Introduction:

  • Practicing spins build 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 (think skid)
  • There is an abrupt loss of control when leaving the stall and entering the spin
  • Certification standards require the practice of spin procedures
  • Ensure to follow appropriate regulations related to spins throughout the conduct of the maneuver

Spin Awareness:

  • A spin is an aggravated stall condition that may result after a stall occurs

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 (think skid)
    • There is an abrupt loss of control when leaving the stall and entering the spin

Spirals:

  • Characterized by low AoA, high airspeed and high rate of descent but neither wing is stalled and the aircraft responds to normal inputs
  • A spiral is not a spin because in fact neither wings are stalled
  • Still extremely dangerous
  • Recovery is simply pushing the stick forward and leveling the wings

Phases of a Spin:

  • The phases of a spin describe spin progression from entry through recovery
  • There are four distinct phases: entry, incipient, developed, and recovery
  • Entry Phase:

    • In the entry phase, the pilot intentionally or accidentally provides the necessary elements for the spin
  • Incipient Phase:

    • The transition from a stall to a full spin is called the incipient phase
    • The incipient phase occurs from the time the airplane stalls and starts rotating until the spin has fully developed
      • This phase may take two to four turns for most airplanes
    • In this phase, the aerodynamic and inertial forces have not achieved a balance
      • As the incipient phase develops, the indicated airspeed will generally stabilize at a low and constant airspeed and the symbolic airplane of the turn indicator should indicate the direction of the spin
      • The pilot should not use the slip/skid ball (inclinometer) to determine spin direction
        • The location of the instrument in the airplane determines how the ball will move rather than the direction of the spin
        • For example, the ball mounted on the left side of the airplane will always move to the left, even in spin with rotation to the right
  • Developed Phase:

    • The developed phase begins when the aerodynamic forces are in balance
    • The spin, although chaotic looking from inside the cockpit, has been established and recovery procedures are now necessary to break the spin
    • The developed phase occurs when the airplane’s angular rotation rate, airspeed, and vertical speed are stabilized in a flightpath that is nearly vertical
    • In the developed phase, aerodynamic forces and inertial forces are in balance, and the airplane’s attitude, angles, and self-sustaining motions about the vertical axis are constant or repetitive, or nearly so
      • Although seemingly chaotic from within the cockpit, the spin is in equilibrium
    • It is important to note that some training airplanes will not enter into the developed phase but could transition unexpectedly from the incipient phase into a spiral dive
      • In a spiral dive the airplane will not be in equilibrium but instead will be accelerating and G load can rapidly increase as a result
  • Recovery Phase:

    • During the recovery phase, controls are applied to stop spin, recover from the unusual attitude and maintain straight and level
    • The recovery phase occurs when rotation ceases and the AOA of the wings is decreased below the critical AOA
    • This phase may last for as little as a quarter turn or up to several turns depending upon the airplane and the type of spin
    • To recover, the pilot applies control inputs to disrupt the spin equilibrium by stopping the rotation and unstalling the wing
    • To accomplish spin recovery, the pilot should always follow the manufacturer’s recommended procedures
      • In the absence of the manufacturer’s recommended spin recovery procedures and techniques, use the six-step spin recovery procedure in Figure 5-17
    • If the flaps and/or retractable landing gear are extended prior to the spin, they should be retracted as soon as practicable after spin entry

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

Aircraft Requirements:

  • Airplane flying handbooks will dictate specific requirements to conduct spin training
    • This includes configurations as well as weight and balance conditions which are required to conduct the maneuver
  • Also essential is a thorough airplane preflight inspection, with special emphasis on excess or loose items that may affect the weight, CG, and controllability of the airplane
  • It is also important to ensure that the airplane is within any CG limitations as determined by the manufacturer
  • Slack or loose control cables (particularly rudder and elevator) could prevent full anti-spin control deflections and delay or preclude recovery in some airplanes

Spin Recovery Procedure:

  • 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)

