Human Errors

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What factors cause us to make mistakes, and how can we fix this?

A canopy collision is always caused by human error, by one or both pilots

This is the second in a series of articles in the field of human factors, threats and error management, written by Phong Son Ho, a very well-informed skydiver and pilot.

We saw in Son’s previous article how Situational Awareness is built, and how thanks to it we can decide and act. In this article, we will see the cognitive strategies that we put in place to be able to act in a dynamic environment…


To complete a task, we must pay attention to what we are doing. We can think of attention as a ‘reservoir’; it is limited and we must use it carefully. We call this reservoir the ‘attentional resources’. To perceive, understand, decide, and act we use part of these resources. When we are in our ‘comfort zone’ we have available resources and we do not use our full capabilities. However, if the workload increases, we may find ourselves running out of them. 

Let’s take a concrete example: driving a car is for many of us an automatic task and does not demand all of our resources. Writing a text message is also an obvious task that we accomplish without difficulty. But driving in a complex environment while texting puts us on the verge of overload. If we are now asked to hold a conversation at the same time, we will not be able to do everything and we will have to drop one of the tasks to do the others, due to lack of availability of attentional resources. 

Unfortunately, one of the problems of human functioning is that the task that we are going to abandon to the detriment of others is not within our control; we do not choose it and we suffer a brain load shed. 

And that’s the whole trap of our brain! When we are overworked, we can:

  • No longer perceive correctly or have tunnel vision on information
  • No longer able to think, remember, or make sense of a situation (the brain lock)
  • Make absurd or urgent decisions
  • Act erratically or not be able to act at all
  • Or a combination of several of these elements

This is why it is essential to manage our resources upstream so as not to find ourselves overworked and ‘freezing’ instead of acting.

This jumper has just opened and is in danger of an imminent canopy collision – it’s vital that he has available resources to act correctly. But if his resources are already depleted, perhaps due to focussing on cloud and the poor break-off, he could easily make a serious error

We have all seen videos of landings where, overloaded with information, decisions to make and actions to perform, skydivers injure themselves by flying straight towards obstacles and not changing trajectory, or not even flaring. This is typically caused by a lack of attentional resources allocated to piloting, due to a sudden overload of work. The brain tries to understand and uses all its resources for perception and understanding, at the expense of action. 

Plan, anticipate ‘hot times’, assign the right amount of energy to the appropriate tasks and make sure to have enough resources available by taking decisions very early so as not to find yourself in these situations. We all should think about this behavior and work on it often. For example, making an early decision to land out in a safe place in the case of a bad spot, or choosing at altitude to aim for the alternate landing area as you realise the main landing area will be congested.

Making an early decision to avoid congested landing areas conserves your resources

Resource-saving strategy

Fortunately, the brain also implements strategies to save these resources. Indeed, we see that the usual tasks that we repeat all the time cost us less and less energy. Packing for example; at the beginning of our training, this requires a lot of us physically and mentally because we have to understand why we fold in a specific way and integrate the technical actions. Then we learn the procedure and repeat the actions following the method. After a certain number of packjobs we do it almost instinctively.

It’s the same for everything we learn. Let’s take the example of belly flying; at the beginning we must understand how to go up and down and what body positions to use. Then we follow the rules (I push my right elbow in, I turn to the right; I arch, I go down; I extend, I go up), then after several minutes of flight and a number of jumps, all these movements become instinctive and no longer cost any attentional resources to be done correctly. It is then possible to concentrate on other things and free up time to accomplish other tasks. 

This is why it is important to take skydiving progression at the right pace. For example, waiting until belly skills are instinctive before jumping a camera or wingsuit. 

SRK Model– Skills, Rules, Knowledge

This operating principle of automating behavior to save attentional resources was described by Rasmussen in his SRK (Skill, Rules, Knowledge) model. It is by automating our behaviors that we save our resources. 

However, it is also by using these strategies that we make mistakes.

Human error

Let’s start by defining what an error is. A human error is an unintentional inappropriate action or response, which ends or could end in a result that is not as expected. In this sense it is completely different from a violation, which is a voluntary act of deviation from a procedure or voluntary non-compliance with a rule. 

Human beings are made in such a way that we all make errors; it is part of our intrinsic functioning. Unmanaged or poorly-managed errors can lead to unwanted situations and tend to reduce safety margins. 

This is why it is essential to understand where our errors come from and how to better detect or avoid them. 

We make 3 main types of errors:

  • Routine errors [skills]
  • Rule errors
  • Errors due to lack of knowledge

Indeed, to think, make decisions and act, we automate our behaviors in an energy-saving strategy (attentional resources). This cognitive automation model is known by the acronym SRK (Rasmussen model).

