In aviation, a
spin is an aggravated stall resulting in rotation about the spin axis wherein the aircraft follows a downward corkscrew path. Spins can be entered unintentionally or intentionally, from any flight attitude and from practically any airspeed—all that is required is sufficient yaw rate while an aircraft is stalled. In either case, however, a specific and often counterintuitive set of actions may be needed to effect recovery. If the aircraft exceeds published limitations regarding spins, or is loaded improperly, or if the pilot uses incorrect technique to recover, the spin can lead to a fatal crash.
In a spin, both wings are in a stalled condition, however one wing will be in a deeper stall condition than the other. This causes the aircraft to autorotate due to the non-symmetric lift and drag. Spins are characterized by high
angle of attackAngle of attack is a term used in fluid dynamics to describe the angle between a reference line on a body and the vector representing the relative motion between the body and the fluid through which it is moving. In general, the reference line could be any line on any arbitrarily shaped body in...
, low
airspeedAirspeed is the speed of an aircraft relative to the air. There are several different measures of airspeed: indicated airspeed, calibrated airspeed, equivalent airspeed and true airspeed....
, and high rate of descent.
Spins differ from spiral dives which are characterized by low angle of attack and high airspeed. A spiral dive is not a type of stall because the wing is not stalled and the airplane will respond to the pilot's inputs to the flight controls.
How a spin occurs
Certificated, light, single-engine aircraft must meet specific criteria regarding stall and spin behavior. Even so, it is generally true that such an airplane will only depart into a spin if the pilot simultaneously yaws and stalls the airplane (intentionally or unintentionally). Under these circumstances, one wing tends to stall more deeply than the other. The wing that stalls first will drop, increasing its
angle of attackAngle of attack is a term used in fluid dynamics to describe the angle between a reference line on a body and the vector representing the relative motion between the body and the fluid through which it is moving. In general, the reference line could be any line on any arbitrarily shaped body in...
and deepening the stall. Both wings must be stalled for a spin to occur. The other wing will rise, decreasing its
angle of attackAngle of attack is a term used in fluid dynamics to describe the angle between a reference line on a body and the vector representing the relative motion between the body and the fluid through which it is moving. In general, the reference line could be any line on any arbitrarily shaped body in...
, and the aircraft will yaw towards the more deeply-stalled wing. The difference in
liftA fluid flowing past the surface of a body exerts a force on it. Lift is defined to be the component of this force that is perpendicular to the oncoming flow direction. It contrasts with the drag force, which is defined to be the component of the fluid-dynamic force parallel to the flow...
between the two wings causes the aircraft to roll, and the difference in
dragParasitic drag is drag caused by moving a solid object through a fluid medium . Parasitic drag is made up of many components, the most prominent being form drag...
causes the aircraft to yaw.
One common scenario that can lead to an unintentional spin is an uncoordinated turn towards the runway during the landing sequence. A pilot who is overshooting the turn to final approach may be tempted to apply rudder to increase the rate of turn. The result is twofold: the nose of the airplane drops below the horizon and the bank angle increases. Reacting to these unintended changes, the pilot may then begin to pull the elevator control aft (thus increasing the angle of attack) while applying opposite aileron to decrease bank angle. Taken to its extreme, this can result in an uncoordinated turn with sufficient
angle of attackAngle of attack is a term used in fluid dynamics to describe the angle between a reference line on a body and the vector representing the relative motion between the body and the fluid through which it is moving. In general, the reference line could be any line on any arbitrarily shaped body in...
to cause the aircraft to stall. This is called a
cross-control stall, and is very dangerous if it happens at low altitude where the pilot has little time to recover. In order to avoid this scenario, pilots are taught the importance of always making coordinated turns.
Spins can also be entered intentionally for training, flight testing, or aerobatics.
Phases
In aircraft that are capable of recovering from a spin, the spin has four phases. In aircraft that cannot recover from a spin, there are only three phases—the developed phase is continuous and can only be terminated by using some special spin-recovery device such as a spin-recovery parachute.
Developed
The aircraft's rotation rate, airspeed, and vertical speed are stabilized. At least one wing of the aircraft is stalled.
