Fatigue Hazard | How Does It Decrease the Human Performance

Human error in aviation can be happened due to many human factors that affecting human performance. Apart from human factors are the individual factors such as fatigue, stress, peer pressure, body size or strength, personal events [ e.g., family problems], workplace Distraction/interruption, memory labs [forgot], situational awareness, time constraints, job experience, and other factors.

In this article, I will further your knowledge about fatigue and how does it affect human performance and cause human errors.

Fatigue isn’t just a problem for aviation safety managers or other safety-critical personnel involved in the air transport business. It’s a problem for all safety managers in all modes of transportation. Writing about fatigue is not easy, but I will do my best to focus on one context. 

 

After giving you a short introduction about fatigue, I will tell you a real story for more understanding of the fatigue effects on human performance and how it led to human error.

Fatigue Did This

In 2003, during the holy month of Ramadan in Yemen, one of our loading workers was loading a Yemen Airways aircraft - narrow body - which was prepared for take off on a scheduled flight.

A worker loaded the passengers' luggage in the front cargo hold, and as a result of waiting to load the rest of the luggage, the worker thought of sleeping a little! His colleagues did not notice that he was sleeping in the forward cargo hold, and the cargo hold door was closed.

After completing loading activities, the aircraft took off from Sana'a International Airport to "Riyan then to Bombay ". About 25 minutes after take-off, the captain heard three knocks on the roof of the lower cargo compartment. So, the captain was surprised that the knocks were repeated in different numbers. After evaluating the situation, the captain proceeded in the same way – knocks - with changing the number. Then, he waited for a while, he heard the same number of knocks from below.

Finally, the captain made sure that there was a person inside the cargo hold. The captain returned to Sana'a airport. While arriving, the door of the cargo hold was opened, and the worker safely got off.

I met this worker during my first job - as a secretary - in the security department of the Yemen Airways, I met this worker, and asked him with a laugh, "How did that happen?" He replied laughing, "I was tired and I did not sleep well." He was experiencing Cumulative " Chronic "fatigue.

 

Note:

In Holy Ramadan month, most people sleep after 5:30 a.m.

Do you sleep well before going to you work shifts?

What is fatigue?

A physiological state of reduced mental or physical performance capability resulting from sleep loss, extended wakefulness, circadian phase, and/or workload (mental and/or physical activity) that can impair a person’s alertness and ability to perform safety related operational duties. [ ref. ICAO FMG for Airline Operators]

Are you satisfied with this definition? for sure you are. But I will add to this the two fatigue types.

What is the Difference Between Tiredness and Fatigue?

To differentiate between fatigue and tiredness, the tiredness that we feel is often alleviated through sleep and rest. while fatigue, is an extension and continuation of tiredness without reducing it by sleep and rest.

 

How many fatigue types?

There are Three classification of fatigue:

1- Transient " Acute " Fatigue 

Is acute fatigue brought on by extreme sleep restriction or extended hours awake within 1 or 2 days.

 

Let's explain this "Acute Fatigue is any intense mental load or physical activity"

 

For e.g., climbing a long set of stairs is considered acute physical fatigue while hand flying on instruments in turbulence is considered mental fatigue.

 

2- Cumulative " Chronic "Fatigue 

Is fatigue brought on by repeated mild sleep restriction or extended hours awake across a series of days.

Let's explain this " Chronic fatigue accumulates over time and is caused by lack of sleep, stress and emotional trauma .etc."

 

3- Circadian fatigue 

Refers to the reduced performance during nighttime hours, typically between (2:00 a.m. and 05:59 a.m.) during an individual’s “window of circadian low” (WOCL).

 

What are the Common Symptoms of Fatigue?

Fatigue can cause a vast range of physical, mental and emotional symptoms.

Physical Symptoms 1)      Chronic tiredness or sleepiness 2)      Headache 3)      Dizziness 4)      Sore or aching muscles 5)      Muscle weakness 6)      Slowed reflexes and responses 7)      Impaired hand-to-eye coordination 8)      Appetite loss 9)      Reduced immune system function

 

Mental Symptoms 1)      Short-term memory problems 2)      Poor concentration 3)      Lapses of attention and vigilance 4)      Impaired logical reasoning and decision making, including a reduced ability to assess [impaired decision-making and judgement]. 5)      Delayed reactions (sometimes). 6)      Risk or appreciate consequences of actions. 7)      In some cases- hallucinations

 

Emotional Symptoms 1)      Moodiness, such as irritability 2)      Low motivation. 3)      Feeling of isolation 4)      Being annoyed

In addition, increased error while performing tasks.

 

Causes of fatigue

Fatigue can be caused from a variety of sources. The important factor is not what causes the fatigue but rather the negative impact fatigue has on individual's ability to perform tasks.

There are wide range of causes that can trigger fatigue. Also, fatigue can be caused by a number of factors working in combination.

 I will category causes to four main factors:

1- Medical Causes

e.g., Illness, such as a thyroid disorder, heart disease or diabetes.

You should consult your doctor.

2- Lifestyle Causes

e.g., lack of sleep, individual factors, alcohol or drugs etc.

3- Workplace Causes

e.g., workplace stress, shift work, poor workplace practices etc.

4- Emotional Causes

e.g., mental health problems, such as stress, depression and grief.

How fatigue affects human performance?

Fatigue can affect individual's performance in a variety of ways. As I said before fatigue can cause a vast range of other physical, mental and emotional symptoms. The individual who are fatigued is more easily distracted, are less able to concentrate, tend to forget things more easily, take longer to solve problems, make more mistakes, have slower reaction times, and take more risks than they might otherwise.

 

How to manage fatigue?

Fatigue in individuals who are responsible for aviation safety is a risk that needs to be understood and managed. Each individual is responsible for managing their own fatigue levels.

You first need to understand what the underlying causes for your fatigue are. Second, I will give you a short tips for good fatigue management.

1- Sleep well

Research has indicated that most people need eight hours of sleep in 24 hours to perform effectively, and the average person needs in excess of nine hours of sleep per night to recover from accumulated sleep debt.

Improve your sleep, improve your life.

2- Eat well

A good way to keep up your energy through the day is to eat regular meals.

3-Improve your lifestyle

You should manage your daily activities and lifestyle to maximize rest.

4- Do Exercises

While do exercises regularly you will experience more deep sleep.

5- Make a balance between your family and work

This is very important for those who work irregular schedule

6- Report fatigue Issues

By doing this, you help your SMS manager to manage this hazard.

Note: You can add to this list by writing your comments below.

 

Conclusion

Fatigue is a physiological state of reduced mental or physical performance capability resulting from sleep loss, extended wakefulness, circadian phase, and/or workload (mental and/or physical activity) that can impair a person’s alertness and ability to perform safety related operational duties.

There are differences between fatigue and tiredness, the tiredness that we feel is often alleviated through sleep and rest. while fatigue, is an extension and continuation of tiredness without reducing it by sleep and rest.

There are Three classification of fatigue transient " acute ", Cumulative " Chronic " and Circadian fatigue.

Fatigue can cause a vast range of physical, mental and emotional symptoms. There are wide range of causes that can trigger fatigue. Also, fatigue can be caused by a number of factors working in combination.

The individual who are fatigued is more easily distracted, are less able to concentrate, tend to forget things more easily, take longer to solve problems, make more mistakes, have slower reaction times, and take more risks than they might otherwise.

Fatigue in individuals who are responsible for aviation safety is a risk that needs to be understood and managed. Each individual is responsible for managing their own fatigue levels.

 

We recommend that you further read  :

1- ICAO Fatigue Management Guide for Airline Operator.