![1915ca abger fluegel (cropped and mirrored)](https://upload.wikimedia.org/wikipedia/commons/f/f2/1915ca_abger_fluegel_%28cropped_and_mirrored%29.jpg)
In
fluid dynamics
In physics and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids— liquids and gases. It has several subdisciplines, including ''aerodynamics'' (the study of air and other gases in motion) an ...
, a stall is a reduction in the
lift coefficient
In fluid dynamics, the lift coefficient () is a dimensionless quantity that relates the lift generated by a lifting body to the fluid density around the body, the fluid velocity and an associated reference area. A lifting body is a foil or a com ...
generated by a
foil
Foil may refer to:
Materials
* Foil (metal), a quite thin sheet of metal, usually manufactured with a rolling mill machine
* Metal leaf, a very thin sheet of decorative metal
* Aluminium foil, a type of wrapping for food
* Tin foil, metal foil ...
as
angle of attack
In fluid dynamics, angle of attack (AOA, α, or \alpha) is the angle between a reference line on a body (often the chord line of an airfoil) and the vector representing the relative motion between the body and the fluid through which it is m ...
increases.
[Crane, Dale: ''Dictionary of Aeronautical Terms, third edition'', p. 486. Aviation Supplies & Academics, 1997. ] This occurs when the
critical angle of attack
In fluid dynamics, angle of attack (AOA, α, or \alpha) is the angle between a reference line on a body (often the chord line of an airfoil) and the vector representing the relative motion between the body and the fluid through which it is mo ...
of the foil is exceeded. The critical angle of attack is typically about 15°, but it may vary significantly depending on the
fluid
In physics, a fluid is a liquid, gas, or other material that continuously deforms (''flows'') under an applied shear stress, or external force. They have zero shear modulus, or, in simpler terms, are substances which cannot resist any shear ...
, foil, and
Reynolds number
In fluid mechanics, the Reynolds number () is a dimensionless quantity that helps predict fluid flow patterns in different situations by measuring the ratio between inertial and viscous forces. At low Reynolds numbers, flows tend to be domi ...
.
Stalls in fixed-wing flight are often experienced as a sudden reduction in lift as the pilot increases the wing's angle of attack and exceeds its critical angle of attack (which may be due to slowing down below
stall speed
In fluid dynamics, a stall is a reduction in the lift coefficient generated by a foil as angle of attack increases.Crane, Dale: ''Dictionary of Aeronautical Terms, third edition'', p. 486. Aviation Supplies & Academics, 1997. This occurs when t ...
in level flight). A stall does not mean that the engine(s) have stopped working, or that the aircraft has stopped moving—the effect is the same even in an
unpowered glider aircraft
A glider is a fixed-wing aircraft that is supported in flight by the dynamic reaction of the air against its lifting surfaces, and whose free flight does not depend on an engine. Most gliders do not have an engine, although motor-gliders have ...
.
Vectored thrust
Thrust vectoring, also known as thrust vector control (TVC), is the ability of an aircraft, rocket, or other vehicle to manipulate the direction of the thrust from its engine(s) or motor(s) to control the attitude or angular velocity of the v ...
in aircraft is used to maintain
altitude
Altitude or height (also sometimes known as depth) is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The exact definition and reference datum varies according to the context ...
or controlled flight with wings stalled by replacing lost wing lift with engine or
propeller
A propeller (colloquially often called a screw if on a ship or an airscrew if on an aircraft) is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon ...
thrust
Thrust is a reaction force described quantitatively by Newton's third law. When a system expels or accelerates mass in one direction, the accelerated mass will cause a force of equal magnitude but opposite direction to be applied to that syst ...
, thereby giving rise to post-stall technology.
Because stalls are most commonly discussed in connection with
aviation
Aviation includes the activities surrounding mechanical flight and the aircraft industry. ''Aircraft'' includes fixed-wing and rotary-wing types, morphable wings, wing-less lifting bodies, as well as lighter-than-air craft such as hot air ...
, this article discusses stalls as they relate mainly to aircraft, in particular
fixed-wing aircraft
A fixed-wing aircraft is a heavier-than-air flying machine, such as an airplane, which is capable of flight using wings that generate lift caused by the aircraft's forward airspeed and the shape of the wings. Fixed-wing aircraft are distinc ...
. The principles of stall discussed here translate to foils in other fluids as well.
Formal definition
![StallFormation](https://upload.wikimedia.org/wikipedia/commons/8/8d/StallFormation.svg)
A stall is a condition in
aerodynamics
Aerodynamics, from grc, ἀήρ ''aero'' (air) + grc, δυναμική (dynamics), is the study of the motion of air, particularly when affected by a solid object, such as an airplane wing. It involves topics covered in the field of fluid dyn ...
and aviation such that if the angle of attack increases beyond a certain point, then lift begins to decrease. The angle at which this occurs is called the ''critical angle of attack''. This angle is dependent upon the airfoil section or profile of the wing, its
planform
In technical drawing and computer graphics, a multiview projection is a technique of illustration by which a standardized series of orthographic two-dimensional pictures are constructed to represent the form of a three-dimensional object. Up to ...
, its
aspect ratio, and other factors, but is typically in the range of 8 to 20 degrees relative to the incoming wind (
relative wind
In aeronautics, the relative wind is the direction of movement of the atmosphere relative to an aircraft or an airfoil. It is opposite to the direction of movement of the aircraft or airfoil relative to the atmosphere. Close to any point on the su ...
) for most subsonic airfoils. The critical angle of attack is the angle of attack on the
lift coefficient
In fluid dynamics, the lift coefficient () is a dimensionless quantity that relates the lift generated by a lifting body to the fluid density around the body, the fluid velocity and an associated reference area. A lifting body is a foil or a com ...
versus angle-of-attack (Cl~alpha) curve at which the maximum lift coefficient occurs.
Stalling is caused by
flow separation
In fluid dynamics, flow separation or boundary layer separation is the detachment of a boundary layer from a surface into a wake.
A boundary layer exists whenever there is relative movement between a fluid and a solid surface with viscous fo ...
which, in turn, is caused by the air flowing against a rising pressure. Whitford describes three types of stall: trailing-edge, leading-edge and thin-aerofoil, each with distinctive Cl~alpha features. For the trailing-edge stall, separation begins at small angles of attack near the trailing edge of the wing while the rest of the flow over the wing remains attached. As angle of attack increases, the separated regions on the top of the wing increase in size as the flow separation moves forward, and this hinders the ability of the wing to create lift. This is shown by the reduction in lift-slope on a Cl~alpha curve as the lift nears its maximum value. The separated flow usually causes buffeting. Beyond the critical angle of attack, separated flow is so dominant that additional increases in angle of attack cause the lift to fall from its peak value.
