Stalls, Spins, and Recovery Procedures: RPL/PPL Study Guide

This is safety-critical knowledge. A significant proportion of fatal general-aviation accidents worldwide involve loss of control related to stalls, spins, or spiral dives. You must understand the aerodynamics, recognition, and recovery procedures thoroughly — not just for the exam, but for your survival as a pilot.

The aerodynamic stall — what it is

A stall is an aerodynamic event that occurs when the critical angle of attack (AoA) is exceeded. It is not defined by a particular airspeed, attitude, or power setting — it is defined solely by the angle between the relative airflow and the chord line of the wing.

• For most general-aviation aerofoils, the critical angle of attack is approximately 16°.
• At angles of attack below the critical value, increasing AoA increases the coefficient of lift (C_L). The airflow remains largely attached to the upper surface of the wing.
• At the critical angle of attack, C_L reaches its maximum value (C_{L max}). This corresponds to the maximum lift the wing can produce at that speed.
• Beyond the critical AoA, the smooth airflow over the upper wing surface separates from the wing. This separation begins at the trailing edge and progresses forward as AoA increases further.
• The result is a sudden, dramatic loss of lift and a large increase in drag. The wing is now stalled.

Key principle: A wing can be stalled at any airspeed, any attitude, and any power setting, provided the critical angle of attack is exceeded. A stall in a steep turn at high speed is just as real as a stall in level flight at low speed.

Symptoms and warning signs approaching the stall

As the angle of attack increases toward the critical value, several cues alert the pilot that a stall is imminent. You must learn to recognise all of them:

• Decreasing airspeed: In level flight, the airspeed will be low and decreasing as the nose is raised to maintain altitude. The ASI reading approaches or falls below the bottom of the green arc (V_S1) or white arc (V_S0).
• High nose attitude at low speed: In a "normal" stall (level flight, wings level), the nose will be noticeably high relative to the horizon. However, remember that stalls can occur at any attitude.
• Mushy, ineffective controls: Because airspeed is low, there is less airflow over the control surfaces. The ailerons, elevator, and rudder feel "sloppy" or "mushy" and require larger deflections for reduced effect.
• Aerodynamic buffet: As the airflow begins to separate from the upper wing surface near the trailing edge, the turbulent wake strikes the tailplane and elevator. This produces a noticeable buffet (vibration) felt through the control column and airframe. This is one of the most important natural stall warnings.
• Stall warning device activation: Most training aircraft are equipped with a stall warning horn (or light, or both). This is typically activated by a small vane or sensor on the leading edge of the wing that detects the change in local airflow direction as AoA approaches the critical value. It is designed to activate 5–10 knots before the stall. Treat the stall warning as a command to take corrective action immediately.
• Reducing or abnormal engine sound: In a power-off stall, the engine note will be low. In a power-on stall, the nose-high attitude combined with low speed may produce an unusual combination of high engine note and low airspeed.
• High rate of sink: The VSI may show an increasing rate of descent even though the nose is high.

Remember: In certain manoeuvres (e.g., steep turns, abrupt pull-ups), the buffet and warning horn may activate with very little prior notice. You must respond immediately.

Why an aeroplane stalls at different speeds

The critical angle of attack at which the wing stalls is essentially constant for a given aerofoil (approximately 16°). However, the indicated airspeed (IAS) at which the wing reaches that critical AoA can vary significantly depending on several factors.

Weight: A heavier aeroplane requires more lift to maintain flight. To generate more lift at the same speed, the wing must fly at a higher angle of attack. Alternatively, to maintain the same angle of attack, the aeroplane must fly faster. Increased weight therefore produces a higher stall speed (IAS). The relationship is: V_S(new) = V_S(original) × √(New Weight / Original Weight).

Load factor (G-loading): In any manoeuvre where the load factor exceeds 1G (turns, pull-ups, turbulence encounters), the wing must produce more lift than in straight-and-level 1G flight. Increased load factor therefore produces a higher stall speed. See the stall speed in turns section below for the formula and examples.

Flap configuration: Extending flaps increases the wing's camber and therefore its C_{L max}. The wing can produce the required lift at a lower speed before reaching the critical AoA. Extending flaps therefore produces a lower stall speed. This is why V_S0 (stall speed in landing configuration — full flap) is lower than V_S1 (stall speed in clean configuration).

Power (thrust): With power applied, the thrust vector has a vertical component (when the nose is pitched up) that partially supports the aircraft's weight, reducing the lift the wing must produce. Additionally, propwash over the wing root increases local airflow velocity, enhancing lift in that region. Increased power therefore produces a lower stall speed (IAS).

