Dataset Viewer
id
int64 2.08k
79.3M
| title
stringlengths 3
34
| text
stringlengths 55
3.97k
|
|---|---|---|
4,585,965 | Aircraft upset | Aircraft upset is an unacceptable condition, in aircraft operations, in which the aircraft flight attitude or airspeed is outside the normally intended limits. This may result in the loss of control (LOC) of the aircraft, and sometimes the total loss of the aircraft itself. Loss of control may be due to excessive altitude for the airplane's weight, turbulent weather, pilot disorientation, or a system failure.
The U.S. NASA Aviation Safety Program defines upset prevention and upset recovery as to prevent loss-of-control accidents due to aircraft upset after inadvertently entering an extreme or abnormal flight attitude.
A Boeing-compiled list determined that 2,051 people died in 22 accidents in the years 1998–2007 due to LOC accidents. NTSB data for 1994–2003 count 32 accidents and more than 2,100 lives lost worldwide. |
2,984,169 | Aviation archaeology | Aviation archaeology is a recognized sub-discipline within archaeology and underwater archaeology as a whole. It is an activity practiced by both enthusiasts and academics in pursuit of finding, documenting, recovering, and preserving sites important in aviation history. For the most part, these sites are aircraft wrecks and crash sites, but also include structures and facilities related to aviation. It is also known in some circles and depending on the perspective of those involved as aircraft archaeology or aerospace archaeology and has also been described variously as crash hunting, underwater aircraft recovery, wreck chasing, or wreckology.
|
7,092,977 | Aviation insurance | Aviation insurance is insurance coverage geared specifically to the operation of aircraft and the risks involved in aviation. Aviation insurance policies are distinctly different from those for other areas of transportation and tend to incorporate aviation terminology, as well as terminology, limits and clauses specific to aviation insurance.
|
1,197,818 | Bird strike | A bird strike (sometimes called birdstrike, bird ingestion (for an engine), bird hit, or bird aircraft strike hazard (BASH)) is a collision between an airborne animal (usually a bird or bat) and a moving vehicle (usually an aircraft). The term is also used for bird deaths resulting from collisions with structures, such as power lines, towers and wind turbines (see bird–skyscraper collisions and towerkill).
A significant threat to flight safety, bird strikes have caused a number of accidents with human casualties. There are over 13,000 bird strikes annually in the US alone. However, the number of major accidents involving civil aircraft is quite low and it has been estimated that there is only about one accident resulting in human death in one billion (109) flying hours. The majority of bird strikes (65%) cause little damage to the aircraft; however, the collision is usually fatal to the bird(s) involved.
Vultures and geese have been ranked the second and third most hazardous kinds of wildlife to aircraft in the United States, after deer, with approximately 240 goose–aircraft collisions in the United States each year. 80% of all bird strikes go unreported.
Most accidents occur when a bird (or group of birds) collides with the windscreen or is sucked into the engine of jet aircraft. These cause annual damages that have been estimated at $400 million within the United States alone and up to $1.2 billion to commercial aircraft worldwide. In addition to property damage, collisions between man-made structures and conveyances and birds is a contributing factor, among many others, to the worldwide decline of many avian species.
The International Civil Aviation Organization (ICAO) received 65,139 bird strike reports for 2011–14, and the Federal Aviation Administration counted 177,269 wildlife strike reports on civil aircraft between 1990 and 2015, growing 38% in seven years from 2009 to 2015. Birds accounted for 97%. |
11,917,956 | Brownout (aeronautics) | In aviation, a brownout (or brown-out) is an in-flight visibility restriction due to dust or sand in the air.
In a brownout, the pilot cannot see nearby objects which provide the outside visual references necessary to control the aircraft near the ground. This can cause spatial disorientation and loss of situational awareness leading to an accident. Pilots have compared landing during brownouts to parallel parking an automobile with one's eyes closed. |
10,630,682 | 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, making it very difficult to keep an airplane in stable flight. Because the stall speed is the minimum speed required to maintain level flight, any reduction in speed will cause the airplane to stall and lose altitude. Because the critical Mach number is the maximum speed at which air can travel over the wings without losing lift due to flow separation and shock waves, any increase in speed will cause the airplane to lose lift, or to pitch heavily nose-down, and lose altitude.
The "corner" refers to the triangular shape at the top of a flight envelope chart where the stall speed and critical Mach number are within a few knots of each other at a given gross weight and G-force loading. The "coffin" refers to the possible death in these kinds of stalls. The speed where they meet is the ceiling of the aircraft. This is distinct from the same term used for helicopters when outside the auto-rotation envelope as seen in the height-velocity diagram. |
1,612,558 | 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 the phenomenon ranges from a momentary power drop barely registered by the engine instruments to a complete loss of compression in case of a surge, requiring adjustments in the fuel flow to recover normal operation.
Compressor stalls were a common problem on early jet engines with simple aerodynamics and manual or mechanical fuel control units, but they have been virtually eliminated by better design and the use of hydromechanical and electronic control systems such as full authority digital engine control. Modern compressors are carefully designed and controlled to avoid or limit stall within an engine's operating range.
|
66,722,214 | Continued VFR into IMC | Continued VFR into IMC is when an aircraft operating under visual flight rules intentionally or unintentionally enters into instrument meteorological conditions. Flying an aircraft without visual reference to the ground can lead to a phenomenon known as spatial disorientation, which can cause the pilot to misperceive the angle, altitude, and speed at which the aircraft is traveling. This is considered a very serious safety hazard in general aviation. According to AOPA’s Nall Report, approximately 4% of general aviation accidents are weather related, yet these accidents account for more than 25% of all fatalities. |
406,231 | Control reversal | Control reversal is an adverse effect on the controllability of aircraft. The flight controls reverse themselves in a way that is not intuitive, so pilots may not be aware of the situation; to roll to the left, they have to push the control stick to the right, the opposite of the normal direction.
|
490,866 | Controlled flight into terrain | In aviation, a controlled flight into terrain (CFIT; usually SEE-fit) is an accident in which an airworthy aircraft, fully under pilot control, is unintentionally flown into the ground, a body of water or other obstacle. In a typical CFIT scenario, the crew is unaware of the impending collision until impact, or it is too late to avert. The term was coined by engineers at Boeing in the late 1970s.
Accidents where the aircraft is out of control at the time of impact, because of mechanical failure or pilot error, are classified instead as uncontrolled flight into terrain, or UFIT. Incidents resulting from the deliberate action of the person at the controls, such as a forced landing, an act of terrorism, or suicide by pilot, are also excluded from the definition of CFIT.
According to Boeing in 1997, CFIT was a leading cause of airplane accidents involving the loss of life, causing over 9,000 deaths since the beginning of the commercial jet aircraft era. CFIT was identified as a cause of 25% of USAF Class A mishaps between 1993 and 2002. According to data collected by the International Air Transport Association (IATA) between 2008 and 2017, CFITs accounted for six percent of all commercial aircraft accidents, and was categorized as "the second-highest fatal accident category after Loss of Control Inflight (LOC-I)". |
6,529,198 | Core lock | Core lock is a turbine engine failure that can happen to aircraft in flight. When an engine is shut down in flight, the design of the engine causes some parts to cool quicker than others. Since materials change sizes in different temperatures, this happens to the turbine engine. Core lock happens if the engine's parts change too much in size, then some parts will get stuck, reducing or even stopping rotation.
Core lock makes it difficult for pilots to perform either a windmill restart or an APU-assisted engine restart.
When the engine parts’ temperature is allowed to normalize, after time is given, the parts will normalize in sizes, removing the core lock condition. |
1,428,177 | Deicing | De-icing is the process of removing snow, ice or frost from a surface. Anti-icing is the application of chemicals that not only de-ice but also remain on a surface and continue to delay the reformation of ice for a certain period of time, or prevent adhesion of ice to make mechanical removal easier.
De-icing can be accomplished by mechanical methods (scraping, pushing); through the application of heat; by use of dry or liquid chemicals designed to lower the freezing point of water (various salts or brines, alcohols, glycols); or by a combination of these different techniques. |
7,797,960 | Dissymmetry of lift | Dissymmetry of lift: 2–20 (also known as asymmetry of lift: 342 or asymmetric lift) in rotorcraft aerodynamics refers to an unequal amount of lift on opposite sides of the rotor disc. It is a phenomenon that affects single-rotor helicopters and autogyros in forward flight.
A rotor blade that is moving in the same direction as the aircraft is called the advancing blade and the blade moving in the opposite direction is called the retreating blade. When viewed from above, most American helicopter rotors turn counter-clockwise; French and Russian helicopters turn clockwise.: 141
Balancing lift across the rotor disc is important to a helicopter's stability. The amount of lift generated by an airfoil is proportional to the square of its airspeed (velocity). In a hover, the rotor blades have equal airspeeds and therefore equal lift. However, in forward flight the advancing blade has a higher airspeed than the retreating blade, creating uneven lift across the rotor disc.: 1–104 |
11,954,900 | Dynamic rollover | A helicopter is susceptible to a rolling tendency,
called dynamic rollover, when close to the ground,
especially when taking off or landing.
