Airplane stall: Definition, Cause, Effect, Formula

An airplane stall is an aerodynamic condition where the wings lose their ability to generate sufficient lift. Airplane stalls are characterized by two factors: angle of attack and airspeed. Airplane stalls occur when the critical angle of attack is exceeded, regardless of the aircraft's airspeed. Airplane stalls lead to a loss of altitude and potential loss of control if not corrected. Understand the relationship between angle of attack and airspeed to recognize and prevent airplane stalls.

Wing stall causes stem from exceeding the critical angle of attack, between 15-20 degrees. Airflow separates from the wing's upper surface during a stall, resulting in decreased lift and increased drag resistance. Wing geometry and airfoil shape influence stall characteristics and the critical angle of attack. Sharp leading edges promote sudden leading-edge stalls.

Airplane stall consequences include a loss of lift and descent. Control surfaces lose effectiveness during an airplane stall, compromising flight stability and directional control. The stalled aircraft experiences reduced control effectiveness, making it less responsive to pilot inputs. Stall warning systems provide alerts when the wing nears its critical angle of attack, using stick shakers or pushers to assist pilot recovery. Stall recovery requires reducing the angle of attack by pushing the airplane's nose down and adding engine power to regain airspeed and airflow over the wings.

Stall speed calculation uses the formula V = sqrt((2L)/(ρ S C_L)). Engineers determine aircraft weight, air density, wing surface area, and maximum coefficient of lift to calculate stall speed. Increased weight raises stall speed, while flap settings increase lift by 50-100%. Air density decreases by 10% for every 1,000 meters (3,281 feet) of altitude gain. Load factor increases stall speed in turns and pullups, with a 60-degree bank angle increasing stall speed by 41%. Engineers adjust calculations for flight conditions and turning flight to check stall speed assessments.

What is an airplane stall?

An airplane stall occurs when lift decreases due to airflow separation from the wing. The angle of attack exceeds its critical value by 15-20 degrees. Lift decreases, and the aircraft cannot generate enough lift to sustain level flight. Stalls happen at any speed but are likely at slower speeds.

The angle of attack represents the angle between the wing's chord line and the relative airflow. Angle of attack determines lift generation, with lift increasing as the angle increases up to the critical threshold. The critical angle of attack ranges from 15 to 20 degrees for aircraft. Exceeding this angle leads to airflow separation and an airplane stall.^[a]

Airflow separation causes turbulent flow over the wing during a stall. Turbulent flow results in decreased lift and increased drag resistance. The boundary layer detaches from the wing surface, leading to flow separation onset instability. Lift loss during stall and drag increase characterize the airplane stall condition.

Wing airfoil shape and geometry influence stall characteristics and the critical angle of attack. Airplane aerodynamic design affects stall behavior and flight performance. The airplane flight envelope defines the range of safe operating conditions, including stall speed and angle of attack limits. Exceeding these limits results in an airplane stall flight situation.

What is an accelerated stall?

An accelerated stall occurs when an airplane exceeds its critical angle of attack during maneuvers involving more than 1G (1G = 9.81 m/s²) force. Accelerated stalls happen at higher airspeeds than stalls at lower airspeeds and provide less warning to pilots. Recovery techniques involve reducing angle of attack and leveling wings.

Accelerated stalls occur when an aircraft exceeds its critical angle of attack under increased G-force loading. The angle of attack ranges from 8 to 20 degrees for most airfoils. Stall aerodynamic separation happens when airflow over the wing becomes separated, leading to a loss of lift. G-force loading and acceleration increase the load factor, requiring more lift to maintain flight. The load factor in a turn is greater than 1, necessitating additional lift to counteract centrifugal force.

Aircraft wing design influences the critical angle of attack limit. Wing shape, aspect ratio, and planform affect the stall characteristics. The accelerated stall maneuver involves stalling an aircraft in a turn, demonstrating stalls at higher speeds than the standard stall speed. Pilots roll the aircraft into a 45-degree bank angle to perform an accelerated stall. The bank angle inclination in a stall maneuver exceeds 45 degrees. Airspeed decreases as the aircraft banks due to increased drag. The accelerated stall airspeed is higher compared to a stall due to the increased load factor. A 45-degree bank results in a stall speed 20% higher than in level flight.

What causes a secondary stall during stall recovery?

A secondary stall during a stall recovery is caused by excessive back-pressure on controls. A secondary stall during stall recovery causes the wing to exceed its critical angle of attack. Pilots add power without sufficiently lowering the nose. Proper recovery requires reducing angle of attack and adding power to regain airspeed.

