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Introduction:

  • Develops awareness regarding the recognition of, entry into, and recovery from spins
  • An aggravated stall resulting in auto-rotation about the spin axis wherein the aircraft follows a corkscrew path due to one wing being more stalled than another
  • Characterized by high AoA, low airspeed, and high rate of descent where all aerodynamic and inertial forces are balanced
    • It is this balance that must be upset to recover
  • Spins can be entered from any flight attitude and from practically any airspeed
  • A spin is initiated where the pilot includes or fails to include rudder, aileron, or power individually or in combination during a stall
  • Auto-rotation occurs from an asymmetrical stall and sideslip
  • There is an abrupt loss of control when leaving the stall and entering the spin

WARNING:
All procedures here are GENERALIZED for learning, fly the maneuver in accordance with the Pilot Operating Handbook (POH) or current Standard Operating Procedures (SOPs)


Sources of inadvertent stalls becoming spins:

  • Inadequate rudder application in steep climbs
  • False concept of airspeed when on base to final due to tailwind
  • Having aircraft in "reverse command" area in then pattern

Auto-rotation:

  • A combination of roll and yaw about the C.G. That propagates itself and progressively gets worse due to asymmetrically stalled wings
    • A combination of roll and yaw about the C.G. That propagates itself and progressively gets worse due to asymmetrically stalled wings
    • The inertial forces on the aircraft exceed the aerodynamic control authority
    • A control input in any one of the three axes does not affect an immediate response about that axis
    • Auto-rotation occurs from an asymmetrical stall and a side-slip
    • There is an abrupt loss of control when leaving the stall and entering the spin

Spiral:

  • Characterized by low AoA, high airspeed and high rate of descent but neither wing is stalled and the aircraft responds to normal inputs
  • Not a spin because neither wing is stalled and recovery is simply pushing the stick forward and leveling the wings but extremely dangerous

Phases:

  • There are 3 phases of a spin:
    • Incipient: transition from a stall to a full spin, where final balancing of aerodynamic forces have not balanced
    • Developed: fully developed and aerodynamic forces are in balance
    • Recovery: controls are applied to stop spin and maintain straight and level

Regulations:

  • Any maneuver that exceeds 60° of bank of 30° of pitch is prohibited unless occupants have parachutes
  • Does not apply if qualified instructor is doing required maneuvers of pilot or certificate rating?
  • Solo pilots may perform these maneuvers without parachutes?
  • Flight instructor applicants must have flight training in stall awareness, spin entry, spins, and spin recovery
    • Parachutes are not required for this training?

Aerodynamics:

  • All that is required is sufficient yaw rate while an aircraft is stalled
  • In a spin, one or both wings are in a stalled condition, if both are stalled one wing will be in a deeper stall condition than the other
  • The wing that stalls first will drop, increasing its angle of attack and deepening the stall. Both wings must be stalled for a spin to occur
  • The other wing will rise, decreasing its angle of attack, and the aircraft will yaw toward the more deeply-stalled wing. The difference in lift between the two wings causes the aircraft to roll, and the difference in drag causes the aircraft to yaw

Cessna-172 Procedure:

  1. Select an altitude no lower than 6000' AGL
  2. Perform clearing turns
  3. Reduce power to 1500 RPM, adjusting pitch (trimming) to maintain altitude
    • The use of power at the entry will assure more consistent and positive entries to the spin
  4. At the first indication of stall (entry phase):
    • Smoothly pull the elevator control to the full aft position
    • Just prior to reaching the stall "break," apply rudder in the desired direction of spin rotation so that full rudder deflection is achieved almost simultaneously with reaching full aft elevator
  5. As the spin is entered (incipient phase), reduce the throttle to the idle position and ensure that the ailerons are in the neutral position
  6. Hold the elevator and rudder controls in full until the spin recovery is initiated (developed phase)
    • Verify that the throttle is in the idle position and the ailerons are in the neutral position
    • Apply and HOLD full rudder opposite to the direction of the rotation
    • Just after the rudder reaches the stop, move the control wheel briskly forward, far enough to break the stall
    • HOLD these flight control inputs until the rotation stops
  7. As the rotation stops, neutralize the rudder and make a smooth recovery from the resulting dive
  8. As cruise airspeed is attained, set cruise power and re-trim as necessary
  9. Complete cruise checklist

Common Errors:

  • Failure to apply full rudder pressure in the desired spin direction during spin entry
  • Failure to apply and maintain full up-elevator pressure during spin entry, resulting in a spiral
  • Failure to achieve a fully stalled condition prior to spin entry
  • Failure to apply full rudder against the spin during recovery
  • Failure to apply sufficient forward-elevator pressure during recovery
  • Failure to neutralize the rudder during recovery after rotation stops, resulting in a possible secondary spin
  • Slow and overly cautions control movements during recovery
  • Excessive back-elevator pressure after rotation stops, resulting in possible secondary stall
  • Insufficient back-elevator pressure during recovery resulting in excessive airspeed

Practical Test Standards/Airman Certification Standards:


Case Studies:

  • NTSB Identification: ERA14FA345 The National Transportation Safety Board determines the probable cause(s) of this accident to be: The pilot's failure to maintain adequate airspeed for the airplane’s configuration and flight profile, which resulted in an exceedance of the wing’s critical angle-of-attack and a subsequent aerodynamic stall/spin

Conclusion:


References: