The first step to understanding the critical impact<unk>  can have on flight safety is to quantify it within the airline environment. An airline's management often struggles to balance rest with duty periods because it strives for maximum crew productivity. However,<unk>  comes as a limitation needing increasing consideration. A study by Reis et Al. investigated the prevalence of<unk>  on a group of Portuguese airline<unk> s. 1500 active airline<unk> s who had all flown within the past six months received a questionnaire. Out of the population, 456 reliable responses were received. A pretest was conducted to determine the viability of the<unk>  scale adopted during the test, called<unk>  Severity Scale (FSS). The purpose of the validation survey was to set a benchmark (i.e. FSS=4) on an acceptable level of<unk>  for the Portuguese culture. The scale ranged from 1 meaning no<unk>  to 7 being high. Participants had one month and a half to respond to the inquiry. Results on physical<unk>  found that 93% of short/medium haul<unk> s scored higher than 4 on the FSS while 84% of long-haul<unk> s scored greater than 4. Mental<unk>  found short/medium haul at 96% and long haul at 92%. The Questionnaire also asked: "Do you feel so tired that you shouldn’t be at the controls?". 13% of<unk> s said that this never happened. 51% of all participants said it happened a few times. Limitations of the study were:<unk>  levels are subjective and research did not attempt to control the number of times<unk> s had available to respond to the questionnaires. Overall the study establishes that<unk> s are subject to high levels of<unk>  on the job. Levels of<unk>  collected were also compared with a validation test conducted on multiple sclerosis patients in Switzerland. These patients showed average<unk>  levels of 4.6 while<unk> s in the Portuguese study scored an average of 5.3. Electroencephalogram probes monitoring physiological activity during a<unk>  study. High prevalence of<unk>  was also revealed in a study by Jackson and Earl investigating prevalence among short haul<unk> s. The study consisted of a questionnaire that was posted on a website, Professional<unk> ’s Rumour network (PPRUNE) and was able to obtain 162 respondents. Of the 162, all being short haul<unk> s, 75% were classified to have experienced severe<unk> . Based on questionnaire results, the study also demonstrated that<unk> s who were highly concerned about their level of<unk>  during the flight often scored higher on the<unk>  scale and thus were likely to experience more<unk> . Not only this, operational factors, for example a change in flights, or from flight into discretionary time often cause the<unk>  to experience greater<unk> . On the other hand, research by Samen, Wegmann, and Vejvoda investigated the variation of<unk>  among long-haul<unk> s. 50<unk> s all from German airlines participated in the research. As participants,<unk> s were subject to physiological measures pre-departure and during flight and filled out routine logs recording their times of sleep and awakening.<unk> s also completed two questionnaires. The first reflecting feelings of<unk>  before and after the flight, recorded before departure, 1-hour intervals during the flight and then immediately after landing. The second questionnaire was the NASA task load index. The second questionnaire also administered during flight, assessed different dimensions including mental, physical and temporal demand as well as performance. Key findings from the study conveyed that: outgoing flights from the home base were rated as less stressful and night flights were rated as the most stressful. The physiological measures found that microsleeps recorded by the EEGs increased progressively with flight duty. Microsleeps are recordings of alpha wave activity and they occur during wakeful relaxation often resulting in loss of attention. They are considered microsleeps if they last less than thirty seconds. Microsleep cases for<unk> s on outgoing flights were half compared to the number on incoming flights back to the home base showing that<unk>  is more prevalent on flights returning home.<unk> s are more prone to microsleeps during the cruise phase of the flight while they are more alert and less likely to experience microsleeps during the take-off, approach and landing phases of the flight. Findings also show that<unk>  was greater during night flights because<unk> s had already been awake for more than 12 hours and would begin duty by the time they were due to go to sleep. Self-assessment<unk> s often have to rely on self-assessment in order to decide if they are fit to fly. The IMSAFE checklist is an example of self-assessment. Another measure that a<unk>  can employ to more accurately determine his level of<unk>  is the Samn- Perelli Seven Point<unk>  Scale (SPS). The evaluation has a scale of 1-7, 1 described as “Fully, Alert and Wide Awake” while 7 “Completely exhausted, unable to function effectively”. All levels in between have descriptions aiding the<unk>  with his decision. Another example of self-assessment is simply a visual and analogue scale. The test is represented by a line with No<unk>  and<unk>  labeled on two ends. The<unk>  will then draw a mark where he feels to be. Advantages of self-assessment include that they are quick and easy to administer, can be added to routine checklists and being more descriptive allow<unk>  to make a better decision. Disadvantages include that it is easy for the<unk>  to cheat and are often hard to disprove. Between 2010 and 2012, more than 6.000 European<unk> s have been asked to self-assess the level of<unk>  they are experiencing. These surveys revealed that well over 50% of the surveyed<unk> s experience<unk>  as impairing their ability to perform well while on flight duty. The polls show that e.g. 92% of the<unk> s in Germany report they have felt too tired or unfit for duty while on flight deck at least once in the past three years. Yet, fearing disciplinary actions or stigmatization by the employer or colleagues, 70-80% of<unk> d<unk> s would not file a<unk>  report or declare to be unfit to fly. Only 20-30% will report unfit for duty or file a report under such an occurrence.
Pilot fatigue
Alarm fatigue
Sympathicolysis
Overpressure
Hypnic jerk
Peroneal strike
Simulator sickness
Contracture