Human Factors and the Tenerife Airport Disaster

Embry Riddle Aeronautical University
Human Factors in Aviation Safety

August 24, 2012

Abstract

To err is human, or at least that’s how the saying goes. Most mistakes that people make are small, but then there are those mistakes that can be life threatening. On March 27, 1977, two Boeing 747 passenger aircraft collided on the runway of Los Rodeos Airport, on the island of Tenerife, in the Canary Islands. A combination of factors contributed to the collision, but the end result fell on human factors. Due to several instances of miscommunication, misunderstandings, over-confidence, and lack of patience, the lives of 583 people were taken. This paper discusses what actually happened, and utilizes information gathered from the Netherlands Investigation Board, the research and input discussed by ALPA (Air Line Pilots Association), and human factors that were involved.
Human Factors and the Tenerife Airport Disaster
To err is human, or at least that’s how the saying goes. Most mistakes that people make are small, but then there are those mistakes that can be life threatening. On March 27, 1977, two Boeing 747 passenger aircraft collided on the runway of Los Rodeos Airport, on the island of Tenerife, in the Canary Islands. A combination of factors contributed to the collision, but the end result fell on human factors. When it comes to human error, specifically in the aviation field, situational awareness is the key. The weather conditions, in conjunction with the unusual parking conditions at the smaller airport, were only two of the major ingredients in this horrible disaster.
Human error can be defined as inappropriate human behavior that lowers levels of system effectiveness or safety, which may or may not result in accident or injury (Wickens, Gordon, Liu, 1998). The term is usually used to describe operator error, or the inappropriate behavior of the person, or persons, directly involved with the failure. Operator errors can occur for many reasons, including poor work habits, poor decision making, social pressures, personality traits, inattentiveness, lack of training, and even over-confidence.
There were about 70 crash investigators from Spain, the Netherlands, the United States, Pan Am, and KLM all involved in the investigation. Facts showed that there had been misinterpretations and false assumptions. Analysis of the CVR transcript showed that the KLM pilot was convinced that he had been cleared for takeoff. While according to the tower recording, the Tenerife control tower was certain that the KLM 747 was still sitting at the end of the runway and awaiting takeoff clearance. It appears KLM's co-pilot was not as certain about take-off clearance as the captain.
KLM Flight 4805 and Pan Am Flight 1736 were only two of the many aircraft that had to be diverted to Los Rodeos Airport from Gran Canaria Airport after a bomb explosion and a second threat. While Gran Canaria authorities were searching the premises for the second bomb, all of the aircraft were sent to the much smaller airport on Tenerife. Air traffic controllers(ATC) were forced to park the overflow aircraft on the taxiway. When the Gran Canaria opened back up, in order to clear the runway and allow the Pan Am aircraft to leave, the KLM 747 that was parked on the taxiway needed to line up for takeoff. With the fog that had developed, the aircraft could not see each other, and the ATC tower could not see the aircraft. Due to several instances of miscommunication, misunderstandings, and lack of patience, the lives of 583 people were taken.
Pan Am Flight 1736 and KLM Flight 4805 had both been bound to Gran Canaria Airport. The Pan Am flight originated out of Los Angeles, CA, had a pit-stop at John F Kennedy International Airport to crew change and added a few passengers, and then left for the Canary Islands with a total of 396 souls on board; 335 of which lost their lives. The KLM flight originated out of the Netherlands, with no stops in between and contained a total of 248 souls, all of which were lost. With a stroke of luck, a single passenger, a Dutch tour guide named Robina van Lanschot, who was supposed to be on board the KLM aircraft was saved by making a last minute decision to visit with her boyfriend on the island of Tenerife instead of continuing on to Gran Canaria (Public Broadcasting Station [PBS], 2006).
The KLM crew included Captain Jacob Veldhuyzen van Zanten, First Officer Klaas Meurs and 12 other crew members. There were 234 passengers, including 48 children and three infants on the aircraft ("KLM Pass," n.d.). Every person on board KLM Flight 4805 perished that day.
The crew for the Pan Am flight included Captain Victor Grubbs, First Officer Robert Bragg, Flight Engineer George Warns, 13 other crew members, two observers located in the jump seats, and one first class purser. Of the passengers, the details were not as detailed regarding age as the KLM passenger report. Unfortunately, ten of the 72 survivors died later, due to injuries received from the crash ("Pan Am Pass," n.d.).
Los Rodeos was not designed to accommodate large aircraft, and the deviation from the other island caused major congestion at the small airport. With all of the additional aircraft blocking the taxiway, the departing aircraft had to accomplish a procedure known as runway backtaxi by taxiing along the runway and positioning themselves at the end of the runway.
While waiting for permission to continue on to Gran Canaria, the KLM Flight decided to fuel the aircraft in order to save time at their next stop. Speculatively, the extra fuel the KLM plane took on added several factors. First, it delayed takeoff an extra 35 minutes, which gave time for the fog to settle in. Second, the extra fuel added over forty tons of weight to the plane, which made it more difficult to clear the Pan Am aircraft when taking off. Also,,it may have increased the size of the fire from the crash that ultimately killed everyone on board. The KLM aircraft and fuel truck were blocking the taxiway when the Pan Am aircraft was ready to position for takeoff Preventing the Pan Am aircraft from maneuvering into position.
