Can aviators life and home-based stressors impair aviation safety?


Photo US Air Force

On a scheduled passenger flight, shortly before the descent into Dublin (EIDW), the Co-pilot of a Bombardier DHC 8-402 (Q400) began to feel unwell and requested to leave the flight deck for a few minutes. Before the Co-pilot left his seat, the Commander felt an unexpected aircraft upset in the form of a yaw and roll to the left. The Co-pilot, who had become incapacitated, had inadvertently made an input to the left rudder pedal. The Commander returned the aircraft to normal flight and the aircraft landed without further incident. There were no injuries. The investigation authority stated that the Co-pilot was probably under some stress on the morning of the flight considering that his young child had a hospital appointment the following day and that stress and lack of quality sleep may have been factors in his feeling unwell and incapacitation during the flight. (See: Stress and lack of quality sleep, factors leading to serious incident)


Life-stress is defined as physical and psychological symptoms that are often a product of difficult life circumstances. Some of this symptoms can be, muscle tension, worry or preoccupation, disrupted sleep and fatigue, change in appetite, or alterations in social interactions such as withdrawal, irritability, or difficulty concentrating.

Can life stressors impair aviation safety?

Pilots are often reluctant to report physical complaints or illnesses because of fear of being temporarily or definitely grounded. Now let‘s consider the aviator who struggles with psychological or emotional issues, it may be even more difficult. Losing flying status is one of the greater fears for any pilot. Can this lead to dangerous situations because aviators are very reluctant to seek help for these problems?

It might be assumed that higher levels of life stress substantially increase vulnerability to error, but many aviators claim that they can compartmentalize to protect performance. What does the research literature tell us about this issue?

Home-based stressors are important chronic stresses for a pilot and should be given consideration when studying the relationship between the pilot, work effectiveness, and safe performance. The study of the degree and effect of home stress on job performance is a necessary part of preventive aviation safety and efforts to create a more effective workplace.

But, only limited research has examined the effects of life stress on skilled performance. Moreover, despite the importance placed on the family as a social support, there has been a little systematic study of the relationships between the pilot’s family life, workplace stress, and performance.

The latter can be a consequence of methodological and ethical limitations inherent in the experimental manipulation of life-stress. This is not a subject easily studied in the laboratory or the field.

There could be at least three specific reasons to explain why strong evidence for a connection between life-stress and performance has been elusive:

(1) Difficulties in the measurement of life-stress

(2) Individual differences in reactions to stressors

(3) Luck. Probably the influence of life stress will go undetected because it only infrequently joins with other circumstances to cause a mishap.

The fact that pilots are unlikely to report stress symptoms makes the life-stress–performance relationship even more difficult to investigate. This under-reporting could occur for at least two reasons:

(1) It is possible that pilots are not fully aware of the effect that stress has on them

(2) Even when they are aware of these effects, a variety of internal and external pressures make it less likely that a pilot will report or seek help for symptoms

Since 1969 several authors have suggested a relationship between life stress and pilot performance but most of these studies suffer from methodological problems. Therefore, confidence in their interpretation and conclusions are limited. The most rigorous studies provide only correlational data which does not allow inferring causality. None the less, the lack of strong empirical support does not mean that life-stress does not impair performance, and a causal relationship might be revealed with other methods.

In the mean time let’s review some of these studies about how life stress affects performance that, as stated before, have provided correlational data that is noteworthy.

There have been many hypotheses about how life stress affects pilot performance. Several authors have suggested that those experiencing life stressors may be more likely to commit errors because they are likely to be thinking about the stressor rather than devoting all of their cognitive resources to the task at hand. A senior U.S. Air Force flight surgeon suggests that, while pilots may have some ability to keep life-stressors from entering the cockpit and interfering with performance, each also has a level of stress or a specific stressor that is likely to significantly interfere with this ability to compartmentalize. Another author contends that even high-functioning pilots under some combination of stresses—intrapersonal or interpersonal—may develop personality reactions, anxiety and somatic symptoms, which reduce effectiveness and produce inadequate functioning and other hypothesize that stress indirectly impairs performance by disrupting sleep and impairing one‘s ability to pay attention.

Several US Navy studies explored the influence of personality and life changes on the likelihood of having an accident. Results indicated that certain items discriminated between those who were causally involved in aircrew error accidents and those who were not. Five items were more likely to be causal:

(1) Recently became engaged

(2) Made any recent decisions regarding the future

(3) Have difficulty with interpersonal relationships

(4) Recently have a death in the family or recently lose a close friend through death

(5) Recently have trouble with superiors or recently have trouble with peers or subordinates.

Another study surveyed 8,800 Canadian airline transport, commercial and senior commercial, helicopter and private pilots in an attempt to establish a link between certain life events, pilot characteristics, and accidents. While the analysis revealed many accident markers, preoccupations about separation, divorce or business decisions appeared most frequently. Although it‘s impossible to determine the direction of the relationship (Did accidents prompt preoccupation with a business decision or vice versa?), it is noteworthy that many of these background stressors and accidents are frequently correlated.

Across the Atlantic one study discussed results from 149 British military flying accident investigations. The author reported a direct link between a stressful life event and accidents in two cases and life stress as a possible contributing factor in 11% of the accidents.

Near in space and time was completed an in-depth study of various sources of stress and coping mechanisms in British commercial pilots. The authors found that home-based factors were important in both their impact on work itself and on the ability to cope with stress. While there were many interesting findings, some appear particularly relevant to the discussion of pilot‘s perception of the stress–performance relationship.

Taking into account those that answered the symptoms occurring “usually” or” almost always”, some of the findings are:

  • 2% of the pilots said they could tell when they experienced stress because at work they usually or ―almost always felt tired
  • 1% said they experienced recurring thoughts during periods of low workload
  • 1% experienced a tendency to not listen as intently
  • 4% had a tendency to worry
  • 4% reported decreased concentration
  • 2% reported becoming detached from tasks at hand.

When the pilots who reported these symptoms occurring “sometimes” are included, the percentages increase substantially. For example, using this less conservative approach, over 45% indicated that they experienced decreased concentration at least sometimes as a result of stress. Nearly 93% indicated that they thought negative life events could affect pilot performance. The authors suggest that many of the noted effects are cognitive in nature.

Back in America, a study of U.S. civilian pilots examined the effects of corporate instability on commercial pilots by contrasting pilots from stable airlines with pilots from unstable airlines. The authors noted substantial and statistically significant differences between the two groups. Pilots from unstable airlines were far more likely to report symptoms such as feeling hopeless about the future, irritability, inability to concentrate, decreased attention, excessive anger, procrastination, general dissatisfaction, crying easily or feeling like crying, and having a pessimistic attitude.

The FAA published a study which purpose was to examine the relationship between self-reported home stress, work stress, and perceived performance in U.S. coast guard (USCG) pilots. The results showed that as Home Stress scores increased, so did pilots’ rating of Job Stress. However, neither Home Stress nor Job Stress, by itself, was significantly related to self-reported Flying Performance. However, pilots perceived their own Flying Performance to be detrimentally affected when stress in the home carried over to the work setting. The more home stress was felt in the workplace (Home Stress at Work), the higher pilots’ ratings of Job Stress.

Specific life/home stresses

Life stress is a product of difficult life circumstances. Among those circumstances are relationship difficulties, financial worries, health concerns, bereavement issues, work related problems, and separation from family. Also, irregular duty periods and missing out on activities at home can spur a significant and detrimental cycle of stress.


Photo Daily Record 

Stability at home often is undermined by the nature of the profession. Stability is difficult to achieve when dealing with extended absences or irregular duty periods. Demanding schedules with very little flexibility could have social consequences that often are not appreciated by those who work 9-to-5. Moreover, many people who work rotating shifts reduce their social activities because such schedules do not allow consistent involvement, which can lead to a feeling of social isolation. Limiting relationships to workplace colleagues can also lead to feelings of social isolation among the family.

On the other hand, it is common to end a duty cycle or shift period feeling too exhausted to participate in family functions, this can cause spouses and children to feel neglected. This is especially true when the duty period occurs between 1500 and 2300 while the family is home and family and evening social activities are missed. Friends or relatives with no exposure to the same lifestyle may not understand.

The “intermittent husband syndrome” is an example of situations common to professions in which a spouse is regularly away from home for extended periods. The much-anticipated reunion can create as much stress as joy. In situations where male pilots are away and their female partners are left at home, research suggests that families suffer from more stress-related illness and marital difficulties than those where husbands do not travel. Family routines become disrupted, with negative effects on wives and children.

In addition to these known effects of irregular duty periods, the way aviation jobs can consume attention while on duty and affect personalities while off duty may often produce difficulty in readjusting to life back at home.

Aviation professionals often experience high job demands, inflexibility and time pressure. They live with strict deadlines, often balancing conflicting demands, and stress is the body’s natural response. Stress, combined with the competitive “Type A personality” so common in the industry, can take a toll on physical or psychological health, or on satisfaction with the job or with a marriage. The inability to meet family obligations because of the time and energy required for work compounds the stress felt on the job. A vicious cycle can develop.

One study asked pilots to rank order the sources of stress in their lives. Of the 53 items in the questionnaire only 14 items related to domestic stress even so 7 domestic stress items were among the top ten stressors. The top three ratings of the most stressful situations were domestic stress items. They were

(1) Death of a child

(2) Death of a mate

(3) Death of a parent

In the FAA study previously mentioned of the 29 items measuring home stress the following were found as causing much stress and very much stress:

  • Build up of tasks, duties, and things to do
  • Degree to which home life is way I want it
  • Quality of relationship with partner
  • Lack of money
  • Disappointed others don’t meet expectations
  • Constant, ongoing irritations
  • ‘Good’ use of time at home and how spent
  • Conflicts of interests, resulting compromises
  • Issues associated with children
  • Others not obeying / things that go wrong

How home stress is experienced at work

The most frequently reported ways in which home stress was felt at work were fatigue and rumination about the home based stress.

As found in the civilian British pilots cited previously, the FAA study found that about one-fifth of pilots reported that they could usually or always tell when they were experiencing home stress at work by experiencing the following symptoms:

  • Feeling tired due to disrupted sleep
  • Having a tendency to worry
  • Intruding thoughts during low workload.

On the other hand items of home stress at work that were significantly correlated with poorer flying performance were

  • Tendencies to worry at work
  • Not listen as intently
  • Feeling slowed down at work

Meanwhile, home stress at work was significantly and negatively related to specific flying performance items of:

  • Being ahead of the game
  • Smoothness and accuracy of landings
  • Degree of airmanship exhibited
  • Ability to divide attention

Other symptoms noted by several authors were:

  • Irritability
  • Inability to concentrate
  • Decreased attention
  • Memory difficulty


Photo Adventures of Cap’n Aux

By what mechanisms might life stress impair performance?

There are hints in the studies described above that cognitive processes may be affected by life-stress.

With regard to mechanisms by which life stress may impair performance several researchers found that pilots report concentration and attention management issues when under life stress. Also, some evidence suggests that life-stress may negatively influence underlying cognitive processes such as information processing, working memory, problem-solving and decision-making. To the degree that these important processes are affected, it might be expected an associated decrement in performance.

Additionally, there is evidence suggesting that life-stress disrupts sleep and leads to increased levels of fatigue, which in turn impairs cognitive and social performance.

Studies offer some support for the notion that life-stress might impair performance by diverting attention from the task at hand or by pre-empting working memory. If we cautiously extend these findings to pilots performing real world tasks, it is possible that pilots may pay more attention to stress-related thoughts (e.g., thinking about relationship problems, a recent argument, problems on the job) or to increases in autonomic arousal. Acting as a secondary task, these preoccupations would divide attention and lead to deficits in working memory capacity, making it more probable that a pilot might fail to notice critical phenomena and forget to perform tasks that are not strongly cued by the environment.

There are several potential routes by which life-stress may directly or indirectly impair performance:

  1. It may lead to decreased quantity and quality of sleep, leading to a state of fatigue, which is known to impair performance in specific ways.
  2. It may undercut motivation to perform one‘s job well. While the approach to tasks perceived to be critical may not change, tasks viewed as less significant (e.g., following checklist procedures) may receive less attention than is appropriate.
  3. It may negatively influence affective state, leading to higher levels of frustration, irritability/ anger, anxiety, or depression. These mood states can negatively influence the interpersonal atmosphere in the cockpit, potentially leading to ineffective crew resource management. To the degree that life-stress creates a sense of dissatisfaction, pessimism and depression, motivation and task engagement may decrease. A crewmember may become more hostile or withdrawn, creating an interpersonal environment that might lead to a less than the optimal exchange of important task–related information.
  4. Life-stressors may increase levels of off-task thinking or worry, which acts to divide finite attentional resources necessary for acquiring new information and effectively managing tasks.
  5. Efforts to suppress unwanted (stressful) thoughts consume a portion of finite cognitive resources, thereby impairing task performance.
  6. Emotionally draining events, such as arguments with a spouse or boss, may cause fatigue or demotivation.

In other words, demands at home can produce preoccupied, distracted and fatigued workers, a perilous condition in a safety sensitive job.

Coping strategies

The importance of home life in mediating stress was also seen when pilots rated the importance of various coping strategies. Stability in relationships and home life were the most important factors in helping pilots cope with stress.


Photo U.S. Air Force

From a list of 33 coping strategies, over 80% of pilots rated 11 coping mechanisms as having importance to paramount importance. The three most important strategies all involved family support. The first two, stability of relationship with spouse and a smooth and stable home life, were rated as important to paramount importance by 100% of the pilots. The third item, talking to an understanding spouse or partner, was rated as important to paramount importance by 89% of the pilots.

Potential coping strategies, such as fostering stability at home, often are undermined by the nature of the profession. As a pilot’s partner/spouse support system became less effective, the pilot began to lose the most important ways of coping with stressors. It might be speculated that, if home-based stress increases significantly and partner support lessens, the pilot’s cognitive functioning may be at risk for compromise and reduced efficiency. If additionally, the pilot may be moving closer to a negative significant life event such as divorce, separation, or alienation, the possible ramifications on cockpit error could be even higher.

Other coping mechanisms rated as very useful in coping were:

  • Psychological detachment (physical separation from the workplace and mental disengagement through activities that put focus on something else)
  • Sleep
  • Planning ahead
  • Working things out by logic
  • Physical pastimes/exercise
  • Partner efficient at looking after things

Coping strategies significantly correlated with higher ratings of flying performance were spouse/partner who had prior knowledge of flying or who flies and hobbies. The coping strategy of living in a nonflying social environment was significantly related to a lower Flying Performance score.

It is suggested that the first warning signs of home-based psychological distress may be more evident in the daily work activities rather than in cockpit error. If support services and management recognized the early warning signs at work that were symptomatic of home-based stress, they could provide timely intervention before the occurrence of more serious flying performance decrements.

Certainly, continued support of family and home services will have beneficial effects.

Having a better appreciation of the effects of life stress on skilled performance is underscored by the likelihood that the majority of skilled performers are prone to under-report such effects. Aviators will be much more likely to acknowledge the effects of life–stress to the degree that their organizations destigmatize emotional and psychological issues and improve the medical community‘s handling of these cases.

The importance of stress to pilot job performance has been an aviation safety issue for many years often discussed under the category of pilot error or human factors. However, many questions remain regarding the relationship between life stress and flying performance.

The interconnections of stress variables and their effects on flying performance are undoubtedly very complex. Moreover, subjects cannot be randomly assigned to levels of life stress; thus, other undetermined variables may co-vary with stress.

Even for the most expert or skilled performers, it is likely that cognitive processes, at one time or another, will be affected by life stress in a way that impairs performance. We must continue to look for better methodologies and should not dismiss the potential influence of life stress on performance because of the current lack of strong empirical data

Further research into the impact of the family as both a source of stress and support could help the aviation community make wise policy decisions regarding family-work issues and appropriate intervention, giving insight into the interplay of the pilot’s coping strategies and personal support system.


  1. The Effects of Life-Stress on Pilot Performance. James A. Young. NASA Ames Research Center, Moffett Field, California. December 2008
  2. The relationship between aviator’s home-based stress to work stress and self-perceived performance. Fiedler, E.R., Della Rocco, P.S., Schroeder, D.J., & Nguyen, K.DOT/FAA/AM-00/32. Oklahoma City, Oklahoma, US. U.S. Federal Aviation Administration (FAA). October 2000
  3. On the Home Front. A stressful family life can affect performance in the cockpit. Patrick Chiles. AeroSafety World August July–August 2011.


  1. Stress and lack of quality sleep, factors leading to serious incident
  2. Sleep loss in aviation. Let’s review


minime2By Laura Duque-Arrubla, a medical doctor with postgraduate studies in Aviation Medicine, Human Factors and Aviation Safety. In the aviation field since 1988, Human Factors instructor since 1994. Follow me on facebook Living Safely with Human Error and twitter@dralaurita. Human Factors information almost every day 


Stress and lack of quality sleep, factors leading to serious incident


Photo (C) Steve Morris

Final report published: 20 January 2017

Serious incident: An incident involving circumstances indicating that an accident nearly occurred. Note 1.— The difference between an accident and a serious incident lies only in the result… ICAO ANNEX 13 Chapter 1, Definitions.

Air Accident Investigation Unit Ireland


Bombardier DHC 8-402 (Q400), G-ECOP

Dublin CTA near point VATRY. 27 April 2016 

Published: 20 January 2017

 AAIU Report No: 2017-002

State File No: IRL00916026

Report Format: Factual Report

Aircraft Type and Registration: Bombardier DHC 8-402 (Q400), G-ECOP

Date and Time (UTC)4: 27 April 2016 @ 14.16 hrs (Timings in this Report are quoted in UTC; to obtain local time add 1 hour )

Location: Dublin CTA5 near point VATRY (Reporting point at position N52 33.3’ W005 30.0)

Type of Operation: Commercial Air Transport

Persons on Board: Crew – 4 Passengers – 33

Injuries: Crew – Nil Passengers – Nil

Nature of Damage: None


On a scheduled passenger flight, shortly before descent into Dublin (EIDW), the Co-pilot began to feel unwell and requested to leave the flight deck for a few minutes. Before the Co-pilot left his seat, the Commander felt an unexpected aircraft upset in the form of a yaw and roll to the left. The Co-pilot, who had become incapacitated, had inadvertently made an input to the left rudder pedal. The Commander returned the aircraft to normal flight and the aircraft landed without further incident. There were no injuries.


1.1 History of the Flight

The aircraft departed Exeter Airport (EGTE) at 13.37 hrs on a scheduled flight to EIDW with 33 passengers, two flight crew members, a Senior Cabin Crew Member (SCCM) and a Cabin Crew Member (CCM) on board. On this sector, the Commander was Pilot Flying (PF) and the Co-pilot was Pilot Monitoring (PM). Having briefed the expected approach and completed the descent checklist, the aircraft was cleared to descend to FL150. As the aircraft entered the Dublin CTA at point VATRY, the Co-pilot made a request to leave the flight deck to use the lavatory. The Commander called the SCCM to attend the flight deck while the Co-pilot was absent. Following this call the seatbelt sign was switched on. After the call was completed the Commander felt the aircraft unexpectedly yaw to the left and rolled approximately 18 degrees. The Commander disconnected the autopilot, restored a wings level condition and retarded the engine power to maintain a stable descent. He then tried to ascertain what had caused the unexpected aircraft upset. The aircraft symbol showed at full deflection on the PFD Primary Flight Display so he checked for a possible runaway of the rudder trim but this indicated normal. Simultaneously, the SCCM called the flight deck to see if all was okay and the Commander told her to standby. Asking the Co-pilot for his opinion, the Commander then realised that the Co-pilot was unwell. The Commander stated that the Co-pilot had become incapacitated and was not responsive to verbal communication or physical stimulation for a period of less than one minute.

Having ensured that the aircraft was on a safe flight path, the Commander called the Cabin Crew for assistance. He then made a PAN (Urgency) call to Dublin ATC, informed them of pilot incapacitation and requested priority for an approach to Runway (RWY) 28. The SCCM proceeded to the flight deck and rendered assistance to the Co-pilot. It was decided that for the approach and landing that the CCM would occupy the crew jump-seat once she had secured the cabin for landing and that the SCCM would manage the cabin. They ensured that the Co-pilot’s seat was moved back from the controls and that his harness was locked.

The Co-pilot gradually recovered and was able to converse approximately five minutes after his initial symptoms arose. He did not take any further part in the conduct of the flight and declined therapeutic oxygen which had been made available by the Cabin Crew. With the CCM occupying the jump-seat, an able-bodied passenger (ABP) was briefed and occupied the CCM crew seat at the rear of the passenger cabin for landing.

Some holding delays were being experienced by inbound traffic at EIDW. However, ATC facilitated the flight with a direct routing and priority approach. The aircraft landed without further incident at 14.37 hrs and taxied to Stand 205L, where it was met by the Emergency Services. Paramedics immediately attended to the Co-pilot while the passengers remained seated. When the aircraft arrived on stand, the Co-pilot had recovered considerably; however, he was brought to a hospital in Dublin as a precaution.

1.2 Subsequent Events

The remainder of the Crew were stood down from subsequent duties and positioned home to the UK later that day.

The Co-pilot was kept in hospital overnight for observation before being released. It was determined that the Co-pilot suffered a brief loss of consciousness (syncope) due to a sudden drop in blood pressure. This condition can commonly occur in healthy people and recovery is normally prompt and without any persisting ill effects. At the time of writing, the Co-pilot had not yet returned to flying duties with the Operator.

1.3 Human Factors

Prior to the flight, the Crew positioned by taxi from their base at Southampton (EGHI) to EGTE. None of the other crew observed anything unusual about the Co-pilot that would highlight any form of medical issue, only that he seemed distracted due to the fact that his young child had a hospital appointment the following day. It was also reported that his recent sleep pattern had been disrupted.

1.4 Operator’s Safety and Emergency Procedures

The Operator prescribes the actions to be taken in the event of Pilot incapacitation in its Operations Manual Part B (Ops Part B), Safety and Emergency Procedures (SEP) and the aircraft’s Quick Reference Handbook (QRH). The procedure states that the flight crew may require assistance of a CCM to secure the seat and harness of the incapacitated flight crew member, administer oxygen if required and to occupy the flight deck jump-seat in order to assist with checklists. In this case, the CCM had some problems setting up the spare headset from the jump-seat position as the headset jack plugs had not been connected to the communications box nor was the microphone selected.

The event unfolded rapidly and consequently the Crew dealt with the situation without reference to the QRH or Ops Part B, SEP; however, the required elements of the relevant drills were covered. The Operator subsequently found that the QRH ‘Pilot Incapacitation’ checklist incorrectly referred to Ops Manual Part B, SEP Section 4-17 (the correct reference should have been Section 4-16).

Whilst the Operator monitored the developing situation, it did not activate its Crisis Management Centre (CMC). As part of its own investigation, the Operator chose to review the criteria used for activation of the CMC.

1.5 Personnel Details

1.5.1 Commander

The Commander was the holder of an Airline Transport Pilot Licence (Aeroplanes) issued by the UK CAA on 1 February 2013. This licence contained a Type and Instrument Rating on the DHC 8; he completed an Operator Proficiency Check (OPC) on 2 March 2016. His Medical Certificate (Class 1) was valid to 9 March 2017. At the time of the event, the Commander had 5,100 hours total flying time, of which 4,300 hours were on the DHC 8.

1.5.2 Co-pilot

The Co-pilot was the holder of an Airline Transport Pilot Licence (Aeroplanes) issued by the UK CAA on 2 March 2010. This licence contained a Type and Instrument Rating on the DHC 8; he completed an OPC on 17 December 2015. His Medical Certificate (Class 1) was valid to 27 April 2017. At the time of the event, the Co-pilot had 5,400 hours total flying time, of which 200 hours were on the DHC 8.

1.6 Crew Resource Management

Crew Resource Management (CRM) is an essential element in the operation of commercial aircraft. Both Flight Crew and Cabin Crew are trained in CRM procedures, which involve efficient crew co-ordination, effective communications, improved situational awareness and conflict resolution techniques. CRM optimises the use of all available resources, facilitating safe and effective operation of the aircraft.

1.7 Safety Actions by the Operator

As a result of this occurrence, the Operator conducted an internal safety investigation and undertook the following actions:

  • An amendment was made to the Q400 QRH, Page 8.7, with reference to ‘SEP Manual, Section 4.16’.
  • A review of its CMC activation criteria was carried out.
  • Cabin Crew Initial and Cabin Crew Refresher Training programmes were revised to include the use of the flight deck jump-seat headset.


The Co-pilot was probably under some stress on the morning of the flight considering that his young child had a hospital appointment the following day. Stress and lack of quality sleep may have been factors in his feeling unwell and incapacitation during the flight. In this event the Co-pilot requested permission to leave the flight deck at a time when the flight crew’s workload began to increase at the commencement of descent. Before the Copilot could leave the flight deck, the Commander responded to an unexpected aircraft upset caused by an involuntary input from the Co-pilot as he became increasingly unwell.

Following the unexpected aircraft upset, the Commander reacted promptly and ensured that the aircraft was returned to a safe flight path. Only then did he realise that the Co-pilot was unresponsive and had become incapacitated.

As the Commander was already in communication with the SCCM, he considered the standard call to alert Cabin Crew was not required. The Crew reacted to the situation in an effective and co-ordinated manner, carried out the incapacitation drills and the CCM occupied the jump-seat for approach and landing. Notwithstanding a minor issue with a headset, there was good communication between the Commander and Cabin Crew. The Commander, assisted by the Cabin Crew, ensured that the Co-pilot was secure in his seat and away from the controls while the cabin was secured for the approach and landing with an ABP occupying the aft crew seat.

The situation was dealt with in an efficient manner by the Commander with good use of CRM by the Crew; in its own safety report the Operator commented that ‘the reaction by the rest of the crew was swift and effective and they should be commended for their calmness, initiative and attitude throughout the incident.’

The Operator took action to correct some minor issues identified by its internal safety investigation. As a result, this Investigation does not make any Safety Recommendations.


Stress and fatigue can affect pilot performance in many ways. Usually, we look at them and their effects in their chronic states. The cognitive and performance decrements due to chronic stress and sleep loss are very well and widely known. Nonetheless, as this case dramatically shows, the effects of acute stress and sleep loss should not be neglected. Special attention has to be given to high acute stress induced by family and life issues and its capacity to induce in-flight pilot incapacitation and/or negatively affect pilot performance.

This arises, again, the need and high importance of airline support and counselling services for flight crews to which the pilot can go freely without worrying about the decline in their income or the fear of reprisals from the airline.

Pilot in-flight incapacitation always has the potential to produce an aviation serious event.The safe operation of an aircraft places many demands on the pilot and crew. In order to meet these demands, a crew member requires good mental and physical health. The impairment of physical or mental capability, acute o chronic, has serious implications for the safety of flight.



minime2By Laura Duque-Arrubla, a medical doctor with postgraduate studies in Aviation Medicine, Human Factors and Aviation Safety. In the aviation field since 1988, Human Factors instructor since 1994. Follow me on facebook Living Safely with Human Error and twitter@dralaurita. Human Factors information almost every day 

Sleep loss in aviation. Let’s review

On January 25, 2016, in darkness and hazy weather conditions, the flight crew of an ATR 72 lined up the aircraft on the runway edge lights along the right-hand side of runway 27L instead of the runway centerline lights of runway 27L.

This resulted in a misaligned take-off roll over the elevated runway edge lights along the right-hand side of runway 27L leading to damages to the runway edge lights and the aircraft itself.

A combination of environmental, operational, and human factors contributed to the sequence of events:

– Dark night operation

– Reduced visibility

– Runway and taxiway environment, including an extra tarmac width on runway 27L, the absence of runway shoulder markings, the absence of taxiway centerline lighting, and the use of a displaced threshold

– Flight crew divided attention unintentionally provoked by the before take-off procedures and checks

– Flight crew fatigue

The serious incident occurred in dark night and under instrument meteorological conditions (IMC).

Despite the fact that the actual flight and duty time of the flight crew did not violate any flight and duty time requirements, the Danish Investigation Authority considered the flight crew to be fatigued in the morning of the accident day. Because of fatigue, flight crew performance was impaired equivalent to more than 0.05% blood alcohol concentration impairing flight crew vigilance and reaction times and might have impaired the flight crew decision- making process and the flight crew night vision adaptation and visual acuity.

(See: Pilots fatigue lead to a Danish Air Transport ATR 72 serious incident)


Sleep loss and circadian disruption created by flight operations can degrade performance and alertness, we all know that. Scientific examination of these psychological/physiological parameters has established a direct relationship between their degradation and errors, incidents and accidents. We all know that, too. Nevertheless, despite that knowledge, fatigue remains an ever present danger in flight operations.

The operational demands of the aviation industry and the growth in global long-haul, regional, overnight, and short-haul operations will continue to increase the 24hour/7days requirement on flight crews. Therefore, shift work, night work, irregular work schedules, unpredictable work schedules, and time zone changes will continue to be commonplace components of the aviation industry. These factors pose known challenges to human physiology, and because they result in fatigue and performance impairment they pose a risk to safety.

Extensive data are available that clearly establish fatigue as a significant safety concern in all modes of transportation and in 24-hr shift work settings. The safety risk posed by human fatigue in transportation has been recognized and addressed over 100 years. Its 24/7 operational demands can easily lead to degradation or impairment in all aspects of human capability particularly cognitive performance including decision-making, attention, reaction time, learning, memory and communication skills. When individuals performing safety-critical functions are affected by fatigue, there is a high risk of fatalities, injuries and environmental hazards as a result of accidents or incidents.

Additionally, there are other associated costs of fatigue, such as the financial costs of reduced productivity and potential liability issues.


On 2006 a study at UCE Birmingham on the effect of fatigue on 162 short-haul pilots reported 75% of the pilots had experienced severe fatigue with 81% considering the fatigue to be worse than two years previously.

On 2012 the European Cockpit Association carried out a survey about self-assess of the level of fatigue experienced by pilots. More than 6.000 European pilots were surveyed between 2010 and 2012 and the results were published as Barometer on Pilot Fatigue. Some of the survey results are:

  • Over 50% of surveyed pilots reported having experienced fatigue as impairing their ability to perform well while on flight duty.
  • 4 out of 5 pilots reported having coped with fatigue while in the cockpit, according to polls carried out in Austria (85%), Sweden (89%), Germany (92%) and Denmark (93%).
  • In the UK (43%), Denmark (50%), Norway (53%) and Sweden (54%) the surveyed pilots reported falling asleep involuntarily in the cockpit while flying. In the UK, a third of the pilots said to have woken up finding their colleague sleeping as well. 65% of Dutch and French pilots stated they have trouble with “heavy eyelids” during flight.
  • 70-80% of fatigued pilots would not file a fatigue report or declare to be unfit to fly. Only 20-30% will report unfit for duty or file a report under such an occurrence.
  • More than 3 out of 5 pilots in Sweden (71%), Norway (79%) and Denmark (80-90%) acknowledge having already made mistakes due to fatigue, while in Germany it was 4 out of 5 pilots.

On August 2013 was published the study Prevalence of Fatigue in a Group of Airline Pilots based on a 2012 survey of 1500 commercial airline Portuguese pilots, commanders (captains) or first officers between the ages of 20 and 65 who were on active duty and had flown during the previous six months. The assessed their fatigue using the nine-item Fatigue Severity Scale. Some of the results of the study are:

  • More than 90 percent reported having made fatigue-related mistakes in the cockpit
  • 66% said that they had more than once been so tired that they should not have been at the controls
  • Despite they admitted having been fatigued while flying, 82% said they had never reported themselves as “unfit for flight as a result of accumulated fatigue,” and only 11 percent said they had done so only once
  • Pilots flying medium- and short-haul flights —typically less than six hours long with multiple legs — reported higher levels of fatigue than those who flying long-haul flights

The US National Sleep Foundation published in March 2012 a 1,087 transportation professionals poll, which included 220 pilots, interviewed about their sleep habits and work performance. Some of the results of the pilot survey are:

  • 23% admitted sleepiness has affected their job performance at least once a week
  • 20% said sleepiness had caused safety problems on the job
  • 37% of pilots reported that their current work schedule did not allow adequate time for sleep
  • 50% said they rarely or never got a good night’s sleep on work nights

Fatigue was identified as probable cause, contributing factor, or a finding in 20% of 182 major NTSB investigations completed between 1 January 2001 and 31 December 2012, ranging from 40% of highway investigations to 4% of marine investigations.

Human fatigue can have a role in accidents causation by producing performance impairment when the individual is awake, or by inducing microsleeps or producing an uncontrolled and unintentional full sleep episode.



Fatigue refers to a physiological state of reduced mental or physical performance capability in which there is a decreased capacity to perform cognitive tasks and an increased variability in performance. It is an enabler of poor judgment and decision-making, slowed reaction times, and loss of situational awareness and control. It degrades a person’s ability to stay awake, alert, and attentive to the demands of controlling a vehicle safely.


Fatigue increases the desire to obtain sleep. It is also associated with tiredness, weakness, lack of energy, lethargy, depression and lack of motivation. To make matters worse, fatigue actually impairs the ability to self-judge just how fatigued the person is.

Fatigue results from an imbalance between:

  • The physical and mental exertion of all waking activities (not only duty demands); and
  • Recovery from that exertion, which, except for recovery from muscle fatigue, requires sleep.

It is associated with sleep loss, extended wakefulness, high mental and/or physical workload, long unbroken periods of work -known as ‘time-on-task’ fatigue-, and circadian phase. In addition, there are acute influences such as monotony, boredom and environmental factors at the workplace (i.e. at the airport during long breaks or on the flight deck) that can interact with the factors cited above to precipitate the apparition of fatigue.

Sleep loss and extended wakefulness

Several factors are involved in the development of a loss of sleep and fatigue in aviation: less-than-optimal sleeping conditions, early reporting time, rotating and non-standard work shifts, night duty, the time on duty, long spans of wakefulness during the working day, the number of sectors, the number of time- zones crossed and the number of consecutive flying days.

There are other factors, like stress, disease, noise, vibrations/movement, or an upright sleep posture that can also influence sleep quantity and quality. Indeed, it should be emphasized that 8 hours of sleep may fail to provide restitution if it is highly fragmented as a result of these or other disturbing factors. This is particularly likely to be the case with sleep taken during the day when a range of environmental factors often contributes to sleep disturbance.

The main cause of problems associated with the unusual rest and activity patterns experienced by aircrew is the conflict with the biological clock which synchronizes our activity with that of the environment. This clock guides the circadian rhythm by activating the body, through increased metabolism during the day, and reduced levels at night, to promote recuperation. The result is an increased alertness during the day and lowered wakefulness and functional capability at night, being the lowest point of performance at around 05:00h (Window Of Circadian Low-WOCL). The reduction in performance at the lowest point during WOCL is severe and will markedly impair various aspects of performance including attention, reaction time and co-ordination. Humans simply are not designed to operate under the pressured 24/7 schedules that often define aviation operations, whether the operations are short-haul commercial flights, long-range transoceanic operations, or around-the-clock and shift work operations.


Because performance and alertness levels are largely influenced by the complex interaction between sleep and the 24-hour biological clock, the cited factors determine in a predictable way the background level of fatigue/alertness at any given moment.

The various factors that contribute to fatigue are individually capable of causing dangerous impairments in performance. Using a standardized performance test in, both, sleep loss and alcohol consumption conditions, investigators could provide a blood alcohol concentration metric to compare results from the sleep loss condition. Results demonstrated that after 17 hours of continuous wakefulness, cognitive psychomotor performance decreased to a level equivalent to a blood alcohol concentration of 0.05%. After 24 hours of continuous wakefulness, performance was approximately equal to a blood alcohol concentration of 0.10%.(Dawson D and Reid K. Fatigue, alcohol and performance impairment. Nature, 388:235, 1997.)

There is a discernible pattern of increased probability of an accident as duty time increases for commercial aircraft pilots. For 10-12 hours of duty time, the proportion of accident pilots with this length of duty period is 1.7 times as large as for all pilots. For pilots with 13 or more hours of duty, the proportion of accident pilot duty periods is over five and a half times as high. 20% of human factor accidents occurred to pilots who had been on duty for 10 or more hours, but only 10% of pilot duty hours occurred beyond the 10th duty hour. Similarly, 5% of human factor accidents occurred to pilots who had been on duty for 13 or more hours, where only 1% of pilot duty hours occur beyond the 13th duty hour. The greater the hours of duty time for pilots the greater probability of an accident.

The ability of aircrew to sustain levels of alertness during long flight duty periods has been the subject of many scientific investigations. There is an interaction between time of day, or circadian factors, on the one hand, and time since sleep and time on task on the other, with the result that duties at certain times of day are particularly susceptible to the effects of fatigue:

1. Night duty (flights ending during / extending through the Window of Circadian Low- WOCL): Night duty hours are especially vulnerable to severe fatigue. The longer the duty period extends the greater the pressure for sleep becomes, and there is strong evidence to show that many crews fall asleep, either voluntarily or involuntarily, on the flight deck. The longer the flight, the greater the risk that both pilots will fall asleep at the same time. Their ability to respond to an emergency situation, or to land the plane in adverse conditions, may also be severely impaired.

2. Duty during day time – early departures: Whereas long duty hours can be sustained during many day-time flights, specific problems are associated with early starts. Early start times are inevitably associated with a loss of sleep, the result of which is lower levels of alertness throughout the entire duty period. The effect is exacerbated over several successive early starts, due to an accumulating sleep deficit.

However, the most serious problems arise when the factor combine to provide even larger impairments. Night duty will involve work at the circadian low and an extended time awake. The two together will cause psychomotor impairment similar to that which is seen after the ingestion of enough alcohol to generate a blood alcohol level of 0.08% (which is significantly beyond the drink-drive limit in most European countries).

If the lack of sleep extends into the next day (comparable to the late morning after a 6-hour time-zone crossing without any post-flight sleep), there is a large impact on memory processes – with an impairment in the ability to respond to changed circumstances. The effects are further exacerbated in the event that prior sleep (i.e. before the flight/night duty) has also been disturbed.

Moreover, sleep taken after night duty will be truncated by 1-2 hours, because the circadian rise of metabolism in the morning will interfere with the sleep process. Sleep during the day on layover (before commencing another flight duty) is shallow, disrupted and shorter than during the WOCL. This has a detrimental effect on alertness during the subsequent flight duty.

Time-zone transitions

Flights across 4 or more time zones lead to the disturbance of sleep and circadian rhythms. If in addition, the flight is performed at night it magnifies performance decrements and increases the desire to sleep. As a result of these disturbances, more time is required to recuperate, both during layover and after return to base, before further flying duty is undertaken.

Night flights from west to east (North America to Europe – Europe to Asia) have an inherent augmented risk of fatigue. To counter fatigue, some pilots will try to nap before a night–time leg. While this can be helpful in some cases, it cannot prevent fatigue in all pilots. Moreover, it is not always possible to obtain an adequate amount of good quality sleep during the day and performance decrements will persist.

In addition, these types of flights are characterized by long periods of darkness with few operational demands while on cruise altitude, creating inherently soporific conditions. It is not until the flight approaches dawn that pilots experience reduced sleepiness as the daylight and circadian rhythms start to alleviate some of the fatigue. Nonetheless, the high workload requirements of approach and landing have to be borne at a time when there is a significant risk of pilot fatigue.

Most of these pilots fly a small number of night-time legs per month and revert to sleeping at night when not working. The circadian system of pilots who fly only a small number of night–time legs will not adapt to working at night, and these pilots are likely to display performance decrements during the night–time leg in spite of any countermeasures.

 Quality of In-Flight Sleep

Crewmembers’ sleep in onboard crew rest facilities is lighter and more fragmented than sleep on the ground. Sleep during flight deck naps is also lighter and more fragmented than would be predicted from laboratory studies.


Sleep debt

A sleep deficit of more than 2 hours has a discernible effect in performance capability. An acute reduction of sleep to below 6 hours will cause increased fatigue and reduced performance in most individuals. Sleep loss will also accumulate across time: 5 hours of sleep per day will be equivalent, in terms of fatigue and performance, to one full night of sleep loss after 5 days.

The effects of restricting sleep night after night accumulate, so that people become progressively less alert and less functional day after day. This is sometimes described as accumulating a sleep debt. This is a common occurrence for crewmembers when minimum rest periods are scheduled for several days in a row.

The shorter the time allowed for sleep each night, the faster alertness and performance decline. Spending 7 hours in bed for 7 consecutive nights is not enough to prevent a progressive slowing down in reaction time. The decline is more rapid if spent only 5 hours in bed each night, and even more rapid for those who spent only 3 hours in bed each night. This is described as a dose-dependent effect of sleep restriction.

The pressure for sleep increases progressively across successive days of sleep restriction. Eventually, it becomes overwhelming and people begin falling asleep uncontrollably for brief periods, known as micro-sleeps. During a micro-sleep, the brain disengages from the environment (it stops processing visual information and sounds.

Full recovery of waking function after sleep restriction can take longer than two nights of recovery sleep (i.e., longer than it takes the non-REM/REM cycle to recover). Indeed, chronic sleep restriction may have effects on the brain that can affect alertness and performance days to weeks later.

For the first few days of severe sleep restriction (for example, 3 hours in bed), people are aware that they are getting progressively sleepier. However, after several days they no longer notice any difference in themselves, even although their alertness and performance continues to decline. In other words, as sleep restriction continues, people become increasingly unreliable at assessing their own functional status. This finding raises a question about the reliability of subjective ratings of fatigue and sleepiness as measures of a crewmember’s level of fatigue-related impairment

The sleep-restricted brain can stabilize at a lower level of functioning for long periods of time (days to weeks).


Recovery from sleep loss

Lost sleep is not recovered hour-for-hour therefore recovery sleep should be longer than usual. The restorative value of sleep quality (sleep quality) depends on going through unbroken non-REM/REM cycles, which suggests that both types of sleep are necessary and one is not more important than the other.

The more the non-REM/REM cycle is fragmented by waking up, or by arousals that move the brain to a lighter stage of sleep without actually waking up, the less restorative value sleep has in terms of how a person feel and function the next day.

Once out of duty and given the opportunity to sleep at leisure, on the first recovery night, there is more slow-wave sleep than usual. Indeed, there can be so much slow-wave sleep that there is not enough time to make up REM sleep. On the second recovery night, there is often more REM sleep than usual. Only by the third recovery night, the non-REM/REM cycle is usually back to normal.

To reduce crewmember fatigue requires reducing the exertion of waking activities and/or improving sleep.


Managing fatigue is a very complex task that must go far beyond flight/duty/rest time limitations. All the cited factors preclude a simple solution. There is no a simple and unique one-size-fits-all approach strategy that works for everybody.

A variety of regulatory actions to address fatigue-related safety risks has been implemented, reviewed and revised. A lot of information has been published, multiple training courses and strategies have been designed. However, fatigue continues to cause and contribute to transportation safety events.

Sometimes, because of global and national economic issues civil aviation authorities may be compelled by commercial pressures to ease their national regulations with respect to the provisions of regulations of other nations. Loopholes could be exploited by the industry, within the different regulations, to promote their economic benefit.

Regulators must be aware that flight/duty/rest regulatory schemes loopholes when taken together, and applied in an environment of increasing competition, may encourage, or indeed compel, individual airlines to operate everywhere close to the defined limits by business considerations. In that case, it is likely that this would lead to a significant reduction in the safety of airline operations. There would be a clear competitive advantage for those airlines that operate as close as possible to the limits specified in the regulations, but there would be a significant increase in the risk of fatigue-related incidents and accidents if operators were permitted to operate to the limits.

The complexity and diversity of operational requirements demand a variety of approaches. Concept development should be initiated to move beyond current flight/duty/rest regulatory schemes and toward operational models that provide flexibility and maintain the safety margin.

Scientific evidence has remarked the vital importance of adequate sleep, not just rest, for restoring and maintaining all aspects of waking function and the importance of daily rhythms in the ability to perform mental and physical work, and in sleep propensity (the ability to fall asleep and stay asleep). Therefore it is critical that the core human requirement for sleep be managed effectively and operations should reflect the fact that the basic properties of the circadian clock directly affect an operator’s performance, productivity, and safety.

Some Mitigation Strategies that could be taken into account are:

  • Proper work/rest scheduling is of primary importance
  • Duty periods should not be as long as 12 hours when they surpass the window of circadian low- WOCL
  • If there is early starts the flight duty periods should be shorter than the allowed by the regulations
  • There shouldn’t be more than 2 consecutive night duties
  • There shouldn’t be more than 2 consecutive early starts
  • Strategic napping and strategic use of caffeine as alertness-enhancing compound must be considered
  • There is good evidence that in-flight sleep improves subsequent alertness and reaction speed and is a valuable mitigation strategy. The 40 minutes planned rest period provide time for preparation for the rest period, falling asleep and sufficient length time for an approximately 26 to 30 minutes nap to occur. After the nap, a recovery period of 15-20 minutes allows time for sleep inertia to dissipate if present and to brief the rested pilot before reentering the operational loop. The amount of sleep obtained in cockpit nap does not affect subsequent layover sleep or circadian rest/activities patterns.
  • Rest is not the same as sleep. A rest period with reduced physical or mental activity does not produce the same effects of sleep. Only sleep can reverse the physiological sleepiness.
  • Layover rest periods should provide sufficient time to recover from the immediate effects of the previous flight and to obtain sufficient sleep prior to the next report
  • A sleep opportunity of 8 hours may not be sufficient after a night flight or a flight with a large (= 4 hours) time difference. Thus, even a minimum rest period of 10 hours in many cases may not provide sufficient time for recovery.
  • Schedules must be designed to allow periodic opportunities for recovery and periodically include an opportunity for at least two consecutive nights of unrestricted sleep, to enable crewmembers to recover from the effects of sleep loss. This does not equate to 48 hours off. For example, 48 hours off duty starting at 02:00 would only give most people the opportunity for one full night of unrestricted sleep. On the other hand, 40 hours off starting at 21:00 would give most people the opportunity for two full nights of unrestricted sleep.
  • Additional nights may be needed for recovery if a crewmembers’ circadian body clock is not already adapted to the local time zone.
  • Recovery opportunities need to occur more frequently when daily sleep restriction is greater, because of the more rapid accumulation of fatigue.
  • Rest periods should include defined blocks of time (sleep opportunities) during which crewmembers are not contacted except in emergencies. These protected sleep opportunities need to be known to flight crews and all other relevant personnel. For example, calls from crew scheduling should not occur during a rest period as they can be extremely disruptive.
  • Operators should also develop procedures to protect crewmember sleep at layover and napping facilities. if a rest period occurs during the day at a layover hotel, the operator could make arrangements with the hotel to restrict access to the section of the hotel where crewmembers are trying to sleep (such as no children, crewmembers only) and instruct their staff to honor the necessary quiet periods (for example, no maintenance work or routine cleaning)
  • There are computer models that incorporate the schedule information and provide an instant evaluation of alertness levels on any given roster. It is possible to compare the effects on fatigue of different rosters and to estimate the effects of modifying the pattern of duty in different ways as well as estimate the probability that either a single pilot or both pilots will be asleep on the flight deck at any particular time
  • Good sleep hygiene by flight crew is essential. Therefore, pilots and other aviation personnel, particularly those performing overnight operations especially during the window of circadian low, must be deeply and recurrently trained about the physiology of sleep and circadian rhythm and the causes, effects and risks associated with fatigue as well as it’s prevention and mitigation strategies, personal responsibility during non-work periods, rest environments, and commuting and/or napping. The fatigue training should include personnel involved in crew scheduling and senior management too.

Managing fatigue must take into account operational differences and differences among crew members and requires a comprehensive approach that focuses on research, education and training, technologies, treatment of sleep disorders, hours-of-service regulations, and on- and off-duty scheduling policies and practices.

Ultimately, fatigue-related accidents can be avoided with a combination of science-based regulations, comprehensive fatigue risk management programs, and individual responsibility.

To be continued…


  1. Paper prepared for the European Transportation Safety Council “Meeting to discuss the role of EU FTL legislation in reducing cumulative fatigue in civil aviation” in Brussels on Wednesday 19th February 2003. Akerstedt, R. Mollard, A. Samel, M. Simons, M. Spencer. European Committee for Aircrew Scheduling and Safety.
  2. Fatigue in transportation: NTSB investigations and safety recommendations. Jeffrey H Marcus, Mark R Rosekind. Marcus JH, Rosekind MR. Inj Prev Published Online First: February 29, 2016. doi:10.1136/injuryprev-2015-041791
  3. Prevalence of fatigue among commercial pilots. Jackson CA1, Earl L. Occupational Medicine (Lond). 2006 Jun;56(4):263-8
  4. Barometer on pilot fatigue European Cockpit Association. 2012
  6. Are pilots at risk of accidents due to fatigue?. Goode, J. H. Federal Aviation Administration, Office of Aviation Policy and Plans, Washington, DC 20591, USA, March 2003
  7. Pitch Excursion Air Canada Boeing 767–333, C–GHLQ North Atlantic Ocean, 55°00’N029°00’W 14 January 2011. Transportation Safety Board of Canada (TSB)
  9. FAA Advisory Circular AC No: 120-100. Subject: Basics of Aviation Fatigue. Federal Aviation Administration, June 7th, 2010.
  10. Crew factors in flight operations IX: Effects of planned cockpit rest on crew performance and alertness in long-haul operations. Rosekind, Mark R, Graeber, R. Curtis, Dinges, David F., Connell, Linda J., Rountree, Michael S, Spinweber, Cheryl L, Gillen, Kelly A
    Mark R. Rosekind, Ph.D.1, LCDR David F. Neri, Ph.D. 1,2, and David F. Dinges, Ph.D. 3
    1NASA Ames Research Center, 2United States Navy Medical Service Corps, 3University of Pennsylvania School of Medicine.
  12. NTSB Most wanted list 2017. Reduce Fatigue-Related Accidents. National Transportation Safety Board, January 2017.


  1.  Stress and lack of quality sleep, factors leading to serious incident
  2. Pilots fatigue lead to a Danish Air Transport ATR 72 serious incident


minime2By Laura Duque-Arrubla, a medical doctor with postgraduate studies in Aviation Medicine, Human Factors and Aviation Safety. In the aviation field since 1988, Human Factors instructor since 1994. Follow me on facebook Living Safely with Human Error and twitter@dralaurita. Human Factors information almost every day 

CRM at its best: Qantas flight 32, learning from the recent past

“Let’s look at what’s working. If all we could do is build ourselves a Cessna aircraft out of the rubble that remained, we would be happy.”

qantas-1Photo:  ATSB Aviation Occurrence Investigation AO-2010-089 Final Report

In homage to an outstanding performance of an A380 flight crew facing a catastrophic failure of an inboard engine following an uncontained explosion on the morning of November 4th, 2010.


The aircraft departed Changi Airport, Singapore on a scheduled passenger flight to Sydney, Australia. About 4 minutes after take-off, while the aircraft was climbing through about 7,000 ft, the flight crew heard two ‘bangs’ and a number of warnings and cautions were displayed on the electronic centralised aircraft monitor (ECAM).

Initially, the ECAM displayed a message warning of turbine overheat in the No. 2 (inner left) engine. That warning was followed soon after by a multitude of other messages relating to a number of aircraft system problems. After assessing the situation and completing a number of initial response actions, the flight crew was cleared by ATC to conduct a holding pattern to the east of Changi Airport. While in the holding pattern, the flight crew worked through the procedures relevant to the messages displayed by the ECAM. During that time the flight crew was assisted by an additional crew that were on the flight deck as part of a check and training exercise. The aircraft sustained significant impact damage from a large number of disc fragments and associated debris. The damage affected the aircraft’s structure and a number of its systems.

A large fragment of the turbine disc penetrated the left wing leading edge before passing through the front spar into the left inner fuel tank and exiting through the top skin of the wing. The fragment initiated a short duration low-intensity flash fire inside the wing fuel tank.

Another fire has occurred within the lower cowl of the No. 2 engine as a result of oil leaking into the cowl from the damaged oil supply pipe. The fire lasted for a short time and self-extinguished.

The large fragment of the turbine disc also severed wiring looms inside the wing leading edge that connected to a number of systems.

A separate disc fragment severed a wiring loom located between the lower centre fuselage and body fairing. That loom included wires that provided redundancy (back –up) for some of the systems already affected by the severing of wires in the wing leading edge. This additional damage rendered some of those systems inoperative.

The aircraft’s hydraulic and electrical distribution systems were also damaged, which affected other systems not directly impacted by the engine failure. (Excerpted from In-flight Uncontained Engine Failure. Airbus A380-842, VH-OQA. Australian Transportation Safety Board Transport Safety Report Executive Summary)

We, aviation professionals and aviation safety scholars, sometimes tend to focus, perhaps too much, in aviation accidents and incidents. They are a great source of knowledge and learning that we later try to convert in accident prevention strategies. The human limitations, the error and its multiple causes and sometimes terrible consequences have a charming effect on us.

This time I want to do something different. This time I want to highlight the positive aspects of human performance: those unique things human beings do well, presented to us as outstanding airmanship, leadership and teamwork. All my respect to those five pilots, impeccably led by Captain Richard de Crespigny.

Next, I share the article published in AeroSafety World, with Captain de Crespigny’s first-hand testimony. All credit to the author and the publisher. The photos were added by me:


Singapore — First, came the matter of determining how much of the Airbus A380 was still functioning. Then the issue was maintaining control of the crippled aircraft flying on the edge of a stall during approach with marginal aileron control effectiveness. Finally, there was the problem of sitting over a rapidly spreading pool of jet fuel in an aircraft with white-hot brakes and an engine that refused to shut down.

The uncontained engine failure on a Qantas A380 on Nov. 4, 2010, did not precipitate a catastrophic accident, and 469 people returned safely to the ground at Singapore, said the Qantas Flight 32 captain, Richard de Crespigny, because five experienced pilots in the cockpit — three in the regular crew and two check captains — worked as a unified team with cool heads and a singleness of purpose.

In his keynote speech opening Flight Safety Foundation’s 64th International Air Safety Seminar in Singapore in November 2011, and in an extensive interview with AeroSafety World, de Crespigny detailed the accident. What follows are just a few of the significant details of this incredibly complicated situation.

The triggering failure that launched the drama was the uncontained failure while climbing through 7,000 ft, of the airplane’s no. 2 Rolls-Royce Trent 972 three-spool turbofan, perceived in the cockpit as “two bangs, not terribly loud,” de Crespigny said. The aircraft damage caused by the heavy, high-speed engine parts leaving the nacelle created what he called “a black swan event, unforeseen, with massive consequences.qantas-2qantas-6qantas-adicional

Photos:  ATSB Aviation Occurrence Investigation AO-2010-089 Final Report

“What did we know? We knew that engine no. 2 had failed, there was a hole in the wing, fuel was leaking from the wing and we had unending checklists. What we didn’t know is that no. 2 had had a failure of the intermediate pressure turbine, engine no. 1 had also been damaged, we had 100 impacts on the leading edge, 200 impacts on the fuselage, impacts up to the tail and seven penetrations of the wing, going right through the wing and up through the top. We had lost 750 wires…. We lost 70 systems, spoilers, brakes, flight controls. … Every system in the aircraft was affected.

“Flight controls were also severely damaged. It wasn’t just the slats; we [lost] a lot of our ailerons … lost 65 percent of our roll control,” de Crespigny said. The situation was made worse, he said, because, with fuel flowing out of the left wing, the aircraft was laterally unbalanced.

“We were getting pretty close to a [cockpit work] overload situation,” working through the checklists, cancelling the alarms. “It was hard to work out a list of what had failed. It was getting [to be] too much to follow. So we inverted our logic. Like Apollo 13, instead of worrying about what failed, I said, ‘Let’s look at what’s working.’ If all we could do is build ourselves a Cessna aircraft out of the rubble that remained, we would be happy.”

Wanting to be well prepared and drop as much fuel as possible before making what would still be an overweight landing, de Crespigny entered a holding pattern. “We had seven fuel leaks coming out of multiple parts of the wing. At 50 tonnes overweight, and no [working] fuel jettisoning system, this was our jettisoning system.”

Fortunate to have the longest runway in Southeast Asia available to them, the crew still had slim margins. Taking into account the known problems — including no slats and no drooping ailerons on final — the crew computed that the aircraft could be stopped 100 m (328 ft) before the runway end.

“We briefed the approach, and then — one of the more emotional events of the crisis — we did … three control checks. We proved the aircraft safe for landing in a landing configuration. We did a rehearsal for the landing with the gear down,” using gravity to drop the gear, he said, “flaps out and at approach speed, and the aircraft proved out.”

Knowing that the fly-by-wire stick would mask the aileron movement needed to maintain attitude, de Crespigny “went to the control page to look at the percentage of effort of the flight controls we had remaining. We had normal flight controls except for the ailerons, and there we’d lost 65 percent of our roll control, lost both outer ailerons, lost one of the mids, and we were left with … one mid and the high-speed ailerons, small and inboard.

“But we also had imbalances” due to fuel issues, he said. “I was very concerned about controllability. So we did the control check, and as I rolled the aircraft up to about 10 degrees of bank, we looked at the flight controls [ECAM page] and it looked like we were using like 60 to 70 percent of the remaining ailerons just to do a very gentle turn.

“I could easily reach maximum deflection of the ailerons, and when you reach that point, the spoilers come up next. You keep getting roll control by dumping more lift, increasing your stall speed. I was really worried, [knowing I had] to be so careful to not get the spoilers coming up. I had to keep the heading and yaw as accurate as possible, so I decided to use the automatic pilot for the approach — its accelerometers sense small changes and put in tiny corrections earlier than I will.”

qantas-3qantas-4qantas-5Photos: ATSB Aviation Occurrence Investigation AO-2010-089 Final Report

Manual thrust control can allow for unbalanced thrust, which would induce destabilizing yaw. “We had a long approach, so to get stable thrust I exactly matched [engines] one and four and locked them down, and used engine three to adjust the approach speed, using that [engine] because it is inboard and produces less yaw. So I had accurate heading control, controls were not used very much, and with only one engine used to fine tune the speed, [we maintained] minus 2 kt to plus 3 kt for the whole approach.”

Another pilot in the cockpit warned, “‘Richard, you can’t be fast.’ During approach, our air speed margin was very small. Put in 3 kt, we run off the end of the runway.”

As it turned out, he couldn’t be slow, either. “I slowed down 1 kt and we got a speed warning,” he said. “That was unexpected, absolutely. We clearly didn’t have a 17 to 18 percent stall margin. We had two speed warnings” during the approach, and “in the flare, we got a stall warning.”
“We landed 40 tonnes overweight, a relatively good landing. When we stopped, the brakes said 900 degrees C (1,650 degrees F), but it takes five minutes for heat to get to the sensor, so 900 degrees on stopping meant that those brakes were going to go well beyond 2,000 degrees C.”

However, on landing “fuel sloshed to the front” and began gushing out of the holes in the wing leading edge. “The auto-ignition point of kerosene is 220 degrees C, so we were concerned.” Happily, the Singapore crash rescue crew’s response was superb, de Crespigny said. “Firemen came in and put foam down over the fuel, over the brakes, and the temps started going down.”

Finally, though, the engine no. 1 refused to shut down, further delaying evacuation. But with the threat of fire mitigated, the aircraft was evacuated before the engine was killed with massive amounts of fire-fighting foam.


Photo: ATSB Aviation Occurrence Investigation AO-2010-089 Final Report


  1. In-flight Uncontained Engine Failure. Airbus A380-842, VH-OQA. Australian Transportation Safety Board. ATSB Transport Safety Report.  Aviation Occurrence Investigation AO-2010-089. Final Report 
  2. A Black Swan Event. Saving a crippled A380. DonoghueJ.A. AeroSafety World December 2011/January 2012
  3. Interview with Capt. Richard de Crespigny – Part 1
  4. Interview with Capt. Richard de Crespigny – Part 2


minime2By Laura Duque-Arrubla, a medical doctor with postgraduate studies in Aviation Medicine, Human Factors and Aviation Safety. In the aviation field since 1988, Human Factors instructor since 1994. Follow me on facebook Living Safely with Human Error and twitter@dralaurita. Human Factors information almost every day 


LaMía CP2933 accident in Colombia, preliminary report



Aircraft: AVRO 146-RJ85

Date and time: 29 November 2016, 02:58UTC (All times in this report are UTC. Five (5) hours should be subtracted to obtain the legal time in Colombia)

Location: “Cerro Gordo”, Municipality of La Unión Antioquia – Colombia.

Coordinates: N05°58’43.56″ – W075°25’7.86″

Type of operation: Commercial Air Transport (Passengers) Charter Flight


Persons on board: 04 Crew, 73 Passengers


Background to the flight

The operator had been chartered to fly the Chapecoense football team and associated personnel from São Paulo, Brazil (Guarhulos SKGR airport) to Rionegro, Colombia (Jose Maria Cordoba Airport in Rionegro, near Medellin). Under Brazilian regulations, charter flights may only normally be operated by an operator based in either the country of departure or arrival. The operator was based in Bolivia and was unable to get the necessary permission to operate the flight as planned. Arrangements were made instead for the passengers to be flown from São Paulo – Brazil (ICAO: SBGR) on a scheduled flight to Santa Cruz – Bolivia (ICAO: SLVR) where they boarded the charter flight to Rionegro – Colombia (ICAO: SKRG).

History of flight

The history of the flight has been compiled from a number of sources, including preliminary information from the flight data recorder (FDR), cockpit voice recorder (CVR) and recorded ATC and radar data. The ATC transcript is a translation of the original transmissions which were in Spanish.

On 28 November 2016, the aircraft departed the operator’s maintenance base at Cochabamba (OACI: SLCB), Bolivia, at 17:19hrs and positioned to Viru Viru International Airport (OACI: SLVR), Santa Cruz in Bolivia, landing at 17:58hrs.

After the arrival of the aircraft at Santa Cruz, it was refueled, with witness information indicating that the commander had instructed the maximum fuel load of 9,300 kg to be used.

It was reported that some of the crew had thought the aircraft would be refueling enroute at Cobija Airport (OACI: SLCO). Cobija Airport is located close to the border between Bolivia and Brazil and normally only operates during daylight hours. On 28 November 2016, it closed at 22:43hrs.

After the passengers had all arrived at Santa Cruz they boarded the aircraft and at 22:08hrs engine start commenced. On board were the operating crew; comprising a commander, co-pilot and two cabin crew members; and 73 passengers; including an engineer and dispatcher from the operator, and a private pilot who occupied the flight deck jump seat.

The aircraft took off at 22:18hrs and climbed to an initial cruising flight level of FL260, levelling at 22:41hrs. It then climbed again at 22:49hrs to FL280, levelling at 22:58hrs. It then started climbing to its final cruising level of FL300 at 23:54hrs, levelling at 00:14hrs. The cruising speed was recorded as 220 kt CAS. The route flown is shown in Figure 1.


During the cruise, the CVR recorded various crew conversations about the fuel state of the aircraft and they could be heard carrying out fuel calculations. At 00:42:18hrs one of the pilots could be heard to say that they would divert to Bogota (ICAO: SKBO) to refuel but at 00:52:24hrs a further conversation took place, shortly after the aircraft was transferred to Colombian ATC, with the crew deciding to continue to Rionegro (ICAO: SKRG). At 01:03:01hrs the crew began their brief for the approach to Jose Maria Cordoba Airport, Rionegro.

At 01:15:03hrs the CVR ceased recording.

The aircraft commenced decent at 02:30:30hrs at which time it was about 75NM to the south of Rionegro. It levelled at FL250 at 02:36:40hrs and at 02:40hrs ATC transferred the crew to Medellin Approach at 02:40hrs who instructed them to descend to FL230 and to hold at Rio Negro VOR (VOR RNG).

At 02:42:12hrs the crew was instructed to continue descent to FL210. At 02:43:09hrs the crew asked to hold at GEMLI RNAV Point (Figure 2), which was approved. It overflew GEMLI at 02:43:39hrs and entered the hold. (Figure 3 – each complete hold has a ground track of approximately 24 nm).

At this time there were three other aircraft holding at the Rio Negro VOR, at FL190, 18,000ft and 17,000ft. There was also an aircraft diverting into Rionegro with a reported fuel leak, about to commence its final approach to Runway 01 at Rionegro (SKRG).



At 02:43:52hrs the aircraft was levelled off at FL210, the flaps lowered to FLAP18 and the speed reduced to 180 kt CAS. At 02:45:03hrs the crew informed ATC that they had entered the hold at GEMLI at FL210.

The subsequent radio communications between the crew (callsign LMI 2933) and ATC have been tabulated below.


ATC then cleared LAN3020, the aircraft holding at 17,000ft for the approach.


ATC then cancelled the approach clearance for LAN 3020


At 02:53:07 hrs the thrust levers were reduced and the aircraft commenced a descent.

At 02:53:09 hrs the airbrake was extended


At 02:53:24 hrs the gear was selected down.


At 02:53:36 hrs FLAPS24 were selected and the aircraft speed began to reduce and continued to do so until the end of the FDR recording.

At 02:53:45hrs the Number 3 engine speed no longer matched the thrust lever demand and began to run down. 13 seconds later the same occurred on the Number 4 engine.


At 02:54:36hrs the FDR recorded FLAPS33 selected.

At 02:54:47 hrs the Number 3 and Number 4 engine low oil pressure states were recorded on the FDR together with a MASTER WARNING. At the same time, over a 12 second period, the Number 1 engine N1 reduced from 39.5% to 29.0% and recovered (N1 value indicates the rotation speed of the 1st (compression) stage of a turbojet engine).

At 02:55:04hrs the Number 2 engine speed no longer matched the thrust lever demand and began to run down.


At 02:55:19hrs, over a period of 10 seconds, the Number 1 engine N1 reduced again, from 38.1% to 29.9%, and recovered.

At 02:55:27hrs the Number 2 engine low oil pressure state and a MASTER WARNING were recorded on the FDR.


At 02:55:41hrs the Number 1 engine began to run down Following the loss of all engines, at 02:55:48hrs the FDR ceased recording. At this time the FDR data showed that the aircraft was at a CAS of 115 kt, a ground speed of 142 kt and a pressure altitude of 15,934 ft msl.

The aircraft was 15.5 nm to the south of the threshold of Rionegro Runway 01 and 5.4 nm south of the accident site (which was at an elevation of about 8,500 ft amsl).

Radar recording report indicates Mode C lost at 02:55:52hrs at which time there was only a primary radar contact for the aircraft.


No further response was received from LMI 2933 despite repeated calls by ATC.

Organization of Investigation

At 03:10hrs, the Grupo de Investigación de Accidentes Aéreos (GRIAA) from the Civil Aviation Authority of Colombia was alerted of the disappearance and subsequent location of the aircraft AVRO RJ85 accident in “Cerro Gordo”, Municipality of La Unión – Antioquia.

Immediately in accordance with the provisions of Colombian Aeronautical Regulations – RAC 8, a safety investigation was immediately initiated by GRIAA.

A team of 8 investigators traveled to the accident site on the morning of 29 November 2016, arriving at 11:30hrs. The access to the crash site was done by land and air.

Flight Recorders (FDR, CVR) were found on 29, November 2016 at 17:09hrs and placed in custody of GRIAA investigators for further preparation for readout.

Following the International Civil Aviation Organization (ICAO) Annex 13 provisions, the GRIAA made the formal Notification of the Accident to:

– International Civil Aviation Organization – OACI

– The Dirección General de Aeronáutica Civil – AIG (Bolivia), as State of Registration of the aircraft.

– The Air Accident Investigation Branch – AAIB (United Kingdom), as State of Manufacture of the aircraft. This allowed the assistance of technical advisors of the aircraft manufacturer.

– The National Transportation Safety Board – NTSB (United States), as State of Engine Manufacturer. This allowed the assistance of technical advisors of the engine manufacturer.

– The Centro de Investigação e Prevenção de Acidentes Aeronáuticos – CENIPA (Brazil), As State of the Nationals involved in the accident.

The Investigation was organized in different working groups in the areas of Airworthiness, Power Plants, Flight Operations, Human Factors, Survival and Air Traffic. The Accredited Representatives and Technical Advisors were divided into the formed working groups.

This preliminary report contains facts which have been determined up to the time of issue.

This information is published to inform the aviation industry and the public of the general circumstances of the accident and should be regarded as tentative and subject to alteration if additional evidence becomes available.

Injuries to persons


 Damage to the aircraft


Other Damage

Damage to surrounding vegetation.

Personnel Information

  1. Captain

Age: 36

Licence: Airline Transport Pilot – ATP

Nationality: Bolivian

Medical Certificate: 1st. Class

Last proeficience check: 03, July 2016

Total flying hours: 6,692.51 (Ref: LAMIA status documents 20 Nov 2016)

Total RJ85 flying hours: 3,417.41 (Ref: LAMIA status documents 20 Nov 2016

2. Co-pilot

Age: 47

Licence: Airline Transport Pilot – ATP

Nationality: Bolivian

Medical Certificate: 1st. Class

Last proeficience check: 03, July 2016

Total flying hours: 6,923.32 (Ref: LAMIA status documents 20 Nov 2016

Total RJ85 flying hours: 1,474.29 (Ref: LAMIA status documents 20 Nov 2016)

Flight Recorders

The aircraft was fitted with a CVR and FDR, both of which were powered by the aircraft’s AC Essential electrical bus which required one or more of the engines or the APU to be running. Both recorders were recovered to the Air Accidents Investigation Branch (AAIB) in the UK for download.

1 Flight data recorder

The FDR download revealed approximately 54 hours of operation which included the accident flight. A number of flight parameters were recorded including flight control positions, autopilot and autothrust modes, aircraft position, engine fan speed (N1) and thrust lever position. Fuel flow was recorded for each engine every 64 seconds. APU operation, fuel quantity, fuel and master cautions were not recorded.

2 Cockpit voice recorder

The CVR was successfully downloaded and recorded just over two hours of operation.

Using the recorded UTC timings from radio transmissions and the FDR, the CVR was timealigned and revealed a recording start time of 23:08:33hrs on 28 November 2016. The following two hours of recording was of the accident flight. The recording then ceased at 01:15:0hrs at which time the aircraft was about 550 nm from Rionegro and was one hour,40 minutes and 45 seconds prior to the end of the FDR recording.

There was no recorded discussion about the CVR and the reason for the CVR recording ceasing early is unknown at this stage in the investigation.

Wreckage and impact information

The crash site was known as “Cerro Gordo”, which belonged to the Municipality of La Unión in the Department of Antioquia – Colombia. The wreckage were disturbed during search and rescue operations following the accident. Access to the crash site was limited several days and lifting equipment was not available.