Frost, ice, or contamination on the wing: Even a thin layer of frost on the wing surface disrupts the smooth airflow, causing premature boundary-layer separation. This reduces C_{L max} significantly. Ice accumulation changes the aerofoil shape, further reducing C_{L max} and increasing drag. Frost or ice therefore produces a higher stall speed and degraded stall warning (buffet may be reduced or absent). Even frost that looks insignificant can increase stall speed by 10–15% or more and can reduce C_{L max} by 30% or more.

Wind shear and gusts: A sudden change in wind speed or direction (wind shear) can abruptly alter the relative airflow over the wing, causing a rapid change in angle of attack. A decreasing headwind (or increasing tailwind) shear causes a temporary reduction in airspeed and, if the pilot maintains pitch attitude, a sudden increase in AoA — potentially exceeding the critical AoA. A vertical gust (updraft or downdraft) can also rapidly change the AoA. Wind shear and gusts can therefore cause the aircraft to stall at a higher IAS than normal, with little or no warning.

Altitude (density altitude): The indicated airspeed at which the stall occurs remains approximately constant regardless of altitude, because the IAS reflects dynamic pressure, which is what generates lift. However, the true airspeed (TAS) at the stall increases with altitude. This means the aircraft covers more ground, has higher kinetic energy at the stall, and ground references may be misleading. For exam purposes: stall IAS is essentially unaffected by altitude; stall TAS increases with altitude.

The table below summarises the effect of each factor on stall IAS:

Factor	Change	Effect on stall IAS
Weight	Increased	Increases
Load factor (G)	Increased	Increases
Flap	Extended	Decreases
Power	Increased	Decreases
Frost / ice	Present	Increases
Wind shear (decreasing headwind)	Encountered	May stall at higher IAS
Altitude	Increased	Approximately no change (TAS increases)
Manoeuvres (turns, pull-ups)	Increased G	Increases

Effect of using ailerons approaching and during the stall

This is a critically important concept for safety. Ailerons work by differentially changing the angle of attack of the two wings. When you deflect the control column (or yoke) to the left, the left aileron goes up (decreasing AoA on the left wing) and the right aileron goes down (increasing AoA on the right wing).

When the aircraft is near the stall — both wings at a high AoA, close to the critical value — deflecting the aileron down on one wing may push that wing's AoA beyond the critical angle. That wing stalls first, producing a sudden loss of lift on that side. The result is a rapid, uncommanded wing drop — the wing you were trying to raise actually drops instead. This is known as a wing drop at the stall, and it can be the entry to a spin.

Rule: Near the stall, do not use ailerons to level the wings. Use rudder to control any wing drop or yaw. This is why the stall recovery procedure specifies "level wings with rudder." At the stall itself, ailerons may also produce adverse yaw — the nose yaws toward the raised aileron and dropped wing — further aggravating the asymmetry and potentially initiating a spin.

Stall recovery procedure

The stall recovery must be instinctive. The priority is to reduce the angle of attack below the critical value and recover with minimum altitude loss.

1. Lower the nose (reduce the angle of attack): Smoothly but positively move the control column forward to reduce the AoA below the critical value. This is the single most important action — it unstalls the wing. You are not "diving at the ground"; you are restoring smooth airflow over the wing.
2. Apply full power: Simultaneously apply maximum available power (full throttle). This provides thrust to minimise altitude loss and increases airflow over the wing. Apply carburettor heat to COLD if it was on HOT.
3. Level the wings with rudder: If a wing has dropped, use rudder (not aileron) to prevent further yaw and to level the wings. Use rudder to stop any rotation.
4. Recover from the descent: As airspeed increases and the wing is flying again, smoothly ease back on the control column to return to level flight (or a climb). Do not pull back too aggressively, as this may cause a secondary stall.
5. Climb away: Establish a positive climb, retract flaps as appropriate (incrementally, not all at once), and resume normal flight.

The recovery must achieve minimum altitude loss. This is especially critical close to the ground (e.g., during approach, base-to-final turn, go-around). Avoid the temptation to pull back on the stick when the nose drops — this will deepen the stall. Be prepared for the aircraft to pitch down noticeably; this is normal and necessary. Also monitor for a secondary stall: if you recover too aggressively by pulling back too hard, you will re-exceed the critical AoA.

Stall speed in turns — the load factor relationship

In a banked turn, the load factor increases because the lift must support the aircraft's weight and provide the centripetal force for the turn. The relationship between bank angle and load factor is:

Load Factor (n) = 1 / cos(bank angle)

The stall speed in a turn is related to the straight-and-level stall speed by:

V_S(turn) = V_S(1G) × √n = V_S(1G) × √(1 / cos θ)

where θ is the bank angle and n is the load factor. The following worked examples assume V_S(1G) = 50 kt (clean configuration, wings level).