While waiting for clearance to continue the scheduled flight, inclement weather proceeded to roll in. Tenerife airport is located at 2073 feet above sea level, and in turn has very different cloud patterns and characteristics from most airports. “In addition to the unusual cloud conditions, local high terrain around Tenerife causes a venturi effect at the airport…increased wind speed and decreased pressure can result in increased cloud density” (ALPA Study Group, n.d., p. 8). The Spanish report stated that “Because of its altitude and location in a sort of hollow between mountains, the airport has distinctive weather conditions, with frequent presence of low-lying clouds” ("Part One of the Spanish Report," n.d., p. 12). The accident occurred within heavy fog, where there were no eye witnesses. The only indication that something had happened was when the tower controllers heard two separate explosions close together ("Final Dutch Report," 1977, para. 1.14.1).
The human mind is a magnificent thing; creative, robust, and often flexible. The same characteristics that enable the human mind to be imaginative are also the downfall that produces the errors that are the most dangerous. When the KLM captain decided to take on a fuel load, he was trying to be proactive regarding duty time restraints, knowing that other aircraft that had been diverted would be trying to refuel at Gran Canaria (ALPA Study Group, n.d., p. 7). This choice may have been a good idea, if not for the unusual circumstances in place. Considering where the aircraft was parked, it and the fuel truck were then blocking the taxiway for the Pan Am aircraft. When KLM was cleared to backtaxi, after fueling, the ATC asked the flight crew to report when ready to copy for clearance.
By looking at the cockpit voice recorder (CVR) transcript, once KLM started to taxi is where the confusion and miscommunication really began ("Part Two," n.d., p. 2). The Human Factors Report on the Tenerife Accident points out that there were only two air traffic controller positions being filled at that time, and that both Pan Am and KLM were both given clearance to start engines and position themselves for takeoff, but on different frequencies (ALPA Study Group, n.d., p. 6). While the KLM first officer was still repeating ATC instructions given by the controller, the DFDR (digital flight data recorder) shows that the captain had already begun the ground run by accelerating the engines. There was a whistling sound in the tower transmission when Pan Am reported that they were “still taxiing down the runway” and the controller was telling KLM to “stand by for take-off…I will call you” ("Final Dutch Report," 1977, p. 47).
The Final Dutch Report also points out the lack of crew resource management with the statement of “both the co-pilot and flight engineer made no further objections” regarding the captain’s response to the Pan Am aircraft being clear of the runway. “Perhaps influenced by his great prestige, making it difficult to imagine an error of this magnitude on the part of such an expert pilot” would be the greatest example of CRM failure ("Final Dutch Report," 1977, p. 47). CRM did not become part of aircrew training at this time until 1979, when the training was shared by NASA (Cooper, White, Lauber, 1980).
Situational awareness, as agreed upon by the Enhanced Safety through Situation Awareness Integration in training consortium (ESSAI) is “the perception of the elements in the environment within a volume of time and space, the comprehension of their meaning, and the projection of their status in the near future” (Enhanced Safety through Situation Awareness Integration in training [ESSAI], 2000, p. 36). It can be said that while the crew was aware, it may have been too late to question the captain, even had they wanted to.
In part two of the Final Dutch Report, the considerations and conclusions are listed in detail. The conclusion shows no evidence of any one single thing or person being the main cause for the accident that claimed the lives of many. The Dutch even researched the possibility of stress, but ruled that out by taking into account the experience of all persons involved. Every possible aspect was researched, and with the inclusion of multiple countries, the research was very thorough.
Considering that no single aspect could be pin-pointed as the primary cause, the Dutch board could only recommend regulations in order to prevent a future occurrence, of the same nature. The recommendation that a pilot not request taxi clearance until departure instructions are requested, received, and read back. This suggestion comes from the take off clearance being requested before the take off checklist was ever completed. If the aircraft was not completely ready, the aircrew was not paying attention and could have only been listening for key words, like its call sign or a specific word. There was speculation the reason that only the flight engineer reacted to the radio transmission "Papa Alpha one seven three six report when runway clear" might lie in the fact that this was the first and only time the Pan Am flight was referred to by that name. Before that, the plane was called "Clipper one seven three six" ("Final Dutch Report," 1977, p. 64). The flight engineer, having completed his pre-flight checks, might have recognized the numbers but his colleagues, preparing themselves for take-off, might have subconsciously been tuned in to "Clipper".
Another idea was to ensure that a pilot does not combine any message with the take-off clearance request. In addition to that suggestion, different radio frequencies should be used for in-coming and departing aircraft. Utilizing the phrase “take-off” should only be used by the controller when issuing the clearance and then the pilot can say it when confirming clearance from the controller.