Excessive back-pressure on controls is a primary cause of secondary stalls. Pilots apply back pressure, causing the wing to exceed its critical angle of attack. Delayed or improper corrective actions exacerbate stall situations. Pilots fail to reduce back pressure and lower the nose to increase airspeed during recovery. Inadequate pitch reduction prevents wings from regaining lift. Aircraft must regain flying speed before leveling off, requiring a minimum of 17 degrees angle of attack reduction.

Low airspeed reduces aircraft momentum during recovery, making it susceptible to stalling. Maintaining nose-up pitch attitudes prevents airspeed regain. Some aircraft have sensitive elevator controls, making inadvertent back pressure application possible. Over-deflecting elevators increases angle of attack beyond critical limits in low-speed conditions.

Power management issues contribute to secondary stalls. Insufficient thrust application hinders airspeed regain. Engine output fails to provide enough power to overcome drag and accelerate the aircraft. Relying on power without reducing pitch attitude is ineffective for breaking stalls. Power cannot reduce angle of attack without proper pitch control.

Ineffective recovery techniques result in secondary stalls. Abrupt control inputs cause angle of attack overshoots. Incomplete recoveries lead to stall recurrence. Secondary stalls occur when pilots attempt to hasten recovery without regaining sufficient flying speed. These secondary stalls are more aggressive than initial stalls, leading to increased altitude loss of 500-1000 feet (152.4-304.8 meters) or more. Recovery requires reducing angle of attack, adding full power, and regaining 5-10 knots of airspeed before attempting to level off or climb.

What is a deep stall?

A deep stall is a dangerous aircraft condition where the elevator becomes ineffective due to the wing's turbulent wake. Deep stalls occur at high angles of attack, beyond 30°, causing airflow separation over the wing surface. T-tail aircraft are susceptible to deep stalls, which lead to unrecoverable descending trajectories.

Deep stalls occur when the angle of attack exceeds a threshold beyond 30°. Boundary layer detachment leads to airflow separation over the wing surface. Loss of lift and increased drag result from this separation, causing a reduction in aircraft performance.

T-tail aircraft exhibit vulnerability to deep stalls due to their aerodynamic configuration. Horizontal stabilizer effectiveness decreases as it becomes blanketed by turbulent airflow from the stalled wing. Wing wake vortex formation and interference impact elevator pitch control. Elevator control effectiveness diminishes to near-zero levels, leaving pilots with minimal ability to adjust the aircraft's attitude.

Deep stall effects manifest as an unrecoverable aircraft attitude. The aircraft enters a descending trajectory with little forward speed, approaching angles of attack near 90 degrees. Deep stalls are deemed more severe than regular stalls, earning the terminology "super stall^[b]" to emphasize their gravity.

Standard stall recovery procedures prove ineffective in deep stall conditions. Specialized stall recovery maneuvers, namely pitch rocking techniques, have been experimented with but show inconsistent results. The loss of elevator authority complicates recovery efforts, leading to flight situations that cannot be recovered from.

T-tail aircraft designs face susceptibility to deep stalls. Other vulnerable configurations include aircraft with rear-mounted engines. Aircraft designers implement preventive measures like stick pusher systems to reduce the angle of attack before reaching critical thresholds. Center of gravity management helps mitigate the risk of entering deep stall conditions.

What is a tail stall?

A tail stall occurs when airflow separates from the horizontal stabilizer of an aircraft. Tailplane stalls result in nose-down pitching moments, compromising aircraft stability. Recovery involves reducing angle of attack and increasing airspeed. Pilots must recognize warning signs and practice recovery techniques to prevent loss of control.

The horizontal stabilizer functions as an inverted wing, generating downward lift to counteract nose-down pitching moments. Downward lift maintains pitch stability and control authority. Elevator control surfaces on the horizontal stabilizer allow pilots to adjust pitch attitude. Tail stalls occur when the angle of attack exceeds the limit, between 15-20 degrees. Airflow separation on the horizontal stabilizer leads to loss of lift and compromised pitch control.

Tail stall causes include flap extension, icing, and aft center of gravity. Flap extension increases wing downwash, raising the tailplane's angle of attack. Icing disrupts airflow over the horizontal stabilizer, reducing the angle of attack. Aft center of gravity requires more downward lift from the tailplane, increasing stall risk. T-tail configurations place the horizontal stabilizer above the vertical stabilizer, making them prone to aerodynamic interference.

Tail stalls result in loss of pitch control and nose-down pitch. Unrecovered tail stalls lead to considerable altitude loss and are fatal. Tail stall recovery involves reducing angle of attack and increasing airspeed. Pilots must lower the nose, trade altitude for airspeed, and adjust elevator control to restore pitch authority.

What causes a wing stall?