For dynamic rollover to occur, some factor has to first
cause the helicopter to roll or pivot around a skid, or
landing gear wheel, until its critical rollover angle is
reached. Then, beyond this point, main rotor thrust continues
the roll and recovery is impossible. If the critical
rollover angle is exceeded, the helicopter rolls on its
side regardless of the cyclic control corrections made.
Dynamic rollover begins when the helicopter starts to
pivot around its skid or wheel. This can occur for a
variety of reasons, including the failure to remove a
tiedown or skid securing device, or if the skid or wheel
contacts a fixed object while hovering sideward, or if
the gear is stuck in ice, soft asphalt, or mud. Dynamic
rollover may also occur if the pilot does not use the proper
landing or takeoff technique or while performing slope
operations. Whatever the cause, if the gear or skid
becomes a pivot point, dynamic rollover is possible if
the pilot does not use the proper corrective technique.
Once started, dynamic rollover cannot be stopped by
application of opposite cyclic control alone. For example, if
the right skid contacts an object and becomes the
pivot point while the helicopter starts rolling to the
right, even with full left cyclic applied the main rotor
thrust vector and its moment follows the aircraft as it
continues rolling to the right. Quickly applying down
collective is the most effective way to stop dynamic
rollover from developing. Dynamic rollover can occur
in both skid and wheel equipped helicopters, and all
types of rotor systems. |
1,451,948 | Flameout | In aviation, a flameout (or flame-out) is the run-down of a jet engine or other turbine engine due to the extinguishment of the flame in its combustor. The loss of flame can have a variety of causes, such as fuel starvation, excessive altitude, compressor stall, foreign object damage deriving from birds, hail, or volcanic ash, severe precipitation, mechanical failure, or very low ambient temperatures. |
20,723,955 | Flight envelope protection | Flight envelope protection is a human machine interface extension of an aircraft's control system that prevents the pilot of an aircraft from making control commands that would force the aircraft to exceed its structural and aerodynamic operating limits. It is used in some form in all modern commercial fly-by-wire aircraft. The professed advantage of flight envelope protection systems is that they restrict a pilot's excessive control inputs, whether in surprise reaction to emergencies or otherwise, from translating into excessive flight control surface movements. Notionally, this allows pilots to react quickly to an emergency while blunting the effect of an excessive control input resulting from "startle," by electronically limiting excessive control surface movements that could over-stress the airframe and endanger the safety of the aircraft.
In practice, these limitations have sometimes resulted in unintended human factors errors and accidents of their own.
One example of such a flight envelope protection device is an anti-stall system which is designed to prevent an aircraft from stalling, for example in the form of a stick pusher that pushes the aircraft nose downward based on an input signal from a stall warning system, or by means of other fly-by-wire actions. Anti-stall systems are used on most modern swept wing aircraft, and are used on a large variety of civilian and military jet airplanes. |
904,516 | Foreign object damage | In aviation and aerospace, the term foreign object damage (FOD) refers to any damage to an aircraft attributed to foreign object debris (also referred to as "FOD"), which is any particle or substance, alien to an aircraft or system which could potentially cause damage to it.
External FOD hazards include bird strikes, hail, ice, sandstorms, ash-clouds or objects left on a runway or flight deck. Internal FOD hazards include items left in the cockpit that interfere with flight safety by getting tangled in control cables, jam moving parts or short-out electrical connections. |
27,329,045 | Fume event | A fume event occurs when bleed air used for cabin pressurisation and air conditioning in a pressurised aircraft is contaminated by fluids such as engine oil, hydraulic fluid, anti-icing fluid, and other potentially hazardous chemicals. |
29,042,494 | Global Safety Information Exchange | The Global Safety Information Exchange (GSIE) is a system launched by ICAO in September 2010 to confidentially share information about aviation safety incidents; enabling ICAO to identify trends may make it possible to improve safety through risk reduction. |
8,216,292 | Graveyard spiral | In aviation, a graveyard spiral is a type of dangerous spiral dive entered into accidentally by a pilot who is not trained or not proficient in flying in instrument meteorological conditions (IMC). Other names for this phenomenon include suicide spiral, deadly spiral, death spiral and vicious spiral.
Graveyard spirals are most common at night or in poor weather conditions where no horizon exists to provide visual correction for misleading inner-ear cues.
Graveyard spirals are the result of several sensory illusions in aviation which may occur in actual or simulated IMC, when the pilot experiences spatial disorientation and loses awareness of the aircraft's attitude. The pilot loses the ability to judge the orientation of their aircraft due to the brain's misperception of spatial cues.
The graveyard spiral consists of both physiological and physical components. Mechanical failure is often a result, but generally not a causal factor, as it is the pilot's sense of equilibrium which leads to the spiral dive. Flying by "the seat of the pants", and failing to recognize and/or respond to instrument readings, is the most common source of controlled flight into terrain (CFIT), where an airplane controlled by a pilot hits the ground. |
72,805,505 | Ground collision | A ground collision (also known as a terrain collision, or simply GCOL) is a collision that occurs while an aircraft is taxiing to or from its runway. Ground collisions occur when an aircraft collides with another aircraft and/or structure on the runway. |
940,299 | Ground loop (aviation) | In aviation, a ground loop is a rapid rotation of a fixed-wing aircraft in the horizontal plane (yawing) while on the ground. Aerodynamic forces may cause the advancing wing to rise, which may then cause the other wingtip to touch the ground. In severe cases (particularly if the ground surface is soft), the inside wing can dig in, causing the aircraft to swing violently or even cartwheel. In their early gliding experiments, the Wright Brothers referred to this action as well-digging. |
1,565,547 | Ground resonance | Ground resonance is an imbalance in the rotation of a helicopter rotor when the blades become bunched up on one side of their rotational plane and cause an oscillation in phase with the frequency of the rocking of the helicopter on its landing gear. The effect is similar to the behavior of a washing machine when the clothes are concentrated in one place during the spin cycle. It occurs when the landing gear is prevented from freely moving about on the horizontal plane, typically when the aircraft is on the ground.
|
9,468,288 | Hard landing | A hard landing occurs when an aircraft or spacecraft hits the ground with a greater vertical speed and force than in a normal landing. The terms hard landing and firm landing are often confused though are inherently different. A hard landing is never intended and if an aircraft has had a hard landing, it must be inspected for damage before its next flight.
In contrast, depending on aircraft type (e.g. Boeing 737) and/or environmental conditions (e.g. gusty or crosswind conditions, wet runway, etc.) a firm landing is intended and even demanded by the aircraft manual.
Landing is the final phase in flight, in which the aircraft returns to the ground. The average vertical speed in a landing is around 2 metres per second (6.6 ft/s); any greater vertical speed should be classed by crew as hard. Crew judgment is most reliable to determine hard landing, as determination based on recorded acceleration value is difficult and not advisable, partially because there is no recording of true vertical acceleration.
Hard landings can be caused by weather conditions, mechanical problems, overweight aircraft, pilot decision and/or pilot error. The term hard landing usually implies that the pilot still has total or partial control over the aircraft and is aware of the terrain proximity, as opposed to a uncontrolled descent into terrain or a controlled flight into terrain (both of which can be called a crash). Hard landings can vary in their consequences, from mild passenger discomfort to vehicle damage, structural failure, injuries, and/or loss of life.
Hard landings can cause extensive damage to aircraft. For example, on 20 June 2012, a Boeing 767 of All Nippon Airways landed with such force that a large crease formed in the aircraft's skin.
When the final approach isn't stabilised, the crew is to abort and go around; this was the recommendation of the Australian Transport Safety Bureau after investigating the hard landing of a Malaysia Airlines Airbus A330 at Melbourne Airport after arriving from Kuala Lumpur on 14 March 2015.
For helicopters, a hard landing can occur after mechanical or engine damage or failure when the rotor(s) are still intact and free to turn. Autorotation, in which airflow over the rotors keeps them turning and provides some lift, can allow limited pilot control during descent. As an unpowered descent, it requires considerable pilot skill and experience to safely execute.
A hard landing of a spacecraft such as a rocket stage usually ends with its destruction and can be intentional or unintentional. When a high-velocity impact is planned (when its purpose is to study consequences of impact), the spacecraft is called an impactor. This is sometimes humorously referred to as lithobraking.
|
2,239,013 | Helicopter height–velocity diagram | The FAA states "The height–velocity diagram or H/V curve is a graph charting the safe/unsafe flight profiles relevant to a specific helicopter. As operation outside the safe area of the chart can be fatal in the event of a power or transmission failure it is sometimes referred to as the dead man's curve." The EASA refers to it as the "height/velocity avoid curve".
The H/V curve is a diagram indicating the combinations of height above ground and airspeed that should be avoided due to safety concerns relating to emergency landings. It is dangerous to operate within the shaded regions of the diagram, because it may be impossible for the pilot to complete an emergency autorotation from a starting point within these regions. The H/V curve also contains a take-off profile, indicating how a pilot can start from 0 height and 0 speed, and safely traverse to cruise. At low heights with low airspeed, such as a hover taxi, the pilot can simply cushion the landing with collective by converting rotational inertia into lift. Conversely, a complete power loss, and resultant crash landing, from a three-foot hover taxi at walking pace may be survivable. Multi-engine helicopters capable of flying and hovering on a single engine, don't depict this second region.