Recovery
In a normal erect spin, after the input of opposite rudder, the
angle of attackAngle of attack is a term used in fluid dynamics to describe the angle between a reference line on a body and the vector representing the relative motion between the body and the fluid through which it is moving. In general, the reference line could be any line on any arbitrarily shaped body in...
of both wings decreases below the critical angle of attack and
autorotationIn aviation, the word autorotation is applied to operation of fixed-wing aircraft and rotary-wing aircraft. The word has significantly different meanings in each of these two applications....
slows. The nose attitude of the aircraft steepens, airspeed increases and autorotation stops. The idea of recovering from a spin is to make the aircraft fly again.
Modes
The US National Aeronautics and Space Administration (NASA) has defined four different modes of spinning. These four modes are defined by the angle of attack of the airflow on the wing.
NASA Spin Mode Classification
| Spin mode |
Angle-of-attack range, degrees |
| Flat |
65 to 90 |
| Moderately flat |
45 to 65 |
| Moderately steep |
30 to 45 |
| Steep |
20 to 30 |
During the 1970s
NASAThe National Aeronautics and Space Administration is an agency of the United States government, responsible for the nation's public space program. NASA was established by the National Aeronautics and Space Act on July 29, 1958, replacing its predecessor, the National Advisory Committee for...
used its spin tunnel at the Langley Research Center to investigate the spinning characteristics of single-engine general aviation airplane designs. A 1/11-scale model was used with nine different tail designs.
Some tail designs that caused inappropriate spin characteristics had two stable spin modes – one steep or moderately steep; and another that was either moderately flat or flat. Recovery from the flatter of the two modes was usually less reliable or impossible. The further aft that the center of gravity was located the flatter the spin and the less reliable the recovery. For all tests the center of gravity of the model was at either 14.5% of Mean Aerodynamic
ChordIn aeronautics, chord refers to the imaginary straight line joining the trailing edge and the center of curvature of the leading edge of the cross-section of an airfoil...
(MAC) or 25.5% of MAC.
Single-engine airplane types certified in the normal category must be demonstrated to recover from a spin of at least one turn, while single-engine aircraft certified in the utility category must demonstrate a six turn spin that cannot be unrecoverable at any time during the spin due to pilot action or aerodynamic characteristic. NASA recommends various tail configurations and other strategies to eliminate the flatter of the two spin modes and make recovery from the steeper mode more reliable.
History
In aviation's early days, spins were poorly understood and often fatal. Proper recovery procedures were unknown, and a pilot's instinct to pull back on the stick served only to make a spin worse. Because of this, the spin earned a reputation as an unpredictable danger that might snatch an aviator's life at any time, and against which there was no defense.
The spin was initially explored by individual pilots performing ad-hoc experiments (often accidentally) and by aerodynamicists. In August 1912, Lieutenant
Wilfred ParkeLieutenant Wilfred Parke RN was a British aviator and became the first British airman to recover from an accidental spin.-Family:Parkes's father was Alfred Watlington Parke, the Rector of Uplyme and his mother was Hilda Fort...
RNThe Royal Navy of the United Kingdom is the oldest of HM Armed Forces . From the beginning of the 18th century until well into the 20th century, it was the most powerful navy in the world, playing a key part in establishing the British Empire as the dominant world power from 1815 until the early...
became the first aviator to recover from an accidental spin when his
Avro biplaneThe Avro Type G was an early British aircraft from A.V.Roe and Company, designed to participate in the British Military Aeroplane Trials of 1912.-Design and development:...
entered a spin at 700 feet AGL in the traffic pattern at
LarkhillLarkhill is a garrison town in the civil parish of Durrington, Wiltshire, England. It is a short distance west of Durrington village proper and 1 mile north of the prehistoric monument of Stonehenge. It is about ten miles north of Salisbury....
. Parke attempted to recover from the spin by increasing engine speed, pulling back on the stick, and turning into the spin, with no effect. The aircraft descended 450 feet, and horrified observers braced themselves for a fatal crash.
Parke was disabled by centrifugal forces but was still considering a means of escape. In an effort to neutralize the forces pinning him against the right side of the cockpit, he applied full right rudder, and the aircraft leveled out fifty feet above the ground. With the aircraft now under control, Parke climbed, made another approach, and landed safely.