A wing stall is caused when the critical angle of attack is exceeded leading to a reduction in lift. Airflow separates from the wing's upper surface, increasing drag. Stalls occur at any airspeed if the angle of attack becomes large, past 15 degrees.

Wing geometry and configuration influence stall characteristics. Swept wings tend to stall at the wingtips due to higher lift coefficients on outer wing panels. Airfoil profile and camber determine the lift curve slope and stall behavior. Cambered airfoils stall at lower angles than symmetric airfoils, around 8-15 degrees. Leading edge shape impacts stall abruptness - sharp leading edges promote sudden leading-edge stalls.

Angle of Attack (AoA) magnitude relates to lift generation and stall onset. The AoA threshold occurs around 15 degrees for most subsonic airfoils. Exceeding this limit causes flow separation and lift reduction. AoA incidence varies with aircraft attitude and flight conditions. Higher weights and load factors increase the required AoA to maintain lift.

Flow velocity increases over the wing's upper surface as AoA rises. Flow separation begins at the trailing edge when the angle is exceeded. Separation extent grows with increasing AoA, moving along the wing surface. Separation eliminates lift in affected areas and makes reattachment difficult.

Lift force depends on airflow velocity squared and varies with the lift coefficient. Lift magnitude peaks near the critical AoA and decreases above it. Stall causes a drop in lift force on the wing. Weights raise stall speed by requiring more lift. Load factor increases stall speed in turns and pullups by 41% at 60-degree bank angles.

What causes a tip stall in an airplane?

Tip stalls occur during slow-speed maneuvers or sharp turns when the angle of attack exceeds the critical threshold. A tip stall in an airplane causes one wing to lose lift at its edge. The inside tip of the wing is prone to stalling, leading to a loss of roll control.

Airplane configuration and wing geometry influence tip stall occurrence. Wing tip design affects airflow patterns and separation characteristics. Wings with insufficient washout are prone to tip stalls. Wing twist (washout) reduces the angle of attack at the tips by 2-3 degrees compared to the root. Operational conditions are factors causing tip stalls. Angle of attack incidence beyond 15-20 degrees exceeds the threshold for most wings. Yaw deviation of 5-10 degrees creates asymmetric lift distribution across the wingspan. Airflow velocity decreases by up to 30% near the wing tips during high-angle-of-attack maneuvers.

Aerodynamic phenomena contribute to the onset of tip stalls. Flow separation initiates at the trailing edge and progresses forward as the angle of attack increases. Boundary layer detachment occurs when the angle of attack exceeds the critical value by 1-2 degrees. Separation point moves from 70% chord to 30% chord during stall progression. Lift magnitude decreases once flow separation begins, with up to 50% loss of lift within 2-3 degrees past the critical angle of attack.

Stall onset and progression follow a pattern in tip stalls. Tip stall formation starts at the outermost 10-20% of the wingspan. Lift loss propagates inboard at a rate of 5-10% of wingspan per second if not corrected. Wing stall occurs within 2-3 seconds of tip stall onset. Tip stalls result in a 15-30 degree wing drop on the affected side.

What happens when an airplane stalls?

When an airplane stalls, the wing exceeds its critical angle of attack. Airflow separates from the wing's surface, causing loss of lift. The plane stops producing lift, begins to fall, and becomes less responsive to control inputs. Pilots recover by reducing the angle of attack.

The wing's aerodynamic shape and incidence angle determine the critical angle of attack threshold. Most general aviation aircraft have a critical angle threshold around 15 degrees. The airplane's velocity gradient near the wing surface changes during a stall. Lift force reaches a maximum at the critical angle before decreasing. Flow separation causes the airflow over the wing to become turbulent. The disrupted boundary layer results in a loss of lift for the aircraft.

An airplane's flight stability becomes compromised during a stall. Control surfaces lose effectiveness during an airplane stall. The wing's inability to produce sufficient lift results in loss of control for the pilot. The stalled airplane descends rapidly due to loss of lift. The stalled aircraft loses directional control.

Stall warning systems provide alerts when the wing nears its critical angle of attack. Some stall warning systems use a stick shaker or pusher to assist pilot recovery. Stall recovery requires the pilot to reduce the angle of attack. The pilot pushes the airplane's nose down to reduce angle of attack during stall recovery. Adding engine power helps the aircraft regain airspeed and airflow over the wings. Pilots release back pressure on the controls during stall recovery.

How does a plane stall?

A plane stalls when its wing exceeds the critical angle of attack. Stalls occur at low airspeeds, causing insufficient lift. Recovery involves reducing the angle of attack, leveling wings, and applying power. Stalls occur at any attitude and are not dependent on airspeed.

