The risk of a Brazilian commercial aviation pilot or co-pilot making a serious mistake is about 50% greater when working from midnight to 6 in the morning. For every 100 hours of flying conducted during this period, jet captains make, on average, 9.5 mistakes of the level 3 type, the most dangerous for the aircraft’s safety. During the other times of day, the likelihood of a major operating mistake being made drops by almost half. In the morning, afternoon and evening, the frequency of this type of mistake drops to around 6.5 per every 100 hours of flying. The data are part of a study by researchers from Cemsa, the Center for Multidisciplinary Studies on Sleepiness and Accidents, and from the Department of Psychobiology of the Federal University of São Paulo (Unifesp), whose activities are financed primarily by the Sleep Institute, one of the Cepids (Centers for Research, Innovation and Dissemination) maintained by FAPESP. The work was published last December in the Brazilian Journal of Medical and Biological Research.
The study analyzed level 3 errors of 987 pilots over six months (from April 1 to September 30, 2005). During this time, these pilots totaled 155,337 hours of flying and, despite the 1,065 failures registered by the electronic systems that record aircraft’s maneuvers, there were no accidents with victims among Brazil’s large airlines. Level 3 errors are those that exceed the standard international operating security limits, such as pushing the control stick beyond the recommended angle, or ignoring the standard, specified procedures of jet use (a classic example is to start descending toward landing without having the plane’s height and speed stabilized at the recommended levels). Although worrying, the study’s conclusion should not be regarded with alarm, because almost all errors are neutralized by corrective maneuvers, do not lead to accidents and are not noticed by the passengers.
The increased incidence of inadequate procedures in the wee hours of the morning did not surprise the scientists. Like truck or bus drivers, or people in the many other professions that require them to start working long after the sun has set or who often work alternating shifts, aircraft pilots are obliged to work for many hours at a time of day when their bodies, like any person’s, should be resting. The outcome of such a journey into the night, which upsets the body’s so-called circadian rhythm, could be no different: tiredness, sleepiness, stress and a bad mood. In sum, a succession of factors that raises the risk of human error in any profession. In aviation, where serious accidents are imputed to human failure in 80% of the cases, things are no different. “Night work causes pilots to perform tasks at a time when they should be resting, and the increased incidence of mistakes is of the same order as what we have found among bus and truck drivers,” states Marco Túlio de Mello, coordinator of Cemsa and of the studies with aircraft pilots. “It is not realistic to be against night flights, but we want to have the information, in order to create strategies to minimize possible errors.”
It is not merely physical tiredness that makes one prone to operating failures. The stress of working alternating shifts, and of sleeping away from home and family often undermines the psychological balance of pilots, who must constantly make delicate decisions in a matter of fractions of seconds in their profession. In another study, not yet published, but presented at congresses, the Cemsa researchers found that the mood of the aircraft captains’ who start their work day between midnight and six in the morning is weaker than the state of mind of those who wield the airplane’s control stick at other times of day. The deterioration was identified even though all pilots state that they often sleep six to eight hours, that they sleep soundly, and that their daily life is not stressful. “Their cognitive capacity is below normal, increasing the likelihood of having accidents due to human failure in the wee hours of the morning,” says Mello.
The study collected information from 91 pilots of commercial lines operating in Brazil, all of whom had been flying for at least ten years and who fly in equal proportion at night and during the day. They answered a questionnaire formulated by a research tool originally designed to measure the psychological state of athletes in competitions: the Brazilian Mood Scale (Brams). This methodology, which can also be applied to non-sportspersons, encompasses 24 items and measures six mood-related topics. In regard to five of them (tension, depression, anger, fitness and fatigue) the performance of the captains that began flying in the wee hours of the morning is worse than that of those who started their work journey at other times of day. On only one item, mental confusion, which measures emotional control and attention level, was the index the same for all the pilots, regardless of when they started flying. According to the researchers, this last piece of data indicates that even when they are tired and eventually sleepy, “red eye” flight captains manage to stay alert. This, however, does not offset the second study’s main conclusion: starting the workday in the middle of the night is far more uncomfortable for a pilot than ending the workday in the wee hours of the morning.