Piston-engined and early jet transports had very good stall behaviour with pre-stall buffet warning and, if ignored, a straight nose-drop for a natural recovery. Wing developments that came with the introduction of turbo-prop engines introduced unacceptable stall behaviour. Leading-edge developments on high-lift wings, and the introduction of rear-mounted engines and high-set tailplanes on the next generation of jet transports, also introduced unacceptable stall behaviour. The probability of achieving the stall speed inadvertently, a potentially hazardous event, had been calculated, in 1965, at about once in every 100,000 flights, often enough to justify the cost of development of warning devices, such as stick shakers, and devices to automatically provide an adequate nose-down pitch, such as stick pushers.
When the mean angle of attack of the wings is beyond the stall a
spin
Spin or spinning most often refers to:
* Spinning (textiles), the creation of yarn or thread by twisting fibers together, traditionally by hand spinning
* Spin, the rotation of an object around a central axis
* Spin (propaganda), an intentionally b ...
, which is an
autorotation
Autorotation is a state of flight in which the main rotor system of a helicopter or other rotary-wing aircraft turns by the action of air moving up through the rotor, as with an autogyro, rather than engine power driving the rotor. Bensen, Igor ...
of a stalled wing, may develop. A spin follows departures in roll, yaw and pitch from balanced flight. For example, a roll is naturally damped with an unstalled wing, but with wings stalled the damping moment is replaced with a propelling moment.
Variation of lift with angle of attack
![Lift curve](https://upload.wikimedia.org/wikipedia/commons/d/d1/Lift_curve.svg)
The graph shows that the greatest amount of lift is produced as the critical angle of attack is reached (which in early-20th century aviation was called the "burble point"). This angle is 17.5 degrees in this case, but it varies from airfoil to airfoil. In particular, for aerodynamically thick airfoils (thickness to
chord ratios of around 10%), the critical angle is higher than with a thin airfoil of the same
camber
Camber may refer to a variety of curvatures and angles:
* Camber angle, the angle made by the wheels of a vehicle
* Camber beam, an upward curvature of a joist to compensate for load deflection due in buildings
* Camber thrust in bike technology
* ...
. Symmetric airfoils have lower critical angles (but also work efficiently in inverted flight). The graph shows that, as the angle of attack exceeds the critical angle, the lift produced by the airfoil decreases.
The information in a graph of this kind is gathered using a model of the airfoil in a
wind tunnel
Wind tunnels are large tubes with air blowing through them which are used to replicate the interaction between air and an object flying through the air or moving along the ground. Researchers use wind tunnels to learn more about how an aircraft ...
. Because aircraft models are normally used, rather than full-size machines, special care is needed to make sure that data is taken in the same
Reynolds number
In fluid mechanics, the Reynolds number () is a dimensionless quantity that helps predict fluid flow patterns in different situations by measuring the ratio between inertial and viscous forces. At low Reynolds numbers, flows tend to be domi ...
regime (or scale speed) as in free flight. The separation of flow from the upper wing surface at high angles of attack is quite different at low Reynolds number from that at the high Reynolds numbers of real aircraft. In particular at high Reynolds numbers the flow tends to stay attached to the airfoil for longer because the inertial forces are dominant with respect to the viscous forces which are responsible for the flow separation ultimately leading to the aerodynamic stall. For this reason wind tunnel results carried out at lower speeds and on smaller scales models of the real life counterparts often tend to overestimate the aerodynamic stall angle of attack. High-pressure wind tunnels are one solution to this problem.
In general, steady operation of an aircraft at an angle of attack above the critical angle is not possible because, after exceeding the critical angle, the loss of lift from the wing causes the nose of the aircraft to fall, reducing the angle of attack again. This nose drop, independent of control inputs, indicates the pilot has actually stalled the aircraft.
This graph shows the stall angle, yet in practice most pilot operating handbooks (POH) or generic flight manuals describe stalling in terms of
airspeed
In aviation, airspeed is the speed of an aircraft relative to the air. Among the common conventions for qualifying airspeed are:
* Indicated airspeed ("IAS"), what is read on an airspeed gauge connected to a Pitot-static system;
* Calibrated a ...
. This is because all aircraft are equipped with an
airspeed indicator
The airspeed indicator (ASI) or airspeed gauge is a flight instrument indicating the airspeed of an aircraft in kilometers per hour (km/h), knots (kn), miles per hour (MPH) and/or meters per second (m/s). The recommendation by ICAO is to use km/h, ...
, but fewer aircraft have an angle of attack indicator. An aircraft's stalling speed is published by the manufacturer (and is required for certification by flight testing) for a range of weights and flap positions, but the stalling angle of attack is not published.
As speed reduces, angle of attack has to increase to keep lift constant until the critical angle is reached. The airspeed at which this angle is reached is the (1g, unaccelerated) stalling speed of the aircraft in that particular configuration. Deploying
flaps/slats decreases the stall speed to allow the aircraft to take off and land at a lower speed.
Aerodynamic description
Fixed-wing aircraft
A
fixed-wing aircraft
A fixed-wing aircraft is a heavier-than-air flying machine, such as an airplane, which is capable of flight using wings that generate lift caused by the aircraft's forward airspeed and the shape of the wings. Fixed-wing aircraft are distinc ...
can be made to stall in any
pitch attitude or bank angle or at any airspeed but deliberate stalling is commonly practiced by reducing the speed to the unaccelerated stall speed, at a safe altitude. Unaccelerated (1g) stall speed varies on different fixed-wing aircraft and is represented by colour codes on the
airspeed indicator
The airspeed indicator (ASI) or airspeed gauge is a flight instrument indicating the airspeed of an aircraft in kilometers per hour (km/h), knots (kn), miles per hour (MPH) and/or meters per second (m/s). The recommendation by ICAO is to use km/h, ...
. As the plane flies at this speed, the angle of attack must be increased to prevent any loss of altitude or gain in airspeed (which corresponds to the stall angle described above). The pilot will notice the
flight controls have become less responsive and may also notice some buffeting, a result of the turbulent air separated from the wing hitting the tail of the aircraft.
In most
light aircraft
A light aircraft is an aircraft that has a maximum gross takeoff weight of or less.Crane, Dale: ''Dictionary of Aeronautical Terms, third edition'', page 308. Aviation Supplies & Academics, 1997.
Light aircraft are used as utility aircraft c ...
, as the stall is reached, the aircraft will start to descend (because the wing is no longer producing enough lift to support the aircraft's weight) and the nose will pitch down. Recovery from the stall involves lowering the aircraft nose, to decrease the angle of attack and increase the air speed, until smooth air-flow over the wing is restored. Normal flight can be resumed once recovery is complete. The maneuver is normally quite safe, and, if correctly handled, leads to only a small loss in altitude (20–30 m/50–100 ft). It is taught and practised in order for pilots to recognize, avoid, and recover from stalling the aircraft. A pilot is required to demonstrate competency in controlling an aircraft during and after a stall for certification in the United States, and it is a routine maneuver for pilots when getting to know the handling of an unfamiliar aircraft type. The only dangerous aspect of a stall is a lack of altitude for recovery.