As the airspeed increases without an increase in height, there comes a point where the pilot's reaction time would be insufficient to initiate a flare, and prevent a high-speed ground impact. Each increase in height increases the pilot reaction time. This is the reason the bottom right part of the H/V curve has a shallow gradient. If above ideal autorotation speed, a pilot can avoid the deadman's curve by flaring, converting airspeed into height, and increasing rotor RPM through coning.
Likewise, an increase in height without a corresponding increase in airspeed is dangerous, as a crash from this height may not be survivable. Airspeed has to increase beyond the 40–80 knot range, allowing the safe initiation of an autorotation. Thus a safe take-off profile, initiating forward flight from a low hover, involves gaining height as airspeed approaches a safe autorotation speed. |
2,075 | Aircraft hijacking | Aircraft hijacking (also known as airplane hijacking, skyjacking, plane hijacking, plane jacking, air robbery, air piracy, or aircraft piracy, with the last term used within the special aircraft jurisdiction of the United States) is the unlawful seizure of an aircraft by an individual or a group. Dating from the earliest of hijackings, most cases involve the pilot being forced to fly according to the hijacker's demands. There have also been incidents where the hijackers have overpowered the flight crew, made unauthorized entry into the cockpit and flown them into buildings—most notably in the September 11 attacks—and in some cases, planes have been hijacked by the official pilot or co-pilot, such as with Ethiopian Airlines Flight 702.
Unlike carjacking or sea piracy, an aircraft hijacking is not usually committed for robbery or theft. Individuals driven by personal gain often divert planes to destinations where they are not planning to go themselves. Some hijackers intend to use passengers or crew as hostages, either for monetary ransom or for some political or administrative concession by authorities. Various motives have driven such occurrences, such as demanding the release of certain high-profile individuals or for the right of political asylum (notably Ethiopian Airlines Flight 961), but sometimes a hijacking may have been affected by a failed private life or financial distress, as in the case of Aarno Lamminparras in Finnair Flight 405. Hijackings involving hostages have produced violent confrontations between hijackers and the authorities, during negotiation and settlement. In several cases – most famously Air France Flight 139, Lufthansa Flight 181, and Air France Flight 8969 – the hijackers were not satisfied and showed no inclination to surrender, resulting in the deployment of counterterrorist police tactical units or special forces to rescue the passengers.
In most jurisdictions of the world, aircraft hijacking is punishable by life imprisonment or a long prison sentence. In most jurisdictions where the death penalty is a legal punishment, aircraft hijacking is a capital crime, including in China, India, Liberia, and the U.S. states of Georgia and Mississippi. |
76,238,515 | In-flight fire | In aviation, an in-flight fire is a type of aviation accident where an aircraft catches on fire in-flight. They are considered one of the most dangerous hazards in aviation, with a report from the British Civil Aviation Authority showing that after a fire on an aircraft starts, flight crews only have on average 17 minutes to land their aircraft before it becomes uncontrollable. Between 1981 and 1990, approximately 20% of all fatalities on US airlines were caused by in-flight fires. |
3,252,568 | Inertia coupling | In aeronautics, inertia coupling, also referred to as inertial coupling and inertial roll coupling, is a potentially catastrophic phenomenon of high-speed flight in a long, thin aircraft, in which an intentional rotation of the aircraft about one axis prevents the aircraft's design from inhibiting other unintended rotations. The problem became apparent in the 1950s, when the first supersonic jet fighter aircraft and research aircraft were developed with narrow wingspans, and caused the loss of aircraft and pilots before the design features to counter it (e.g. a big enough fin) were understood.
The term "inertia/inertial coupling" has been criticized as misleading, because the phenomenon is not solely an instability of inertial movement, like the Janibekov effect. Instead, the phenomenon arises because aerodynamic forces react too slowly to track an aircraft's orientation. At low speeds and thick air, aerodynamic forces match aircraft translational velocity to orientation, avoiding the dangerous dynamical regime. But at high speeds or thin air, the wing and empennage may not generate sufficient forces and moments to stabilize the aircraft.
|
7,813,665 | Jet blast | Jet blast is the phenomenon of rapid air movement produced by the jet engines of aircraft, particularly on or before takeoff. A large jet-engine aircraft can produce winds of up to 100 knots (190 km/h; 120 mph) as far away as 60 metres (200 ft) behind it at 40% maximum rated power. Jet blast can be a hazard to people or other unsecured objects, and can reach wind speeds comparable to those of a Category 5 hurricane, causing roof failure or total collapse in buildings, and severely damaging or destroying things like mobile homes, utility buildings, and trees.
Despite the power and potentially destructive nature of jet blast, there are relatively few jet blast incidents. Due to the invisible nature of jet blast and the aerodynamic properties of light aircraft, light aircraft moving about airports are particularly vulnerable. Pilots of light aircraft frequently stay off to the side of the runway, rather than follow in the centre, to negate the effect of the blast. Occasionally, when the ground surface is badly chosen, jet blast from aircraft can rip up sections of asphalt weighing up to tens of kilograms (double-digits of pounds), damaging the aircraft.
Maho Beach in Sint Maarten is famous for its unique proximity to the runway of Princess Juliana International Airport, allowing people to experience jet blast, a practice that is discouraged by the local authorities. A tourist was killed on 12 July 2017 when she was blown away by jet blast, which caused her head to smash into concrete. Skiathos Airport in Greece similarly allows people to experience jet blast, as its runway is located near a public road.
Propeller planes are also capable of generating significant rearwards winds, known as prop wash.
|
34,002,651 | The leans | The leans is the most common type of spatial disorientation for aviators. Through stabilization of the fluid in the semicircular canals, a pilot may perceive straight and level flight while actually in a banked turn. This is caused by a quick return to level flight after a gradual, prolonged turn that the pilot failed to notice. The phenomenon consists of a false perception of angular displacement about the roll axis and therefore becomes an illusion of bank. This illusion is often associated with a vestibulospinal reflex that results in the pilot actually leaning in the direction of the falsely perceived vertical. Other common explanations of the leans are due to deficiencies of both otolith-organ and semicircular-duct sensory mechanisms. |
15,789,615 | List of aircraft hijackings | The following is a list of notable aircraft hijackings. |
24,815,659 | List of aircraft upset factors | The U.S. FAA lists factors of aircraft upset in the Airplane Upset Recovery Training Aid as follows:
Turbulence causes:
Clear air turbulence
Mountain wave turbulence
Windshear
Thunderstorms
Microbursts
Wake turbulence
Aircraft icing
Systems anomalies:
Flight instruments
Autoflight systems
Flight control and other anomalies
Pilot-Induced
Instrument cross-check
Adjusting attitude and power
Inattention
Distraction from primary cockpit duties
Vertigo or spatial disorientation
Pilot incapacitation
Improper use of airplane automation
Pilot techniques
Pilot induced oscillation avoidance and recovery
Combination causes:
Swept-wing airplane fundamentals for pilots
Flight dynamics
Energy states
Load factor (flight mechanics)
Aerodynamic flight envelope
Aerodynamic causes:
Angle of attack and stall
Camber
Control surface fundamentals
Spoiler-type devices
Trim
Lateral and directional aerodynamic considerations
Angle of sideslip
Wing dihedral effects
Pilot-commanded sideslip
Crossover speed
Static stability
Maneuvering in pitch
Mechanics of turning flight
Lateral and directional maneuvering
Flight at extremely low airspeeds
High-altitude factors
Stall
icing
Automation during high-altitude flight
Primary flight display airspeed indications
Human factors and high altitude upsets
Additional considerations:
Multi-engine flame out
Core lock
Engine rollback
Flight at extremely high speeds
Defensive, aggressive maneuvers
Situation awareness
Startle factor
Negative G-force
Use of full control inputs
Counter-intuitive factors
Previous training in non-similar airplanes
Engine performance in upset situation
Post-upset conditions |
34,461,092 | Loss of control (aeronautics) | In aeronautics, loss of control (LOC) is the unintended departure of an aircraft from controlled flight and is a significant factor in several aviation accidents worldwide. In 2015 it was the leading cause of general aviation accidents. Loss of control may be the result of mechanical failure, external disturbances, aircraft upset conditions, or inappropriate crew actions or responses. |
3,512,082 | Low-g condition | Low-g condition is a phase of aerodynamic flight where the airframe is temporarily unloaded. The pilot—and the airframe—feel temporarily "weightless" because the aircraft is in free-fall or decelerating vertically at the top of a climb. It may also occur during an excessively rapid entry into autorotation. This can have a disastrous effect on the aircraft, particularly in the case of helicopters, some of which need the rotor to constantly be under a non-zero amount of load. |
1,467,543 | Mobile phones on aircraft | In the U.S., Federal Communications Commission (FCC) regulations prohibit the use of mobile phones aboard aircraft in flight. Contrary to popular misconception, the Federal Aviation Administration (FAA) does not actually prohibit the use of personal electronic devices (including cell phones) on aircraft. Paragraph (b)(5) of 14 CFR 91.21 permits airlines to determine if devices can be used in flight, allowing use of "any other portable electronic device that the operator of the aircraft has determined will not cause interference with the navigation or communication system of the aircraft on which it is to be used."
