Human Factors in Aviation: Mitigating the Danger of Distraction

by HPA · July 21, 2017

Human Factors in Aviation: Mitigating the Danger of Distraction

by Scott Kellam

What is Human Factors?

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The Federal Aviation Administration (FAA) defines Human Factors (HF) as: “A multidisciplinary effort to generate and compile information about human capabilities and limitations and apply that information to equipment, systems, facilities, procedures, jobs, environments, training, staffing, and personnel management for safe, comfortable, and effective human performance.” Basically, what this means is that HF engineers are trained extensively in human psychology and physiology to understand the abilities and limitations of humans. This knowledge is utilized to predict how humans will interact with different components in what is called the “SHELL” model. This model describes how humans, (liveware) (L), interact with software (S), hardware (H),environment (E), and liveware (L) (other humans). The edges of the individual components in this model are irregular, indicating that each component must be carefully matched to avoid an eventual system breakdown.

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HF is extremely useful in identifying potential hazards in research and development, the work environment, as well as identifying the cause of aviation accidents in a unified effort to increase risk management, safety, and productivity. Although the study of HF is a relatively new scientific discipline, its acceptance and usefulness has grown exponentially in recent years, proving essential for the aviation industry, healthcare industry, and nuclear power industry.

As we are all aware, humans are fallible. Human factors theory calls this Human Error (HE), which can be a slip, lapse, error in judgement or misunderstanding. HE can be mitigated using training, crew resource management (CRM), and the use of computer systems (automation) to improve overall safety and human performance. Human error can be devastating in high-risk environments where the outcome of an HE related accident may cause tragic loss-of-life, as well as significant property loss.

Tenerife, Spain – March 27, 1977

The aviation industry quickly realized the usefulness of utilizing human factors studies to mitigate accidents in the late 1970s after a rash of high-profile aviation accidents took place around the world. Most notable was the Tenerife, Spain accident occurring on March 27, 1977 when two Boeing 747s collided on the runway. The haunting nature of the Tenerife disaster goes well beyond the colossal loss-of-life which subsequently occurred. In fact, neither aircraft was supposed to be at Tenerife that day. An earlier bomb blast in the passenger terminal at Las Palmas de Gran Canaria (Spain) prompted KLM Flight 4805, and Pan American Airlines (PAA) Flight 1736 to divert to their alternate airport, Los Roderos Airport (Tenerife). After landing, both aircraft were required to wait until authorities at Las Palmas could reopen the airport.

Around 1700 local time, Las Palmas reopened and KLM 4805 was advised by ATC to “back track” runway 12 for 30, and perform a 180 degree turn to line up with runway 30. Approximately two minutes later, PAA 1736 was also advised to “back track,” and exit the third taxiway to the left to allow KLM 4805 to depart. Prior to taxiing, a thick layer of fog began to roll in, obstructing visibility of ATC and aircraft operating on the ground. As KLM 4805 reached the end of the runway, they began their 180 degree turn to line up. At the same time, PAA 1736 was approaching the midpoint of the runway, and becoming increasingly unsure of their position on the airport. KLM 4805, now in position on runway 30, radioed ATC that they were “in position and ready.” ATC acknowledged, and provided KLM with departure instructions advising, “standby for takeoff, I will call you.” The crew of KLM 4805 read back their ATC clearance, but were unsure if they had, in fact, received approval for departure. Hastily, the KLM captain pushed the throttles forward, announcing to ATC that they were rolling. Alarmed, PAA 1736 radioed ATC that they were still taxiing on the active runway, but because of another radio transmission (stepped on), their message was never understood.

