Environmental causes of aviation stress

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Five major sources of environmental stress affect pilots. VP-BWD (aircraft).JPG
Five major sources of environmental stress affect pilots.

In aviation, a source of stress that comes from the environment is known as an environmental stressor. [1] Stress is defined as a situation, variable, or circumstance that interrupts the normal functioning of an individual and, most of the time, causes a threat. [2] It can be related not only to mental health, but also to physical health. [3]

Contents

Operating in aviation environments brings a combination of stressors that vary in nature and intensity. In the aviation industry, the main environmental stressors are time pressure, workload and overload, fatigue, noise , and temperature . [4] These stressors are interconnected, meaning that the presence of one may cause others to occur. Scientists have studied each stressor to determine how to minimize its effects. [3]

Environmental stressors

The Bombardier Dash-8 Q400 aircraft involved in the Colgan Air Flight 3407 accident on February 12, 2009. Bombardier Q400 (8960593795).jpg
The Bombardier Dash-8 Q400 aircraft involved in the Colgan Air Flight 3407 accident on February 12, 2009.

Time pressure

Time pressure occurs when there is a time limit on crew members' tasks or operations.[ citation needed ] For instance, China is experiencing more demand for air travel, so airlines in China are offering additional flights with the expectation of high-quality service.[ citation needed ] This puts pressure on crew members to work longer hours on tighter schedules, which causes time pressure [5] [6] and makes human error more likely. Christopher Wickens, a former head of the University of Illinois Urbana-Champaign's Aviation Human Factors Division, found a relationship between response time and error rates: The faster a pilot scans a plane's instrument panel, the less accurate his or her perception will be. [7] James Reason, a researcher of human error, found that time pressure increased the possibility of human error eleven-fold.[ citation needed ]

According to a sample of data from the Aviation Safety Reporting System (ASRS), tight scheduling is the most common cause of time pressure,[ original research? ][ citation needed ] and traffic-jammed fixed-base operators (FBOs) are the second most common cause of aviation stress. [7] The ASRS report showed that various sources of time pressure can cause a chain reaction, with one leading to another.

Sources of time pressure include: [7]

SourcesPercent (%)
Tight scheduling53
Slow FBO servicing39
Passengers showing up late38
Passenger handling issues37
Delays36
ATC congestion32
Inoperative component19
Weather-induced workload18

Time pressure is impossible to avoid entirely, and the goal of researchers is to minimize the resulting human error. Pilots should be careful when facing such pressure, and take time to prioritize and re-evaluate their performances.[ citation needed ] Furthermore, use of checklists is highly recommended.[ citation needed ]

Workload and overload

Workload significantly increases during night flying. Night flight operations DVIDS166818.jpg
Workload significantly increases during night flying.

Workload and overload occurs when the amount of work exceeds a pilot's maximum working capacity. Studies show that this is the most serious environmental cause of aviation stress. [8] There is a strong positive relationship between workload and stress level. [9] According to Karasek’s job strain model, workload stress is caused by shift work and job control. [6] Normally, when pilots get a new job, they start by flying unfamiliar airplanes at unfavorable times, and both of these factors can cause stress. [6] In addition, because fewer people work at night, each person is responsible for more tasks than a daytime employee would be. [6] The second element of Karasek’s model, job control, refers to employees' decision-making responsibility. [6] The higher this responsibility, the higher the stress. [6]

Another study by Wickens, of the University of Illinois, found that workload affects spatial awareness, an essential skill in maneuvering an aircraft through a three-dimensional space with hazards. [10] During flight, pilots must monitor and control six variables. Three of them — yaw, pitch, and roll — relate to aircraft axes and are known as orientation variables. The other three — altitude, position, and lateral deviation — relate to flight path and are known as position variables. [10] Wickens proposes that monitoring and controlling these variables creates a cumulative workload that can lead to poor spatial awareness. [10]

Scientists first tried to minimize human error from workload by enhancing cockpit instrument displays. Cockpit designers studied two elements. [11] The first, frame of instruments, refers to whether the airplane should appear to rotate while the background is stable (exocentric) or the background should rotate while the airplane is stable (egocentric). [10] The designers concluded that, although skilled pilots perform equally well on either type of display, pilots overall perform better with the exocentric display. The second element, degree of integration, refers to whether cockpit displays should be two-dimensional or three-dimensional. The designers found that, even though 2-D displays minimize the ambiguity of information because they require vertical and lateral mental work to convert them into 3-D images, 3-D displays present clearer information for pilots with less work. [10]