1 Initial impact site

The initial point of impact was identified on the south face at the hill just below the hill ridge on an approximately 310° compass heading. According to the GPS readings, an energy path extended from the IPI approximately 140 meters down the north hill face to the main wreckage location, on an approximate 290° compass heading.

The approximate GPS position of the initial impact site was N05°58’43.56″ – W075°25’7.86″. The largest item was the tail unit, complete with rudder and both elevators (Figure 4 and 5). The tail unit had detached from the main fuselage at the pressure bulkhead frame. The leading edges of the horizontal stabilizers and fin were in good condition with little evidence of damage. The airbrakes were close to the tail unit and remained attached to it by electrical wiring.



Components from the hydraulic bay and Environmental Control System (ECS) bay were identified at the initial impact site. These included hydraulic reservoirs and a heat exchanger from the air conditioning packs.

The stick push reservoir was identified at the site. The reservoir is installed in the upper section of the avionics bay, beneath the cockpit floor.

Other noteworthy items identified at the initial site included a main landing gear door, a section of inboard engine accessory gearbox (complete with starter motor), an engine hydro-mechanical unit, the rear section of the outboard fairing from the right wing and a passenger seat cover.

2 Engines

The Number 1 and Number 4 engines were found in the proximity to the initial impact point, with Number 1 engine to the left of the impact site and Number 4 to the right.

Number 2 and Number 3 engines were found in the area of the main wreckage with Number 2 engine to the left of the area and Number 3 to the right (Figure 6). The Number 3 engine was found lying in a large uprooted tree on a slope which was considered unstable and a thorough examination of the engine was not possible.


Examination of the Number 1, 2 and 4 engines revealed no evidence of fire,

uncontainment, or internal engine failure. There were varying amounts of damage to the engines and each had soil and tree debris packed between the fan blades. None of these engines showed any circumferential or spiral scoring to the fan spinner. The state of the engines examined was consistent with these engines not being under power at the time of impact.

3 Main wreckage site

The approximate GPS position of the main wreckage site was N05°58.725, 75◦25.138.

The main site was approximately 140 m from the initial impact site. Major assemblies identified included the cockpit, forward fuselage, wings, rear fuselage and the Number 2 engine. The wreckage had travelled downhill, passing through and disrupting trees (Figure 7).


The wings remained attached to the centre box (which forms the centre fuel tank) and were in the direction of travel but inverted. The orientation of the wings indicates that the centre fuselage rolled through 180° after the tail unit separated. The rear fuselage was upright but was facing opposite to the direction of travel. The majority of the rearpressure bulkhead remained attached to the rear fuselage. The left main landing gear was identified in close proximity to the rear fuselage. The side stay was locked, indicating that the landing gear was DOWN at the time of the accident.

The cockpit was disrupted and had been disturbed during search and rescue operations.

The position of switches and levers could not, therefore, be relied upon as being in the same position as at the time of the accident.

The centre console and throttle quadrant were identified.

The airbrake lever was slightly aft of IN.

All four throttle levers and the flap selection lever had been broken off in the accident.

The remains of the throttle levers were staggered and the remaining section of the flap lever was in the 30 DEG position.

The cockpit overhead panel was identified and its orientation was indicative of the cockpit section coming to rest inverted.

Both starboard wing flap screwjacks were fully extended, indicating that the flaps were in the 33 DEG, fully extended position at the time of impact. The port wing inboard screwjack was in the fully extended position. The port wing outboard screwjack was not accessible.

The starboard aileron, complete with servo and trim tabs, remained partially attached to the wing. It was not possible to identify the position of the aileron when the accident occurred.

The left wing was very badly disrupted and it was not possible to examine the port aileron.

The rudder and both elevators were still attached to the tail unit. It was not possible to identify the position of the control surfaces when the accident occurred.

The airbrakes were found slightly open.

The nose landing gear shock absorber piston, lower torque link and both wheels were identified approximately 15 m from the initial impact point, in the direction of travel.

4. Fuel

The starboard wing fuel tank had been split open during the accident sequence. With the exception of slight fuel odour in the immediate vicinity of the fuel tanks, there was no apparent evidence of fuel anywhere on the crash site.

The refuel panel (Figure 8) had a fuel upload of 9,300 kg selected. All the three fuel contents gauges within the panel indicated below zero, commensurate with readings when electrical power is removed. The three fuel valve selection switches were in the PRE-SELECT position.


There was no evidence of fire.

Fuel Planning Information

The operator had submitted flight information to a commercial flight planning company at1325 on 28 November 2016 in order to create a flight plan for the flight from Santa Cruz to Rionegro.

The route used to create the plan was the same as that used on the ATC flight plan submitted prior to departure. The plan gave a ground distance for the flight of 1,611 nm and a trip fuel requirement of 8,658 kg.

The only other fuel requirement submitted to create the plan was for a taxi fuel requirement of 200 kg. This gave a total fuel requirement for the flight of 8,858 kg, but with no allowance for diversion, holding or contingency fuel requirements.

The plan was created using a cruising flight level of FL300 and an aircraft takeoff weight of 32,991 kg. The plan recorded an increased trip fuel requirement of 64 kg for every additional 1,000 kg above this weight.

Other flight plans were found in the aircraft after the accident covering different routes.

These included a series of three plans created on 26 November 2016 covering separate flights from São Paulo to Santa Cruz, Santa Cruz to Cobija and Cobija to Rionegro. The Cobija to Rionegro plan had used Bogota as a diversion and included a diversion fuel requirement of 837 kg and a 30minute holding fuel requirement of 800 kg.

Estimated Load-sheet

The actual load-sheet was not located at the accident site nor has a copy been located elsewhere. In order to estimate the take-off weight for the flight the following information was used.


It is considered likely that the actual weight of baggage onboard the aircraft at the time of the accident was higher than the weight of the baggage recovered from the accident site. Baggage weight information obtained from the flight transferring passengers from São Paulo to Santa Cruz indicates that the baggage weight of those passengers transferring onto the accident flight was 1,026 kg. This would suggest a minimum estimated takeoff weight of 42,148 kg.

The maximum allowed takeoff weight for the aircraft, recorded in the aircraft Flight Manual is 41,800 kg.

ATC flight plan

The dispatcher accompanying the flight submitted a flight plan on 28 November 2016 at about 20:10hrs at the flight plan office at Santa Cruz Airport. The submitted flight plan gave a departure time of 22:00hrs and a cruising flight level of FL280. The flight time and endurance were both recorded on the plan as 4 hrs 22 minutes.

The flight plan office requested that the flight plan was changed and re-submitted due to the following issues with the plan:

  • The route did not include a standard instrument departure (SID) from Santa Cruz
  • There was no second alternate airport included in the plan
  • The estimated enroute time (EET) was the same as the endurance
  • The dispatcher had only signed the plan but had not printed his name

The dispatcher apparently had refused to change any of the details and explained that, regarding the EET and endurance being the same, the actual flight time would be less than that on the plan. The flight plan office filed the flight plan at about 20:30hrs but sent a report to the DGAC regional office giving details of the incident, stating that under the regulations the office was not empowered to reject the submission.

Further actions

A team of investigators carried out a visit to the DGAC facilities in Bolivia in order to gather information about the Operator and Regulations. The DGAC of Bolivia and the Prosecutors in La Paz, Cochabamba and Santa Cruz contributed and provided all the support to verify the Operators documents; however, the AASANA institution did not provide any information, related to the air navigation services and interviews.

The actions that were taken by DGAC (Bolivia), as result of the information regarding the accident, the operator’s Air Operator Certificate (AOC) was suspended.

The evidence available to the investigation at the time of issue of this preliminary report has not identified a technical failure that may have caused or contributed to the accident.

The available evidence is, however, consistent with the aircraft having suffered fuel exhaustion.

The investigation into the accident continues and will concentrate on issues related to fuel planning, decision making, operational oversight, survival and organizational oversight.

GRIAA will publish a final report once the full investigation is completed.

Information updated on 22, December 2016, 20:26hrs.


Unidad Administrativa Especial de Aeronáutica Civil de Colombia


Excerpted from

  1. PRELIMINARY REPORT Investigation COL-16-37-GIA. Fuel Exhaustion. Accident on 29, November 2016. Aircraft AVRO 146-RJ85, Reg. CP2933. La Unión, Antioquia – Colombia


  1. Normalization of Deviance: when non-compliance becomes the “new normal”
  2. The Organizational Influences behind the aviation accidents & incidents


minime2By Laura Duque-Arrubla, a medical doctor with postgraduate studies in Aviation Medicine, Human Factors and Aviation Safety. In the aviation field since 1988, Human Factors instructor since 1994. Follow me on facebook Living Safely with Human Error and twitter@dralaurita. Human Factors information almost every day 

Pilot performance in emergencies: why it can be so easy, even for experts, to fail

On February 4, 2015, about 1054 Taipei Local Time, TransAsia Airways (TNA) flight GE 235, an ATR72-600 aircraft, registered B-22816, experienced a loss of control during initial climb and impacted Keelung River, three nautical miles from its departing runway 10 of Taipei’s Songshan Airport. Forty-three occupants were fatally injured, including three flight crew, one cabin crew, and 39 passengers. The remaining 13 passengers and one cabin crew sustained serious injuries. One passenger received minor injuries. The aircraft was destroyed by impact forces. The aircraft’s left wing tip collided with a taxi on an overpass before the aircraft entered the river. The taxi driver sustained serious injuries and the only taxi passenger sustained minor injuries.


Photo: Frame of dashboard camera video excerpted from the Final Report- Use of the video was authorized by the TVBS

The accident was the result of many contributing factors which culminated in a stall-induced loss of control. During the initial climb after takeoff, an intermittent discontinuity in engine number 2’s auto feather unit (AFU) may have caused the automatic take off power control system (ATPCS) sequence which resulted in the uncommanded autofeather of engine number 2 propellers.

Following the uncommanded autofeather of engine number 2 propellers, the flight crew did not perform the documented abnormal and emergency procedures to identify the failure and implement the required corrective actions. This led the pilot flying (PF) to retard power of the operative engine number 1 and shut down it ultimately.

The loss of thrust during the initial climb and inappropriate flight control inputs by the PF generated a series of stall warnings, including activation of the stick shaker and pusher. After the engine number 1 was shut down, the loss of power from both engines was not detected and corrected by the crew in time to restart engine number 1. The crew did not respond to the stall warnings in a timely and effective manner. The aircraft stalled and continued descent during the attempted engine restart. The remaining altitude and time to impact were not enough to successfully restart the engine and recover the aircraft. (See: TransAsia Airways Flight GE235 accident Final Report)


Being the continuation of  When the error comes from an expert: The Limits of Expertise


“Emergencies and other threatening situations require pilots to execute infrequently practiced procedures correctly and to use their skills and judgment to select an appropriate course of action, often under high workload, time pressure, and ambiguous indications.

The performance of even the most skilled experts can be impaired by situational stress, applying equally to the skilled performance of almost all experts, from surgical teams to firefighters.

The term stress refers to the effects and the term stressful situations refer to the causes of a well-defined picture of two neural/hormonal systems that respond to the threat with characteristic changes that prepare the body for “fight or flight” e.g. increased heart rate and hard breathing. However, the psychological mechanisms associated with stress are less clear.

The effects of stress can be explained using the cognitive appraisal model (Lazarus and Folkman, 1984)when individuals encounter challenging situations they orient both their cognitive and physiological resources to deal with the situation.

Physiological responses, such as increased heart rate and force, faster breathing, and restriction of peripheral blood flow, prepare the body for ‘fight or flight.’ Cognitively, the individual focuses attention on the challenging situation, mentally preparing for whatever tasks may be required. Up to this point, the individual’s resources are mobilized to deal with the challenge, the individual can manage the situation effectively and performance may actually improve.

However, if the situation becomes threatening—physically or socially—and the individual is uncertain of his or her ability to manage the threat, anxiety arises. This anxiety plays a central role in altering the individual’s cognitive processes and overall performance, and is maladaptive because it disrupts the individual’s ability to manage the threatening situation, particularly by degrading attention and working memory, both of which are crucial for managing challenging situations effectively (Eysenck, Derakshan, Santos, and Calvo, 2007).”

Stress not necessarily directly caused accident pilots’ errors, but stressful conditions made these errors more likely to occur.

Attention and Working Memory

“Attention is the focus of one’s mind on one task or thought or stream of sensory input from a myriad of other possibilities. Basically, we can only fully attend to one stream of information at a given moment. If we must deal with multiple tasks, we are forced to switch attention back and forth among them, somewhat like a spotlight.

Working memory is a very small subset of the vast store of an individual’s long-term memory, momentarily activated so that it can be quickly accessed and manipulated. It consists of two components: the information stored and the control processes used to manipulate the information. These control processes are known as executive processes and are also involved in directing attention.

Attention and working memory are known as limited cognitive resources; their capacity for processing information is quite small compared to the vast store of information in long-term memory.

The content of working memory (that is, short-term memory store) is generated by the interaction of perceptual input with activation of a very small portion of long-term memory. Central executive processes and some involuntary processes, such as the startle reflex, control movement of the spotlight of attention over this limited store and update its content, holding task-relevant information readily available and updating that information.

The effects of anxiety on attention and working memory are consistent with the attention control theory (Eysenck, Derakshan, Santos, and Calvo,2007).

Attention is known to be controlled by two different brain systems: a top-down system that directs attention to support the individual’s currently active goals, and a bottom-up system that draws attention to environmental stimuli, especially stimuli that are salient, abrupt, or threatening. Attention control theory posits that anxiety disrupts the balance between the two attentional systems, giving the bottom-up system more weight. Consequently, attention is less under the control of task goals and is more easily pulled away by salient or threatening stimuli. Thus, the individual is more easily distracted from task goals. However, if the threatening stimuli are central to the task’s goals, focusing might actually be improved.

Individuals under stress are less able to manage their attention effectively. They are more likely to be distracted from a crucial task by highly salient stimuli, such as an alarm, or by threatening aspects of a situation. They may process information less fully and may have difficulty switching attention among multiple tasks in a controlled fashion, and consequently, their management of the overall situation may become disjointed and chaotic.