In spite of the discovery of "Parke's technique," pilots were not taught spin-recovery procedures until the beginning of World War I.
The first documented case of an intentional spin and recovery is that of
Harry HawkerHarry George Hawker MBE, AFC, was an Australian aviation pioneer and co-founder of Hawker Aircraft, the firm that would later be responsible for a long series of successful military aircraft, including the Fury, Sea Fury, Hurricane, Hunter and Harrier.-Early life:Hawker was born in Moorabbin,...
. In the summer of 1914, Hawker recovered from an intentional spin over Brooklands, England, by centralizing the controls.
In 1917,
Frederick LindemannFrederick Alexander Lindemann, 1st Viscount Cherwell FRS PC CH was an English physicist who was an influential scientific adviser to the British government, particularly Winston Churchill...
conducted a series of experiments that led to the first understanding of the aerodynamics of the spin.
Entry and recovery
Some aircraft cannot be recovered from a spin using only their own flight control surfaces, and must not be allowed to enter a spin under any circumstances. If an aircraft has not been certified for spin recovery, it should be assumed that spins are not recoverable and are unsafe in that aircraft. Important safety equipment, such as stall/spin recovery parachutes, which generally are
not installed on production aircraft, are used during testing and certification of aircraft for spins and spin recovery.
Spin-entry procedures vary with the type and model of aircraft being flown, but there are general procedures applicable to most aircraft. These include reducing power to idle and simultaneously raising the nose in order to induce an upright stall. Then, as the aircraft approaches stall, apply full rudder in the desired spin direction while holding full back-elevator pressure for an upright spin. Sometimes a roll input is applied in the direction opposite of the rudder (i.e., a cross-control).
If the aircraft manufacturer provides a specific procedure for spin recovery, that procedure must be used. Otherwise, to recover from an upright spin, the following generic procedure may be used: Power is first reduced to idle and the ailerons are neutralized. Then, full opposite rudder (that is, against the yaw) is added and held to counteract the spin rotation, and the elevator control is moved briskly forward to reduce the
angle of attackAngle of attack is a term used in fluid dynamics to describe the angle between a reference line on a body and the vector representing the relative motion between the body and the fluid through which it is moving. In general, the reference line could be any line on any arbitrarily shaped body in...
below the critical angle. Depending on the airplane and the type of spin, the elevator action could be a minimal input before rotation ceases, or in other cases, the elevator control may have to be moved to its full forward position to effect recovery from the upright spin. Once the rotation has stopped, the rudder must be neutralized and the airplane returned to level flight. This procedure is sometimes called
PAREIn aviation, PARE is a mnemonic for a generic spin recovery technique applicable to many types of fixed-wing aircraft.-Overview:PARE stands for:*Power -- off*Ailerons -- neutral...
, for
Power idle,
Ailerons neutral,
Rudder opposite the spin and held, and
Elevator through neutral. The mnemonic "PARE" simply reinforces the tried-and-true NASA Standard spin recovery actions—the very same actions first prescribed by NACA in 1936, verified by NASA during an intensive, decade-long spin test program overlapping the 1970s and '80's, and repeatedly recommended by the FAA and implemented by the majority of test pilots during certification spin-testing of light airplanes.
Inverted spinning and erect or upright spinning are dynamically very similar, and require essentially the same recovery process but use opposite elevator control. It must be noted that in an upright spin both roll and yaw are in the same direction, but that an inverted spin is composed of opposing roll and yaw. It is crucial that the yaw be countered to effect recovery. The visual field in a typical spin (as opposed to a flat spin) is heavily dominated by the perception of roll over yaw, which can lead to an incorrect and dangerous conclusion that a given inverted spin is actually an erect spin in the reverse yaw direction (leading to a recovery attempt in which pro-spin rudder is mistakenly applied and then further exaccerbated by holding the incorrect elevator input).