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As KLM 4805 accelerated down the runway, both aircraft slowly became visible to the crews. The crew of PAA 1736 panicked and rushed to get off the runway ahead of the KLM. As KLM 4805 sped through 100 knots, the KLM crew finally saw that PAA 1736 was still on the runway and immediately pulled back hard on the control column to try and get the fully-fueled 747 airborne. Immediately, KLM 4805 began to rotate, striking the tail on the runway just before the plane left the runway. PAA 1736 just began their left turn onto taxiway C-4 as KLM 4805 struck the top of PAA’s fuselage, midway down the aircraft, setting the Boeing 747 on fire, and ripping a huge section of the roof off. KLM 4805 lost control and impacted a half-mile from the PAA 1736 jet, killing all souls on board. Amazingly, some passengers onboard 1736 managed to exit the aircraft before the center fuel tank ruptured and exploded, destroying the aircraft.

The captain of KLM 4805 was Chief of Flight Instruction at KLM, as well as the face of the company. 1977 was prior to the implementation of CRM, and it was common at that time for crews not to second guess or question the captain. Because of this hierarchy, it is thought the flight engineer’s statements to the captain asking if Pan Am was off the runway, went unheard or unheeded, answering with an unintelligible statement.

As with all accidents and incidents, there is never one single causal factor, but rather a chain of events that lead to the moment of impact. The human factors involved, and main contributor in this accident were cited as a deteriorating mental status of the KLM captain due to the organizational stress of delivering the passengers to their final-destination and the deteriorating weather at Tenerife. At the time of the accident, the visibility was approximately 1 km, and deteriorating. The pressure to get the passengers to Las Palmas, along with his status within the company, most likely negatively impacted the captain’s decision making abilities.

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Secondly, the simultaneous radio calls between ATC (“standby for takeoff”) and PAA 1736 (“we are still taxiing down the runway”) significantly affected the message clarity. Communication was further hampered by a hissing sound that lasted about three seconds. Radio interference, along with inadequate language between KLM 4805’s first officer and the controller, caused the captain to mistake the first officer’s readback, and begin the takeoff roll.

Lastly, PAA 1736 neglected to turn onto their assigned taxiway (C-3) and instead began their left turn onto C-4. This may have been a mistaken instruction by the controller, (“turn left on third one”) meaning C-3, regardless, which exit is irrelevant because the crew of PAA 1736 radioed twice that they were still on the runway. However, had PAA 1736 turned onto C-3, they most likely would have avoided the collision. Adding to the confusion, the 1km visibility and the unfamiliarity of the airport, on top of the deteriorated mental status of this crew contributed as well. Furthermore, Los Roderos was unusually busy due to the closing of Las Palmas, and “back taxiing” procedures are not typically authorized due to the increased risk of an incident/accident.

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Unfortunately, on that day, 583 people lost their lives to human error. To this day, it is still the single worst commercial aviation accident in history. The occurrence of this tragedy prompted government agencies (NASA, ICAO) to invest in HF programs to mitigate human error and create what we know today as CRM. Had CRM been in place at the time of this accident, the crew would have been much more confident in alerting the captain, and might have prevented the accident. The replacement of an intimidating leader who makes all the decisions is now an open environment where all team members have a say. It is important to note that although the incorporation of HF and CRM were primarily adopted for the commercial aviation industry, these very same practices can be applied to all aspects of aviation, including private pilots (General Aviation), mechanics, air traffic controllers, ground personnel, and flight attendants. Understanding the role human error plays in aviation, no matter what your affiliation may be, will only serve to increase overall safety and performance throughout the industry. If you would like to view the documentary of the Tenerife disaster, it is available on the YouTube video below. For more information on human factors, visit the Human Factors and Ergonomics Society’s website at:

Scott Kellam is a private pilot with a bachelor’s and master’s degree in Aeronautics from Embry-Riddle Aeronautical University. His interest in human factors has guided his studies in aviation.

How it Started

One of my best friends in high school, (Doug Gray) was a private pilot. He offered to take me up for a flight in a 1967 Cessna 150, N6228S. We took off from Calhoun, Georgia, and he took me on a scenic tour of the area, I was hooked. I later found out that my English teacher, (Jan Haluska) was also a flight instructor and the school was offering a ground school course the next year, which he taught, along with flight training with the goal of becoming a private pilot. I managed to talk my dad into funding the training, at the time the total cost was right around $500. Cessna 150 rental rates where $12 an hour, and the 172 we used for cross country was $15 an hour including fuel.