Because anxious thoughts tend to preempt working memory’s limited storage capacity, the individual may have difficulty performing computations that would normally be easy and have difficulty making sense of the overall situation and updating the mental model of the situation (i.e. situation awareness). In studies of accidents, by far the most common -23%- category of errors involved inadequate comprehension, interpretation, or assessment of the ongoing situation.

To understand how stress affects the skilled performance of pilots, especially in emergencies (which by their nature involve novelty, uncertainty, and threat), one must understand the distinction between the automated performance of highly practiced tasks and the effortful performance of less familiar tasks that draws heavily on attention and working memory. If the threat produces anxiety, pilots’ performance is likely to be undermined in specific ways.

Attention and working memory are essential for tasks involving novelty, complexity, or danger. Performing tasks requiring these two limited cognitive resources is typically slow and effortful. Highly practiced skills, such as manual operation of flight controls, are less vulnerable to stress because they are largely automated and are less dependent on attention and working memory. Studies show that inadequate execution of a physical action occurred only in <5% of accidents.

However, emergencies almost always require interweaving highly practiced tasks with less familiar tasks, novel situational aspects, and uncertainty. Thus, in an emergency situation, overall demands on attention and working memory are very high at a time when these limited cognitive resources may be disrupted by anxiety; consequently, tasks such as decision-making, team performance, and communication that depend heavily on attention and working memory are likely to be impaired.”


Photo:  GE235 loss of control and initial impact sequence, excerpted from the Final Report


“Decision-making under stress becomes less systematic and more hurried, and that fewer alternative choices are considered when making decisions. However, in highly practiced situations experts make decisions largely by automatic recognition of the situation and retrieval of the appropriate response from the long-term memory of previous experiences. This is why pilots are required to practice responding to some emergency situations. Thus, experts such as pilots are protected from impairment from stress under very familiar situations, at least to some extent.

For example, airline pilots are often given an engine failure during recurrent simulator training, and so pilots are typically fairly reliable in executing the appropriate response when experiencing an actual engine failure emergency in flight, even though the situation is somewhat stressful.

Unfortunately, most emergency situations are not rehearsed. Even in cases where the emergency procedures are practiced, the decisions that the pilot needs to make to respond appropriately in a particular emergency may be unique, and thus the required decision-making is not rehearsed. For example, the immediate responses to an engine fire in flight are practiced in recurrent training and are likely to be fairly reliable. But, the decisions about the next steps to take depend on where the aircraft is, fuel remaining, weather, and many other variables. Consequently, deliberate thought is required about these aspects, and such necessary deliberation may be impaired by the stress that is induced during the emergency.

The decisions made by pilots involved in accidents are often criticized. Indeed it is easy to identify, after the fact, what the pilots could have done to avert the accidents. But, as have previously argued, that kind of assessment suffers from hindsight bias (Dismukes, Berman, and Loukopoulos, 2007). In current studies of accident errors, has been found relatively few examples of poor decision making or poor choice of action. Therefore, it is suspected that —at least in the case of experienced airline pilots— “poor decision-making” may be used as a catch-all category, and it is suggested investigations would be better served by a deeper analysis of underlying cognitive factors.”

Team Performance and Communication

“Under acute stress team members search for and share less information, tend to neglect social and interpersonal cues, and often confuse their roles and responsibilities. Stress hinders team performance, including decision-making, primarily by disrupting communication and coordination. Coordination, of course, lies at the heart of effective team performance. Stress significantly reduces both the number of communication channels used and the likelihood that teammates will be provided needed information.

Poor communication and coordination can lead to downstream errors by team members. Studies found that 14% of errors in accidents involved inadequate or improper communication, 17% involved poor management of the competing task demands, and another 17% involved inadvertent omission of required actions. It is suspected that most of the errors of all types may have resulted from an underlying cause already mentioned: disruption of pilots’ executive control of attention and working memory.”

Ways to Reduce Error Vulnerability

“The design of airline operating procedures, training, and cockpit interfaces have evolved and improved steadily over decades of operational experience. However, there could be a hidden vulnerability in the design of three crucial aspects of safety—operating procedures, training, and interfaces—when non-normal situations are encountered. There seems to be an implicit assumption by designers that experienced pilots in emergency situations will be able to perform “normally”: that is to say pilots are assumed to process information, communicate, analyze situations, and make decisions as well as if they were sitting safely on the ground. That assumption is wrong.

Therefore the vulnerability to make errors in stressful situations could be reduced by developing tools to help flight crews:

  1. Recognize, interpret, assess and comprehend the full implications of a challenging situation that may change dynamically.
  2. Keep track of where they are in a procedure or checklist.
  3. Shift attention among competing tasks without becoming locked into just one task.
  4. Identify and analyze decision options.
  5. Step back mentally from the moment-to-moment demands of the flight situation to establish a high-level (meta-cognitive) mental model that guides action.
  6. Continuously update that mental model as the situation unfolds.
  7. Maintain the cognitive flexibility to abandon a previously selected procedure or course of action that has become inappropriate for the situation.

To a large degree, these seven objectives could be supported by revising existing flight deck operating procedures, checklists, and training to reflect diminished attention control and working memory function in threatening situations. This would best be accomplished by collaboration between human factors experts and the operational community. In addition, a longer-range approach would be to support these objectives in the design of future flight deck displays and automation interfaces.

Pilots’ resilience to stressful situations could also be improved by stress exposure training. In its simplest form this training would explain the physiological and cognitive changes that occur in stressful situations, which might help pilots be less disconcerted when they experience the physiological effects and be on guard for the cognitive effects. More advanced training could be incorporated into existing Line Oriented Flight Training (LOFT), allowing pilots to examine their own performance in stressful scenarios.”

Implications for NextGen

“The NextGen environment will present flight crews with operating procedures and demands that could increase stress and the consequences of stress, especially in non-normal situations. Complexity and traffic density will increase in this environment, and thus margins for error and time to respond may decrease. Therefore, it is crucial to identify human factors challenges that may arise during implementation and to develop appropriate countermeasures.

The increased navigational precision and reduced aircraft spacing required for NextGen may sometimes reduce the time flight crews have to interpret emergency situations and to select appropriate courses of action. The complexity of choosing an appropriate course of action may also increase for crews encountering emergencies because options may be constrained while conducting NextGen operations, such as closely spaced parallel operations.

New technologies will generate new failure modes that may increase stress and cognitive demands on flight crews. Research would allow these failure modes to be characterized, well-anticipated, and thoroughly covered in training that is designed to mitigate stress effects on flight crew performance in the NextGen context. Existing alerting features on flight decks may not be adequate for NextGen procedures and failures.

As the airspace system evolves and grows more complex and crowded, the need for ways to help flight crews deal with the heavy cognitive demands of non-normal situations becomes even more important. Transition to complex new technologies poses human factors challenges, and those in NextGen are particularly critical to its successful implementation. Difficulties will be worked out as they appear, but the transition period, including learning new procedures to proficiency, is likely to be especially cognitively demanding on flight crews; thus realistic simulation research to characterize the human factors challenges and develop mitigations should be conducted before NextGen systems are fielded. After NextGen technologies are in operation, it will be important to carefully monitor operations for indicators of latent human factors problems, particularly related to the effects of stress in normal and non-normal operations.”


  1. Excerpted from Dismukes, R.K., Goldsmith, T.E., & Kochan, J.A. (2015).  Effects of Acute Stress on Aircrew Performance: Literature Review and Analysis of Operational Aspects.  NASA Technical Memorandum TM-2015-218930.  Moffett Field, CA: NASA Ames Research Center.
  2. Stress and Flightcrew Performance: Types of Errors Occurring in Airline Accidents, R. Key Dismukes, Janeen A. Kochan, and Timothy E. Goldsmith, July 2014
  3. Aviation Safety Council Taipei-Taiwan Aviation Occurrence Report, 4 February 2015 TransAsia Airways Flight GE235, ATR72-212A, Loss of Control and Crashed into Keelung River Three Nautical Miles East of Songshan Airport. Report Number: ASC-AOR-16-06-001Date: June 2016. English report released on July 1st, 2016.


  1. When the error comes from an expert: The Limits of Expertise
  2. Multitasking in Complex Operations, a real danger
  3. Shutting down the wrong engine
  4. TransAsia Airways Flight GE235 accident Final Report


minime2By Laura Duque-Arrubla, a medical doctor with postgraduate studies in Aviation Medicine, Human Factors and Aviation Safety. In the aviation field since 1988, Human Factors instructor since 1994. Follow me on facebook Living Safely with Human Error and twitter@dralaurita. Human Factors information almost every day 

When the error comes from an expert: The Limits of Expertise

“On Aug 3rd, 2016, an Emirates Airlines Boeing 773 was performing flight EK-521 from Thiruvananthapuram (India) to Dubai (United Arab Emirates) with 282 passengers and 18 crew. As the flight neared Dubai, the crew received the automatic terminal information service (ATIS) Information Zulu, which included a windshear warning for all runways.

The Aircraft was configured for landing with the flaps set to 30, and approach speed selected of 152 knots (VREF + 5) indicated airspeed (IAS) The Aircraft was vectored for an area navigation (RNAV/GNSS) approach to runway 12L. Air traffic control cleared the flight to land, with the wind reported to be from 340 degrees at 11 knots and to vacate the runway via taxiway Mike 9.


Emirates B773 crashed at Dubai on Aug 3rd, 2016. Photo from Malaysian Wings Forum page

During the approach, at 0836:00, with the autothrottle system in SPEED mode, as the Aircraft descended through a radio altitude (RA) of 1,100 feet, at 152 knots IAS, the wind direction started to change from a headwind component of 8 knots to a tailwind component. The autopilot was disengaged at approximately 920 feet RA and the approach continued with the autothrottle connected. As the Aircraft descended through 700 feet RA at 0836:22, and at 154 knots IAS, it was subjected to a tailwind component which gradually increased to a maximum of 16 knots.

At 0837:07, 159 knots IAS, 35 feet RA, the PF started to flare the Aircraft. The autothrottle mode transitioned to IDLE and both thrust levers were moving towards the idle position. At 0837:12, 160 knots IAS, and 5 feet RA, five seconds before touchdown, the wind direction again started to change to a headwind.

As recorded by the Aircraft flight data recorder, the weight-on-wheels sensors indicated that the right main landing gear touched down at 0837:17, approximately 1,100 meters from the runway 12L threshold at 162 knots IAS, followed three seconds later by the left main landing gear. The nose landing gear remained in the air.

At 0837:19, the Aircraft runway awareness advisory system (RAAS) aural message “LONG LANDING, LONG LANDING” was annunciated.

At 0837:23, the Aircraft became airborne in an attempt to go-around and was subjected to a headwind component until impact. At 0837:27, the flap lever was moved to the 20 position. Two seconds later the landing gear lever was selected to the UP position. Subsequently, the landing gear unlocked and began to retract.

At 0837:28, the air traffic control tower issued a clearance to continue straight ahead and climb to 4,000 feet. The clearance was read back correctly.

The Aircraft reached a maximum height of approximately 85 feet RA at 134 knots IAS, with the landing gear in transit to the retracted position. The Aircraft then began to sink back onto the runway. Both crewmembers recalled seeing the IAS decreasing and the Copilot called out “Check speed.” At 0837:35, three seconds before impact with the runway, both thrust levers were moved from the idle position to full forward. The autothrottle transitioned from IDLE to THRUST mode. Approximately one second later, a ground proximity warning system (GPWS) aural warning of “DON’T SINK, DON’T SINK” was annunciated.

One second before impact, both engines started to respond to the thrust lever movement showing an increase in related parameters.

At 0837:38, the Aircraft aft fuselage impacted the runway abeam the November 7 intersection at 125 knots, with a nose-up pitch angle of 9.5 degrees, and at a rate of descent of 900 feet per minute. This was followed by the impact of the engines on the runway. The three landing gears were still in transit to the retracted position.” (See: Going around with no thrust. Emirates B773 accident at Dubai on August 3rd, 2016, interim report)


Emirates B773 crashed at Dubai on Aug 3rd, 2016. Photo from Bureau of Aircraft Accidents Archives B3A


Being the continuation of  Multitasking in Complex Operations, a real danger


The vast majority of airline accidents are attributed to flight crew error. However, the great majority of commercial pilots has received strict training, is checked with punctual regularity, operates advanced safety technology and is highly experienced. They do their job according to a flight operations manual and checklists that prescribe carefully planned procedures for almost conceivable situation, normal or abnormal, they will encounter.

How can all this expertise co-exist with the pilot error that we are told is a factor in more than half of airline accidents? Why these experienced professional pilots make these errors?

“This well-known fact is widely misinterpreted, even by experts in aviation safety. Certainly, if pilots never made mistakes the accident rate would go down dramatically, but is it reasonable to expect pilots not to make mistakes? For both scientific and practical reasons, this expectation is not reasonable.”

“The accident rate for major airlines operations in industrialized nations is already very low. This impressive record has been accomplished by developing very reliable systems, by thorough training, by requiring high levels of experience for captains, and by emphasizing safety. However, this accident rate can be further reduced substantially through the understanding of the underlying causes of human error and better ways of managing human error and changing how we think about the causes of error.”

“It is all too easy to say, because crew errors led to an accident, that the crew was the problem: they should have been more careful or more skilful. This “blame and punish” mentality or even the more benign “blame and train” mentality does not support safety—in fact, it undermines safety by diverting attention from the underlying causes.”

“Admittedly in general aviation, many accidents do show evidence of poor judgment or of marginal skill. This is much less common in airline operations because of the high standards that are set for this type of operation. Nonetheless, whatever discussion about airline operation could have implications for general aviation.”

“There are two common fallacies about pilot error:

  1. Fallacy 1: Error can be eliminated if pilots are sufficiently vigilant, conscientious, and proficient.

The truth is that vigilant, conscientious pilots routinely make mistakes, even in tasks at which they are highly skilled. Helmreich and his colleagues have found that on average airline crews make about two errors per flight leg and even more on challenging flights (Helmreich, Klinect, & Wilhelm, 1999; Klinect, Wilhelm, & Helmreich, 1999). And this is, if anything, an undercount because of the difficulty in observing all errors.

  1. Fallacy 2: If an accident crew made errors in tasks that pilots routinely handle without difficulty, that accident crew was in some way deficient—either they lacked skill, or had a bad attitude, or just did not try hard enough.