• At 30° bank: n = 1 / cos 30° = 1 / 0.866 = 1.15G. V_S(turn) = 50 × √1.15 = 50 × 1.07 = approximately 54 kt. Stall speed increases by approximately 7%.
• At 45° bank: n = 1 / cos 45° = 1 / 0.707 = 1.41G. V_S(turn) = 50 × √1.41 = 50 × 1.19 = approximately 59 kt. Stall speed increases by approximately 19%.
• At 60° bank: n = 1 / cos 60° = 1 / 0.5 = 2.0G. V_S(turn) = 50 × √2.0 = 50 × 1.41 = approximately 71 kt. Stall speed increases by approximately 41%.

This is extremely significant. At 60° of bank, the stall speed is 41% higher than in straight-and-level flight. An aircraft with a normal stall speed of 50 kt will stall at 71 kt in a 60° banked turn — well within the normal operating speed range. This catches many pilots off guard, particularly in steep turns at low altitude such as the base-to-final turn. This is frequently tested in the CASA exam.

Bank angle	Load factor (G)	Stall speed increase factor (√n)	Stall speed (if VS = 50 kt)
0° (wings level)	1.00	1.00	50 kt
30°	1.15	1.07	54 kt
45°	1.41	1.19	59 kt
60°	2.00	1.41	71 kt
75°	3.86	1.97	98 kt

Factors affecting stall IAS — comprehensive summary

Combining the information from the preceding sections, the following factors affect the indicated airspeed at which the aircraft will stall.

• Power: More power = lower stall IAS (thrust supports weight and propwash increases local lift). Less power = higher stall IAS.
• Flap: Flap extended = lower stall IAS (increased C_{L max}). Flap retracted = higher stall IAS.
• Wind shear: A sudden decrease in headwind (or increase in tailwind), or a downdraft, can cause the effective AoA to increase suddenly, resulting in a stall at a higher IAS than expected. Wind shear stalls are particularly dangerous because they happen rapidly and at speeds the pilot considers "safe."
• Manoeuvres (load factor): Any manoeuvre imposing greater than 1G (turns, pull-ups, turbulence encounters) increases stall IAS by the factor √n.
• Weight: Higher weight = higher stall IAS. Lower weight = lower stall IAS.
• Frost or ice on the wing: Even a light coating of frost reduces C_{L max}, increasing stall IAS. Ice is worse. Never take off with frost, ice, or snow on the wings.
• Altitude: Stall IAS remains essentially constant with altitude. Stall TAS increases with altitude because air density decreases, so the aircraft must move faster through the air to generate the same dynamic pressure.
• Centre of gravity (CG) position: A forward CG requires a greater tail-down force, effectively increasing the wing loading and thus slightly increasing the stall speed. An aft CG reduces the tail-down force requirement and slightly reduces the stall speed — but an aft CG also reduces longitudinal stability and may make spin recovery more difficult or impossible.

Spin entry — how a spin develops

A spin requires two conditions simultaneously: the wing must be stalled (the critical angle of attack must be exceeded), and there must be yaw (a rotation about the vertical axis — the aircraft must be in uncoordinated flight).

If, at the point of stall, the aircraft is yawing (e.g., due to uncoordinated rudder/aileron inputs, a skidding or slipping turn, or asymmetric power), one wing will have a higher angle of attack than the other. The wing with the higher AoA stalls more deeply, losing more lift and producing more drag. The wing with the lower AoA may remain partially flying or be less deeply stalled. This asymmetric lift and drag causes the aircraft to roll and yaw further toward the stalled wing, creating a self-sustaining autorotation — a spin.

Common scenarios for inadvertent spin entry include:

• Skidding turn at low speed — for example, overshooting the base-to-final turn and applying excessive inside rudder. This is a leading cause of fatal stall/spin accidents.
• Using ailerons to level wings at the stall, as discussed in the aileron section above.
• Uncoordinated climbing turn — for example, after takeoff with an engine failure in a twin.
• Distraction at low speed leading to an inadvertent stall with a yaw component.

Key takeaway: Prevent the spin by preventing the stall. If you don't stall, you cannot spin. If you are stalled, keep the flight coordinated (balanced ball) to prevent the spin from developing.