Fatigue

The National Transportation Safety Board has suggested that pilots make more procedural and tactical decision errors if they have been awake for a longer-than-average period of time. [12] It reported that, from 1974 to 1992, fatigue was involved in 7.8 percent of Air Force Class A accidents, 4 percent of Army accidents, and 4 to 7 percent of civil aviation accidents. [12] Studies show an inverse relationship between fatigue and physical capability. [13] As fatigue increases, the capability of the body decreases, as do operational tolerance and willingness. [14] Decreasing motivation after a strenuous flight also hurts pilot performance. [14] [15]

Another study showed a similar relationship between fatigue, mental workload, and human performance. Subjective, performance, and psycho-physiological measures were taken for eight participants, ages 22 to 36, on three complexity tasks after sleep loss of one night. [16] The data suggested that as continuous wakefulness increases, simple reaction time also increases, impairing operators' readiness for tasks. [16]

Given the complex operations involved in aviation, avoiding fatigue is challenging. However, research suggests that planning strategies before and after flights can greatly improve pilot alertness and flight safety. [12] The Aerospace Medical Association's Fatigue Countermeasures Subcommittee suggests hypnotics and other substances, some unregulated by the Food and Drug Administration, to maximize the quality of pilots' sleep before flights. The subcommittee's report revealed that the U.S. Air Force uses hypnotic drugs, such as temazepam, zolpidem, and zaleplon, for this purpose. [17] However, since hypnotic drugs can cause sleep inertia upon waking, it is critical to consider the dosage given, the time of day, and the length of the sleep period. A non-medication approach involves healthy sleep practices, naps, exercise, and nutrition. The subcommittee suggested that the quality of sleep can be as important as the quantity, [17] and that taking a nap before a night shift can increase pilot performance. In addition, proper exercise and nutrition help pilots maintain their physical health, which can reduce the negative effects of sleep loss. [17]

Noise

According to research, exposure to noise can cause physical stress and long-term health risks [18] such as hearing impairment, annoyance, and sleep disturbance, [19] all of which can decrease performance.

Hearing impairment can be caused not only by noise during flights, but also by leisure activities like listening to music. According to the International Organization for Standardization (IOS), sound below 70 decibels will not cause hearing impairment for 95 percent of people. [19] However, safe volume thresholds vary based on age and other factors.

Noise can also have the psycho-social effect of annoyance. [18] This occurs between 55 and 60 decibels for about 40 percent of office workers. [18]

A third effect of noise is sleep disturbance. Types of sleep disturbance include: [19]

According to the IOS study, noise affects pilot performance by increasing arousal, decreasing attention to tasks, and altering strategic choices. [18] Furthermore, unwanted noise can drown out other sounds, thus impairing communication between crew members, masking signals in the cockpit, and distracting crew members from significant social cues. [18]

Thermal stress is normally experienced by military pilots. US Navy 030128-N-1810F-004 Hornet launches.jpg
Thermal stress is normally experienced by military pilots.

Temperature

Stress caused by ambient temperature is called thermal stress and is normally experienced by military pilots. Although military aircraft have environmental control systems, the temperature inside the cockpit can quickly rise more than 10 degrees Celsius above the ambient temperature, and the Air Force has suggested that it is possible for cockpit temperatures to exceed 45 degrees Celsius. [20] When such high temperatures occur in humid environments, both mental and physical performance will be degraded. When the aircraft operates close to the ground at high airspeed, the effect is worse because of the aerodynamic heating of the aircraft’s surface. [20]

Thermal stress is also caused by cold temperatures. When military pilots operate at high altitude with low airspeed, the temperature inside the cockpit falls. This affects both health and performance quality. In addition, thermal stress intensifies as the temperature difference between the departing airport and operating altitude increases. For instance, if a military pilot climbs from a 45-degree Celsius departing airport to a –60-degree Celsius operating altitude of 40,000 feet, the rapid change creates thermal stress and hinders pilot performance. [21]