But the truth is that the most skilful, conscientious expert in the world can perform a procedure perfectly a hundred times in a row and then do something wrong on the 101st trial. This is true in every field of expertise—medicine, music, and mountain climbing just as much as aviation (Reason, 1990).”

“It must also be highlighted something called “hindsight bias”. After an accident, all know the outcome of the flight. The thorough investigation by the investigation authorities reveals many details about what happened leading up to the accident. Armed with this information it is easy for everybody to say the crew should have handled things differently. But the crew in that airplane did not know the outcome. They may not have known all of the details later revealed and they certainly did not realize how the factors were combining to create the conditions for an accident.”

“Experts do what seems reasonable, given what they know at the moment and the limits of human information processing. Errors are not de facto evidence of lack of skill or lack of conscientiousness.

In some accidents, crews may not have had access to adequate information to assess the situation and make prudent decisions on how to continue. Many bits and pieces of information may be available to the crew, who weigh the information as well as they can. But comes the question whether crews always have enough information in time to decide and to be absolutely certain that the decision is correct.”

“It is ironic that in some wind shear accidents the crew was faulted for continuing an approach even though an aircraft landed without mishap one minute ahead of the accident aircraft. Both crews had the same information, both made the same decision, but for one crew luck ran the wrong way. We do not like to admit that any element of luck still pertains to airline safety—and in fact, the element of chance in airline operations has been reduced enormously since the 1930s, as described by Ernest Gann in Fate is the Hunter (1984). But there are still a few accidents in which we should admit that the crew made decisions consistent with typical airline practice and still met disaster because risk cannot be completely eliminated.”

“Tension and tradeoffs between safety and mission completion are inherent in any type of real-world operation. Modern airlines have done an extraordinary job of reducing risk while maintaining a high level of performance. Nevertheless, some small degree of risk will always exist. The degree of risk that is acceptable should be a matter of explicit public discussion, which should guide policy. What we must not do is tell the public they can have zero risk and perfect performance—and then say when a rare accident occurs: “it was the crew’s fault”, neglecting to mention that the accident crew did what many other crews had done before.”

“If the investigation of an accident or incident reveals explicit evidence of deliberate misconduct the pilot obviously should be held accountable. If the investigation reveals a lack of competence the pilot obviously should not fly again unless retrained to competency. But with these rare exceptions, identifying “pilot error” as the probable cause of accidents is dangerous because it encourages the aviation community and the public to think something was wrong with the crew and that the problem is solved because the crew is dead or can be fired (or retrained in less serious cases).”

“Rather than labeling probable cause, it is more useful to identify the contributing factors including the inherent human vulnerability to characteristic forms of error, to characterize the interplay of those factors, and to suggest ways errors can be prevented from escalating into accidents. If probable cause must be retained, it would in most cases be better to blame the inherent vulnerability of conscientious experts to make errors occasionally rather than to blame crews for making errors.”

“To improve aviation safety we must stop thinking of pilot errors as the prime cause of accidents, but rather think of errors as the consequence of many factors that combine to create the conditions for accidents. It is easy in hindsight to identify ways any given accident could have been prevented, but that is of limited value because the combination of conditions leading to accidents has a large random component. The best way to reduce the accident rate is to develop ways to reduce vulnerability to error and to manage errors when they do occur.”


Emirates B773 crashed at Dubai on Aug 3rd, 2016. Aerial overview of accident site Photo from The Aviation Herald


“The naïve view is that pilots who make an error are somehow less expert than others. That view is wrong. The pilot who makes an error – as seen in hindsight- typically does not lack skill, vigilance or conscientiousness. He or she is behaving expertly, in a situation that may involve misinformation, lack of information, ambiguity, rare weather phenomena or a range of other stressors, in a possibly unique combination.”

“No one thing “causes” accidents. Accidents are produced by the confluence of multiple events, task demands, actions taken or not taken, and environmental factors. Each accident has unique surface features and combinations of factors.”

Human cognitive processes are by their nature subject to failures of attention, memory and decision-making. At the same time, human cognition, despite all its potential vulnerability to error is essential for safe operations.

“Computers have extremely limited capability dealing with unexpected and novel situations, for interpreting ambiguous and sometimes conflicting information, and for making value judgments on the face of competing goals. Technology helps make up for the limitations of human brainpower, but by the same token, humans are needed to counteract the limitations of aviation technology.”

“Airline crews routinely deal with equipment displays imperfectly matched to human information-processing characteristics, respond to system failures and decide how to deal with threats ranging from unexpected weather condition to passenger medical emergencies. Crews are able to manage the vast majority of these occasions so skillfully that what could have become a disaster is no more than a minor perturbation in the flow of high-volume operations.”

“But on the rare occasions when crews fail to manage these situations, it is detrimental to the case of aviation safety to assume that failure stems from the deficiency of the crews. Rather, these failures occur because crews are expected to perform tasks at which perfect reliability is not possible for either humans or machines. If we insist on thinking of accidents in terms of deficiency, that deficiency must be attributed to the overall system in which crews operate.”

“It has been described six overlapping clusters of error situations:

  • Inadvertent slips and oversights while performing highly practiced tasks under normal conditions
  • Inadvertent slips and oversights while performing highly practiced tasks under challenging conditions
  • Inadequate execution of non-normal procedures under challenging conditions
  • Inadequate response to rare situations for which pilots are not trained
  • Judgment in ambiguous situations
  • Deviation from explicit guidance or SOP

However, error is NOT just part of doing business, it must still be reduced and to reduce it, the factors associated with it must be understood as well as possible.”

“Uncovering the causes of flight crew error is one of the investigators biggest challenges because human performance including that of experts pilots is driven by the confluence of many factors, not all of which are observable in the aftermath of an accident. Although it is often impossible to determine with certainty why accident crewmembers did what they did, it is possible to understand the types of error to which pilots are vulnerable and to identify the cognitive, task and organizational factors that shape that vulnerability”. (Carl W.Wogt, 2007, on his Foreword to the book The Limits of expertise: Rethinking pilot error and the causes of airline accidents. Burlington, VT: Ashgate.)

“Studies have shown the most common cross-cutting factors contributing to crew errors (3):

  • Situations requiring rapid response
  • Challenges of managing concurrent tasks
  • Equipment failure and design flaws
  • Misleading or missing cues normally present
  • Plan continuation bias
  • Stress
  • Shortcomings in training and/or guidance
  • Social/organizational issues”


Emirates B773 crashed at Dubai on Aug 3rd, 2016. Photo from Bureau of Aircraft Accidents Archives B3A


“Studies show that almost all experienced pilots operating in the same environment in which the accidents crews were operating and knowing only what the crews knew at each moment of the flight would be vulnerable to making similar decisions and actions.”

“The skilled performance of experts is driven by the interaction of moment-to-moment task demands, availability of information and social/organizational factors with the inherent characteristics and limitations of human cognitive processes. Whether a particular crew in a given situation makes errors depends as much, or more, on this somewhat random interaction of factors as it does on the individual characteristics of the pilots.”

“The two most common themes saw in aviation accidents are Continuation Bias, –a deep-rooted tendency to continue their original plan of action even when changing circumstances require a new plan– and situations that lead to Snowballing Workload- a workload that builds on itself and increases at accelerating rate.”

Continuation bias

“Too often crew errors are attributed to complacency or intentional deviations from standard procedures, but these are labels, not explanations. To understand why experienced pilots sometimes continue ill-advised actions is important to understand the insidious nature of plan continuation bias which appears to underlie what pilots call “press-on-itis”. This bias results from the interaction of three major components: social/organizational influences, the inherent characteristics and limitations of human cognitive processes and incomplete or ambiguous information.”

“Safety is the highest priority in all commercial flight operations, but there is an inevitable trade-off between and competing goals of schedule reliability and cost effectiveness. To ensure conservative margins of safety, airlines establish written guidelines and standard procedures for most aspects of operations.”

“Yet considerable evidence exist that the norms for actual flight operations often deviate considerably for these ideals. When standard operating procedures are phrased not as requirements but as strong suggestions that may appear to tacitly approve of bending the rules, pilots may -perhaps without realizing it- place too much importance on costs and scheduling.”

“Also, pilots may not understand why guidance should be conservative; that is they may not recognize that the cognitive demands of recovering a plane from an unstabilized approach severely impair their ability to assess whether the approach will work out. For all these reasons many pilots, not only the few who have accidents may deviate from procedures that the industry has set up to build extra safety into flight operations. Most of the time, the result of these deviations are successful landings, which further reinforce deviating norms.”

“As pilots amass experience in successfully deviating from procedures they unconsciously recalibrate their assessment of risk toward taking greater chances.”

“Another inherent and powerful cognitive bias in judgment and decision making is expectation bias- when someone expects one situation, she or he is less likely to notice cues indicating that the situation is not quite what it seems. Human beings become less sensitive to cues that reality is deviating from the mental model of the situation.”

“Expectation bias is worsened when crews are required to ingrate new information that arrives piecemeal over time in incomplete, sometimes ambiguous, fragments. Human working memory has extremely limited capacity to hold individual chunks of information, and each piece of information decays rapidly fro working memory. Further, the cognitive effort required to interpret and integrate this information can reach the limits of human capacity to process information under the competing workload to flying an approach.”

Snowballing Workload

“Errors that are inconsequential on themselves have a way of increasing crews vulnerability to further errors and combining with happenstance events – with fatal results. The abnormal situations can produce acute stress, and acute stress narrows the field of attention (tunnel-vision) and reduces working memory capacity. The combination of a high workload with many other factors, as stress and/or fatigue, can severely undermine cognitive performance.”

“A particularly insidious manifestation of snowballing workload is that it pushes crews into a reactive, rather than proactive stance. Overloaded crews often abandon efforts to think ahead of the situation strategically, instead simply responding to events as they occur not thinking if that is going to work out.”

Implications and countermeasures

“Simply labelling crew errors as simply “failure to follow procedures” misses the essence of the problem. All experts no matter how conscientious and skilled are vulnerable to inadvertent errors. The basis of this vulnerability is in the interaction of task demands, limited availability of information, sometimes conflicting organizational goals and random events with the inherent characteristics and limitations of human cognitive processes. Even actions that are not inadvertent are the consequences of the same interaction.”

“Almost all airline accidents are system accidents. Human reliability in the system can be improved if pilots, instructors, check pilots, managers and the designers of aircraft equipment and procedures understand the nature of vulnerability to error.”

“For example, monitoring and checklists are essential defenses but in snowballing workload situations, when these defenses are most needed they are most likely to be shed in favor of flying the airplane, managing systems and communicating.”

“Monitoring can be more reliable by designing procedures that accommodate the workload and by training and checking monitoring as an essential task more than a secondary one.”

“Checklist use can be improved by explaining the cognitive reasons that effectiveness declines with extensive repetition and showing how this can be countered by slowing the pace of execution to be more deliberate, and by pointing to or touching items being checked.”

“Inevitable variability in skilled performance must be accepted. Because skilled pilots normally perform a task without difficulty, it doesn’t mean they should be able to perform that task without error 100% times.”

“Plan continuation bias is powerful, although it can be countered once acknowledged. One countermeasure is analyze situations explicitly, stating the nature of the threat explicitly, the observable indications of the threat and the initial plan for dealing with it.”

“Questions as what if our assumptions are wrong? How will we know? Will we know on time?, are the basis for forming realistic backup plans and implementing them on time before snowballing workload limits the pilot’s ability to think ahead.”

“Airlines should periodically review normal and non-normal procedures looking for design features that could induce error. Examples of correctable design flaws are checklist conducted during periods of high interruptions, critical items that are permitted to “float” in time and actions that require the monitoring pilot to head down during critical periods such as taxing near runway intersections.”

“Operators should carefully examine whether they are unintentionally giving pilots mixed messages about competing goals such as SOPs adherence versus on-time-performance and fuel costs. If a company is serious about SOPs adherence it should publish, train and check those criteria as hard-and-fast rules rather than as guidelines. Further, it is crucial to collect data about deviation from those criteria (LOSA & FOQA) and to look for organizational factors that tolerate or even encourage those deviations.”

“These are some of the ways to increase human reliability on the flight deck, making errors less likely and helping the system recover from the errors that inevitably occur. This is hard work, but it is the way to prevent accidents. In comparison, blaming flight crews for making errors is easy but ultimately ineffective.”

To be continued on Pilot performance in emergencies: why can be so easy, even for experts, to fail


Excerpted from:

  1. Dismukes, R. K. (2001). Rethinking crew error: Overview of a panel discussion. In R. Jensen (Ed.), Proceedings of the 11th International Symposium on Aviation Psychology. Columbus, OH: Ohio State University.
  2. Darby, Rick & Setze, Patricia. Factors in Vulnerability a book review to The Limits of expertise: Rethinking pilot error and the causes of airline accidents. Dismukes, R. K., Berman, B. A., & Loukopoulos, L. D. (2007). Burlington, VT Ashgate. Aviation Safety World, May, 2007 53-54
  3. Dismukes, R.K., Berman, B., & Loukopoulos, L. D. (2006, April). The limits of expertise: rethinking pilot error and the causes of airline accidents. Presented at the 2006 Crew Resource Management Human Factors Conference, Denver, Colorado. (PDF 232KB)
  4. Berman, B. A. & Dismukes, R. K. (2006) Pressing the approach: A NASA study of 19 recent accidents yields a new perspective on pilot error, Aviation Safety World, December 2006, 28-33.
  5. United Arab Emirates, General Civil Aviation Authority, Air Accident Investigation Sector. Accident Preliminary Report: Runway Impact During Attempted Go-Around. Dubai International Airport. 3 August 2016. Boeing 777-300 operator: Emirates. AAIS Case No: AIFN/0008/2016


  1. Pilot performance in emergencies: why can be so easy, even for experts, to fail
  2. Multitasking in Complex Operations, a real danger
  3. Speaking of going around
  4. Going around with all engines operating
  5. Normalization of Deviance: when non-compliance becomes the “new normal”
  6. The Organizational Influences behind the aviation accidents & incidents


minime2By Laura Duque-Arrubla, a medical doctor with postgraduate studies in Aviation Medicine, Human Factors and Aviation Safety. In the aviation field since 1988, Human Factors instructor since 1994. Follow me on facebook Living Safely with Human Error and twitter@dralaurita. Human Factors information almost every day