A special form of asymmetric stall in which the aircraft also rotates about its yaw axis is called a
spin
Spin or spinning most often refers to:
* Spinning (textiles), the creation of yarn or thread by twisting fibers together, traditionally by hand spinning
* Spin, the rotation of an object around a central axis
* Spin (propaganda), an intentionally b ...
. A spin can occur if an aircraft is stalled and there is an asymmetric yawing moment applied to it. This yawing moment can be aerodynamic (sideslip angle, rudder, adverse yaw from the ailerons), thrust related (p-factor, one engine inoperative on a multi-engine non-centreline thrust aircraft), or from less likely sources such as severe turbulence. The net effect is that one wing is stalled before the other and the aircraft descends rapidly while rotating, and some aircraft cannot recover from this condition without correct pilot control inputs (which must stop yaw) and loading. A new solution to the problem of difficult (or impossible) stall-spin recovery is provided by the
ballistic parachute
A ballistic parachute, ballistic reserve parachute, or emergency ballistic reserve parachute, is a parachute ejected from its casing by a small explosion, much like that used in an ejection seat. The advantage of the ballistic parachute over a co ...
recovery system.
The most common stall-spin scenarios occur on takeoff (
departure stall) and during landing (base to final turn) because of insufficient airspeed during these maneuvers. Stalls also occur during a go-around manoeuvre if the pilot does not properly respond to the out-of-trim situation resulting from the transition from low power setting to high power setting at low speed. Stall speed is increased when the wing surfaces are
contaminated with ice or frost creating a rougher surface, and heavier airframe due to ice accumulation.
Stalls occur not only at slow airspeed, but at any speed when the wings exceed their critical angle of attack. Attempting to increase the angle of attack at 1g by moving the control column back normally causes the aircraft to climb. However, aircraft often experience higher g-forces, such as when turning steeply or pulling out of a dive. In these cases, the wings are already operating at a higher angle of attack to create the necessary force (derived from lift) to accelerate in the desired direction. Increasing the g-loading still further, by pulling back on the controls, can cause the stalling angle to be exceeded, even though the aircraft is flying at a high speed. These "high-speed stalls" produce the same buffeting characteristics as 1g stalls and can also initiate a spin if there is also any yawing.
Characteristics
Different aircraft types have different stalling characteristics but they only have to be good enough to satisfy their particular Airworthiness authority. For example, the
Short Belfast
The Short Belfast (or Shorts Belfast)Mondey 1981, p. 228. is a heavy lift turboprop freighter that was built by British manufacturer Short Brothers at Belfast. Only 10 aircraft were constructed, all of which entered service with the Royal Air ...
heavy freighter had a marginal nose drop which was acceptable to the
Royal Air Force
The Royal Air Force (RAF) is the United Kingdom's air and space force. It was formed towards the end of the First World War on 1 April 1918, becoming the first independent air force in the world, by regrouping the Royal Flying Corps (RFC) and ...
. When the aircraft were sold to a civil operator they had to be fitted with a stick pusher to meet the civil requirements. Some aircraft may naturally have very good behaviour well beyond what is required. For example, first generation jet transports have been described as having an immaculate nose drop at the stall. Loss of lift on one wing is acceptable as long as the roll, including during stall recovery, doesn't exceed about 20 degrees, or in turning flight the roll shall not exceed 90 degrees bank. If pre-stall warning followed by nose drop and limited wing drop are naturally not present or are deemed to be unacceptably marginal by an Airworthiness authority the stalling behaviour has to be made good enough with airframe modifications or devices such as a stick shaker and pusher. These are described in "Warning and safety devices".
Stall speeds
![Airspeed indicator](https://upload.wikimedia.org/wikipedia/commons/c/ce/Airspeed_indicator.svg)
Stalls depend only on angle of attack, not
airspeed
In aviation, airspeed is the speed of an aircraft relative to the air. Among the common conventions for qualifying airspeed are:
* Indicated airspeed ("IAS"), what is read on an airspeed gauge connected to a Pitot-static system;
* Calibrated a ...
. However, the slower an aircraft flies, the greater the angle of attack it needs to produce lift equal to the aircraft's weight.
As the speed decreases further, at some point this angle will be equal to the
critical (stall) angle of attack. This speed is called the "stall speed". An aircraft flying at its stall speed cannot climb, and an aircraft flying below its stall speed cannot stop descending. Any attempt to do so by increasing angle of attack, without first increasing airspeed, will result in a stall.
The actual stall speed will vary depending on the airplane's weight, altitude, configuration, and vertical and lateral acceleration.
Propeller slipstream reduces the stall speed by energizing the flow over the wings. (It also causes increased lift by increasing the airspeed over part of the wings.)
Speed definitions vary and include:
* V
S: Stall speed: the speed at which the airplane exhibits those qualities accepted as defining the stall.
* V
S0: The stall speed or minimum steady flight speed in landing configuration.
The zero-thrust stall speed at the most extended landing flap setting.
* V
S1: The stall speed or minimum steady flight speed obtained in a specified configuration.
The zero thrust stall speed at a specified flap setting.
An airspeed indicator, for the purpose of flight-testing, may have the following markings: the bottom of the white arc indicates V
S0 at maximum weight, while the bottom of the green arc indicates V
S1 at maximum weight. While an aircraft's V
S speed is computed by design, its V
S0 and V
S1 speeds must be demonstrated empirically by flight testing.
In accelerated and turning flight
![Accelerated stall](https://upload.wikimedia.org/wikipedia/commons/a/a4/Accelerated_stall.gif)
The normal stall speed, specified by the V
S values above, always refers to straight and level flight, where the
load factor is equal to 1g. However, if the aircraft is turning or pulling up from a dive, additional lift is required to provide the vertical or lateral acceleration, and so the stall speed is higher. An accelerated stall is a stall that occurs under such conditions.
In a
banked turn
A banked turn (or banking turn) is a turn or change of direction in which the vehicle banks or inclines, usually towards the inside of the turn. For a road or railroad this is usually due to the roadbed having a transverse down-slope towards the ...
, the
lift
Lift or LIFT may refer to:
Physical devices
* Elevator, or lift, a device used for raising and lowering people or goods
** Paternoster lift, a type of lift using a continuous chain of cars which do not stop
** Patient lift, or Hoyer lift, mobil ...
required is equal to the
weight
In science and engineering, the weight of an object is the force acting on the object due to gravity.
Some standard textbooks define weight as a Euclidean vector, vector quantity, the gravitational force acting on the object. Others define weigh ...
of the aircraft plus extra lift to provide the
centripetal force
A centripetal force (from Latin ''centrum'', "center" and ''petere'', "to seek") is a force that makes a body follow a curved path. Its direction is always orthogonal to the motion of the body and towards the fixed point of the instantaneous c ...
necessary to perform the turn:
[
:
where:
: = lift
: = load factor (greater than 1 in a turn)
: = weight of the aircraft
To achieve the extra lift, the ]lift coefficient
In fluid dynamics, the lift coefficient () is a dimensionless quantity that relates the lift generated by a lifting body to the fluid density around the body, the fluid velocity and an associated reference area. A lifting body is a foil or a com ...