One way to minimize thermal stress is to maintain temperature and pressure in the cockpit within acceptable ranges, using a cockpit temperature management system. However, one problem with this system is that it works by measuring the dry bulb temperature of surrounding air without taking radiant temperature and humidity into account. [20] Radiant heat rises when operating at low altitudes because of the greenhouse effect and kinetic heating on the surface of the aircraft. [20] Furthermore, if cockpit temperature exceeds skin temperature, which is 33 degrees Celsius, [20] the pilot will sweat, leading to increased humidity as the sweat evaporates. Today, the Air Force uses a more advanced air-cooling system that assesses pilots' mean skin temperature and wet bulb globe temperature. [20] By directly measuring pilots' condition in the cockpit, the new system minimizes thermal stress and supports performance quality. [21]

See also

Related Research Articles

Aircraft noise pollution

Aircraft noise pollution refers to noise produced by aircraft in flight that has been associated with several negative stress-mediated health effects, from sleep disorders to cardiovascular ones. Governments have enacted extensive controls that apply to aircraft designers, manufacturers, and operators, resulting in improved procedures and cuts in pollution.

Stress management is a wide spectrum of techniques and psychotherapies aimed at controlling a person's level of stress, especially chronic stress, usually for the purpose of and for the motive of improving everyday functioning. Stress produces numerous physical and mental symptoms which vary according to each individual's situational factors. These can include a decline in physical health as well as depression. The process of stress management is named as one of the keys to a happy and successful life in modern society. Life often delivers numerous demands that can be difficult to handle, but stress management provides a number of ways to manage anxiety and maintain overall well-being.

Aviation safety State in which risks associated with aviation are at an acceptable level

Aviation safety is the study and practice of managing risks in aviation. This includes preventing aviation accidents and incidents through research, educating air travel personnel, passengers and the general public, as well as the design of aircraft and aviation infrastructure. The aviation industry is subject to significant regulation and oversight.

Aviation medicine

Aviation medicine, also called flight medicine or aerospace medicine, is a preventive or occupational medicine in which the patients/subjects are pilots, aircrews, or astronauts. The specialty strives to treat or prevent conditions to which aircrews are particularly susceptible, applies medical knowledge to the human factors in aviation and is thus a critical component of aviation safety. A military practitioner of aviation medicine may be called a flight surgeon and a civilian practitioner is an aviation medical examiner. One of the biggest differences between the military and civilian flight doctors is the military flight surgeon's requirement to log flight hours.

Cabin pressurization Process to maintain internal air pressure in aircraft

Cabin pressurization is a process in which conditioned air is pumped into the cabin of an aircraft or spacecraft in order to create a safe and comfortable environment for passengers and crew flying at high altitudes. For aircraft, this air is usually bled off from the gas turbine engines at the compressor stage, and for spacecraft, it is carried in high-pressure, often cryogenic tanks. The air is cooled, humidified, and mixed with recirculated air if necessary before it is distributed to the cabin by one or more environmental control systems. The cabin pressure is regulated by the outflow valve.

The term workload can refer to a number of different yet related entities.

Pilot error Decision, action or inaction by a pilot of an aircraft

Pilot error generally refers to an accident in which an action or decision made by the pilot was the cause or a contributing factor that led to the accident, but also includes the pilot's failure to make a correct decision or take proper action. Errors are intentional actions that fail to achieve their intended outcomes. Chicago Convention defines 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 the "pilot error" does not include deliberate crash.

Effects of fatigue on safety

Fatigue is a major safety concern in many fields, but especially in transportation, because fatigue can result in disastrous accidents. Fatigue is considered an internal precondition for unsafe acts because it negatively affects the human operator's internal state. Research has generally focused on pilots, truck drivers, and shift workers.

An operating temperature is the allowable temperature range of the local ambient environment at which an electrical or mechanical device operates. The device will operate effectively within a specified temperature range which varies based on the device function and application context, and ranges from the minimum operating temperature to the maximum operating temperature. Outside this range of safe operating temperatures the device may fail.

Studies, which include laboratory investigations and field evaluations of population groups that are analogous to astronauts, provide compelling evidence that working long shifts for extended periods of time contributes to sleep deprivation and can cause performance decrements, health problems, and other detrimental consequences, including accidents, that can affect both the worker and others.