Training Begins

It started August of 1977. The fall semester rolls around, and I am enrolled in ground school, and if memory serves me, we met twice a week. First came the paperwork for my student pilot certificate, which at the time was included with the 3rd class medical. I loved ground school, especially learning navigation, plotting courses on the sectional, again this was before iPads and GPS, so we did a lot of dead reckoning and VOR navigation for cross countries. At the end of the course, I made an 83% on the Private Pilot written exam, remember this was before we had the question-and-answer books that on future test I would consume before taking a written.

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The fun really began on August 22, 1977, it was my first flight. To my surprise we used the same Cessna 150, N6228S that my friend Doug Gray had taken me for a ride in. The Cessna 150 had a standard VFR instrument panel, with one NAV/COM, and one VOR CDI. No intercom, so no headset, at the time I didn’t know what I was missing. I didn’t get my first headset until I started my instrument training in 2003. I was a big guy, I was 6’ 4” and weighed 245 lbs. but I do not remember being uncomfortable in the 150 even with the instructor in the right seat.

First flight lasted .8 hours, and we accomplished orentation, shallow turns, stability, and effects of flight controls. Over the next few months we added steep 720’s, slow flight, stalls, turns around a point, S-turns, emergencies, landings, (short field, soft field and normal).


At this point I want to talk about a training experience that still stands out. We were close to solo and were practicing takeoffs and landings. Turning base to final Jan got very upset at the way I was cross controlling the aircraft. Cross control is when you are in, say a left turn, and use opposite rudder to line the nose up with the runway. So, he had me depart the pattern and head east to the practice area, and climbing up to 5500 feet MSL, he had me slow down to just above stalling speed, start a left shallow turn and add right rudder. As the airplane stalled I had the strangest sensation, no roller coaster has ever come close, instead of blue sky in the windscreen I was looking at brown ground, and as far as I could tell we were upside down, through the terror of the moment Jan talked me out of the spin, controls neutral, oposite rudder, pull slowly out of the dive. As we leveled off he asked me what altitude we were at, as I remember it was around 2,800 feet MSL. Then he asked me what would happen if I experenced this on base to final in the traffic pattern. The answer was obvious, I would be a pile of wreckage off the end of the runway with a very short-lived aviation career. Needless to say this cured my cross-control tendencies.

Another training event the sticks out in my mind was the first time we did takeoffs and landings at the High School runway. The runway was 1,500 feet long, not sure of the width, but it seems like we had about 5 feet on each side of the wheels when on the center line of the runway. Landing from the south you also had to go between a cutout in the trees to be able to stop in time on the runway. After getting confortable landing here every runway since seemed huge. I remember landing at Chattanooga (KCHA) on a night cross country and commenting to Jan, that I felt like I could of landed sideways on the runway, it felt that large.

Very soon after this I started wearing old shirts to all my flight lessons, the reason for this occurred on February 8, 1978. The lesson that day was stalls, takeoffs and Landing. As we were taxing back in Jan told me it was time for my first solo. I was very excited, and after some last minute advice from Jan, including watch for floating on landing the plane will be light with him not in the right seat, complete 3 takeoffs and landings to a full stop. It was a blast, and at the end of my shirt was shorter in the back because Jan cut the tail out of it signed and dated my solo [an aviation tradition]. Total flight time accumulated on the day of my solo was 18.1 hours. I was now officially a pilot with solo priveleges.

In my next article I start cross country training, when Jan decided that it would be best accomplished this in the 172. Checking out in N5970R was like moving into a 747, this started a love affair with one of my faviriote planes to date. Since this time I have flown over 900 hours in many different models of the 172 and feel like I am stepping into an old friend every time.

More about Randy here:


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