, and so the angle of attack, will have to be higher than it would be in straight and level flight at the same speed. Therefore, given that the stall always occurs at the same critical angle of attack, by increasing the load factor (e.g. by tightening the turn) the critical angle will be reached at a higher airspeed:[Clancy, L.J., ''Aerodynamics'', Section 5.22]
:
where:
: = stall speed
: = stall speed of the aircraft in straight, level flight
: = load factor
The table that follows gives some examples of the relation between the angle of bank
A banked turn (or banking turn) is a turn or change of direction in which the vehicle banks or inclines, usually towards the inside of the turn. For a road or railroad this is usually due to the roadbed having a transverse down-slope towards the ...
and the square root of the load factor. It derives from the trigonometric relation ( secant) between and .
:
For example, in a turn with bank angle of 45°, Vst is 19% higher than Vs.
According to Federal Aviation Administration
The Federal Aviation Administration (FAA) is the largest transportation agency of the U.S. government and regulates all aspects of civil aviation in the country as well as over surrounding international waters. Its powers include air traffic m ...
(FAA) terminology, the above example illustrates a so-called turning flight stall, while the term ''accelerated'' is used to indicate an ''accelerated turning stall'' only, that is, a turning flight stall where the airspeed decreases at a given rate.
Accelerated stalls also pose a risk in powerful propeller aircraft with a tendency to roll in reaction to engine torque
In physics and mechanics, torque is the rotational equivalent of linear force. It is also referred to as the moment of force (also abbreviated to moment). It represents the capability of a force to produce change in the rotational motion of th ...
. When such an aircraft is flying close to its stall speed in straight and level flight, the sudden application of full power may roll the aircraft and create the same aerodynamic conditions that induce an accelerated stall in turning flight. An aircraft that displays this rolling tendency is the Mitsubishi MU-2
The Mitsubishi MU-2 is a Japanese high-wing, twin-engine turboprop aircraft with a pressurized cabin manufactured by Mitsubishi Heavy Industries. It made its maiden flight in September 1963 and was produced until 1986. It is one of postwar Japa ...
; pilots of this aircraft are trained to avoid sudden and drastic increases in power at low altitude and low airspeed, as an accelerated stall under these conditions is very difficult to safely recover from.
A notable example of an air accident involving a low-altitude turning flight stall is the 1994 Fairchild Air Force Base B-52 crash.
Types
Dynamic stall
Dynamic stall is a non-linear unsteady aerodynamic effect that occurs when airfoils rapidly change the angle of attack. The rapid change can cause a strong vortex
In fluid dynamics, a vortex ( : vortices or vortexes) is a region in a fluid in which the flow revolves around an axis line, which may be straight or curved. Vortices form in stirred fluids, and may be observed in smoke rings, whirlpools in th ...
to be shed from the leading edge of the aerofoil, and travel backwards above the wing. The vortex, containing high-velocity airflows, briefly increases the lift produced by the wing. As soon as it passes behind the trailing edge, however, the lift reduces dramatically, and the wing is in normal stall.
Dynamic stall is an effect most associated with helicopters and flapping wings, though also occurs in wind turbines, and due to gusting airflow. During forward flight, some regions of a helicopter blade may incur flow that reverses (compared to the direction of blade movement), and thus includes rapidly changing angles of attack. Oscillating (flapping) wings, such as those of insects like the bumblebee
A bumblebee (or bumble bee, bumble-bee, or humble-bee) is any of over 250 species in the genus ''Bombus'', part of Apidae, one of the bee families. This genus is the only extant group in the tribe Bombini, though a few extinct related gener ...
—may rely almost entirely on dynamic stall for lift production, provided the oscillations are fast compared to the speed of flight, and the angle of the wing changes rapidly compared to airflow direction.
Stall delay can occur on airfoils
An airfoil (American English) or aerofoil (British English) is the cross-sectional shape of an object whose motion through a gas is capable of generating significant lift, such as a wing, a sail, or the blades of propeller, rotor, or turbine.
A ...
subject to a high angle of attack and a three-dimensional flow. When the angle of attack on an airfoil is increasing rapidly, the flow will remain substantially attached to the airfoil to a significantly higher angle of attack than can be achieved in steady-state conditions. As a result, the stall is delayed momentarily and a lift coefficient significantly higher than the steady-state maximum is achieved. The effect was first noticed on propellers
A propeller (colloquially often called a screw if on a ship or an airscrew if on an aircraft) is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon ...
.
Deep stall
A ''deep stall'' (or ''super-stall'') is a dangerous type of stall that affects certain aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines ...
designs, notably jet aircraft with a T-tail
A T-tail is an empennage configuration in which the tailplane is mounted to the top of the fin. The arrangement looks like the capital letter T, hence the name. The T-tail differs from the standard configuration in which the tailplane is ...
configuration and rear-mounted engines. In these designs, the turbulent wake of a stalled main wing, nacelle-pylon wakes and the wake from the fuselage "blanket" the horizontal stabilizer, rendering the elevators ineffective and preventing the aircraft from recovering from the stall. Taylor states that T-tail propeller aircraft, unlike jet aircraft, do not usually require a stall-recovery system during stall flight testing due to increased airflow over the wing root from the prop wash. Nor do they have rear-mounted nacelles, which can contribute substantially to the problem. The A400M
The Airbus A400M AtlasNamed after the Greek mythological figure. is a European four-engine turboprop military transport aircraft. It was designed by Airbus Military (now Airbus Defence and Space) as a tactical airlifter with strategic capabi ...
was fitted with a vertical tail booster for some flight tests in case of deep stall.
Trubshaw gives a broad definition of deep stall as penetrating to such angles of attack that pitch control effectiveness is reduced by the wing and nacelle wakes. He also gives a definition that relates deep stall to a locked-in condition where recovery is impossible. This is a single value of , for a given aircraft configuration, where there is no pitching moment, i.e. a trim point.
Typical values both for the range of deep stall, as defined above, and the locked-in trim point are given for the Douglas DC-9
The McDonnell Douglas DC-9 is an American five-abreast single-aisle aircraft designed by the Douglas Aircraft Company. It was initially produced by the developer company as the Douglas DC-9 until August 1967 and then by McDonnell Douglas.
After ...
Series 10 by Schaufele. These values are from wind-tunnel tests for an early design. The final design had no locked-in trim point, so recovery from the deep stall region was possible, as required to meet certification rules. Normal stall beginning at the "g break" (sudden decrease of the vertical load factor[) was at , deep stall started at about 30°, and the locked-in unrecoverable trim point was at 47°.