Wing geometry and airfoil profile affect the critical angle of attack. Most airfoils have a critical angle between 8 to 20 degrees. Airfoil camber impacts stall characteristics. A cambered wing produces more lift at lower angles of attack but stalls. Angle of attack magnitude is the primary determinant of stall occurrence. Stalls happen at any airspeed velocity when the critical angle of attack is exceeded.

Flow separation and detachment begin at the critical angle, 15° for most airfoils. Boundary layer thickness on the wing's upper surface increases with angle of attack. The thickening boundary layer contributes to flow separation and stall onset. A reduction in lift force results from the disrupted airflow. Lift decreases beyond the critical angle due to turbulent flow conditions.

How to calculate stall speed?

To calculate stall speed, use the formula V = sqrt((2L)/(ρ S C_L)). Stall speed (V) is the minimum velocity for flight. Lift force (L) equals aircraft weight at stall. Air density (ρ), wing surface area (S), and maximum coefficient of lift (C_L) are factors in the calculation.

To calculate stall speed, follow the bullet points listed below.

• Determine the aircraft's weight at stall, which equals the lift force (L).
• Measure or obtain the air density (ρ) for the current flight condition.
• Calculate or reference the wing surface area (S) of the aircraft.
• Identify the maximum coefficient of lift (C_L) for the aircraft.
• Use the formula V = sqrt((2L)/(ρ S C_L)) to calculate the basic stall speed.
• Adjust the calculated stall speed for changes in aircraft weight, taking into account that increased weight raises stall speed.
• Take into account the impact of wing loading ratio and planform on lift generation.
• Factor in the performance of the maximum lift coefficient, particularly changes due to flap settings, which can increase lift by 50-100%.
• Account for variation in air density due to altitude and temperature changes.
• Recognize the influence of the gravitational acceleration constant, using 9.81 m/s².
• Take into consideration the critical angle of attack, typically between 15-20 degrees.
• Adjust the stall speed calculation for load factor changes during maneuvers, like increased stall speed in a 60-degree bank angle due to a load factor of 2.
• Include any adjustments for turning flight and specific flight conditions to guarantee accurate stall speed assessments.

Increased aircraft weight causes stall speed to increase. Wing loading ratio impacts stall speed. Wing area planform determines lift generation capabilities. Maximum lift coefficient performance affects stall characteristics. Critical angle of attack limit defines stall onset point, around 15-20 degrees. Flap setting position modifies wing lift capabilities. Flap setting configuration alters maximum lift coefficient, increasing it by 50-100%.

Air density varies with altitude and temperature. Air density at sea level is 1.225 kg/m³ (0.0765 lb/ft³), decreasing by 10% for every 1,000 meters (3,280.84 feet) of altitude gain. The gravitational acceleration constant influences stall speed formulas, with a value of 9.81 m/s² (32.2 ft/s²). Engineers design wings to produce lift at low speeds, aiming for stall speeds below 61 knots (113 km/h) for aircraft.

Pilots must define variables including weight, wing area, and maximum lift coefficient to calculate stall speed. The formula involves multiplying and dividing factors. Taking the square root achieves the result. Load factor ratio increases stall speed in accelerated flight. A 60-degree bank angle creates a load factor of 2, increasing stall speed by 41%. Variations in maximum lift coefficient due to flap settings must be accounted for. Adjustments for flight conditions, including turning flight, are vital for accurate calculations.

What is a stall warning?

A stall warning is a device that alerts pilots of impending aircraft stalls. Stall warnings occur when airflow over wings becomes turbulent, causing lift to drop. Warning systems must begin 5-10% above stall speed, providing pilots time for corrective action. Audible horns or stick shakers are warning methods.

Angle-of-attack sensors are pivotal components of stall warning systems. These sensors measure the angle between the wing's chord line and the relative wind. Accuracy and reliability of angle-of-attack sensors are vital for stall warnings. Warning devices include auditory alarms like horns or tones, visual indicators on the instrument panel, and tactile warnings like stick shakers.

Stall speed is the critical velocity below which an aircraft cannot generate sufficient lift. The critical angle of attack for most airfoils is 15°. Stall warning systems activate 5-10% above the stall speed, providing pilots with time to respond. Aerodynamic stalls occur when airflow separates from the wing's upper surface, resulting in a loss of lift. Angle of attack correlates with the onset of stalls, regardless of airspeed.

Stall warning systems integrate with aircraft avionics to provide alerts. Pilots receive notifications through cues, including audible horns, visual indicators, and stick vibrations. Pilot response involves immediate corrective actions to reduce the angle of attack and increase airspeed. Stall warning systems are decisive in preventing aerodynamic stalls and loss-of-control incidents. These systems contribute to flight safety by alerting pilots to impending stall conditions before they become serious.