Fully Developed Spin
Understand the phases of a fully developed spin, autorotation mechanics, and the standard PARE recovery procedure.
Phases of a Spin
A spin progresses through three distinct phases, each with different aerodynamic characteristics and recovery considerations:
| Phase | Duration | Characteristics |
|---|---|---|
| 1. Incipient | Approximately 1-2 turns | Transition from stall to spin. Rotation rate, pitch attitude, and descent rate are all changing. Recovery is simplest during this phase. |
| 2. Developed (Steady-State) | Continues until recovery action is taken | Rotation rate, airspeed, pitch attitude, and rate of descent have stabilized. The aircraft is in equilibrium — forces and moments are balanced in the spinning condition. |
| 3. Recovery | Typically 1/4 to 1 full turn after inputs | From initiation of recovery inputs to cessation of rotation and return to unstalled flight. The aircraft transitions through a steep dive. |
Note
During the incipient phase, the spin may appear chaotic — the pitch, bank, and rotation rate are all changing. Once the spin becomes fully developed, these parameters stabilize and the motion becomes more predictable, though no less dangerous.
Autorotation Mechanics in Detail
In a fully developed spin, the aircraft rotates about a vertical (or near-vertical) axis while both wings remain stalled. The autorotation is sustained by the aerodynamic imbalance between the two wings:
The Down-Going (Inner) Wing
- Has a higher effective angle of attack due to the rotation
- Is deeply stalled — well beyond the critical angle of attack
- Produces very little lift but very high drag
- The high drag on this wing sustains the yawing moment
The Up-Going (Outer) Wing
- Has a lower effective angle of attack due to the rotation
- Is still stalled, but less deeply than the inner wing
- Produces relatively more lift and less drag than the inner wing
- The lift difference sustains the rolling moment
The combination of these asymmetric forces creates a self-sustaining rotation. The aircraft descends in a helical path around a near-vertical spin axis, with the nose pitched steeply downward (typically 60-90 degrees below the horizon depending on aircraft type).
Equilibrium in the Developed Spin
In the steady-state developed spin, the following are in equilibrium:
- Pro-spin yawing moment (from drag differential) is balanced by the anti-spin yawing moment (from the fuselage and fin acting as a weathervane)
- Pro-spin rolling moment (from lift differential) is balanced by the anti-spin rolling moment (from the aircraft's lateral stability)
- Weight is balanced by the total drag in the vertical direction — the aircraft descends at a constant rate
Spin Characteristics by Aircraft Type
Different aircraft exhibit markedly different spin characteristics based on their design:
| Design Factor | Effect on Spin |
|---|---|
| Wing position (high vs low) | High-wing aircraft tend to have a flatter spin attitude; low-wing aircraft tend to have a steeper nose-down attitude |
| Tail configuration | T-tail aircraft may have the elevator blanketed by the wing wake in a spin, making recovery more difficult |
| Mass distribution | Aircraft with mass concentrated in the wings (fuel) tend to spin flatter and may be more resistant to recovery |
| CG position | Aft CG makes spin entry easier and recovery more difficult. Forward CG provides more resistance to spinning. |
CG and Spins
An aircraft loaded with the CG behind the aft limit may enter a flat spin from which recovery is impossible. Always ensure the aircraft is loaded within the approved CG envelope — this is not merely a performance consideration but a safety-of-flight issue.
Height Loss During Spins
A fully developed spin results in significant altitude loss with each turn. Typical values for light training aircraft:
- Incipient phase: 300-500 feet lost during the first 1-2 turns
- Developed spin: 500+ feet per turn (varies by aircraft type)
- Recovery phase: Additional 500-1,000 feet lost during recovery from the dive
A spin of just 3 turns could easily result in a total altitude loss of 2,000-3,000 feet from entry to return to level flight. This underscores why an inadvertent spin at traffic pattern altitude (800-1,000 feet AGL) is typically unrecoverable.
Height Awareness
During spin training, always note your altitude at entry and monitor altitude throughout. Your instructor will specify a minimum recovery altitude — if this altitude is reached before recovery is complete, additional emergency procedures may be required.
Aircraft Certification for Spins
Not all aircraft are approved for intentional spins. FAA certification categories determine what maneuvers are permitted:
| Category | Spin Approval | Notes |
|---|---|---|
| Normal | NOT approved for spins | Must demonstrate recovery from a one-turn spin or one 3-second spin during certification, but intentional spins are prohibited in service |
| Utility | May be approved for spins | Check the POH/AFM — spin approval depends on weight, CG, and configuration. Often approved only at reduced weight. |
| Aerobatic | Approved for spins | Tested for at least 6 turns of a spin. No specific limitations beyond POH/AFM restrictions. |
Critical Safety Point
Many training aircraft are NOT approved for intentional spins. Always verify in the POH/AFM before attempting spin training. A "normal category" placard on the instrument panel means intentional spins are prohibited. Some aircraft (like certain Cessna 172 models) are certified in both normal and utility categories depending on weight and CG — check carefully.
These lesson plans are provided as supplementary training guidance only. They do not supersede FAA publications, aircraft manufacturer documentation, or your instructor's direction. Always refer to the FAA Instrument Flying Handbook, Airplane Flying Handbook, AIM, and applicable POH/AFM as the official sources.