The very high for a deep stall locked-in condition occurs well beyond the normal stall but can be attained very rapidly, as the aircraft is unstable beyond the normal stall and requires immediate action to arrest it. The loss of lift causes high sink rates, which, together with the low forward speed at the normal stall, give a high with little or no rotation of the aircraft.]["Accident Report No. EW/C/039, Appendix IV in "Trubshaw Test Pilot". Trubshaw and Edmondson, Sutton Publishing 1998, , p. 182.] BAC 1-11
The BAC One-Eleven (or BAC-111/BAC 1-11) was an early jet airliner produced by the British Aircraft Corporation (BAC).
Originally conceived by Hunting Aircraft as a 30-seat jet, before its merger into BAC in 1960, it was launched as an 80-s ...
G-ASHG, during stall flight tests before the type was modified to prevent a locked-in deep-stall condition, descended at over and struck the ground in a flat attitude moving only forward after initial impact.[ Sketches showing how the wing wake blankets the tail may be misleading if they imply that deep stall requires a high body angle. Taylor and Ray] show how the aircraft attitude in the deep stall is relatively flat, even less than during the normal stall, with very high negative flight-path angles.
Effects similar to deep stall had been known to occur on some aircraft designs before the term was coined. A prototype Gloster Javelin
The Gloster Javelin is a twin-engined T-tailed delta-wing subsonic night and all-weather interceptor aircraft that served with Britain's Royal Air Force from the mid-1950s until the late 1960s. The last aircraft design to bear the Gloster name ...
( serial ''WD808'') was lost in a crash on 11 June 1953 to a "locked-in" stall. However, Waterton["The Quick and the Dead". W. A. Waterton, Frederick Mueller, London 1956, p. 216.] states that the trimming tailplane was found to be the wrong way for recovery. Low-speed handling tests were being done to assess a new wing.[ ]Handley Page Victor
The Handley Page Victor is a British jet-powered strategic bomber developed and produced by Handley Page during the Cold War. It was the third and final '' V bomber'' to be operated by the Royal Air Force (RAF), the other two being the Avro ...
''XL159'' was lost to a "stable stall" on 23 March 1962. It had been clearing the fixed droop leading edge with the test being stall approach, landing configuration, C of G aft. The brake parachute had not been streamed, as it may have hindered rear crew escape.
The name "deep stall" first came into widespread use after the crash of the prototype BAC 1-11
The BAC One-Eleven (or BAC-111/BAC 1-11) was an early jet airliner produced by the British Aircraft Corporation (BAC).
Originally conceived by Hunting Aircraft as a 30-seat jet, before its merger into BAC in 1960, it was launched as an 80-s ...
G-ASHG on 22 October 1963, which killed its crew. This led to changes to the aircraft, including the installation of a stick shaker
A stick shaker is a mechanical device designed to rapidly and noisily vibrate the control yoke (the "stick") of an aircraft, warning the flight crew that an imminent aerodynamic stall has been detected. It is typically present on the majority of ...
(see below) to clearly warn the pilot of an impending stall. Stick shakers are now a standard part of commercial airliners. Nevertheless, the problem continues to cause accidents; on 3 June 1966, a Hawker Siddeley Trident
The Hawker Siddeley HS-121 Trident (originally the de Havilland DH.121 and briefly the Airco DH.121) is a British airliner produced by Hawker Siddeley.
In 1957, de Havilland proposed its DH.121 trijet design to a British European Airways (BEA ...
(G-ARPY), was lost to deep stall; deep stall is suspected to be cause of another Trident (the British European Airways Flight 548
British European Airways Flight 548 was a scheduled passenger flight from London Heathrow to Brussels that crashed near Staines, Surrey, England, soon after take-off on 18 June 1972, killing all 118 people on board. The accident became known a ...
''G-ARPI'') crash – known as the "Staines Disaster" – on 18 June 1972, when the crew failed to notice the conditions and had disabled the stall-recovery system. On 3 April 1980, a prototype of the Canadair Challenger
The Bombardier Challenger 600 series is a family of business jets developed by Canadair after a Bill Lear concept, and then produced from 1986 by its new owner, Bombardier Aerospace.
At the end of 1975, Canadair began funding the developmen ...
business jet crashed after initially entering a deep stall from 17,000 ft and having both engines flame-out. It recovered from the deep stall after deploying the anti-spin parachute but crashed after being unable to jettison the chute or relight the engines. One of the test pilots was unable to escape from the aircraft in time and was killed. On 26 July 1993, a Canadair CRJ-100
The Bombardier CRJ100 and CRJ200 (previously Canadair CRJ100 and CRJ200) is a regional jet designed and manufactured by Bombardier Aerospace between 1991 and 2006, the first of the Bombardier CRJ family.
The ''Canadair Regional Jet'' (CRJ) pro ...
was lost in flight testing due to a deep stall. It has been reported that a Boeing 727
The Boeing 727 is an American narrow-body airliner that was developed and produced by Boeing Commercial Airplanes.
After the heavy 707 quad-jet was introduced in 1958, Boeing addressed the demand for shorter flight lengths from smaller airpo ...
entered a deep stall in a flight test, but the pilot was able to rock the airplane to increasingly higher bank angles until the nose finally fell through and normal control response was recovered. A 727 accident on 1 December 1974, has also been attributed to a deep stall. The crash of West Caribbean Airways Flight 708
West Caribbean Airways Flight 708 was a West Caribbean Airways charter flight that crashed in northwest Venezuela in the early hours of Tuesday, 16 August 2005, killing all 160 passengers and crew on board. The plane, a McDonnell Douglas MD-80, ...
in 2005 was also attributed to a deep stall.
Deep stalls can occur at apparently normal pitch attitudes, if the aircraft is descending quickly enough. The airflow is coming from below, so the angle of attack is increased. Early speculation on reasons for the crash of Air France Flight 447
Air France Flight 447 (AF447 or AFR447) was a scheduled international passenger flight from Rio de Janeiro, Brazil, to Paris, France. On 1 June 2009, inconsistent airspeed indications led to the pilots inadvertently stalling the Airbus A330 ser ...
blamed an unrecoverable deep stall, since it descended in an almost flat attitude (15°) at an angle of attack of 35° or more. However, it was held in a stalled glide by the pilots, who held the nose up amid all the confusion of what was actually happening to the aircraft.
Canard-configured aircraft are also at risk of getting into a deep stall. Two Velocity
Velocity is the directional speed of an object in motion as an indication of its rate of change in position as observed from a particular frame of reference and as measured by a particular standard of time (e.g. northbound). Velocity is a ...
aircraft crashed due to locked-in deep stalls. Testing revealed that the addition of leading-edge cuff
A leading-edge cuff is a fixed aerodynamic wing device employed on fixed-wing aircraft to improve the stall and spin characteristics. Cuffs may be either factory-designed or an after-market add-on modification.Crane, Dale: ''Dictionary of Aeron ...
s to the outboard wing prevented the aircraft from getting into a deep stall. The Piper Advanced Technologies PAT-1, N15PT, another canard-configured aircraft, also crashed in an accident attributed to a deep stall. Wind-tunnel testing of the design at the NASA Langley Research Center
The Langley Research Center (LaRC or NASA Langley), located in Hampton, Virginia, United States of America, is the oldest of NASA's field centers. It directly borders Langley Air Force Base and the Back River on the Chesapeake Bay. LaRC has fo ...
showed that it was vulnerable to a deep stall.
