Human Factor in Aviation
The collision of two Boeing 747 aircraft caused a surge in the development and implementation of more effective measures aimed at managing the human factor and minimizing the inherent risks. The catastrophe that occurred on March 27, 1977, at Los Rodeos Airport on Tenerife has remained the deadliest event in the history of aviation, with a dreadful total of 583 fatalities (Smith, 2017). The purpose of this paper is to critically analyze the details of the accident using modern methods to identify its causes. This essay also includes an overview of lessons learned from the Tenerife disaster and the systems that were created because of it.
Outline of the Accident
Prior to discussing the human factors contributing to the catastrophe, it is crucial to gain an understanding of the events by recounting them. Major accidents in aviation rarely happen due to a single fault, and the collision of the two Boeing 747 jets was no exception. The tragedy was caused by a sequence of errors and mishaps that combined in a terrible way. Thus, the description of the circumstances must be comprehensive and precise.
The first unusual occurrence was the very fact that the planes had to land on Tenerife, even though their destination was on the neighboring island of Gran Canaria. The routes were altered due to a bomb that was detonated at the Las Palmas airport, where they were scheduled to land (Smith, 2017). Since numerous other flights also had to land at Los Rodeos, the airport was experiencing abnormally high traffic. The taxiway was blocked with parked planes, which meant that the departing flights had to taxi on the runway until the starting point before turning around and taking off in the correct direction.
When the Las Palmas airport resumed functioning, the KLM and Pan Am flights were preparing to take off. The lack of space for maneuvering the planes meant that the KLM flight had to depart first, but the captain decided to spend 35 minutes refueling, which delayed the Pan Am flight as well. A further delay was caused by a family that did not return to the plane on time after it finished refueling. When the two aircraft were finally ready to taxi, the Pan Am 1736 was ordered to follow the KLM 4805 and park at exit C3, which was the first one not occupied by another plane. The 4805 was supposed to drive to the end of the runway and await permission for takeoff.
A thick for descended onto the airport as the Pan Am crew entered the runway, leaving the crew with appalling visibility. The weather conditions and a lack of signs caused them to misread their position on the runway and attempt to park exit C4 instead of C3. While 1736 was still on the runway, the captain of the 4805 was anxious to take off, as he began advancing the engines without ATC and takeoff clearance. The crew contacted the tower over the radio and received the standard information regarding their route – the ATC clearance, but no expressed permission to take off.
The captain of the 4805, impatient with the whole situation, interpreted the message as authorization to begin takeoff. He communicated that to the tower, interrupting the first officer’s “we’re now at takeoff” with a short “We’re going” (ASN aircraft accident Boeing 747-121 N736PA, no date). Since neither of these phrases was standard terminology, the controller, who had no visual on the runway, misunderstood the KLM crew and responded with “OK,” before realizing the potential mistake. He then tried to rectify any confusion by saying, “stand by for takeoff, I will call you,” but the message was interrupted by a transmission from the Pan Am aircraft filled with similar concerns. Either of the messages would have alerted the KLM crew to the fact that the runway was not clear, but because they were transmitted simultaneously, the result was inaudible. After hearing another message from the Pan Am, stating that they will report when clear, the KLM flight engineer asked the captain if the other plane could still be on the runway (CVR 721229, no date). The captain replied with an emphatic, “Oh yes,” and continued accelerating.
At that point, neither could one plane see the other because of the fog, nor did the controller have a ground radar to reliably monitor the situation. When the distance between the two aircraft was about 700 meters, the Pan Am crew noticed the incoming KLM and tried to turn toward the grass and leave the runway. The 4805 attempted to avoid the collision by lifting off, but only managed to clear the front landing gear. The hit sheered off the top part of the Pan Am’s fuselage, destroying the emergency cutoff switches located on the roof of the cockpit. Finally, the firefighters, who had very little information, came to the wreckage of the exploded 4805, which had no survivors, while the 61 passengers and crew members were jumping off the burning 1736.
SHELL Model
The SHELL model is a tool for conceptualizing human factor issues in aviation. The main constituents of the model are software, hardware, environment, and liveware (ICAO SHELL model, 2019). The software component refers to the rules and regulations governing most procedures. Hardware is the system used by air traffic controllers to monitor all relevant activity. The environment is the set of natural circumstances that affect the functioning of the other three-part of the system. Finally, liveware refers to all people involved in the industry, including management and maintenance personnel (ICAO SHELL model, 2019). The model focuses on the interaction of liveware with the other components being as smooth as possible to minimize human error. Although humans are inherently prone to mistakes, the supporting systems can be optimized in order to reduce the risks.
Analysis of the Human Factors
This section of the paper aims to provide a critical analysis of the numerous issues that led to the Tenerife disaster. It will discuss CRM issues, Cockpit Gradient differences, poor communication, expectation bias, language difficulties, autocratic management style, stress, company pressure, and others. The SHELL model will be used to link these aspects to the socio-technical system. Thus, a more profound study of the contributing factors is vital to the last part of the essay, which looks at the Human Factors measures that were implemented in response to the catastrophe.
Crew resource management or CRM is comprised of two main elements: cognitive abilities and interpersonal skills. The former includes decision-making, problem-solving, and situation awareness, while the latter consists of communication, teamwork, and other aptitudes connected with working as part of a large company (Crew resource management (CRM), 2020). As such, CRM covers a major portion of human factors contained in this paper. CRM issues are also the most prominent in this accident, as they contributed to the severity of each other, resulting in the grim outcome that was mentioned above.