Automation bias Propensity for humans to favor suggestions from automated decision-making systems

Automation bias is the propensity for humans to favor suggestions from automated decision-making systems and to ignore contradictory information made without automation, even if it is correct. Automation bias stems from the social psychology literature that found a bias in human-human interaction that showed that people assign more positive evaluations to decisions made by humans than to a neutral object. The same type of positivity bias has been found for human-automation interaction, where the automated decisions are rated more positively than neutral. This has become a growing problem for decision making as intensive care units, nuclear power plants, and aircraft cockpits have increasingly integrated computerized system monitors and decision aids to mostly factor out possible human error. Errors of automation bias tend to occur when decision-making is dependent on computers or other automated aids and the human is in an observatory role but able to make decisions. Examples of automation bias range from urgent matters like flying a plane on automatic pilot to such mundane matters as the use of spell-checking programs.

Sleep in space Sleep in an unusual place

Sleeping in space is an important part of space medicine and mission planning, with impacts on the health, capabilities and morale of astronauts.

Threat and error management Safety management approach

In aviation safety, threat and error management (TEM) is an overarching safety management approach that assumes that pilots will naturally make mistakes and encounter risky situations during flight operations. Rather than try to avoid these threats and errors, its primary focus is on teaching pilots to manage these issues so they do not impair safety. Its goal is to maintain safety margins by training pilots and flight crews to detect and respond to events that are likely to cause damage (threats) as well as mistakes that are most likely to be made (errors) during flight operations.

Pilot decision making is a process that aviators perform to effectively handle troublesome situations that are encountered. Pilot decision-making is applied in almost every stage of the flight as it considers weather, air spaces, airport conditions, ETA and so forth. During the flight, employers pressure pilots regarding time and fuel restrictions since a pilots’ performance directly affects the company’s revenue and brand image. This pressure often hinders a pilot's decision-making process leading to dangerous situations as 50% to 90% of aviation accidents are the result of pilot error.

Pilot fatigue Reduced pilot performance from inadequate energy

The International Civil Aviation Organization (ICAO) defines fatigue as "A physiological state of reduced mental or physical performance capability resulting from sleep loss or extended wakefulness, circadian phase, or workload." The phenomenon places great risk on the crew and passengers of an airplane because it significantly increases the chance of pilot error. Fatigue is particularly prevalent among pilots because of "unpredictable work hours, long duty periods, circadian disruption, and insufficient sleep". These factors can occur together to produce a combination of sleep deprivation, circadian rhythm effects, and 'time-on task' fatigue. Regulators attempt to mitigate fatigue by limiting the number of hours pilots are allowed to fly over varying periods of time.

Stress in the aviation industry

Stress in the aviation industry is a common phenomenon composed of three sources: physiological stressors, psychological stressors, and environmental stressors. Professional pilots can experience stress in flight, on the ground during work-related activities, and during personal time because of the influence of their occupation. An airline pilot can be an extremely stressful job due to the workload, responsibilities and safety of the thousands of passengers they transport around the world. Chronic levels of stress can negatively impact one's health, job performance and cognitive functioning. Being exposed to stress does not always negatively influence humans because it can motivate people to improve and help them adapt to a new environment. Unfortunate accidents start to occur when a pilot is under excessive stress, as it dramatically affects his or her physical, emotional, and mental conditions. Stress "jeopardizes decision-making relevance and cognitive functioning" and it is a prominent cause of pilot error. Being a pilot is considered a unique job that requires managing high workloads and good psychological and physical health. Unlike the other professional jobs, pilots are considered to be highly affected by stress levels. One study states that 70% of surgeons agreed that stress and fatigue don't impact their performance level, while only 26% of pilots denied that stress influences their performance. Pilots themselves realize how powerful stress can be, and yet many accidents and incidents continues to occur and have occurred, such as Asiana Airlines Flight 214, American Airlines Flight 1420, and Polish Air Force Tu-154.

The SHELL model is a conceptual model of human factors that clarifies the scope of aviation human factors and assists in understanding the human factor relationships between aviation system resources/environment and the human component in the aviation system.

Healthy building refers to an emerging area of interest that supports the physical, psychological, and social health and well-being of people in buildings and the built environment. Buildings can be key promoters of health and well-being since most people spend a majority of their time indoors. According to the National Human Activity Pattern Survey, Americans spend “an average of 87% of their time in enclosed buildings and about 6% of their time in enclosed vehicles.”