In some aircraft that spin readily upright and inverted—such as Pitts- and Christen Eagle-type high-performance aerobatic aircraft—an alternative spin-recovery technique may effect recovery as well, namely: Power off, Hands off the stick/yoke, Rudder full opposite to the spin (or more simply "push the rudder pedal that is hardest to push") and held (aka the Mueller/Beggs technique). An advantage of the Mueller/Beggs technique is that no knowledge of whether the spin is erect or inverted is required during what can be a very stressful and disorientating time. Even though this method does work in a specific subset of spin-approved airplanes, the NASA Standard/PARE procedure can also be effective provided that care must be taken to ensure the spin does not simply cross from positive to negative (or vice versa) and that a too-rapid application of elevator control is avoided as it may cause aerodynamic blanketing of the rudder rendering the control ineffective and simply accelerate the spin. The converse, however, may not be true at all—many cases exist where Beggs/Mueller fails to recover the airplane from the spin, but NASA Standard/PARE will terminate the spin. Before spinning any aircraft the flight manual should be consulted to establish if the particular type has any specific spin recovery techniques that differ from standard practice.
Although entry techniques are similar, modern military fighter aircraft often tend to require yet another variation on spin recovery techniques. While power is still typically reduced to idle thrust and pitch control neutralized, opposite rudder is almost never used. Adverse yaw created by the rolling surfaces (ailerons, differential horizontal tails, etc.) of such aircraft is often more effective in arresting the spin rotation than the rudder(s), which usually become blanked by the wing and fuselage due to the geometric arrangement of fighters. Hence, the preferred recover technique has a pilot applying full roll control in the direction of the rotation (
i.e., a right-hand spin requires a right stick input), generally remembered as "stick into the spin." Likewise, this control application is reversed for inverted spins.
Center of gravity
The characteristics of an airplane with respect to spinning are significantly influenced by the position of the center of gravity. In general terms, the further forward the center of gravity the less readily the airplane will spin, and the more readily it will recover from a spin. Conversely, the further aft the center of gravity the more readily the airplane will spin, and the less readily it will recover from a spin. In any airplane the forward and aft limits on center of gravity are carefully defined. In some airplanes that are approved for intentional spinning the aft limit at which spins may be attempted is not as far aft as the aft limit for general flying. Intentional spinning should not be attempted casually, and the most important pre-flight precaution is to determine that the airplane's center of gravity will be within the range approved for intentional spinning.
Unrecoverable spins
If the center of gravity of the airplane is behind the aft limit approved for spinning, any spin may prove to be unrecoverable except by using some special spin-recovery device such as a spin-recovery
parachuteA parachute is a device used to slow the motion of an object through an atmosphere by creating drag. Parachutes are made out of cloth, most commonly nylon....
specially installed in the tail of the airplane; or by jettisoning
leadLead is a main-group element with symbol Pb and atomic number 82. Lead is a soft, malleable poor metal, also considered to be one of the heavy metals. Lead has a bluish-white color when freshly cut, but tarnishes to a dull grayish color when exposed to air...
pellets specially installed as ballast at the tail of the airplane.
In the past, some airplanes displayed an unrecoverable spin in which the nose was higher, relative to the horizon, than in conventional spins. This is sometimes called a
flat spin, although whether a flat spin is indeed unrecoverable depends on aircraft type and loading. The plane spins on its belly around the normal axis. The empennage will feel very light and loose. Depending on the aircraft, rudder and aileron inputs and changing engine power settings may have little effect. There is a small number of accounts of heroic pilots recovering from flat spins by loosening their restraint harnesses and leaning forward in an attempt to favourably alter the position of the center of gravity. Unfortunately, the great majority of pilots who have experienced an unrecoverable spin have not lived to talk about it if they could not
bail outA parachute is a device used to slow the motion of an object through an atmosphere by creating drag. Parachutes are made out of cloth, most commonly nylon....
of/eject from the aircraft. Generally speaking, such characteristics are confined to high-performance aircraft, primarily fighters.
Some
World War IIWorld War II, or the Second World War , was a global military conflict which involved a majority of the world's nations, including all great powers, organized into two opposing military alliances: the Allies and the Axis...
airplanes were notoriously prone to flat spins when loaded erroneously, such as the Bell
P-39 Airacobra. The P-39 was a unique design with the engine behind the pilot's seat and a large cannon in the front. Without ammunition or a counterbalance load in the nose compartment, the P-39's center of gravity was too far aft to recover from a spin. Soviet pilots did numerous tests of the P-39 and were able to demonstrate its dangerous spinning characteristics. Bell then issued a recommendation to bail out if the airplane entered a spin.