Extreme authority gradients can have detrimental effects on the crew’s performance as a team since they tend to cause subordinates to refrain from providing valuable input, which in turn drastically increases risks. Extremely steep gradients are especially dangerous, as they result in abnormal obedience and suppression of valuable inputs (Authority Gradients, 2017). The last conversation in the cockpit of the KLM aircraft is indicative of an authority gradient issue. Captain Veldenhuyzen van Zanten’s autocratic management style, combined with his rank of Chief Flying Instructor, undermined the team’s confidence in openly correcting his mistakes (B742 / B741, Tenerife Canary Islands Spain, 1977, 2018). Cultural differences between crewmembers could also contribute to the deterioration of teamwork; however, there is no indication that they played a role in this incident. Nonetheless, dismissing a colleague’s remark without considering it is an example of poor leadership in any field, and unacceptable in aviation. According to the SHELL model, this is a liveware-liveware issue, since it is based on the lack of cooperation.
Another group of factors that contributed to the crisis can be called poor communication. The issue manifested in several forms, some related to the human factor, others being technological limitations. The initial miscommunication, when the KLM crew interpreted ATC clearance as permission for takeoff, belongs to the first group and has several plausible causes. Most reports conclude that the use of non-standard language by both the controller and the KLM crew was one of the main reasons for the crash, but there are other ones. One of them is expectation bias – a change in one’s perception of a certain event caused by the subject’s expectations; in this case, it means “that we sometimes hear what we expect to hear” (Expectation bias, 2012). Since the KLM crew was anxious to finish the flight, they assumed that takeoff clearance was given with the ATC clearance.
In addition to the captain’s fatigue from the unexpectedly long flight, there were several external factors that affected his decision to refuel at Los Rodeos. It is possible that the recently implemented company-wide duty-time regulations caused additional stress. The pressure to use time as efficiently as possible might have compromised van Zanten’s decision-making, causing him to compromise the chance to take off before the emergence of the fog. Although the company policy might be overlooked by some, similar deceptively minor details lay the foundation of such accidents. In the SHELL model, the liveware-software interaction between the captain and the new company policy caused the plane to refuel prematurely.
The Pan Am crew, which had a more passive role in this story, was faced with a different set of human factor issues. In addition to having to deal with the same frustrating circumstances as the KLM, 1736 was forced to delay their own takeoff to let the other plane refuel fully. Poor visibility caused by the fog meant that the team had to rely on radio communication to verify the status of the other flight and report their own. This shows the crew adapting to unfavorable weather conditions – a liveware-environment interaction.
At this point, there is no doubt that there were severe flaws in the social part of the socio-technical system, but the technology did not work perfectly either. In regular circumstances, the quality of radio transmissions can be imperfect, containing a considerable amount of static noise, sometimes rendering the original message incomprehensible. In this case, two transmissions were received simultaneously by the KLM aircraft, resulting in strong interference. The crew’s reaction to the cognitive overload was also problematic, as the captain did not become concerned with the content of the transmissions and continued accelerating. Moreover, the poor workload management in the KLM cockpit meant that neither of the other crew members was tasked with clarifying the information. This segment has both liveware-liveware complications regarding the inner workings of the KLM crew, and liveware-hardware issues with the incomprehensible radio messages.
Human Factors Advancements
The deadliest accident in the history of air travel was bound to cause everyone in the aviation industry to reconsider their safety standards. The Tenerife catastrophe has been subjected to meticulous investigation, which resulted in several crucial lessons. This section of the paper aims to outline, discuss, and evaluate the most important human factors measures that have been implemented in response to the disaster at Los Rodeos.
Since the KLM captain taking off without clearance was the central issue in this accident, the recommendations of the report largely focus on preventing similar occurrences in the future. The first recommendation is quite straightforward, simply stating that following the instructions strictly is of utmost importance (K.L.M. and P.A.A., 1977). While compliance with clearance was never optional in aviation, this case showed that bending the rules even slightly can have devastating consequences, and cannot be excused.
The second recommendation was also aimed at ensuring compliance with instructions. The experts have declared that the use of “standard, concise and unequivocal aeronautical language” is indispensable (K.L.M. and P.A.A., 1977). If it had not been for the unusual phrases used by the KLM crew, the controller would have known that the aircraft is beginning to accelerate. To prevent such misunderstandings, pilots, traffic controllers, cabin crew, and other relevant personnel use a standardized variant of the English language – aviation English (The language of aviation, no date). Although it is based on English, the Aviation language is very different from it, having many specialized phrases, collocations, and abbreviations. The use of this language is crucial, as it saves valuable time and eliminates the need for additional clarifications.
The final recommendation was the most specific, as it addressed an aspect of a specific procedure. The suggestion’s two main ideas were to avoid the use of the word “takeoff” in the ATC clearance and to ensure proper separation between ATC and takeoff clearance (K.L.M. and P.A.A., 1977). This is certainly a welcome change, since the chances of other pilots confusing the two concepts or making assumptions based on only one of them are relatively high. With the new system, the crew will know to expect two distinct messages before beginning takeoff. Assuming the controller uses the correct phrasing and adheres to this recommendation, the risk of an unauthorized takeoff would be drastically reduced. Even though this change might seem minor, and does not require any resources or time to implement, its positive impact cannot be understated.
Reference list
ASN Aircraft accident Boeing 747-121 N736PA.
Authority gradients (2017).
B742 / B741, Tenerife Canary Islands Spain, 1977 (2018).
Crew resource management (CRM) (2020).
Expectation bias (2012).
ICAO SHELL model (2019).
K.L.M. and P.A.A. (1977) The collision of the Boeing 747 aircraft.
Smith, P. (2017) ‘The true story behind the deadliest air disaster of all time’, The Telegraph.
The language of aviation. Web.