In Europe, regulations and technology have allowed the limited introduction of the use of passenger mobile phones on some commercial flights, and elsewhere in the world many airlines are moving towards allowing mobile phone use in flight. Many airlines still do not allow the use of mobile phones on aircraft. Those that do often ban the use of mobile phones during take-off and landing.
Many passengers are pressing airlines and their governments to allow and deregulate mobile phone use, while some airlines, under the pressure of competition, are also pushing for deregulation or seeking new technology which could solve the present problems. Official aviation agencies and safety boards are resisting any relaxation of the present safety rules unless and until it can be conclusively shown that it would be safe to do so. There are both technical and social factors which make the issues more complex than a simple discussion of safety versus hazard.
|
68,150,155 | Parts departing aircraft | In aviation safety, parts departing aircraft or parts detached from aeroplanes (PDA), also known as objects falling off airplanes (OFA), things falling off aircraft (TFOA), and other analogous variations, can range from small fasteners like screws and rivets up to major sub-assemblies like hatch covers and doors. PDA are a safety concern because they may be critical parts needed to continue safe flight, may damage other critical parts of the aircraft as they depart, may cause foreign object damage to other aircraft, or may cause serious injuries or damage to people and property on the ground. These occurrences are a longstanding worldwide problem in aviation.
In a 2018 study, the European Aviation Safety Agency concluded that the likelihood of fatally injuring people on the ground due to a PDA event is low enough that it does not constitute an unsafe condition according to their standards; they also noted the absence of any people fatally injured from PDA. But in Japan, preventing objects falling off airplanes is required by all air carriers after a series of serious incidents at Haneda Airport which is close to Tokyo.
Regardless of whether PDA are considered acceptable risk by aviation regulators, things that fall from the sky are generally not well tolerated outside the aviation community. The United States Navy found complaints about TFOA increased as residential development has encroached around naval air stations. Leaking aviation lavatory liquids have been known to build up on the exterior of the aircraft in sub-freezing temperatures at altitude, only to fall to earth as blue ice after the airplane descends to land. London Heathrow Airport has had a recurring problem of wheel-well stowaway bodies dropping in residential areas around the airport when airplanes extend their landing gear as they prepare to land. |
2,328,078 | Pilot error | In aviation, pilot error generally refers to an action or decision made by a pilot that is a substantial contributing factor leading to an aviation accident. It also includes a pilot's failure to make a correct decision or take proper action. Errors are intentional actions that fail to achieve their intended outcomes. The Chicago Convention defines the term "accident" as "an occurrence associated with the operation of an aircraft [...] in which [...] a person is fatally or seriously injured [...] except when the injuries are [...] inflicted by other persons." Hence the definition of "pilot error" does not include deliberate crashing (and such crashes are not classified as accidents).
The causes of pilot error include psychological and physiological human limitations. Various forms of threat and error management have been implemented into pilot training programs to teach crew members how to deal with impending situations that arise throughout the course of a flight.
Accounting for the way human factors influence the actions of pilots is now considered standard practice by accident investigators when examining the chain of events that led to an accident.
|
365,362 | Pilot-induced oscillation | Pilot-induced oscillations (PIOs), as defined by MIL-HDBK-1797A, are sustained or uncontrollable oscillations resulting from efforts of the pilot to control the aircraft. They occur when the pilot of an aircraft inadvertently commands an often increasing series of corrections in opposite directions, each an attempt to cover the aircraft's reaction to the previous input with an overcorrection in the opposite direction. An aircraft in such a condition can appear to be "porpoising" switching between upward and downward directions. As such it is a coupling of the frequency of the pilot's inputs and the aircraft's own frequency. In order to avoid any assumption that oscillation is necessarily the fault of the pilot, new terms have been suggested to replace pilot-induced oscillation. These include aircraft-pilot coupling, pilot–in-the-loop oscillations and pilot-assisted (or augmented) oscillations.
The physics of flight make such oscillations more probable for pilots than for automobile drivers. An attempt to cause the aircraft to climb, say, by applying up-elevator, will also result in a reduction in airspeed.
Another factor is the response rate of flight instruments in comparison to the response rate of the aircraft itself. For example, an increase in power will not result in an immediate increase in indicated airspeed, nor will an increase in climb rate show up immediately on the vertical speed indicator. A pilot aiming for a 500-foot per minute descent, for example, may find themselves descending more rapidly than intended. They begin to apply up elevator until the vertical speed indicator shows 500 feet per minute. However, because the vertical speed indicator lags the actual vertical speed, the aircraft is actually descending at much less than 500 feet per minute. The pilot then begins applying down elevator until the vertical speed indicator reads 500 feet per minute, starting the cycle over. In this way, stabilizing vertical speed can be difficult due to constantly variable airspeed. In a controls sense, the oscillation is the result of reduced phase margin induced by the lag of the pilot's response. The problem has been mitigated in some cases by adding a latency term to the instruments – for example, to cause the climb rate indication to not only reflect the current climb rate, but also be sensitive to the rate of change of the climb rate.
Pilot-induced oscillations may be the fault of the aircraft, the pilot, or both. It is a common problem for inexperienced pilots, and especially student pilots, although it was also a problem for the top research test pilots on the NASA lifting body program. The problem is most acute when the wing and tail section are close together in so called "short coupled" aircraft. During flight test, pilot-induced oscillation is one of the handling qualities factors that is analyzed, with the aircraft being graded by an established scale (chart at right).
The most dangerous pilot-induced oscillations can occur during landing. Too much up elevator during the flare can result in the plane getting dangerously slow and threatening to stall. A natural reaction to this is to push the nose down harder than one pulled it up, but then the pilot ends up staring at the ground. An even larger amount of up elevator starts the cycle over again.
While pilot-induced oscillations often start with fairly low amplitudes, which can adequately be treated with small perturbation linear theory, several PIOs will incrementally increase in amplitude. |
5,096,257 | 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. |
43,342,601 | Propeller strike | In aviation, a propeller strike, or prop strike, also called a sudden stoppage, is an event in which an aircraft's propeller contacts any object and is forcibly stopped or slowed. Propeller strikes can be the result of the propeller contacting the ground due to landing gear collapse, failure to extend the landing gear, or nose-over. However, the term also includes the damage incurred from contacting any object, such as a hangar door or fuselage (such as the case in Reeve Aleutian Airways Flight 8), or even the sudden rpm loss from contacting a yielding substance such as water or heavy tall grass.
As well as damaging the propeller itself, a prop strike with the engine running can cause severe damage to the engine and its connected accessories, such as the alternator. An engine tear-down and rebuild is usually recommended, otherwise there is a risk of an in-flight engine failure, broken crankshaft or loss of propeller.
|
607,446 | Ramp strike | A ramp strike or rampstrike is when an aircraft coming to land aboard an aircraft carrier impacts the rear of the carrier, also called the ramp, below the level of the flight deck.
Damage from a ramp strike to the aircraft can range from broken hook or undercarriage to total loss of airframe; damage to the carrier can range from injured deck plating to a severe fire.
One of the most famous non-fatal ramp strike accidents occurred on 23 June 1951 when Cdr. George Chamberlain Duncan attempted to land a Grumman F9F-2 Panther on USS Midway in BuNo 125228, during carrier suitability tests in the Atlantic Ocean. The forward fuselage broke away and tumbled down the deck, which Duncan survived, suffering burns. Footage of this accident has been used in several films including Men of the Fighting Lady, Midway, and The Hunt for Red October. |
1,565,409 | Retreating blade stall | Retreating blade stall is a hazardous flight condition in helicopters and other rotary wing aircraft, where the retreating rotor blade has a lower relative blade speed, combined with an increased angle of attack, causing a stall and loss of lift. Retreating blade stall is the primary limiting factor of a helicopter's never exceed speed, VNE.
Retreating blade stall occurs at high forward speeds, and should not be confused with rotor stall, which is caused by low rotor RPM and can occur at any forward speed. |
8,731,144 | Runway excursion | A runway excursion is a runway safety incident in which an aircraft makes an inappropriate exit from the runway. This happens mainly due to late landings or inappropriate runway choice.
There are several types of runway excursions:
A departing aircraft fails to become airborne or successfully reject the takeoff before reaching the end of the designated runway.
A landing aircraft is unable to stop before the end of the designated runway is reached, causing it to keep moving and leave the runway.
An aircraft taking off, rejecting takeoff or landing departs the side of the designated runway, not airborne.
When an aircraft exits the end of the runway, this is referred to as runway overrun (or informally, runway overshoot). Runway excursions can happen because of pilot error, poor weather, or a fault with the aircraft. Runway excursions may occur both during takeoff or landing.
