# AIRCRAFT SPIN:

Table of Contents:

  1. What Is Aircraft Spin?
  2. Four Phases of Aircraft Spin
  3. Aircraft Spin – Entry Phase
  4. Aircraft Spin – Incipient Phase
  5. Aircraft Spin – Developed Phase
  6. Aircraft Spin – Recovery Phase

What Is Aircraft Spin

In aviation, an aircraft spin is an aggravated stall that causes autorotation about the spin axis and a downward corkscrew path for the aircraft. The outboard wing is less stalled than the inboard wing when the aircraft spins around a vertical axis, causing a rolling, yawing, and pitching action. In essence, the aircraft is descending because of gravity while rolling, yawing, and pitching in a spiral motion.

 

aircraft_spin
The airplane wings’ uneven AOA is what causes the rotation. The rising wing that is less stalled has a decreasing AOA, where the relative lift rises and the drag falls. The descending wing’s AOA is rising, which causes the relative lift to decrease and the drag to rise. When an airplane experiences a sideslip or yaw at or above the real stall, it enters a spin because its wings are extended beyond their critical AOA (stall). The adverse yaw caused by aileron deflection, engine/prop effects like as p-factor, torque, spiraling slipstream, and gyroscopic precession, and wind shear, including wake turbulence, may cause an airplane to yaw in addition to erroneous rudder application. The pilot might not be aware that a critical AOA has been surpassed until the airplane yaws out of control in the direction of the falling wing if the yaw had been caused by improper rudder application on their part. No matter which wingtip is elevated, a stall that happens when the aircraft is in a sliding or skidding turn might cause a spin entry and rotation in that direction. The aircraft may spin if the pilot does not start stall recovery right away. Avoiding a spin requires maintaining directional control and preventing the nose from yawing before starting stall recovery. In order to prevent the wings from banking and the nose from yawing, the pilot must use the proper amount of rudder. With the right yaw rate while an aircraft is stalled, spins can be initiated purposefully or accidentally from any flying attitude and velocity. When a spin or impending spin is detected, the pilot should initiate spin recovery techniques right away.

Four Phases of Aircraft Spin

An airplane spins in four stages, and they are:

  1. Entry phase
  2. Incipient phase
  3. Developed phase
  4. Recovery phase
aircraft_spin_phases

1. Entry Phase (Aircraft Spin)

The pilot purposefully or accidentally supplies the components for the spin during the entry phase. A power-off stall’s entry technique is similar to that of a spin demonstration. The pilot should raise the nose to a pitch attitude that ensures a stall while gradually reducing power to idle all through the entry. Apply full back (up) elevator and full rudder (in the direction of the desired spin rotation) smoothly as the aircraft approaches a stall. Unless otherwise instructed by AFM/POH, always keep the ailerons in the neutral position when doing the spin operation.

2. Incipient Phase (Aircraft Spin)

From the moment the aircraft stalls and begins to rotate until the spin has completely formed, it enters the incipient phase. For the majority of aircraft, this phase may need two to four spins. The equilibrium between the inertial and aerodynamic forces has not been reached at this point. The indicated airspeed will typically settle at a low and consistent airspeed as the incipient phase progresses, and the turn indicator’s symbolic airplane should point in the direction of the spin. When spinning, the slip/skid ball is unreliable.

Before completing 360 ° rotation, the pilot should start incipient spin recovery techniques. Full rudder should be applied by the pilot in the opposite direction of rotation. If the driver becomes disoriented, the turn indicator will deviate in the rotational direction. In initial spin training and recovery approaches, the most often employed maneuver is an initial spin that is prevented from developing into a steady state spin.

 

3. Developed Phase (Aircraft Spin)

The airplane enters the developed phase when its angular rotation rate, airspeed, and vertical speed are stabilized in a nearly vertical flightpath. The airplane’s attitude, angles, and self-sustaining movements along its vertical axis are continuous or repeated, or nearly so, during the developed phase when aerodynamic forces and inertial forces are in balance. The spin is in a stable state. It is crucial to remember that certain training aircraft could abruptly go from the incipient phase into a spiral dive instead of entering the mature phase. The airplane will not be in equilibrium during a spiral dive; instead, it will be accelerating, which might cause the G load to rise quickly.

4. Recovery Phase (Aircraft Spin)

When rotation stops and the wings’ AOA drops below the crucial AOA, the recovery phase begins. Depending on the style of spin and the type of airplane, this phase might take anywhere from a quarter turn to multiple rotations. The pilot utilizes control inputs to break the spin equilibrium by stalling the wing and stopping rotation in order to recover. Always follow the manufacturer’s suggested techniques to complete spin recovery. Use the spin recovery methods if the manufacturer’s suggested spin recovery techniques are not available. If the retractable landing gear or flaps are extended before the spin, they should be retracted as soon as is safely possible.

 

  1. Power (throttle) should be reduced to idle.
  2. Ailerons should be in neutral position.
  3. Completely oppose the rotation by using the rudder.
  4. Apply the positive, quick, and elevator in a straight line (Forward of Neutral).
  5. Remove the rudder once the spin stops rotating.
  6. Put pressure on the back elevator to go back to level flight.

Each of the six steps is explained in the discussion that follows:

1. Power (throttle) should be reduced to idle – Spin characteristics are aggravated by power. It often speeds up rotation and might lead to a flatter spin attitude. 

2. Ailerons should be in neutral position – Spin recovery may suffer as a result of ailerons. Aileron control in the spin-direction may quicken rotational speed, steepen the spin attitude, and prolong the recovery. Aileron control in the spin’s opposite direction may flatten the spin attitude, delay recovery, or possibly be the source of an unrecoverable spin. Making sure the ailerons are neutral is the best approach to take. 

3. Completely oppose the rotation by using the rudder – Full opposite rudder should be applied and held until rotation ceases. In conventional single-engine airplanes, the rudder is usually the most crucial control for recovery, and its application should be quick and completely in the opposite direction from the rotation. When recovering from a spin, avoid moving the opposite rudder slowly and too cautiously since this might cause the airplane to continue spinning endlessly even with anti-spin inputs. A quick and confident approach leads to a better spin recovery. 

4. Apply the positive, quick, and elevator in a straight line (Forward of Neutral) – Following a complete application of the rudder, this action should be executed quickly. This action should be carried out without waiting for the rotation to complete. The elevator’s strong movement reduces the AOA and propels the aircraft toward unstalled flight. For recovery in some circumstances, a complete forward elevator may be needed. Till the spinning stops, firmly maintain these positions for the controls. (Note: If the airspeed is rising, the airplane is no longer in a spin. The aircraft is stuck during a spin, therefore the indicated airspeed should be low, stable, and not accelerating.)

5. Remove the rudder once the spin stops rotating – At this point, while airspeed is increasing, failure to neutralize the rudder results in a yawing or sideslipping impact. 

6. Put pressure on the back elevator to go back to level flight – After the rotation stops and the rudder is neutralized, take care not to press too hard on the back elevator. Extra rear elevator pressure may result in another spin and a subsequent stall. During the pull out, the pilot must also stay within the allowed G-load and airspeed restrictions.

 

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