North American P-51 MustangsThe North American Aviation P-51 Mustang was a long-range single-seat World War II fighter aircraft. Designed, built and airborne in just 117 days, the Mustang first flew in RAF service as a fighter-bomber and reconnaissance aircraft before conversion to a bomber escort, employed in raids over...
with auxiliary fuel tanks not originally designed for the P-51 suffered from the same problem. Similarly, the
VoughtVought is the name of several related aerospace firms. These have included, in the past, Lewis and Vought Corporation, Chance Vought, Vought Sikorsky, LTV Aerospace , Vought Aircraft Companies, and the current Vought Aircraft Industries. The first incarnation of Vought was established by Chance M...
F4U CorsairThe Chance Vought F4U Corsair was a carrier-capable fighter aircraft that saw service primarily in World War II and the Korean War. Goodyear-built Corsairs were designated FG and Brewster-built aircraft F3A. The Corsair served in smaller air forces until the 1960s, following the longest production...
was reputed to have appalling stall and spin recovery characteristics, even in the "clean" (no stores) configuration.
Modern fighter aircraft are not immune to the phenomena of unrecoverable spin characteristics. Although highly resistant to entering into a spin, once caught in one the Grumman
F-14 TomcatThe Grumman F-14 Tomcat is a supersonic, twin-engine, two-seat, variable-sweep wing aircraft. The F-14 was the United States Navy's primary maritime air superiority fighter, fleet defense interceptor and tactical reconnaissance platform from 1974 to 2006...
can exhibit a fast, flat spin from which it is nearly impossible to recover. Another example of a nonrecoverable flat spin occurred in 1963, with
Chuck YeagerCharles Elwood "Chuck" Yeager is a retired General in the United States Air Force and noted test pilot. He is widely considered to be the first pilot to travel faster than sound...
at the controls of the NF-104A rocket-jet hybrid: during his fourth attempt at setting an altitude record, Yeager lost control and entered a flat spin, then ejected and survived.
The
mathematicsMathematics is the science and study of quantity, structure, space, and change. Mathematicians seek out patterns, formulate new conjectures, and establish truth by rigorous deduction from appropriately chosen axioms and definitions....
of the flat spin are that if the center of lift force is ahead of the center of gravity on longitudinal axis, the
real numberIn mathematics, the real numbers include both rational numbers, such as 42 and −23/129, and irrational numbers, such as pi and the square root of two; or, a real number can be given by an infinite decimal representation, such as 2.4871773339..., where the digits continue in some way; or, the real...
components of the eigenvalues of the stability matrix exceed zero and the poles of the stability matrix migrate to the positive half of the
complex numberA complex number, in mathematics, is a number comprising a real number and an imaginary number; it can be written in the form a + bi, where a and b are real numbers, and i is the standard imaginary unit, having the property that i
2 = −1...
plane. This will indicate
positive feedbackPositive feedback, sometimes referred to as "cumulative causation", refers to a situation where some effect causes more of itself. A system undergoing positive feedback is unstable, that is, it will tend to spiral out of control as the effect amplifies itself....
on attempts at control: the plane will resist any attempts at recovery and stabilizing the plane. Some modern fighter aircraft, like the
F-16 Fighting FalconThe Lockheed Martin F-16 Fighting Falcon is a multirole jet fighter aircraft originally developed by General Dynamics for the United States Air Force. Designed as a lightweight, daytime Visual Flight Rules fighter, it evolved into a successful multirole aircraft...
and the
Saab GripenThe Saab JAS 39 Gripen is a fighter aircraft manufactured by the Swedish aerospace company Saab. Gripen International acts as a prime contracting organisation and is responsible for marketing, selling and supporting the Gripen fighter around the world....
have, for greater maneuverability, been intentionally designed to be unstable and are controlled by a computer to stabilize the plane.
