2-5 Spins

An aggravated stall that results in autorotation

• Two conditions required:
• the aircraft must be stalled
• yaw must be present

a combination of roll and yaw that propagates itself due to asymmetrically stalled wings.

The spin axis is the aerodynamic axis around which stall and yaw forces act to sustain spin rotation.

• Poststall Gyration Phase
• During a stall, lift and drag of both wings are equal unless yaw is introduced.
• Yaw creates an AOA difference between the left and right wings.
• For example, an aircraft stalls and rolls left. The down-going (left) wing senses a roll relative wind from beneath. This relative wind is added to existing relative wind and creates an average relative wind that is further from the chordline.
• Down-going wing has a higher AOA and becomes more stalled.
• The up-going wing senses a roll relative wind from above. It is added to the existing relative wind which creates a lower AOA and the wing is less stalled.
• The AOA differential results in two cases:
• Up-going wing: lower AOA, more lift, less drag
• Down-going wing: higher AOA, less lift, more drag
• The lift differential results in a continued rolling motion of the plane.

• Erect spins
• Upright
• Result from positive-g stall entries.
• 

• Inverted spins
• occur from a negative-g stall.
• 

Flat spin is characterized by a flat attitude and transverse or "eyeball out" Gs. The cockpit indications will be similar to an erect spin, except airspeed may vary depending on how flat the spin is.

• Ailerons
• Applied in the direction of spin will cause increased roll and yaw oscillations
• Applied in the opposite direction of spin will tend to dampen roll and yaw.
• In the T-6B, apply neutral ailerons since the wings are in a deep stall.

• Rudder
• The principal control for stopping autorotation in the T-6B.
• Deflected in the same direction of the spin, the amount of rudder exposed to the relative wind will be minimized and result in less drag.
• Deflected in the opposite direction of the spin will maximize the amount of rudder exposed to the relative wind and the amount of drag.
• The drag is divided into a horizontal and vertical component.
• The horizontal component creates a force that oppose the yaw to slow the rotating rate.
• The vertical component creates a force that pulls the tail up and pitches the nose-down, reducing the AOA on both wings.

• Elevator
• The drag will cause a more nose down pitch attitude.
• Full aft stick results in the flattest pitch attitude and slowest spin rate.

• Weight
• A heavier plane will have a slower spin entry with lesser oscillations due to this large moment of inertia
• A lighter plane will enter a spin more quickly, with greater oscillations possible, but will also recover faster.

• Pitch Attitude
• Will have a direct impact on the speed the aircraft stalls.
• As a plane increases its attitude, a larger portion of thrust is in the vertical, adding lift.
• This additional lift reduces the load seen by the wings allowing for a slower stall speed, making the spin entry slower and with less oscillations.
• At lower pitch attitudes, the aircraft stalls at a higher airspeed and entries are faster and more oscillations.

• Spin Direction
• If in a right spin, the T-6B will tend to pitch down due to gyroscopic precession.
• If in a left spin, the T-6B will tend to pitch up due to gyroscopic precession.
• The T-6B will have a flatter attitude when spinning to the left than to the right.

• Weight
• A heavier plane will have a slower spin entry with lesser oscillations due to this large moment of inertia
• A lighter plane will enter a spin more quickly, with greater oscillations possible, but will also recover faster.

• Pitch Attitude
• Will have a direct impact on the speed the aircraft stalls.
• As a plane increases its attitude, a larger portion of thrust is in the vertical, adding lift.
• This additional lift reduces the load seen by the wings allowing for a slower stall speed, making the spin entry slower and with less oscillations.
• At lower pitch attitudes, the aircraft stalls at a higher airspeed and entries are faster and more oscillations.

• Spin Direction
• If in a right spin, the T-6B will tend to pitch down due to gyroscopic precession.
• If in a left spin, the T-6B will tend to pitch up due to gyroscopic precession.
• The T-6B will have a flatter attitude when spinning to the left than to the right.

• The T-6B uses a dorsal fin, strakes, and ventral fins to decrease the severity of spin characteristics.
• Dorsal fin is attached to the front of the vertical stabilizer to increase its surface area to decrease the spin rate and aids in stopping autorotation.
• Ventral fin is located beneath the empennage. It decreases the spin rate and aid in maintaining a nose down attitude.
• Strakes are located in front of the horizontal stabilizer. They increase the surface area of the horizontal stabilizer in order to keep the nose pitched down and prevent a flat spin. The strakes change the airflow over the nose to create an anti-rotational force.

• Erect Spin
• 
• Inverted Spin
• 

• Erected Spin Recovery
• 1. Gear, flaps, and speed brake – Retracted
• 2. PCL – IDLE
• 3. Rudder – Full opposite to turn needle deflection
• 4. Control stick – Forward of neutral with ailerons neutral
• 5. Smoothly recover to level flight after spin rotation stops

• Inverted Spin Recovery
• Look in T-6 Flight Manual.
• The spin will recover to a steep, inverted, nose down dive.
• Roll or split-S out of the dive to level flight in a timely manner as airspeed will build rapidly.

• Occurs if proper recover procedures are not followed and the pilot puts the full opposite rudder but inadvertently maintains full aft stick.
• After one or two more turns, the nose will pitch steeply down and the plane will snap into a reversed direction of rotation.

To recover, apply full rudder opposite the turn needle and stick slightly forward of neutral.

• Caused by maintaining pro-spin rudder while moving the control stick forward of the neutral position.
• Neutralizing rudder while advancing the stick may also cause it.
• Characterized by steep nose-down attitude (approx. 70 degrees nose down) and an increase in spin rate (approx. 280 degrees per second).
• In addition, they tend to induce severe pilot disorientation.
• Recovery is the same as a progressive spin. (apply full rudder opposite the turn needle and stick slightly forward of neutral.)