Accelerated Stalls Lesson by wifiCFI
To determine that the applicant exhibits satisfactory knowledge, risk management, and skills associated with accelerated stalls.
The applicant demonstrates understanding of:
Aerodynamics associated with accelerated 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 (i.e., airplane design) and impending stall and full stall indications (i.e., how to recognize by sight, sound, or feel).
Factors and situations that can lead to an accelerated stall and actions that can be taken to prevent it.
Fundamentals of stall recovery.
The applicant demonstrates the ability to identify, assess and mitigate risks, encompassing:
Factors and situations that could lead to an inadvertent accelerated stall, spin, and loss of control.
Range and limitations of stall warning indicators (e.g., aircraft buffet, stall horn, etc.).
Failure to recognize and recover at the stall warning during normal operations.
Improper stall recovery procedure.
Secondary stalls, cross-control stalls, and spins.
Effect of environmental elements on aircraft performance related to accelerated stalls (e.g., turbulence, microbursts, and high density altitude).
Collision hazards, to include aircraft, terrain, obstacles, and wires.
Distractions, loss of situational awareness, and/or improper task management.
Accelerated Stalls (AFH C4)
The objectives of demonstrating an accelerated stall are to determine the stall characteristics of the airplane, experience stalls at speeds greater than the +1G stall speed, and develop the ability to instinctively recover at the onset of such stalls.
At the same gross weight, airplane configuration, CG location, power setting, and environmental conditions, a given airplane consistently stalls at the same indicated airspeed provided the airplane is at +1G (i.e., steady-state unaccelerated flight).
However, the airplane can also stall at a higher indicated airspeed when the airplane is subject to an acceleration greater than +1G, such as when turning, pulling up, or other abrupt changes in flightpath.
Stalls encountered any time the G-load exceeds +1G are called “accelerated maneuver stalls”.
A pilot should never practice accelerated stalls with wing flaps in the extended position due to the lower design G-load limitations in that configuration.
Accelerated stalls should be performed with a bank of approximately 45°, and in no case at a speed greater than the airplane manufacturer’s recommended airspeed or the specified design maneuvering speed (VA).
Flying the Maneuver
The most common accelerated stall procedure starts from straight-and-level flight at an airspeed at or below VA.
Roll the airplane into a coordinated, level-flight 45° turn and then smoothly, firmly, and progressively increase the AOA through back elevator pressure until a stall occurs.
An airplane typically stalls during a level, coordinated turn similar to the way it does in wings level flight, except that the stall buffet can be sharper.
If the turn is coordinated at the time of the stall, the airplane’s nose pitches away from the pilot just as it does in a wings level stall since both wings will tend to stall nearly simultaneously.
If the airplane is not properly coordinated at the time of stall, the stall behavior may include a change in bank angle until the AOA has been reduced.
It is important to take recovery action at the first indication of a stall (if impending stall training/checking) or immediately after the stall has fully developed (if full stall training/checking) by applying forward elevator pressure as required to reduce the AOA and to eliminate the stall warning, level the wings using ailerons, coordinate with rudder, and adjust power as necessary.
Commercial Pilot ACS Standards
Clear the area.
Select an entry altitude that will allow the Task to be completed no lower than 3,000 feet AGL.
Establish the configuration as specified by the evaluator.
Set power appropriate for the configuration, such that the airspeed does not exceed the maneuvering speed (VA), flap extension speed (VFE), landing gear extended speed (VLE), and any other POH/AFM limitation.
Establish and maintain a coordinated turn in a 45° bank, increasing elevator back pressure smoothly and firmly until an impending stall is reached.
Acknowledge the cues and recover promptly at the first indication of an impending stall (e.g., aircraft buffet, stall horn, etc.).
Execute a stall recovery in accordance with procedures set forth in the POH/AFM.
Retract the flaps to the recommended setting, if applicable; 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.
Failure to adequately clear the area
Over-reliance on the airspeed indicator and slip-skid indicator while excluding other cues
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
Commercial Pilot Airmen Certification Standards
Airplane Flying Handbook (AFH) Chapter 4