In purpose-built aerobatic aircraft, spins may be intentionally flattened through the application of power and aileron within a normal spin. Rotation rates experienced are dramatic and can exceed 400 degrees per second in an attitude that may even have the nose above the horizon. Such maneuvers must be performed with the center of gravity in the normal range and with appropriate training, and consideration should be given to the extreme gyroscopic forces generated by the propellor and exerted on the crankshaft.
Aircraft design
For safety, all certificated, single-engine
fixed-wing aircraftA fixed-wing aircraft, usually called an airplane, aeroplane or plane, is an aircraft capable of flight using forward motion that causes air to pass over its wings to generate lift. Planes include jet engine and propeller driven vehicles propelled forward by thrust, as well as unpowered aircraft...
, including certificated
gliderUnpowered aircraft are a group of aerial vehicles that can fly without propulsion. They can be classified as gliders, balloons and kites. In this instance, 'flight' means a trajectory that is not merely a vertical descent such as a parachute. In the case of kites, the flight is not free, but...
s, must meet published criteria regarding stall and spin behavior. These designs typically have a wing with greater
angle of attackAngle of attack is a term used in fluid dynamics to describe the angle between a reference line on a body and the vector representing the relative motion between the body and the fluid through which it is moving. In general, the reference line could be any line on any arbitrarily shaped body in...
at the wing root than at the wing tip, so that the wing root stalls first, while the
aileronFor the band with a similar name, see The AileronsAilerons are hinged control surfaces attached to the trailing edge of the wing of a fixed-wing aircraft. The ailerons are used to control the aircraft in roll...
s may remain somewhat effective until the stall migrates outward toward the wing tip. One method of tailoring such stall behavior is known as
washoutWashout refers to a feature of wing design to deliberately reduce the lift distribution across the span of the wing of an aircraft. The wing is designed so that lift is strongest at the wing roots and decreases across the span, becoming weakest at the wing tip...
. Some designers of recreational aircraft seek to develop an aircraft that is characteristically incapable of spinning, even in an uncoordinated stall.
Some airplanes have been designed with fixed
leading edge slotThe leading edge slot is an aerodynamic feature of the wing of some airplanes to reduce the stall speed and promote good low-speed handling qualities. A leading edge slot is a span-wise gap in each wing, allowing air to flow from below the wing to its upper surface...
s. Where the slots are located ahead of the ailerons they provide strong resistance to spinning and may even leave the airplane incapable of spinning.
The
flight control systemsAn aircraft flight control system consists of flight control surfaces, the respective cockpit controls, connecting linkages, and the necessary operating mechanisms to control an aircraft's direction in flight. Aircraft engine controls are also considered as flight controls as they change speed.The...
of some gliders and recreational aircraft are designed so that when the pilot moves the elevator control close to its fully aft position, as in slow speed flight and flight at high
angle of attackAngle of attack is a term used in fluid dynamics to describe the angle between a reference line on a body and the vector representing the relative motion between the body and the fluid through which it is moving. In general, the reference line could be any line on any arbitrarily shaped body in...
, the trailing edges of both ailerons are automatically raised slightly so that the
angle of attackAngle of attack is a term used in fluid dynamics to describe the angle between a reference line on a body and the vector representing the relative motion between the body and the fluid through which it is moving. In general, the reference line could be any line on any arbitrarily shaped body in...
is reduced at the outboard regions of both wings. This necessitates an increase in angle of attack at the inboard (center) regions of the wing, and promotes stalling of the inboard regions well before the wing tips.
The US certification standard for civil airplanes up to 12,500 lb maximum takeoff weight is Part 23 of the
Federal Aviation RegulationsThe Federal Aviation Regulations, or FARs, are rules prescribed by the Federal Aviation Administration governing all aviation activities in the United States. The FARs are part of Title 14 of the Code of Federal Regulations...