SRK (Rasmussen model)

SRK (Rasmussen model) – Skills, Rules, Knowledge

S – Skills

Skill-based behavior is based on skills, habits and ‘know-how’ (automatisms, where the action has become automatic). A basic, dominant mode, it represents the automatic nature of behavior, without conscious control. This level of functioning allows work to be performed at the lowest cognitive cost, freeing up mental resources for more reflective activities.

R – Rules

Rule-based behavior is based on logical rules such as ‘if this, then that’. In rather familiar situations, behaviors are based on learned rules (procedural knowledge), previous experiences or transmitted by peers, followed like cooking recipes or recomposed to solve a problem. This is a transitory mode of operation because it is costly in terms of mental resources. As soon as an explanation is found for the situation, the behavior becomes automatic again.

K – Knowledge

Knowledge-based behavior is based on reasoning. In a completely new situation, the individual does not have a suitable resolution plan. He/she must then mobilize all their knowledge to solve the problem as well as possible. It is a creative behavior; slow and even more costly in mental resources than the previous one.

Forgetting to fasten your chest strap is a Skills error, caused by lack of attention or omission

Associated risk of error

Each mode of activity has its types of associated risks and errors: 

  • S = inattention, inversion, omission after interruption
  • R = logical error, or erroneous mental representation (reasoning true in a false world!) 
  • K = mental model errors, panic.

In our activity of skydiving, almost all our behaviors are automated. When we start to become ‘expert’, 

  • 70% of our behaviors are skills
  • 20% are based on procedures 
  • 10% use our knowledge.

For example:-

  • Forgetting to turn on your AAD because you‘ve been interrupted by a friend in your gearing up procedure is a Skill error.
  • Not doing your EPs properly and pulling both handles at the same time is a Rule error.
  • Not knowing what to do when landing in the middle of a city can be a Knowledge error, if you have never faced that situation.
Landing in opposite directions is a Rule error – whether the Rule is, follow the Wind Indicator or the first person down, one of these jumpers has made a Rule error. Photo by Michael McGowan

Once again, the important thing is: always work on understanding our actions. All our automated tasks must, if security depends on it, have gone through the K scheme and the R scheme many times to become S. Thus, since these Skills are understood and integrated, errors based on this type of behavior will be quickly detected (since the response will not conform to expectations) and recovered.

Likewise, procedures and rules must be perfectly understood so that the correct rule is applied to the right situation and thus controls the expected response. And finally, if we encounter an unexpected situation, if we have the right knowledge, we will find the appropriate solution and minimize the risk of knowledge errors.

Landing on a power line is a Knowledge error – this student didn’t have the knowledge or experience to handle the situation. Photo by Michelle Meakins


It is imperative to always manage our resources in advance and plan our jumps in order to never find ourselves in a situation where the ‘reservoir’ of attentional resources is empty. Because, when we need more of them to perceive, use our memory and cognitive faculties, decide, or act, unintentional load shedding will occur and expose us to imminent danger.

  • Brief your jumps
  • Know your technical limits
  • Anticipate complex situations
  • Have strategies already established in case something goes wrong
  • Manage potential situations of mental overload in advance
  • Know how to say NO to a jump if you feel that you are not able to manage it 100%, or to change the jump.

As well as developing good situational awareness, interest in the discipline and the acquisition of solid knowledge on equipment, environment, weather, safety of certain jumps (head up/head down breakoff, what to do if in the wrong quadrant in an angle jump, etc) are essential to create good Rules and good Skills behavior. It will also be helpful if you find yourself in a completely new situation where you’ll have to use your knowledge. It is crucial to act correctly and efficiently in all situations and know how to anticipate, detect and correct your errors and those of others, to increase safety in general.

Fun jumps and blue skies.

Conserving your attentional resources means you can land in safety with a relaxed mind
Photo: Bridget Weaver, with 500 jumps, landing , by Micheal McGowan

Human Factors Series

by Phong Son Ho

Understand the brain’s processes and develop strategies to manage them, to improve your chances of survival, reduce injuries, and make the sport safer for all

  1. Situational Awareness and Decision-making – how to protect ourselves from danger by improving our situational awareness
  2. Human Errors – what causes us to make errors and how can we reduce these to a minimum
  3. Stress Management and Assertiveness – coming soon
  4. Threats and Error Management – coming soon
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Meet: Phong Son Ho

After being trained in the French Air Force. I joined a French airline as a copilot on Boeing 737s. Then I was rapidly promoted as a captain on ATR72-500 then on Boeing 737-NG and now on Boeing 777 and 787. I was also crew resource management and human factor expert and instructor in my company for more than 10 years.

I started skydiving in 2019. I am a camera flyer at my DZ

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