  1. Select a safe location
    • Spins will result in large losses of altitude and so they should be performed free from high traffic areas
    • Always broadcast your intentions over the appropriate deconfliction frequencies, if available
  2. Select a safe altitude
    • Generally, this should be no lower than 6000' AGL
    • The intent is to have enough altitude to enter the spin, stabilize, and recover with plenty of safety margin
  3. Perform clearing turns
    • You are going to lose a lot of altitude so be sure to check below you in addition to around you
  4. Reduce power , adjusting pitch (trimming) to maintain altitude
    • The use of power at the entry will assure more consistent and positive entries to the spin
  5. At the first indication of stall (entry phase):
    • During the entry, the pilot should slowly reduce power to idle, while simultaneously raising the nose to a pitch attitude that ensures a stall
    • As the airplane approaches the stall "break," smoothly apply full rudder in the direction of the desired spin rotation while applying full aft (up) elevator to the limit of travel
    • Always maintain the ailerons in the neutral position during the spin procedure unless AFM/POH specifies otherwise
  6. As the spin is entered (incipient phase), reduce the throttle to the idle position and ensure that the ailerons are in the neutral position
  7. 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 to avoid over-speeding the aircraft
  8. 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
  9. As the rotation stops, neutralize the rudder
    • You want to stabilize the aircraft's directional control
    • Holding the rudder after the rotation stops could induce a spin in the opposite direction
  10. Roll wings level
    • Level wins ensures you are not climbing in a turn
    • Climbing in a turn decreases vertical lift, and causes unnecessary load factors
  11. Pull the nose up to the horizon
    • Be careful not to stall the aircraft by being too aggressive but realize that you'll be in a very nose low altitude losing thousands of feet per minute
  12. Add power
    • You'll need to add power to accelerate to cruise speed
    • Apply power as necessary to avoid stalling but absolutely apply full power once level
  13. As cruise airspeed is attained, set cruise power and re-trim as necessary
  14. Complete cruise checklist

Spin Common Errors:

  • Failure to adequately clear the area
  • Failure to apply full rudder pressure (to the stops) 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 (to the stops) briskly against the spin during recovery
  • Failure to apply sufficient forward-elevator pressure during recovery
  • Waiting for rotation to stop before applying forward elevator
  • 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

Airman Certification Standards:

  • Spin Awareness:

    • To determine that the applicant exhibits satisfactory knowledge, risk management, and skills associated with spins, flight situations where unintentional spins may occur and procedures for recovery from unintentional spins
    • References: FAA-H-8083-2, FAA-H-8083-3; AC 61-67; POH/AFM

    Spin Awareness Knowledge:

    The applicant must demonstrate an understanding of:
    • PA.VII.D.K1:
      Aerodynamics associated with spins in various airplane configurations, to include the relationship between angle of attack, airspeed, load factor, power setting, airplane weight and center of gravity, airplane attitude, and yaw effects
    • PA.VII.D.K2:
      What causes a spin and how to identify the entry, incipient, and developed phases of a spin
    • PA.VII.D.K3:

      Spin recovery procedure

    Spin Awareness Risk Management:

    The applicant demonstrates the ability to identify, assess and mitigate risks, encompassing:
    • PA.VII.D.R1:
      Factors and situations that could lead to inadvertent spin and loss of control
    • PA.VII.D.R2:
      Range and limitations of stall warning indicators (e.g., airplane buffet, stall horn, etc.)
    • PA.VII.D.R3:
      Improper spin recovery procedure
    • PA.VII.D.R5:
      Collision hazards, to include aircraft, terrain, obstacles, and wires
    • PA.VII.D.R6:

      Distractions, loss of situational awareness, or improper task management.

    Spin Awareness Skills:

    N/A

Spin 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:

  • Spin characteristics will vary from aircraft to aircraft depending on design and wear (bends/twists/dents) - see case study
  • For more information check out The Light Airplane Pilot's Guide to Stall/Spin Awareness
  • There is a misconception that a slip (a cross-control maneuver) will result in a spin and while possible it is unlikely
    • In fact aerodynamic forces generally prevent auto-rotations in that scenario however, skids as a cross-controlled maneuver will absolutely promote spins
  • While spins are a required maneuver throughout flight training, they should only be practiced in an aircraft and configuration approved for spins
  • Every aircraft is built or bent slightly differently, which can manifest in aggrevated spin characteristics
    • While unlikely, make sure you have a plan to get out of the aircraft in case of the worst
  • Consider practicing maneuvers on a flight simulator to introduce yourself to maneuvers or knock off rust
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