In the early 1980s, a Schweizer SGS 1-36 sailplane was modified for NASA
The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research.
NASA was established in 1958, succeeding t ...
's controlled deep-stall flight program.
Tip stall
Wing sweep and taper cause stalling at the tip of a wing before the root. The position of a swept wing along the fuselage has to be such that the lift from the wing root, well forward of the aircraft center of gravity (c.g.), must be balanced by the wing tip, well aft of the c.g. If the tip stalls first the balance of the aircraft is upset causing dangerous nose pitch up
In aerodynamics, pitch-up is an uncommanded nose-upwards rotation of an aircraft. It is an undesirable characteristic that has been observed mostly in experimental swept-wing aircraft at high subsonic Mach numbers or high angle of attack.
History
...
. Swept wings have to incorporate features which prevent pitch-up caused by premature tip stall.
A swept wing has a higher lift coefficient on its outer panels than on the inner wing, causing them to reach their maximum lift capability first and to stall first. This is caused by the downwash pattern associated with swept/tapered wings. To delay tip stall the outboard wing is given washout to reduce its angle of attack. The root can also be modified with a suitable leading-edge and airfoil section to make sure it stalls before the tip. However, when taken beyond stalling incidence the tips may still become fully stalled before the inner wing despite initial separation occurring inboard. This causes pitch-up after the stall and entry to a super-stall on those aircraft with super-stall characteristics. Span-wise flow of the boundary layer is also present on swept wings and causes tip stall. The amount of boundary layer air flowing outboard can be reduced by generating vortices with a leading-edge device such as a fence, notch, saw tooth or a set of vortex generators behind the leading edge.
Warning and safety devices
Fixed-wing aircraft can be equipped with devices to prevent or postpone a stall or to make it less (or in some cases more) severe, or to make recovery easier.
* An aerodynamic twist can be introduced to the wing with the leading edge near the wing tip twisted downward. This is called washout and causes the wing root
The wing root is the part of the wing on a fixed-wing aircraft or winged-spaceship that is closest to the fuselage,Peppler, I.L.: ''From The Ground Up'', page 9. Aviation Publishers Co. Limited, Ottawa Ontario, Twenty Seventh Revised Edition, 1996 ...
to stall before the wing tip. This makes the stall gentle and progressive. Since the stall is delayed at the wing tips, where the aileron
An aileron (French for "little wing" or "fin") is a hinged flight control surface usually forming part of the trailing edge of each wing of a fixed-wing aircraft. Ailerons are used in pairs to control the aircraft in roll (or movement around ...
s are, roll control is maintained when the stall begins.
* A stall strip is a small sharp-edged device that, when attached to the leading edge of a wing, encourages the stall to start there in preference to any other location on the wing. If attached close to the wing root, it makes the stall gentle and progressive; if attached near the wing tip, it encourages the aircraft to drop a wing when stalling.
* A stall fence is a flat plate in the direction of the chord to stop separated flow progressing out along the wing
* Vortex generator
A vortex generator (VG) is an aerodynamic device, consisting of a small vane usually attached to a lifting surface (or airfoil, such as an aircraft wing) or a rotor blade of a wind turbine. s, tiny strips of metal or plastic placed on top of the wing near the leading edge that protrude past the boundary layer
In physics and fluid mechanics, a boundary layer is the thin layer of fluid in the immediate vicinity of a bounding surface formed by the fluid flowing along the surface. The fluid's interaction with the wall induces a no-slip boundary condi ...
into the free stream. As the name implies, they energize the boundary layer by mixing free stream airflow with boundary layer flow, thereby creating vortices, this increases the momentum
In Newtonian mechanics, momentum (more specifically linear momentum or translational momentum) is the product of the mass and velocity of an object. It is a vector quantity, possessing a magnitude and a direction. If is an object's mass an ...
in the boundary layer. By increasing the momentum of the boundary layer, airflow separation and the resulting stall may be delayed.
* An anti-stall strake is a leading edge extension
A leading-edge extension (LEX) is a small extension to an aircraft wing surface, forward of the leading edge. The primary reason for adding an extension is to improve the airflow at high angles of attack and low airspeeds, to improve handling an ...
that generates a vortex
In fluid dynamics, a vortex ( : vortices or vortexes) is a region in a fluid in which the flow revolves around an axis line, which may be straight or curved. Vortices form in stirred fluids, and may be observed in smoke rings, whirlpools in th ...
on the wing upper surface to postpone the stall.
* A stick pusher
A stick pusher is a device installed in some fixed-wing aircraft to prevent the aircraft from entering an aerodynamic stall. Some large fixed-wing aircraft display poor post-stall handling characteristics or are vulnerable to deep stall. To preven ...
is a mechanical device that prevents the pilot from stalling an aircraft. It pushes the elevator control forward as the stall is approached, causing a reduction in the angle of attack. In generic terms, a stick pusher is known as a ''stall identification device'' or ''stall identification system''.
* A stick shaker
A stick shaker is a mechanical device designed to rapidly and noisily vibrate the control yoke (the "stick") of an aircraft, warning the flight crew that an imminent aerodynamic stall has been detected. It is typically present on the majority of ...
is a mechanical device that shakes the pilot's controls to warn of the onset of stall.
* A stall warning is an electronic or mechanical device that sounds an audible warning as the stall speed is approached. The majority of aircraft contain some form of this device that warns the pilot of an impending stall. The simplest such device is a ''stall warning horn'', which consists of either a pressure
Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and e ...
sensor
A sensor is a device that produces an output signal for the purpose of sensing a physical phenomenon.
In the broadest definition, a sensor is a device, module, machine, or subsystem that detects events or changes in its environment and sends ...
or a movable metal tab that actuates a switch
In electrical engineering, a switch is an electrical component that can disconnect or connect the conducting path in an electrical circuit, interrupting the electric current or diverting it from one conductor to another. The most common type of ...
and produces an audible warning in response.
* An angle-of-attack indicator for light aircraft, the "AlphaSystemsAOA" and a nearly identical "lift reserve indicator", are both pressure-differential instruments that display margin above stall and/or angle of attack on an instantaneous, continuous readout. The General Technics CYA-100 displays true angle of attack via a magnetically coupled vane. An AOA indicator provides a visual display of the amount of available lift throughout its slow-speed envelope regardless of the many variables that act upon an aircraft. This indicator is immediately responsive to changes in speed, angle of attack, and wind conditions, and automatically compensates for aircraft weight, altitude, and temperature.