According to the Flight Safety Foundation, as of 2008, runway excursions were the most frequent type of landing accident, slightly ahead of runway incursion. For runway accidents recorded between 1995 and 2007, 96% of runway accidents and 80% of accidents with fatalities involved runway excursions. |
10,758,386 | Runway incursion | A runway incursion is an aviation incident involving improper positioning of vehicles or people on any airport runway or its protected area. When an incursion involves an active runway being used by arriving or departing aircraft, the potential for a collision hazard or instrument landing system (ILS) interference can exist. At present, various runway safety technologies and processes are commonly employed to reduce the risk and potential consequences of such an event. |
3,526,639 | Sensory illusions in aviation | Human senses are not naturally geared for the in-flight environment. Pilots may experience disorientation and loss of perspective, creating illusions that range from false horizons to sensory conflict with instrument readings or the misjudging of altitude over water.
|
75,431,441 | Servo transparency | In aviation, and in particular in helicopters, servo transparency (also called servo reversibility or jack stall), is a phenomenon affecting the servomechanisms (or servos) that assist a helicopter's flight controls, which, in certain flight conditions, can result in a significant stiffening of the controls handled by the pilot. The effect, if not promptly recognised by the pilot, can be hazardous as it can lead to partial or total loss of control, which, if encountered at low altitude, could result in impact with terrain.: 101 |
888,928 | Spatial disorientation | Spatial disorientation is the inability to determine position or relative motion, commonly occurring during periods of challenging visibility, since vision is the dominant sense for orientation. The auditory system, vestibular system (within the inner ear), and proprioceptive system (sensory receptors located in the skin, muscles, tendons and joints) collectively work to coordinate movement with balance, and can also create illusory nonvisual sensations, resulting in spatial disorientation in the absence of strong visual cues.
In aviation, spatial disorientation can result in improper perception of the attitude of the aircraft, referring to the orientation of the aircraft relative to the horizon. If a pilot relies on this improper perception, this can result in inadvertent turning, ascending or descending. For aviators, proper recognition of aircraft attitude is most critical at night or in poor weather, when there is no visible horizon; in these conditions, aviators may determine aircraft attitude by reference to an attitude indicator. Spatial disorientation can occur in other situations where visibility is reduced, such as diving operations. |
341,083 | Spin (aerodynamics) | 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 intentionally or unintentionally, from any flight attitude if the aircraft has sufficient yaw while at the stall point.
In a normal spin, the wing on the inside of the turn stalls while the outside wing remains flying. It is possible for both wings to stall, but the angle of attack of each wing, and consequently its lift and drag, are different.
Either situation causes the aircraft to autorotate toward the stalled wing due to its higher drag and loss of lift. Spins are characterized by high angle of attack, an airspeed below the stall on at least one wing and a shallow descent. Recovery and avoiding a crash may require a specific and counter-intuitive set of actions.
A spin differs from a spiral dive, in which neither wing is stalled and which is characterized by a low angle of attack and high airspeed. A spiral dive is not a type of spin because neither wing is stalled. In a spiral dive, the aircraft responds conventionally to the pilot's inputs to the flight controls, and recovery from a spiral dive requires a different set of actions from those required to recover from a spin.
In the early years of flight, a spin was frequently referred to as a "tailspin". |
81,511 | Stall (fluid dynamics) | In fluid dynamics, a stall is a reduction in the lift coefficient generated by a foil as angle of attack exceeds its critical value. The critical angle of attack is typically about 15°, but it may vary significantly depending on the fluid, foil – including its shape, size, and finish – and Reynolds number.
Stalls in fixed-wing aircraft are often experienced as a sudden reduction in lift. It may be caused either by the pilot increasing the wing's angle of attack or by a decrease in the critical angle of attack. The latter may be due to slowing down (below stall speed) or the accretion of ice on the wings (especially if the ice is rough). 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. Vectored thrust in aircraft is used to maintain altitude or controlled flight with wings stalled by replacing lost wing lift with engine or propeller thrust, thereby giving rise to post-stall technology.
Because stalls are most commonly discussed in connection with aviation, this article discusses stalls as they relate mainly to aircraft, in particular fixed-wing aircraft. The principles of stall discussed here translate to foils in other fluids as well. |
43,930,834 | Steep turn (aviation) | A steep turn in aviation, performed by an aircraft (usually fixed wing), is a turn that involves a bank of more than 30 degrees. This means the angle created by the axis running along both wings and the horizon is more than 30 degrees. Generally, for training purposes, steep turns are demonstrated and practiced at 45 degrees, sometimes more. The purpose of learning and practicing a steep turn is to train a pilot to maintain control of an aircraft in cases of emergency such as structural damage, loss of power in one engine etc.
Entry procedure for a steep turn involves putting the aircraft into a bank (left or right), simultaneously increasing the thrust adequately to maintain altitude, while pulling back on the flight stick or flight yoke to speed up the turning process. For Jet training an increase of 7-8% of N1 caters. While doing this the pilot has to ensure no loss or gain of altitude. The pilot is expected to constantly look outside the aircraft while keeping a close check on the Attitude indicator for angle of bank. When the aircraft is in a 45 degree bank, it is common for a certain amount of opposite aileron control to be required to prevent the aircraft from slipping into a steeper bank. |
30,401,564 | Stray animals at Indian airports | Stray animals are common on the runways of Indian airports. They can pose a major threat to air safety in most airports across the nation. According to the Airports Authority of India (AAI) officials, animals straying onto the runway are routine at many airports in India.
Animals found in the runways of Indian airports include dogs, antelope, cows, jackals, snakes, cats, and monkeys.
|
46,233,624 | Suicide by pilot | Suicide by pilot is an aviation event in which a pilot deliberately crashes or attempts to crash an aircraft as a suicide act, with or without the intention of causing harm to passengers on board or people on the ground. If others are killed, it may be considered a type of murder–suicide. It is suspected to have been a possible cause in several commercial flight crashes and has been confirmed as the cause in other instances. Determining the motives of pilots can be challenging for crash investigators, as pilots may intentionally disable recording devices or engage in other actions to impede future investigations. Consequently, definitively proving pilot suicide can be difficult.
Investigators do not classify aircraft incidents as suicides unless there is compelling evidence indicating that the pilot intended suicide. This evidence may include suicide notes, past suicide attempts, explicit threats of suicide, or a documented history of mental illness. A study conducted on pilot suicides between 2002 and 2013 identified eight cases as definite suicides, along with five additional cases of undetermined cause that may have been suicides. In some cases, investigators may collaborate with terrorism experts to investigate potential connections to extremist groups, aiming to ascertain whether the suicide was an act of terrorism.
A Bloomberg News study conducted in June 2022, focusing on crashes involving Western-built commercial airliners, revealed that pilot murder-suicides ranked as the second most prevalent cause of airline crash deaths between 2011 and 2020. Additionally, the study found that deaths resulting from pilot murder-suicides increased over the period from 1991 to 2020, while fatalities due to accidental causes significantly decreased. However, most cases of suicide by pilot involve general aviation in small aircraft, where typically the pilot is the sole occupant of the aircraft. In approximately half of these cases, the pilot had consumed drugs, often alcohol or antidepressants, which would typically result in a ban on flying. Many of these pilots have concealed their mental illness histories from regulators. |
3,057,926 | Tailstrike | In aviation, a tailstrike or tail strike occurs when the tail or empennage of an aircraft strikes the ground or other stationary object. This can happen with a fixed-wing aircraft with tricycle undercarriage, in both takeoff where the pilot rotates the nose up too rapidly, or in landing where the pilot raises the nose too sharply during final approach, often in attempting to land too near the runway threshold. It can also happen during helicopter operations close to the ground, when the tail inadvertently strikes an obstacle.
A minor tailstrike incident may not be dangerous in itself, but the aircraft may still be weakened and must be thoroughly inspected and repaired if a more disastrous accident is to be avoided later in its operating life. |
760,810 | Traffic collision avoidance system | A traffic alert and collision avoidance system (TCAS), pronounced TEE-kas), also known as an Airborne Collision Avoidance System (ACAS), is an aircraft collision avoidance system designed to reduce the incidence of mid-air collision (MAC) between aircraft. It monitors the airspace around an aircraft for other aircraft equipped with a corresponding active transponder, independent of air traffic control, and warns pilots of the presence of other transponder-equipped aircraft which may present a threat of MAC. It is a type of airborne collision avoidance system mandated by the International Civil Aviation Organization to be fitted to all aircraft with a maximum take-off mass (MTOM) of over 5,700 kg (12,600 lb) or authorized to carry more than 19 passengers. In the United States, CFR 14, Ch I, part 135 requires that TCAS I be installed for aircraft with 10–30 passengers and TCAS II for aircraft with more than 30 passengers. ACAS/TCAS is based on secondary surveillance radar (SSR) transponder signals, but operates independently of ground-based equipment to provide advice to the pilot on potentially conflicting aircraft.
In modern glass cockpit aircraft, the TCAS display may be integrated in the navigation display (ND) or electronic horizontal situation indicator (EHSI).
