Stalls


Development:

When does it occur?

  1. A stall occurs when the smooth airflow over the airplane’s wing is disrupted, and the left degenerates rapidly; airflow separation.  This is caused when the wing exceeds its critical angle of attackThis can occur at any airspeed, in any attitude, with any power setting.

How do I recognize a stall?

  1. Unusual attitude—nose of aircraft is just too high.  When you exceed the critical angle of attack, the wings stall.
  2. Audible reduction in RPM—this means you’re climbing
  3. Controls become “mushy”—less airflow over the control surfaces
    1. Stall warning horn: most obvious warning; make sure it works in preflight (suck, don’t blow)

How do I recover from a stall?

  1. Reduce the angle of attack; (pitch attitude)by applying forward elevator pressure.  This will break the stall
  2. Advance the throttle.  This helps increase airspeed.
  3. Simultaneously maintain directional control with coordinated use of the aileron and rudder.

Types of stalls:

  1. Power-off stalls: as if coming in to land
  2. Power-on stalls: as if taking off
  3. Secondary stalls: too much back elevator after recovery into another stall
  4. Accelerated stall: too much elevator in a bank or abrupt maneuver
  5. Cross-control stall:  too much rudder to try and change direction (to runway)
  6.  Elevator Trim stall: not using rudders to coordinate turns at slower airspeeds

Conclusion and Evaluation: 

  1. Remember to fly with your feet to stay coordinated at all times
  2. Airplanes do not fly without airspeed, especially in T/O and Landings
  3. Quiz on underlined portion of III, and review part D.
  4. Read about stalls in AFH (chapter 5)

 

Types of stalls:

  1. Power-off stalls: as if coming in to land
  2. Power-on stalls: as if taking off
  3. Secondary stalls: too much back elevator after recovery into another stall
  4. Accelerated stall: too much elevator in a bank or abrupt maneuver
  5. Cross-control stall:  too much rudder to try and change direction (to runway)
  6. Elevator Trim stall: not using rudders to coordinate turns at slower airspeeds

GROUND LESSON:

Ever have your car “stall”? Well, when an airplane stalls, it has nothing to do with the engine.

Development:

What is a stall and when does it occur?

  1. A stall is a rapid decrease in lift caused by the separation of airflow from the wing’s surface.
  2. Aerodynamics: Draw wing profile
    1. Smooth airflow over wings

a)       Hand in river/pool: whitewater is like airflow separation

  1. Air will become turbulent over a wing by exceeding the critical angle of attack.
    1. 1.       Varied angle of incidence in wing design

a)       Stall strip encourages a stall by disrupting airflow at the root of the wing.

  1. Define Critical Angle of Attack (chord line, relative wind)
  2. A stall can occur at any pitch attitude, airspeed or power setting.
    1. 1.       Balloon in Hollywood, pitch up too fast can stall wing at high airspeed

How do I recognize a stall and why is it important?          Use your senses (not taste or smell): See, Hear, Feel

  1. Vision: Unusual attitude—nose of aircraft is higher than normal.  When you exceed the critical angle of attack, the wings stall.
  2. Hearing: Audible reduction in RPM—this means you’re climbing
    1. Hearing:  Stall warning horn: most obvious warning; make sure it works in preflight

a)       Explain how it works: (suck, don’t blow to test)

  1. Feeling: Controls become “mushy”—less airflow over the control surfaces
    1. Feeling: (buffet for power off stalls)

How do I recover from a stall and why is it important?

  1. Simultaneously: Reduce the angle of attack; (pitch attitude)by applying forward elevator pressure.  This will break the stall.
  2. Advance the throttle.  This helps increase airspeed.
  3. Level the wings to return to straight and level flight with minimal loss of altitude.

a)       Load factor: level wings mean less force for the wings to counter

  1. Simultaneously maintain directional control with coordinated use of the aileron and rudder.
  2. Secondary stalls: too much back elevator after recovery into another stall
  3. Spins: an aggravated stall resulting in auto rotation (corkscrew downward path).  The rising wing is less stalled than the descending wing, creating a rolling, yawing, and pitching motion.

Complete clearing turns before every performance maneuver—usually at least 180° change in direction, looking for traffic (Jeppesen Private Pilot pg. 4-6). Review flight procedure below.

Flight:

Technical Subject Areas:

Visual scanning/collision avoidance

Preflight preparation

Preflight procedures

Airport operations

Traffic patterns

Takeoff and climb

Recover:

  • Max Power
  • Reduce angle of attack (Pitch for Horizon)
  • Level the wings, return to straight and level flight.
  • After reverse of trend, flaps up, power cruise

 

Common errors: (3 minutes)

Not clearing the area
Improper configuration
Losing heading
Not slowing to rotation speed
Must increase back pressure progressively
Uncoordinated (very bad)
Lack of recognition of stall characteristics
Stall not achieved, or excessive altitude loss
Panicking: improper control order/recovery
Secondary stall (unsat.)
Flaps or gear not retracted

 

After landing

Parking & securing

Special Emphasis Areas:

Positive aircraft control

Positive exchange of flight controls

Visual scanning/collision avoidance

Stall/spin awareness

Oral evaluation of understanding through discussion/quiz: (2 minutes)
Q: What are the PTS tolerances?
Q: Why do wing roots stall first? Why are planes designed that way?
Q: What is a spin? How do we avoid them?
Q: What is a secondary stall?

 

Completion Standards:

PTS Power Off:

1. Exhibits knowledge of the elements related to power-off stalls.

2. Selects an entry altitude that allows the task to be completed no

lower than 3,000 feet (460 meters) AGL.

3. Establishes a stabilized descent in the approach or landing

configuration, as specified by the examiner.

4. Transitions smoothly from the approach or landing attitude to a pitch

attitude that will induce a stall.

5. Maintains a specified heading, ±10°, in straight flight; maintains a

specified angle of bank not to exceed 20°, ±10°; in turning flight,

while inducing the stall.

6. Recognizes and recovers promptly after a stall occurs by

simultaneously reducing the angle of attack, increasing power to

maximum allowable, and leveling the wings to return to a straight and-

level flight attitude with a minimum loss of altitude appropriate

for the airplane.

7. Retracts the 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 specified by the examiner.

 

Oral evaluation of understanding through discussion/quiz: (2 minutes)
Q: What are the PTS tolerances?
Q: Review: What is a spin? How do we avoid them?

Definitions:

Stall: a loss of lift due to airflow separation, brought on by exceeding the critical Angle of Attack

Angle of Attack: angle between an airfoil’s cord line, and oncoming air

Power on stall: to simulate an accidental stall occurring during takeoffs and climbs

P-factor: creates the left turning tendency in a positive angle of attack (four factors: Torque, corkscrew of slipstream, gyroscopic propeller effect, asymmetric loading)

 

Post-Flight Debriefing:

Identify tasks that were completed to standards or above.

Identify and discuss tasks that were not completed to standards.

Record and grade completed tasks in the training record

Record training in the student’s logbook (reference the Areas of Operation above).

Give an assignment for the next flight session.

 

Conclusion and Evaluation: 

  1. Remember to fly with your feet to stay coordinated at all times
  2. Airplanes do not fly without airspeed, especially in T/O and Landings
  3. Quiz on underlined portion of III, and review part D.
  4. Read about stalls in AFH (chapter 5)