* An angle of attack limiter or an "alpha limiter" is a flight computer that automatically prevents pilot input from causing the plane to rise over the stall angle. Some alpha limiters can be disabled by the pilot.
Stall warning systems often involve inputs from a broad range of sensors and systems to include a dedicated angle of attack sensor.
Blockage, damage, or inoperation of stall and angle of attack (AOA) probes can lead to unreliability of the stall warning and cause the stick pusher, overspeed warning, autopilot, and yaw damper to malfunction.
If a forward canard is used for pitch control, rather than an aft tail, the canard is designed to meet the airflow at a slightly greater angle of attack than the wing. Therefore, when the aircraft pitch increases abnormally, the canard will usually stall first, causing the nose to drop and so preventing the wing from reaching its critical AOA. Thus, the risk of main-wing stalling is greatly reduced. However, if the main wing stalls, recovery becomes difficult, as the canard is more deeply stalled, and angle of attack increases rapidly.
If an aft tail is used, the wing is designed to stall before the tail. In this case, the wing can be flown at higher lift coefficient (closer to stall) to produce more overall lift.
Most military combat aircraft have an angle of attack indicator among the pilot's instruments, which lets the pilot know precisely how close to the stall point the aircraft is. Modern airliner instrumentation may also measure angle of attack, although this information may not be directly displayed on the pilot's display, instead driving a stall warning indicator or giving performance information to the flight computer (for fly-by-wire systems).
Flight beyond the stall
As a wing stalls, aileron
An aileron (French for "little wing" or "fin") is a hinged flight control surface usually forming part of the trailing edge of each wing of a fixed-wing aircraft. Ailerons are used in pairs to control the aircraft in roll (or movement around ...
effectiveness is reduced, rendering the plane difficult to control and increasing the risk of a spin. Post stall, steady flight beyond the stalling angle (where the coefficient of lift is largest) requires engine thrust to replace lift, as well as alternative controls to replace the loss of effectiveness of the ailerons. For high-powered aircraft, the loss of lift (and increase in drag) beyond the stall angle is less of a problem than maintaining control. Some aircraft may be subject to post-stall gyration (e.g. the F-4
The McDonnell Douglas F-4 Phantom II is an American tandem two-seat, twin-engine, all-weather, long-range supersonic jet interceptor and fighter-bomber originally developed by McDonnell Aircraft for the United States Navy.Swanborough and Bo ...
) or susceptible to entering a flat-spin (e.g. F-14
The Grumman F-14 Tomcat is an American carrier-capable supersonic, twin-engine, two-seat, twin-tail, variable-sweep wing fighter aircraft. The Tomcat was developed for the United States Navy's Naval Fighter Experimental (VFX) program after the ...
). Control beyond stall can be provided by reaction control systems (e.g. NF-104A), vectored thrust, as well as a rolling stabilator
A stabilator is a fully movable aircraft horizontal stabilizer. It serves the usual functions of longitudinal stability, control and stick force requirements otherwise performed by the separate parts of a conventional horizontal stabilizer and el ...
(or taileron). The enhanced manoeuvering capability by flights at very high angles of attack can provide a tactical advantage for military fighters such as the F-22 Raptor
The Lockheed Martin F-22 Raptor is an American single-seat, twin-engine, all-weather stealth tactical fighter aircraft developed for the United States Air Force (USAF). As the result of the USAF's Advanced Tactical Fighter (ATF) program, th ...
. Short-term stalls at 90–120° (e.g. Pugachev's cobra
In aerobatics, the cobra maneuver (or just the ''cobra''), also called ''dynamic deceleration'', among other names (see Etymology), is a dramatic and demanding maneuver in which an airplane flying at a moderate speed abruptly raises its nose mom ...
) are sometimes performed at airshows. The highest angle of attack in sustained flight so far demonstrated was 70° in the X-31
The Rockwell-Messerschmitt-Bölkow-Blohm X-31 was an experimental jet fighter designed to test fighter thrust vectoring technology.
It was designed and built by Rockwell and Messerschmitt-Bölkow-Blohm (MBB), as part of a joint US and German ' ...
at the Dryden Flight Research Center
The NASA Neil A. Armstrong Flight Research Center (AFRC) is an aeronautical research center operated by NASA. Its primary campus is located inside Edwards Air Force Base in California and is considered NASA's premier site for aeronautical rese ...
. Sustained post-stall flight is a type of supermaneuverability
Supermaneuverability is the capability of fighter aircraft to execute tactical maneuvers that are not possible with purely aerodynamic techniques. Such maneuvers can involve controlled side-slipping or angles of attack beyond maximum lift.
...
.
Spoilers
Except for flight training, airplane testing, and aerobatics
Aerobatics is the practice of flying maneuvers involving aircraft attitudes that are not used in conventional passenger-carrying flights. The term is a portmanteau of "aerial" and "acrobatics". Aerobatics are performed in aeroplanes and glid ...
, a stall is usually an undesirable event. Spoilers (sometimes called lift dumpers), however, are devices that are intentionally deployed to create a carefully controlled flow separation
In fluid dynamics, flow separation or boundary layer separation is the detachment of a boundary layer from a surface into a wake.
A boundary layer exists whenever there is relative movement between a fluid and a solid surface with viscous fo ...
over part of an aircraft's wing to reduce the lift it generates, increase the drag, and allow the aircraft to descend more rapidly without gaining speed. Spoilers are also deployed asymmetrically (one wing only) to enhance roll control. Spoilers can also be used on aborted take-offs and after main wheel contact on landing to increase the aircraft's weight on its wheels for better braking action.
Unlike powered airplanes, which can control descent by increasing or decreasing thrust, gliders have to increase drag to increase the rate of descent. In high-performance gliders, spoiler deployment is extensively used to control the approach to landing.
Spoilers can also be thought of as "lift reducers" because they reduce the lift of the wing in which the spoiler resides. For example, an uncommanded roll to the left could be reversed by raising the right wing spoiler (or only a few of the spoilers present in large airliner wings). This has the advantage of avoiding the need to increase lift in the wing that is dropping (which may bring that wing closer to stalling).
History
German aviator Otto Lilienthal
Karl Wilhelm Otto Lilienthal (23 May 1848 – 10 August 1896) was a German pioneer of aviation who became known as the "flying man". He was the first person to make well-documented, repeated, successful flights with gliders, therefore making ...
died while flying in 1896 as the result of a stall. Wilbur Wright encountered stalls for the first time in 1901, while flying his second glider. Awareness of Lilienthal's accident and Wilbur's experience, motivated the Wright Brothers to design their plane in " canard" configuration. This purportedly made recoveries from stalls easier and more gentle. The design allegedly saved the brothers' lives more than once. Although, canard configurations, without careful design, can actually make a stall unrecoverable.