In older glass cockpit aircraft and those with mechanical instrumentation, an integrated TCAS display including an instantaneous vertical speed indicator (IVSI) may replace the mechanical IVSI, which only indicates the rate at which the aircraft is descending or climbing. |
11,709,087 | Turbine engine failure | A turbine engine failure occurs when a gas turbine engine unexpectedly stops producing power due to a malfunction other than fuel exhaustion. It often applies for aircraft, but other turbine engines can also fail, such as ground-based turbines used in power plants or combined diesel and gas vessels and vehicles.
|
8,886,080 | Unstart | In supersonic aerodynamics, an unstart refers to a generally violent breakdown of the supersonic airflow. The phenomenon occurs when mass flow rate changes significantly within a duct. Avoiding unstarts is a key objective in the design of the engine air intakes of supersonic aircraft that cruise at speeds in excess of Mach 2.2. |
22,811,297 | Volcanic Ash Advisory Center | A Volcanic Ash Advisory Center (VAAC) is a group of experts responsible for coordinating and disseminating information on atmospheric volcanic ash clouds that may endanger aviation. As at 2019, there are nine Volcanic Ash Advisory Centers located around the world, each one focusing on a particular geographical region. Their analyses are made public in the form of volcanic ash advisories (VAAs), involving expertise analysis of satellite observations, ground and pilot observations and interpretation of ash dispersion models.
The worldwide network of Volcanic Ash Advisory Centers was set up by the International Civil Aviation Organization (ICAO), an agency of the United Nations, as part of the International Airways Volcano Watch (IAVW), an international set of arrangements for monitoring and providing warnings to aircraft of volcanic ash. The operations and development of the IAVW are coordinated by the Meteorology Panel (METP) established by the ICAO Air Navigation Commission. The individual VAACs are run as part of national weather forecasting organisations of the country where they are based, e.g. the US National Weather Service or the British Met Office. |
33,253,560 | Volcanic ash and aviation safety | Plumes of volcanic ash near active volcanoes are a flight safety hazard, especially for night flights. Volcanic ash is hard and abrasive, and can quickly cause significant wear to propellers and turbocompressor blades, and scratch cockpit windows, impairing visibility. The ash contaminates fuel and water systems, can jam gears, and make engines flame out. Its particles have low melting points and readily melt in the engines' combustion chambers; this creates a ceramic mass that sticks to turbine blades, fuel nozzles, and combustors, which can quickly lead to total engine failure. Ash can also contaminate the cabin and damage avionics.
In 1991, the aviation industry decided to set up Volcanic Ash Advisory Centers (VAACs) for liaison between meteorologists, volcanologists, and the aviation industry. Before 2010, aircraft engine manufacturers had not defined specific particle levels above which they considered engines at risk. Airspace regulators took the general approach that if ash concentration rose above zero, they considered airspace unsafe, and consequently closed it.
The costs of air travel disruption in Europe after a volcanic eruption in 2010 forced aircraft manufacturers to specify limits on how much ash they considered acceptable for a jet engine to ingest without damage. In April, the UK CAA, in conjunction with engine manufacturers, set the safe upper limit of ash density at 2 mg per cubic metre of air space. From May 2010, the CAA revised the safe limit upwards to 4 mg per cubic metre of air space.
To minimise further disruption that this and other volcanic eruptions could cause, the CAA created a new category of restricted airspace called a Time Limited Zone. Airspace categorised as TLZ is similar to airspace under severe weather conditions, in that restrictions should be of a short duration. However, a key difference with TLZ airspace is that airlines must produce certificates of compliance for aircraft they want to enter these areas. Any airspace where ash density exceeds 4 mg per cubic metre is prohibited airspace.
Volcanic ash in the immediate vicinity of the eruption plume is different in particle size range and density than that in downwind dispersal clouds, which contain only the finest particle sizes of ash. Experts have not established the ash loading that affects normal engine operation (other than engine lifetime and maintenance costs). Whether this silica-melt risk remains at the much lower ash densities characteristic of downstream ash clouds is currently unclear.
Experts recognised that there was an issue following British Airways Flight 9 in 1982, and therefore the ICAO established the Volcanic Ash Warning Study Group. Due to the difficulty in forecasting accurate information out to 12 hours and beyond, the ICAO later set up Volcanic Ash Advisory Centers (VAACs).
|
828,001 | Vortex ring | A vortex ring, also called a toroidal vortex, is a torus-shaped vortex in a fluid; that is, a region where the fluid mostly spins around an imaginary axis line that forms a closed loop. The dominant flow in a vortex ring is said to be toroidal, more precisely poloidal.
Vortex rings are plentiful in turbulent flows of liquids and gases, but are rarely noticed unless the motion of the fluid is revealed by suspended particles—as in the smoke rings which are often produced intentionally or accidentally by smokers. Fiery vortex rings are also a commonly produced trick by fire eaters. Visible vortex rings can also be formed by the firing of certain artillery, in mushroom clouds, in microbursts, and rarely in volcanic eruptions.
A vortex ring usually tends to move in a direction that is perpendicular to the plane of the ring and such that the inner edge of the ring moves faster forward than the outer edge. Within a stationary body of fluid, a vortex ring can travel for relatively long distance, carrying the spinning fluid with it.
|
1,565,482 | Vortex ring state | The vortex ring state (VRS) is a dangerous aerodynamic condition that may arise in helicopter flight, when a vortex ring system engulfs the rotor, causing severe loss of lift. Often the term settling with power is used as a synonym, e.g., in Australia, the UK, and the US, but not in Canada, which uses the latter term for a different phenomenon.
A vortex ring state sets in when the airflow around a helicopter's main rotor assumes a rotationally symmetrical form over the tips of the blades, supported by a laminar flow over the blade tips, and a countering upflow of air outside and away from the rotor. In this condition, the rotor falls into a new topological state of the surrounding flow field, induced by its own downwash, and suddenly loses lift. Since vortex rings are a surprisingly stable fluid dynamical phenomenon (a form of topological soliton), the best way to recover from them is to laterally steer clear of them, in order to re-establish lift, and to break them up using maximum engine power, in order to establish turbulence.
This is also why the condition is often mistaken for "settling with insufficient power": high-powered maneuvers can both induce a vortex ring state in free air, and then at low altitude, during landing conditions, possibly break it. If sufficient power is not available to maintain the airfoil of the rotor at a stalled condition, while generating sufficient lift, the aircraft will not be able to stay aloft before the vortex ring state dissipates, and will crash.
This condition also occurs with tiltrotors, and it was responsible for an accident involving a V-22 Osprey in 2000. Vortex ring state caused the loss of a heavily modified MH-60 helicopter during Operation Neptune Spear, the 2011 raid in which Osama bin Laden was killed. |
670,783 | Wake turbulence | Wake turbulence is a disturbance in the atmosphere that forms behind an aircraft as it passes through the air. It includes several components, the most significant of which are wingtip vortices and jet-wash, the rapidly moving gases expelled from a jet engine.
Wake turbulence is especially hazardous in the region behind an aircraft in the takeoff or landing phases of flight. During take-off and landing, an aircraft operates at a high angle of attack. This flight attitude maximizes the formation of strong vortices. In the vicinity of an airport, there can be multiple aircraft, all operating at low speed and low altitude; this provides an extra risk of wake turbulence with a reduced height from which to recover from any upset. |
5,690,654 | Wheel-barrowing | Wheel-barrowing is a problem that may occur in an aeroplane with a tricycle gear configuration during takeoff or landing. As the aeroplane gains speed during takeoff the wing generates an increasing amount of lift although not enough to raise the aeroplane off the ground. The lift reduces the weight supported by the aeroplane's main wheels and this reduces the main wheels' contribution to directional stability, allowing the nose wheel to destabilise the aeroplane's direction along the ground. This form of wheelbarrowing is easily avoided by the pilot applying back-pressure to the elevator control during the takeoff roll to reduce the weight supported by the nose wheel.
Depending on the severity of the wheel-barrowing, damage to the aircraft can be quite extensive: The propeller of a single engine airplane may strike the ground, damaging it and the engine. A wing can be damaged by striking the ground as the aircraft pivots over the nose-wheel and one main wheel.
Wheel-barrowing may also be caused with a tricycle gear when the turn radius is too sharp for the speed of the aircraft on the ground – much like a child on a tricycle taking too sharp a turn. The problem is exacerbated when brakes are applied during the turn. |
1,170,314 | Wingtip vortices | Wingtip vortices are circular patterns of rotating air left behind a wing as it generates lift.: 5.14 The name is a misnomer because the cores of the vortices are slightly inboard of the wing tips.: 369 Wingtip vortices are sometimes named trailing or lift-induced vortices because they also occur at points other than at the wing tips.: 5.14 Indeed, vorticity is trailed at any point on the wing where the lift varies span-wise (a fact described and quantified by the lifting-line theory); it eventually rolls up into large vortices near the wingtip, at the edge of flap devices, or at other abrupt changes in wing planform.
Wingtip vortices are associated with induced drag, the imparting of downwash, and are a fundamental consequence of three-dimensional lift generation.: 5.17, 8.9 Careful selection of wing geometry (in particular, wingspan), as well as of cruise conditions, are design and operational methods to minimize induced drag.