, applicable to airplanes in the normal, utility and acrobatic categories. Part 23, §23.221 requires that single-engine airplanes must demonstrate recovery from either a one-turn spin if intentional spins will be prohibited, or six-turn spins if intentional spins will be approved. Even large, passenger-carrying single-engine airplanes like the
Cessna CaravanThe Cessna 208 Caravan, is a single turboprop engine, fixed-gear short-haul regional airliner and utility aircraft built in the USA by Cessna. The airplane typically seats nine passengers, with a single person crew, although with a FAR Part 23 waiver, it can seat up to fourteen passengers...
must be subjected to one-turn spins by a test pilot, and repeatedly demonstrated to recover within no more than one additional turn. With a small number of airplane types the
FAAThe Federal Aviation Administration is an agency of the United States Department of Transportation with authority to regulate and oversee all aspects of civil aviation in the U.S...
has made a finding of equivalent level of safety (ELOS) so that demonstration of a one-turn spin is not necessary. For example, this has been done with the
Columbia 300/350The Columbia Aircraft Manufacturing Corporation is a former aircraft manufacturer that designed and built light general aviation aircraft. In November 2007 it became a division of Cessna.-History:...
and the
Cirrus SR20/22The SR22, by Cirrus Design, is a high-performance single-engine, four-seat, composite aircraft. It is a more powerful version of the Cirrus SR20, with a larger wing, higher fuel capacity, and a 310 horsepower engine. It is extremely popular among purchasers of new aircraft and has been the world's...
. Successful demonstration of the one-turn spin does not allow an airplane type to be approved for intentional spinning. If an airplane is to be approved for intentional spinning it must be repeatedly subjected to a spin of six turns, and then demonstrated to recover within one and a half additional turns. Spin testing is a potentially hazardous exercise and the test aircraft must be equipped with some spin-recovery device such as a tail parachute or jettisonable ballast, or some method of rapidly moving the center of gravity forward.
Agricultural airplanes are typically certificated in the normal category at a moderate weight. For single-engine airplanes this requires successful demonstration of the one-turn spin. However, with the agriculture hopper full these airplanes are not intended to be spun, and recovery is unlikely. For this reason, at weights above the maximum for the normal category, these airplanes are not subjected to spin testing and, as a consequence, can only be type certificated in the restricted category. As an example of an agricultural airplane see the Cessna AG series.
Spin Kit
To make some sailplanes spin easily for training purposes or demonstrations a
spin kitA few sailplanes are very difficult, if not impossible, to spin under normal conditions.To make these sailplanes spin easily for training purposes or demonstrations a spin kit is available from the manufacturer....
is available from the manufacturer.
Many training aircraft may appear to be resistant to entering a spin even though some are intentionally designed and certified for spins. A well known example of this is the Piper Tomahawk, which is certified for spins, though the Piper Tomahawk's spin characteristics remain
controversial. Aircraft that are not certified for spins may be difficult or impossible to recover once the spin exceeds the one-turn certification standard.
Although it has been removed from most flight test syllabuses, there are some countries that still require
flight trainingFlight training is a course of study used when learning to pilot an aircraft. The overall purpose of primary and intermediate flight training is the acquisition and honing of basic airmanship skills....
on spin recovery. In the U.S. spin training is
required only for flight instructor candidates. A spin occurs only after a stall, so the FAA emphasizes training pilots in
stall recognition, prevention, and recovery as a means to reduce accidents due to unintentional stalls and/or spins.
A spin is often intimidating to the uninitiated, however many pilots trained in spin entry and recovery find that safely spinning is an interesting experience. In a spin the occupants of the airplane will only feel
reduced gravityWeightlessness is a phenomenon experienced by people during free-fall. Although the term zero gravity is often used as a synonym, weightlessness in orbit is not the result of the force of gravity being eliminated or even significantly reduced...
during the entry phase, and then will experience normal gravity, except that the extreme nose-down attitude will press the occupants forward against their restraint harnesses. The rapid rotation, combined with the nose-down attitude, can also be disorienting.
The recovery procedure from a spin requires using rudder to stop the rotation, then elevator to reduce angle of attack to stop the stall, then pulling out of the dive without exceeding the maximum permitted airspeed (VNE) or maximum
G loadingLoad factor is the ratio of the lift on an aircraft to the weight of the aircraft. The load factor is expressed in multiples of g where one g represents conditions in straight and level flight. In straight and level flight the lift is equal to the weight so the ratio of lift to weight is one, and...
. The maximum G loading for a light airplane in the normal category is usually 3.8G. For a light airplane in the acrobatic category it is usually at least 6G.
External links