Spin characteristics

Once a spin is established, it has the following characteristic features:

• The wing is stalled: Throughout the spin, the aircraft's wings remain at or beyond the critical angle of attack. Both wings are stalled, but one is more deeply stalled than the other — the inner (lower) wing has a higher AoA.
• Low, relatively constant airspeed: Because the wing is stalled and the aircraft is essentially falling rather than flying, the airspeed is low and remains approximately constant. It does not increase significantly. The ASI will typically show a speed near or below the normal stall speed.
• High rate of descent: The aircraft descends rapidly — typically 3,000–6,000 ft per minute or more depending on the aircraft type. The descent is steep, with the flight path nearly vertical.
• Rotation (autorotation): The aircraft rotates about its vertical axis (yaw) and rolls simultaneously. The rotation rate is relatively constant once the spin is established. The nose is pitched well below the horizon.
• G-loading: In a steady spin, the G-loading is typically around 1G or slightly above — it is not rapidly increasing.
• Visual cues: The ground appears to be rotating. The pilot may experience disorientation. The controls will feel "wrong" — normal control inputs may seem to have little or no effect.

A spin progresses through three phases:

1. Incipient spin: The initial phase (first 1–2 turns) where the spin is developing. The rotation rate and flight path are changing. Recovery is easiest in this phase.
2. Developed (steady) spin: The spin is fully established with consistent rotation rate, airspeed, and rate of descent.
3. Recovery: The pilot applies the correct recovery inputs as described below.

Spin recovery — the PARE technique

The standard spin recovery procedure can be remembered using the mnemonic PARE. Always follow the specific recovery procedure in the aircraft's Pilot Operating Handbook (POH), as some aircraft have procedures that differ from this generic sequence.

• P — Power: IDLE. Close the throttle fully (power to idle). This eliminates any asymmetric thrust effects (e.g., slipstream, P-factor) that may be sustaining or aggravating the spin, and reduces the tendency of the nose to pitch up (which would deepen the stall).
• A — Ailerons: NEUTRAL. Centralise the ailerons (control column or yoke to the neutral lateral position). Aileron input during a spin can deepen the stall on one wing and complicate recovery. Aileron in the direction of the spin may flatten the spin and make recovery more difficult. Aileron against the spin may also have unpredictable effects depending on aircraft type. Neutral is the safest position.
• R — Rudder: FULL OPPOSITE to the direction of rotation. Apply full rudder deflection opposite to the direction of the spin. If the aircraft is spinning to the left (nose rotating left), apply full right rudder. If spinning to the right, apply full left rudder. This opposes the yaw and stops the autorotation. It must be a firm, positive, full deflection. To determine spin direction, observe which way the ground is rotating, or check the turn coordinator.
• E — Elevator: FORWARD (unstall the wing). After applying full opposite rudder, move the control column positively forward to reduce the angle of attack below the critical value — this breaks the stall. The wing must be unstalled to stop the autorotation; rudder alone may not be sufficient if the wing remains stalled. The forward column movement should be brisk and positive — a tentative movement may be insufficient.

Once the spin stops, centralise the rudder immediately to prevent entering a spin in the opposite direction. The aircraft will now be in a steep nose-down attitude and accelerating rapidly. Ease back on the control column smoothly to recover to level flight — do not pull excessively, as this risks a secondary stall or exceeding the aircraft's structural G limits. Apply power as the aircraft returns to level flight, then climb away and re-establish normal flight.

Altitude loss during spin recovery is significant — typically several hundred to over a thousand feet. A spin at low altitude (e.g., in the circuit) is frequently fatal because there is insufficient altitude for recovery. The best spin recovery is spin prevention: don't stall, and if you do stall, keep the ball centred.

Spiral dive — characteristics

A spiral dive is fundamentally different from a spin, although both involve a descending, rotating flight path. Understanding the differences is critical for applying the correct recovery technique. A spiral dive is essentially a steep, tightening, descending turn in which the wing is NOT stalled.

The characteristics of a spiral dive are as follows:

• The wing is NOT stalled: The angle of attack is below the critical value. The wing is producing lift normally — in fact, it is producing excessive lift for the situation.
• Airspeed is high and rapidly increasing: Because the aircraft is in a steep descent with the wing flying (not stalled), gravity accelerates the aircraft. The ASI will show rapidly increasing speed. This is the key diagnostic difference from a spin.
• Rate of descent is high and increasing: The aircraft is diving, and the dive is getting steeper.
• G-force (load factor) is high and increasing: The aircraft is in a banked, curved flight path. As the speed increases, the lift — and therefore the load factor — continues to rise.

Exam trap: don't confuse a spin with a spiral dive. The single most reliable way to tell them apart is airspeed: in a spin, airspeed is low and approximately constant; in a spiral dive, airspeed is high and rapidly increasing. Applying spin recovery inputs to a spiral dive (or vice versa) will make the situation significantly worse.

Related Resources

• Aerodynamics
• RPL Aerodynamics Blog