Wingtip vortices form the primary component of wake turbulence. Depending on ambient atmospheric humidity as well as the geometry and wing loading of aircraft, water may condense or freeze in the core of the vortices, making the vortices visible. |
10,958,349 | Air-mass thunderstorm | An air-mass thunderstorm, also called an "ordinary", "single cell", "isolated" or "garden variety" thunderstorm, is a thunderstorm that is generally weak and usually not severe. These storms form in environments where at least some amount of Convective Available Potential Energy (CAPE) is present, but with very low levels of wind shear and helicity. The lifting source, which is a crucial factor in thunderstorm development, is usually the result of uneven heating of the surface, though they can be induced by weather fronts and other low-level boundaries associated with wind convergence. The energy needed for these storms to form comes in the form of insolation, or solar radiation. Air-mass thunderstorms do not move quickly, last no longer than an hour, and have the threats of lightning, as well as showery light, moderate, or heavy rainfall. Heavy rainfall can interfere with microwave transmissions within the atmosphere.
Lightning characteristics are related to characteristics of the parent thunderstorm, and could induce wildfires near thunderstorms with minimal rainfall. On unusual occasions there could be a weak downburst and small hail. They are common in temperate zones during a summer afternoon. Like all thunderstorms, the mean-layered wind field the storms form within determine motion. When the deep-layered wind flow is light, outflow boundary progression will determine storm movement. Since thunderstorms can be a hazard to aviation, pilots are advised to fly above any haze layers within regions of better visibility and to avoid flying under the anvil of these thunderstorms, which can be regions where hail falls from the parent thunderstorm. Vertical wind shear is also a hazard near the base of thunderstorms which have generated outflow boundaries. |
2,644,038 | Carburetor icing | In engine design, carburetor icing is an icing condition which can affect carburetors under certain atmospheric conditions. The problem is most notable in aviation engines using float-type carburetors.
Carburetor icing is caused by the temperature drop in the carburetor, as an effect of fuel vaporization, and the temperature drop associated with the pressure drop in the venturi. If the temperature drops below freezing, water vapor will freeze onto the throttle valve, and other internal surfaces of the carburetor. The venturi effect can reduce the air temperature by 39 K; 39 °C (70 °F). In other words, air at an outside temperature of 38 °C (100 °F), can drop to −1 °C (30 °F) in the carburetor. Carburetor icing most often occurs when the outside air temperature is below 21 °C (70 °F) and the relative humidity is above 80 percent. The risk of carburettor icing is significantly increased at partial power settings (such as when power is reduced during descent), due to the cooling effect of the partly-closed throttle.
The high ambient temperature at which it can occur often causes aircraft pilots to overlook the possibility of carb icing. The ice will form on the surfaces of the carburetor throat, further restricting it. This may increase the venturi effect initially, but eventually restricts airflow, perhaps even causing a complete blockage of air to the carburetor. The engine begins to run more rich as ice formation increases. Without intervention (such as carburetor heating or manually adjusting the air–fuel ratio) this can continue until the air–fuel ratio is outside the correct range for proper operation of the engine. Icing may also cause jamming of the mechanical parts of the carburetor, such as the throttle, typically a butterfly valve.
While it can affect any carburetor, carburetor icing is of particular concern in piston-powered aircraft, especially small, single-engine, light aircraft. Aircraft powered by carbureted engines are equipped with carburetor heating systems to counter icing. In road vehicles, carburetor icing can occasionally be a nuisance, although some engine designs are more susceptible to it than others. The inlet manifold and parts of the carburetor often have warm water from the cooling system or exhaust gas circulating through them to combat this problem. Air-cooled engines may be more prone to icing, due to the absence of warm coolant circulating through the engine. |
2,014,417 | Clear-air turbulence | In meteorology, clear-air turbulence (CAT) is the turbulent movement of air masses in the absence of any visual clues such as clouds, and is caused when bodies of air moving at widely different speeds meet.
The atmospheric region most susceptible to CAT is the high troposphere at altitudes of around 7,000–12,000 m (23,000–39,000 ft) as it meets the tropopause. Here CAT is most frequently encountered in the regions of jet streams. At lower altitudes it may also occur near mountain ranges. Thin cirrus clouds can also indicate high probability of CAT.
CAT can be hazardous to the comfort, and occasionally the safety, of air travelers, as the aircraft pilots often cannot see and anticipate such turbulences, and a sudden encounter can impart significant stress to the airframe.
CAT in the jet stream is expected to become stronger and more frequent because of climate change, with transatlantic wintertime CAT increasing by 60% (light), 95% (moderate), and 150% (severe) by the time of CO2 doubling. |
6,153,352 | Cloud suck | Cloud suck is a phenomenon commonly known in paragliding, hang gliding, and sailplane flying where pilots experience significant lift due to a thermal under the base of cumulus clouds, especially towering cumulus and cumulonimbus. The vertical extent of a cumulus cloud is a good indicator of the strength of lift beneath it, and the potential for cloud suck.
Cloud suck most commonly occurs in low pressure weather and in humid conditions.
Cloud suck is typically associated with an increase in thermal updraft velocity near cloud base. As a parcel of air lifted in a thermal rises, it also cools, and water vapour will eventually condense to form a cloud if the parcel rises above the lifted condensation level. As the water vapour condenses, it releases its latent heat of vaporization, thereby increasing the buoyancy of the parcel.
The updraft is amplified by this latent heat release. Although the process that causes this amplification happens above cloud base height, the effect is often noticeable as much as 300 m (1,000 feet) below cloud base. In fact, it is this effect below cloud base, not the effect within the cloud, that is generally referred to by pilots as cloud suck. The telltale signs for a pilot climbing in the thermal under a "sucking" cloud are (1) lift strengthening, (2) lift getting smoother, and (3) widening of the thermal.
Paraglider pilots have reported being unable to descend in strong cloud suck, even after bringing their canopies into deep spiral, which would normally result in a rapid vertical descent. Cloud suck is especially dangerous for paraglider pilots, whose maximum speed is less than 30 knots, because storm clouds (Cumulonimbus) can expand and develop rapidly over a large area with accompanying large areas of strong lift.
On 14 February 2007 while practising for a paragliding contest in Australia, Polish-born
German team pilot Ewa Wiśnierska-Cieślewicz was sucked into a cumulonimbus cloud, climbing at up to 20 m per second (4,000 feet per minute)
to an altitude of 9,946 m (32,600 feet). She lost consciousness due to hypoxia, but regained consciousness after 30 minutes to an hour, and landed still covered in ice after a three and a half hour flight.
In the same storm, 42-year-old Chinese paraglider pilot He Zhongpin died after being sucked into the same storm system and struck by lightning at 5900 m (19,000 feet). His body was found the next day 15 km (9.3 mi) from his last known position prior to entering the cloud.
In 2014 Italian paraglider Paolo Antoniazzi, a 66-year-old retired Army general, died after being sucked into a thunderstorm.
Compared with hang-gliders and paragliders, sailplanes have much higher top speeds (often over 250 km/h), and can more easily escape powerful cumulonimbus clouds by flying away quickly or by using very effective air brakes. A sailplane also has the added benefit of the pilot being able to put the sailplane into a spin to descend rapidly without over speeding.
Cloud suck is also a concern for powered aircraft but is usually not a lethal hazard, except in extreme weather situations. The USS Shenandoah, the first rigid airship built in the United States, and the first in the world to be inflated with helium, was lost in a cloud suck accident associated with a squall line. At about 6:00 AM on 3 September 1925, near Ava in northern Noble County, Ohio, the Shenandoah was suddenly caught in a violent updraft while at an altitude of 2,100 feet (640 m), rising at the rate of a meter per second. At about 6,200 feet (1,900 m) the ascent was checked, but the ship began to descend. When halfway to the ground it was hit by another updraft and began to rise rapidly at an even faster rate. Ultimately the keel snapped, and the ship broke up while still more than a mile above the ground. Shenandoah's commanding officer and 13 other officers and men were killed. Twenty-nine members of the crew survived the break-up, although some received serious injuries.
|
51,560,627 | Cumulonimbus and aviation | Numerous aviation accidents have occurred in the vicinity of thunderstorms due to the density of clouds. It is often said that the turbulence can be extreme enough inside a cumulonimbus to tear an aircraft into pieces, and even strong enough to hold a skydiver. However, this kind of accident is relatively rare. Moreover, the turbulence under a thunderstorm can be non-existent and is usually no more than moderate. Most thunderstorm-related crashes occur due to a stall close to the ground when the pilot gets caught by surprise by a thunderstorm-induced wind shift. Moreover, aircraft damage caused by thunderstorms is rarely in the form of structural failure due to turbulence but is typically less severe and the consequence of secondary effects of thunderstorms (e.g., denting by hail or paint removal by high-speed flight in torrential rain).
Cumulonimbus clouds are known to be extremely dangerous to air traffic, and it is recommended to avoid them as much as possible. Cumulonimbus can be extremely insidious, and an inattentive pilot can end up in a very dangerous situation while flying in apparently very calm air.
While there is a gradation with respect to thunderstorm severity, there is little quantitative difference between a significant shower generated by a cumulus congestus and a small thunderstorm with a few thunderclaps associated with a small cumulonimbus. For this reason, a glider pilot could exploit the rising air under a thunderstorm without recognising the situation – thinking instead that the rising air was due to a more benign variety of cumulus. However, forecasting thunderstorm severity is an inexact science; in numerous occasions, pilots got trapped by underestimating the severity of a thunderstorm that suddenly strengthened. |
586,610 | Downburst | In meteorology, a downburst is a strong downward and outward gushing wind system that emanates from a point source above and blows radially, that is, in straight lines in all directions from the area of impact at surface level. It originates under deep, moist convective conditions like cumulus congestus or cumulonimbus. Capable of producing damaging winds, it may sometimes be confused with a tornado, where high-velocity winds circle a central area, and air moves inward and upward. These usually last for seconds to minutes. Downbursts are particularly strong downdrafts within thunderstorms (or deep, moist convection as sometimes downbursts emanate from cumulonimbus or even cumulus congestus clouds that are not producing lightning).
