inducing the stall.
Acknowledge cues of the impending stall and then recover promptly after a full stall has occurred.
Execute a stall recovery in accordance with procedures set forth in the POH/AFM.
Retract the flaps to the recommended setting; retract the landing gear, if retractable, after a positive rate of climb is established.
Accelerate to VX or VY speed before the final flap retraction; return to the altitude, heading, and airspeed specified by the evaluator.
Common Errors
Failure to adequately clear the area
Over-reliance on the airspeed indicator and slip-skid indicator while excluding other cues
Inadvertent accelerated stall by pulling too fast on the controls during a power-off or power on stall entry
Inability to recognize an impending stall condition
Failure to take timely action to prevent a full stall during the conduct of impending stalls
Failure to maintain a constant bank angle during turning stalls
Failure to maintain proper coordination with the rudder throughout the stall and recovery
Recovering before reaching the critical AOA when practicing the full stall maneuver
Not disconnecting the wing leveler or autopilot, if equipped, prior to reducing AOA
Recovery is attempted without recognizing the importance of pitch control and AOA
Not maintaining a nose down control input until the stall warning is eliminated
Pilot attempts to level the wings before reducing AOA
Pilot attempts to recover with power before reducing AOA
Failure to roll wings level after AOA reduction and stall warning is eliminated
Inadvertent secondary stall during recovery
Excessive forward-elevator pressure during recovery resulting in low or negative G load
Excessive airspeed buildup during recovery
Losing situational awareness and failing to return to desired flightpath or follow ATC instructions after recovery.
FAA Sources Used for This Lesson
Private Pilot Airmen Certification Standards
Commercial Pilot Airmen Certification Standards
Airplane Flying Handbook (AFH) Chapter 4