The aircraft engineer Juan de la Cierva
Juan de la Cierva y Codorníu, 1st Count of la Cierva (; 21 September 1895 in Murcia, Spain – 9 December 1936 in Croydon, United Kingdom) was a Spanish civil engineer, pilot and a self taught aeronautical engineer. His most famous accomplish ...
worked on his "Autogiro
An autogyro (from Greek and , "self-turning"), also known as a ''gyroplane'', is a type of rotorcraft that uses an unpowered rotor in free autorotation to develop lift. Forward thrust is provided independently, by an engine-driven propeller. Whi ...
" project to develop a rotary wing aircraft
A rotorcraft or rotary-wing aircraft is a heavier-than-air aircraft with rotary wings or rotor blades, which generate lift by rotating around a vertical mast. Several rotor blades mounted on a single mast are referred to as a rotor. The Internati ...
which, he hoped, would be unable to stall and which therefore would be safer than aeroplanes. In developing the resulting "autogyro
An autogyro (from Greek and , "self-turning"), also known as a ''gyroplane'', is a type of rotorcraft that uses an unpowered rotor in free autorotation to develop lift. Forward thrust is provided independently, by an engine-driven propeller. Whi ...
" aircraft, he solved many engineering problems which made the helicopter
A helicopter is a type of rotorcraft in which lift and thrust are supplied by horizontally spinning rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forward, backward and laterally. These attributes ...
possible.
See also
;Articles
* Aviation safety
Aviation safety is the study and practice of managing risks in aviation. This includes preventing aviation accidents and incidents through research, educating air travel personnel, passengers and the general public, as well as the design of airc ...
* Coffin corner (aerodynamics)
Coffin corner (also known as the aerodynamic ceiling or Q corner) is the region of flight where a fast but subsonic fixed-wing aircraft's stall speed is near the critical Mach number, at a given gross weight and G-force loading. In this regio ...
* Compressor stall A compressor stall is a local disruption of the airflow in the compressor of a gas turbine or turbocharger. A stall that results in the complete disruption of the airflow through the compressor is referred to as a compressor surge. The severity of ...
* Lift coefficient
In fluid dynamics, the lift coefficient () is a dimensionless quantity that relates the lift generated by a lifting body to the fluid density around the body, the fluid velocity and an associated reference area. A lifting body is a foil or a com ...
* Spin (flight)
In flight dynamics a spin is a special category of stall resulting in autorotation (uncommanded roll) about the aircraft's longitudinal axis and a shallow, rotating, downward path approximately centred on a vertical axis. Spins can be entered ...
* Spoiler (aeronautics)
In aeronautics, a spoiler (sometimes called a lift spoiler or lift dumper) is a device which intentionally reduces the lift (force), lift component of an airfoil in a controlled way. Most often, spoilers are plates on the top surface of a ...
* Wing twist
Wing twist is an aerodynamic feature added to aircraft wings to adjust lift distribution along the wing.
Often, the purpose of lift redistribution is to ensure that the wing tip is the last part of the wing surface to stall, for example when exec ...
;Notable accidents
* 1963 BAC One-Eleven test crash
* 1966 Felthorpe Trident crash
On 3 June 1966, a newly built Hawker Siddeley Trident jetliner crashed during a pre-delivery test flight near the village of Felthorpe, Norfolk, England, killing all four crew. The aeroplane had entered a deep stall from which the crew were u ...
* British European Airways Flight 548
British European Airways Flight 548 was a scheduled passenger flight from London Heathrow to Brussels that crashed near Staines, Surrey, England, soon after take-off on 18 June 1972, killing all 118 people on board. The accident became known a ...
* China Airlines Flight 140
China Airlines Flight 140 was a regularly scheduled passenger flight from Chiang Kai-shek International Airport (serving Taipei, Taiwan) to Nagoya Airport in Nagoya, Japan.China Airlines is based in Taiwan. Air China is the flag carrier for the ...
* China Airlines Flight 676
* Air France Flight 447
Air France Flight 447 (AF447 or AFR447) was a scheduled international passenger flight from Rio de Janeiro, Brazil, to Paris, France. On 1 June 2009, inconsistent airspeed indications led to the pilots inadvertently stalling the Airbus A330 ser ...
* Colgan Air Flight 3407
Colgan Air Flight 3407 (marketed as Continental Connection Flight 3407 under a codeshare agreement with Continental Airlines), was a scheduled passenger flight from Newark, New Jersey, to Buffalo, New York, which crashed on February 12, 2009. Th ...
* Turkish Airlines Flight 1951
Turkish Airlines Flight 1951 (also known as the Poldercrash or the Schiphol Polderbaan incident) was a passenger flight that crashed during landing at Amsterdam Schiphol Airport, the Netherlands, on 25 February 2009, resulting in the deaths of ...
* Indonesia AirAsia Flight 8501
Indonesia AirAsia Flight 8501 was a scheduled international passenger flight operated by Indonesia AirAsia from Surabaya, Java, Indonesia, to Singapore. On 28 December 2014, the Airbus A320 flying the route crashed into the Java Sea, killing ...
* West Caribbean Airways Flight 708
West Caribbean Airways Flight 708 was a West Caribbean Airways charter flight that crashed in northwest Venezuela in the early hours of Tuesday, 16 August 2005, killing all 160 passengers and crew on board. The plane, a McDonnell Douglas MD-80, ...
* Northwest Orient Airlines Flight 6231
Northwest Orient Airlines Flight 6231 was the fatal crash of a Boeing 727 on December 1, 1974 in Harriman State Park near Stony Point, New York, just north of the New York City area. The Northwest Airlines 727 had been chartered to pick up the ...
Notes
References
* USAF & NATO Report RTO-TR-015 AC/323/(HFM-015)/TP-1 (2001
* Anderson, J.D., ''A History of Aerodynamics'' (1997). Cambridge University Press.
* Chapter 4, "Slow Flight, Stalls, and Spins," in the
Airplane Flying Handbook
'' (FAA H-8083-3A)
* L. J. Clancy
Laurence Joseph Clancy (15 March 1929 - 16 October 2014) was an Education Officer in aerodynamics at Royal Air Force College Cranwell whose textbook ''Aerodynamics'' became standard.
He was born in Egypt to Alfred Joseph Clancy and Agnes Hunter. I ...
(1975), ''Aerodynamics'', Pitman Publishing Limited, London.
* Stengel, R. (2004), ''Flight Dynamics'', Princeton University Press,
* Alpha Systems AOA Website for information on AOA and Lift Reserve Indicators
'
* 4239-01 Angle of Attack (AoA) Sensor Specifications
'
* ''Airplane Flying Handbook''. Federal Aviation Administration Pub. Skyhorse Publishing Inc.
* Federal Aviation Administration (25 September 2000)
Stall and Spin Awareness Training
AC No: 61-67C
* Prof. Dr Mustafa Cavcar, "Stall Speed"
'
{{DEFAULTSORT:Stall (Flight)
Aviation risks
Aerodynamics
Aircraft wing design
Aerial maneuvers
Emergency aircraft operations
Aerospace engineering