Night flights make people think about these long international trips that take at least ten hours and that link Brazil to Europe or to the United States. However, according to one of the authors of the second study, an experienced jet captain from a major domestic company that started taking a postgraduate course at Unifesp and who prefers, for the time being, to remain anonymous, said that these intercontinental journeys are not the riskiest. “In this type of flight there are generally two captains and two co-pilots and they take turns during the course of the journey. Therefore, all of them have time to sleep and rest,” states the captain. “The greatest tiredness comes in domestic flights in the wee hours of the morning, when the same crew works for hours on end, doing a number of takeoffs and landings.” During the six months of 2005 analyzed in the first study, the flights between midnight and 6 a.m. accounted for 7% of all trips. It may seem little, but there is a tendency for “red eye” flights to grow. “Ten or fifteen years ago, planes used to stay overnight at certain airports,” says the researcher-pilot. “Now they don’t stop, even at night.”
It is much more unusual for a pilot to fall asleep at the control stick of a plane than for a bus or truck driver to doze off at the steering wheel. But it can happen. In 2007, the captains of a Go! Airlines plane that had left Honolulu at 9:15 p.m. for Hilo in Hawaii, a flight that normally takes half an hour, slept for almost 20 minutes in the cabin. Despite insistent contact from the people in the control tower and from other flights in the vicinity, they flew straight over the airport at which they were meant to land and only woke up 50 kilometers beyond. Luckily for the 40 passengers on board the aircraft, the pilots woke up in time to turn around and land the jet safely. In June of last year, a similar episode occurred with an Air India flight carrying one hundred passengers, on the Dubai-Jaipur-Mumbai route, in the wee hours of the morning. Exhausted, the pilots closed their eyes in the cabin, were totally oblivious of the Mumbai airport (their destination) and were awakened from their deep slumber 500 kilometers further by a type of sound warning set off by the air traffic controllers via radio. The crew regained conscience and, as in the case of Go! Airlines, resumed its route and landed safely. These two stories came to a happy end, but they are a warning about the fact that disregard for pilots’ biological clock increases the risk of accidents.
Studies conducted with several professions that work shifts show that staying awake for more than 19 hours or having workdays longer than 12 hours cause symptoms similar to drunkenness. If these two conditions overlap in the wee hours of the morning, the negative consequences can be substantially leveraged. In the case of aviation, there is the added factor that pilots work at 10 thousand meters from the ground, captaining complex and delicate aircraft, often with more than one hundred passengers on board. “We need to think about the possibility of individualizing aviation work schedules,” says Franco Noce, another author of these studies and a doctoral candidate at Unesp. “Perhaps by adopting fixed shifts.” For such as strategy to work satisfactorily, it will be necessary to establish a partnership with airlines and to determine the time of day in which each pilot feels most comfortable.
Captains classified as night owls or early birds may have their work schedule adapted to encompass the hours at which they feel most comfortable, i.e., at night or in the morning, with long breaks, so as not to jeopardize their personal and social activities. By adjusting the work shifts, Cemsa has reduced the ratio of accidents and deaths in bus companies, railroads, power production enterprises and mining companies, all of which work round the clock, straight across the light-darkness cycle. The center’s work has also led to the amendment of traffic laws, which have recently started including an evaluation of sleep disturbances among the drivers of vehicles.
Marco Túlio de Mello’s team has also started studying the mood of other categories involved in the world of aviation, such as the military air traffic controllers and fighter pilots. The researchers hope to establish a relationship of mutual trust with Anac (the National Civil Aviation Agency), Cenipa (the Aeronautical Accidents Investigation and Prevention Center), Icea (the Air Space Control Institute) and the sector’s companies. “We want to help improve flight safety, not to create problems,” states the researcher and Unifesp professor. “But, to do this, we must be aware of the particularities of the sector and of the people who work in it.” In Brazil, pilots are only allowed to fly 85 hours a month at most, but no scientific principles have been adopted to plan the pilots’ work schedules. Icao, the International Civil Aviation Organization, a United Nations agency that promotes air transport safety, released a guideline that is to go into effect on November 19 of this year, requesting that scientific principles and knowledge be adopted to regulate aircraft crew workdays and rest. As one can see, the subject is a highly current one and the issue is still up in the air.
1. Monitoring the decision making process and the mood of fighter and instruction pilots before and after missions (nº 07/04623-1); Type Regular Research Awards; Coordinator Marco Túlio de Mello – Unifesp; Investment R$ 170,586.93 (FAPESP)
2. The influence of shift work and rest periods on military air traffic controllers’ decision-making (nº 07/04566-8); Type Regular Research Awards; Coordinator Marco Túlio de Mello – Unifesp; Investment R$ 79,248.17 (FAPESP)
DE MELLO, M. T. et al. Relation between Brazilian airline pilot errors and time of day. Brazilian Journal of Medical and Biological Research. v. 41, n.12, p. 1,129-1,131, Dec. 2008.