Recommendations were also made for entrances and exits for taxiways and runways to be more clearly marked. It was suggested that radio communications become more standard. Standard phraseology and terminology, in order that pilots of all nationalities, are able to understand and communicate. “Ground radar, block safety systems, visual confirmation by means of lights and the so-called data-link” were another few items suggested to assist the crews and ATC for those times when there was inclement weather and reduced visibility ("Final Dutch Report," 1977, p. 68).
The Netherlands report also acknowledges and states that, yes, there were coincidences. The fog was the reason that the radio was the only way for the tower and the aircraft to communicate. The congestion at the airport was the explanation for the two aircraft “taxiing simultaneously on the only available and active runway.” Additional coincidences included “the request for the ATC clearance coincided with the request for take-off clearance” and “the misunderstandings between KLM and the tower” ("Final Dutch Report," 1977, p. 65).
The investigation concluded that the fundamental cause of the accident was that Captain Veldhuyzen van Zanten took off without takeoff clearance. The investigators suggested the reason for his mistake might have been a desire to leave as soon as possible in order to comply with KLM's duty-time regulations, and before the weather deteriorated further.
Other major factors contributing to the accident were: * The sudden fog greatly limited visibility. The control tower and the crews of both planes were unable to see one another. * Simultaneous radio transmissions, with the result that neither message could be heard.
The following factors were considered contributing but not critical: * Use of ambiguous non-standard phrases by the KLM co-pilot ("We're at take off") and the Tenerife control tower ("OK"). * The Pan Am aircraft had not exited the runway at C-3. * The airport was (due to rerouting from the bomb threat) forced to accommodate a great number of large aircraft, resulting in disruption of the normal use of taxiways
The Dutch authorities were reluctant to accept the Spanish report blaming the KLM captain for the accident. The Netherlands Department of Civil Aviation published a response that, whilst accepting that the KLM aircraft had taken off "prematurely", argued that he alone should not be blamed for the "mutual misunderstanding" that occurred between the controller and the KLM crew, and that limitations of using radio as a means of communication should have been given greater consideration.
In particular, the Dutch response pointed out that * The crowded airport had placed additional pressure on everyone; the KLM crew, the Pan Am crew, and the tower controllers; * Sounds on the CVR suggested that a football match was on the radio in the Tenerife control tower and they may have been distracted during the incident. * The transmission from the tower in which the controller passed KLM their ATC clearance was ambiguous and could have been interpreted as also giving take-off clearance. In support of this part of their response, the Dutch investigators pointed out that Pan Am's messages "No! Eh?" and "We are still taxiing down the runway, the Clipper 1736!" indicated that Captain Grubbs and First Officer Bragg had recognized the ambiguity (this message was not audible to the control tower or KLM crew due to simultaneous cross-communication); * If the Pan Am aircraft had not taxied beyond the third exit, he would have already been off of the runway and the collision would not have occurred
Although the Dutch authorities were initially reluctant to blame Captain Veldhuyzen van Zanten and his crew, the airline ultimately accepted responsibility for the accident. KLM paid the victims and/or the families’ compensation ranging between $58,000 and $600,000 ("KLM Responsibility," n.d.). “As reported in a March 25, 1980, Washington Post article, the sum of settlements for property and damages was $110 million (an average of $189,000 per victim, due to limitations imposed by European Compensation Conventions in effect at the time)” (Firth, 2012, Chapter 3).
When it comes to human error, specifically in the aviation field, situational awareness is the key. While KLM took responsibility for its employees’ mistakes, we can only hope that they remember the pain and tragedy, not just the money they lost. Worldwide, people learn from other’s mistakes. To err is human, or at least that’s how the saying goes. Most mistakes that people make are small, but then there are those mistakes that can be life threatening. Let us hope that we never have to worry about another disaster of this magnitude, even though it is very possible.

References
ALPA Study Group. (n.d.). Human Factors Report on the Tenerife Accident. Retrieved from http://www.project-tenerife.com/engels/PDF/alpa.pdf
Cooper, G. E., White, M. D., & Lauber, J. K. (Eds). (1980). Resource management on the flightdeck: Proceedings of a NASA/industry workshop (NASA CP-2120). Moffett Field, CA: NASA-Ames Research Center
Final Dutch Report of the Investigation into the Accident with the Collision of KLM Flight 4805, Boeing 747-206B, PH_BUF and Pan American Flight 1736, Boeing 747-121, N736PA at Tenerife Airport, Spain on 27 March 1977. (1977). Retrieved from http://www.project-tenerife.com/nederlands/PDF/finaldutchreport.pdf
Part Two of the Spanish Report. (n.d.). Retrieved from http://www.project-tenerife.com/engels/PDF/spanish_report2.PDF
Public Broadcasting Station. (Producer). (2006). The Deadliest Plane Crash [DVD]. Available from http://www.pbs.org/wgbh/nova/space/deadliest-plane-crash.html.
Wickens, Christoper D., Gordon, Sallie E., and Liu, Yili (1998). An Introduction to Human Factors Engineering. Addison-Wesley Educational Publishers Inc., New York, New York.