Psychological stress and sleep Effects of stress on sleep patterns

Sleep is a naturally recurring state of mind and body, characterized by altered consciousness, relatively inhibited sensory activity, reduced muscle activity, and inhibition of nearly all voluntary muscles during rapid eye movement (REM) sleep, and reduced interactions with surroundings. An essential aspect of sleep is that it provides the human body with a period of reduced functioning that allows for the systems throughout the body to be repaired. This time allows for the body to recharge and return to a phase of optimal functioning. It is recommended that adults get 7 to 9 hours of sleep each night. Sleep is regulated by an internal process known as the circadian rhythm. This 24-hour cycle regulates periods of alertness and tiredness that individuals experience. The correlation between psychological stress and sleep is complex and not fully understood. In fact, many studies have found a bidirectional relationship between stress and sleep. This means that sleep quality can affect stress levels, and stress levels can affect sleep quality. Sleep change depends on the type of stressor, sleep perception, related psychiatric conditions, environmental factors, and physiological limits.

Stress exposure training is the practicing of important existing skills in a stressful and distracting environment to develop the ability to perform them reliably in spite of the circumstances.

References

  1. ↑ Hancok, P.A. (1984). "Environmental Stressor". Sustained Attention in Human Performance: 103–142.
  2. ↑ Staal, Mark A (August 2004). "Stress, Cognition, and Human Performance: A Literature Review and Conceptual Framework": 1–171.{{cite journal}}: Cite journal requires |journal= (help)
  3. 1 2 Motowidlo, Stephan J.; Packard, John S.; Manning, Michael R. (1986). "Occupational Stress: Its Causes and Consequences for Job Performance". Journal of Applied Psychology. 71 (4): 618–627. doi:10.1037/0021-9010.71.4.618. PMID   3804934.
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  5. ↑ Baba, V.V.; Wang, X.; Liu, W.; Tourigny, L. (2009). "Proactive personality and work performance in China: The moderating effects of emotional exhaustion and perceived safety climate". Canadian Journal of Administrative Sciences. 26 (1): 23‐37. doi:10.1002/cjas.90.
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  11. ↑ Mireille, Raby (1994). "Strategic Workload Management and Decision Biases in Aviation". The International Journal of Aviation Psychology. 4 (3): 211–240. doi:10.1207/s15327108ijap0403_2.
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  14. 1 2 George, Shouksmith (Dec 1997). "Flight Stress: Stress, Fatigue and Performance in Aviation". Journal of Occupational and Organizational Psychology. 70 (4): 413.
  15. ↑ G. W., Evans; S. V., Jacobs; D., Dooley; R., Catalano (1987). "The interaction of stressful life events and chronic strain on community mental health". American Journal of Community Psychology. 15 (1): 23–34. doi:10.1007/bf00919755. PMID   3604992. S2CID   35615387.
  16. 1 2 Wilson, Glenn F.; Caldwell, John A.; Russell, Christopher A. (2007). "Performance and Psychophysiological Measures of Fatigue Effects on Aviation Related Tasks of Varying Difficulty". The International Journal of Aviation Psychology. 17 (2): 219–247. doi:10.1080/10508410701328839. S2CID   6517393. Archived from the original on September 25, 2017.
  17. 1 2 3 Caldwell, John A.; Mallis, Melissa M.; Caldwell, J. Lynn; Paul, Michel A.; Miller, James C; Neri, David F. (2009). "Fatigue Countermeasures in Aviation". Aviation, Space, and Environmental Medicine. 80 (1): 29–59. doi:10.3357/asem.2435.2009. PMID   19180856.
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  19. 1 2 3 Passchier-Vermeer, W.; Passchier, W. F. (2000). "Noise exposure and public health". Environmental Health Perspectives. 108 (Suppl 1): 123–131. doi:10.1289/ehp.00108s1123. PMC   1637786 . PMID   10698728.
  20. 1 2 3 4 5 6 Shetty, Janardhana; Lawson, Craig P. (June 2015). "Simulation for temperature control of a military aircraft cockpit to avoid pilot's thermal stress". CEAS Aeronautical Journal. 6 (2): 319–333. doi:10.1007/s13272-015-0149-0. hdl: 1826/14172 . S2CID   110740472.
  21. 1 2 Coffel, E.; Horton, R. (2015). "Climate Change and the Impact of Extreme Temperatures on Aviation". Weather, Climate, and Society. 7 (1): 94–102. doi: 10.1175/wcas-d-14-00026.1 .
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