Downbursts are most often created by an area of significantly precipitation-cooled air that, after reaching the surface (subsiding), spreads out in all directions producing strong winds.
Dry downbursts are associated with thunderstorms that exhibit very little rain, while wet downbursts are created by thunderstorms with significant amounts of precipitation. Microbursts and macrobursts are downbursts at very small and larger scales, respectively. A rare variety of dry downburst, the heat burst, is created by vertical currents on the backside of old outflow boundaries and squall lines where rainfall is lacking. Heat bursts generate significantly higher temperatures due to the lack of rain-cooled air in their formation and compressional heating during descent.
Downbursts are a topic of notable discussion in aviation, since they create vertical wind shear, which has the potential to be dangerous to aviation, especially during landing (or takeoff), where airspeed performance windows are the most narrow. Several fatal and historic crashes in past decades are attributed to the phenomenon and flight crew training goes to great lengths on how to properly recognize and recover from a downburst/wind shear event; wind shear recovery, among other adverse weather events, are standard topics across the world in flight simulator training that flight crews receive and must successfully complete. Detection and nowcasting technology was also implemented in much of the world and particularly around major airports, which in many cases actually have wind shear detection equipment on the field. This detection equipment helps air traffic controllers and pilots make decisions on the safety and feasibility of operating on or in the vicinity of the airport during storms. |
58,991 | Fog | Fog is a visible aerosol consisting of tiny water droplets or ice crystals suspended in the air at or near the Earth's surface. Fog can be considered a type of low-lying cloud usually resembling stratus and is heavily influenced by nearby bodies of water, topography, and wind conditions. In turn, fog affects many human activities, such as shipping, travel, and warfare.
Fog appears when water vapor (water in its gaseous form) condenses. During condensation, molecules of water vapor combine to make tiny water droplets that hang in the air. Sea fog, which shows up near bodies of saline water, is formed as water vapor condenses on bits of salt. Fog is similar to, but less transparent than, mist. |
70,996,357 | Ground deicing of aircraft | In aviation, ground deicing of aircraft is the process of removing surface frost, ice or frozen contaminants on aircraft surfaces before an aircraft takes off. This prevents even a small amount of surface frost or ice on aircraft surfaces from severely impacting flight performance. Frozen contaminants on surfaces can also break off in flight, damaging engines or control surfaces.
Major airports in climates conducive to ground icing will have some kind of ground deicing systems in place. Ultimately it is the pilot-in-command's responsibility to ensure that all necessary deicing processes are carried out before departure.
Planes are often equipped with ice protection systems or icephobic surface coatings to control in-flight atmospheric icing; however, those are not considered substitutes for adequate ground based deicing. |
2,644,317 | Icing (aeronautics) | In aeronautics, icing is the formation of water ice on an aircraft.
Icing has resulted in numerous fatal accidents in aviation history.
Ice accretion and accumulation can affect the external surfaces of an aircraft – in which case it is referred to as airframe icing – or the engine, resulting in carburetor icing, air inlet icing or more generically engine icing. These phenomena may possibly but do not necessarily occur together.
Not all aircraft, especially general aviation aircraft, are certified for flight into known icing (FIKI) – that is flying into areas with icing conditions certain or likely to exist, based on pilot reports, observations, and forecasts. In order to be FIKI-certified, aircraft must be fitted with suitable ice protection systems to prevent accidents by icing. |
79,284,128 | Storm Adam | Storm Adam is a severe polar weather system affecting Lebanon on February 2025 and the surrounding region. |
70,807 | Thunderstorm | A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorms are sometimes called thundershowers. Thunderstorms occur in a type of cloud known as a cumulonimbus. They are usually accompanied by strong winds and often produce heavy rain and sometimes snow, sleet, or hail, but some thunderstorms produce little precipitation or no precipitation at all. Thunderstorms may line up in a series or become a rainband, known as a squall line. Strong or severe thunderstorms include some of the most dangerous weather phenomena, including large hail, strong winds, and tornadoes. Some of the most persistent severe thunderstorms, known as supercells, rotate as do cyclones. While most thunderstorms move with the mean wind flow through the layer of the troposphere that they occupy, vertical wind shear sometimes causes a deviation in their course at a right angle to the wind shear direction.
Thunderstorms result from the rapid upward movement of warm, moist air, sometimes along a front. However, some kind of cloud forcing, whether it is a front, shortwave trough, or another system is needed for the air to rapidly accelerate upward. As the warm, moist air moves upward, it cools, condenses, and forms a cumulonimbus cloud that can reach heights of over 20 kilometres (12 mi). As the rising air reaches its dew point temperature, water vapor condenses into water droplets or ice, reducing pressure locally within the thunderstorm cell. Any precipitation falls the long distance through the clouds towards the Earth's surface. As the droplets fall, they collide with other droplets and become larger. The falling droplets create a downdraft as it pulls cold air with it, and this cold air spreads out at the Earth's surface, occasionally causing strong winds that are commonly associated with thunderstorms.
Thunderstorms can form and develop in any geographic location but most frequently within the mid-latitude, where warm, moist air from tropical latitudes collides with cooler air from polar latitudes. Thunderstorms are responsible for the development and formation of many severe weather phenomena, which can be potentially hazardous. Damage that results from thunderstorms is mainly inflicted by downburst winds, large hailstones, and flash flooding caused by heavy precipitation. Stronger thunderstorm cells are capable of producing tornadoes and waterspouts.
There are three types of thunderstorms: single-cell, multi-cell, and supercell. Supercell thunderstorms are the strongest and most severe. Mesoscale convective systems formed by favorable vertical wind shear within the tropics and subtropics can be responsible for the development of hurricanes. Dry thunderstorms, with no precipitation, can cause the outbreak of wildfires from the heat generated from the cloud-to-ground lightning that accompanies them. Several means are used to study thunderstorms: weather radar, weather stations, and video photography. Past civilizations held various myths concerning thunderstorms and their development as late as the 18th century. Beyond the Earth's atmosphere, thunderstorms have also been observed on the planets of Jupiter, Saturn, Neptune, and, probably, Venus. |
610,527 | Whiteout (weather) | Whiteout or white-out is a weather condition in which visibility and contrast are severely reduced by snow, fog, or sand. The horizon disappears from view while the sky and landscape appear featureless, leaving no points of visual reference by which to navigate.
A whiteout may be due simply to extremely heavy snowfall rates as seen in lake effect conditions, or to other factors such as diffuse lighting from overcast clouds, mist or fog, or a background of snow. A person traveling in a true whiteout is at significant risk of becoming completely disoriented and losing their way, even in familiar surroundings. Motorists typically have to stop their cars where they are, as the road is impossible to see. Normal snowfalls and blizzards, where snow is falling at 3 or 5 centimeters per hour (1 or 2 in/h), or where the relief visibility is not clear yet having a clear field of view for over 9 meters (30 ft), are often incorrectly called whiteouts.
|
454,209 | Wind gradient | In common usage, wind gradient, more specifically wind speed gradient
or wind velocity gradient,
or alternatively shear wind,
is the vertical component of the gradient of the mean horizontal wind speed in the lower atmosphere. It is the rate of increase of wind strength with unit increase in height above ground level. In metric units, it is often measured in units of meters per second of speed, per kilometer of height (m/s/km), which reduces inverse milliseconds (ms−1), a unit also used for shear rate.
|
223,992 | Wind shear | Wind shear (; also written windshear), sometimes referred to as wind gradient, is a difference in wind speed and/or direction over a relatively short distance in the atmosphere. Atmospheric wind shear is normally described as either vertical or horizontal wind shear. Vertical wind shear is a change in wind speed or direction with a change in altitude. Horizontal wind shear is a change in wind speed with a change in lateral position for a given altitude.
Wind shear is a microscale meteorological phenomenon occurring over a very small distance, but it can be associated with mesoscale or synoptic scale weather features such as squall lines and cold fronts. It is commonly observed near microbursts and downbursts caused by thunderstorms, fronts, areas of locally higher low-level winds referred to as low-level jets, near mountains, radiation inversions that occur due to clear skies and calm winds, buildings, wind turbines, and sailboats. Wind shear has significant effects on the control of an aircraft, and it has been the only or a contributing cause of many aircraft accidents.
Sound movement through the atmosphere is affected by wind shear, which can bend the wave front, causing sounds to be heard where they normally would not. Strong vertical wind shear within the troposphere also inhibits tropical cyclone development but helps to organize individual thunderstorms into longer life cycles which can then produce severe weather. The thermal wind concept explains how differences in wind speed at different heights are dependent on horizontal temperature differences and explains the existence of the jet stream. |
README.md exists but content is empty.
- Downloads last month
- 26