The Science behind Go-Arounds
Op-Ed Safety

The Science behind Go-Arounds

DALLAS – Photos of the marooned Korean Air (KE) Airbus A330 following the recent runway overrun in Cebu (CEB) beg the obvious question, “What went so wrong?”

Accidents are rarely the result of a single cause, and there are frequently multiple links in the chain of events that all conspire to produce the unfortunate event. One common analogy that aviators often refer to is linked to the holes within many layers of cheese all lining up at the same time.

Once investigators have sifted through the various streams of data recorded by the aircraft, vital clues should be revealed. The cockpit voice recorder records what the crew was thinking and planning at the time. In contrast, the data recorder provides a highly detailed replay of a wide range of aircraft parameters.

In addition to these recorders located near the tail of the aircraft, multiple channels of engine and system data are frequently streamed to airlines and engine manufacturers.

Combining all of this data will allow accident investigators to build a clear picture of the most dominant factors that contributed to the accident.

DL Airbus A330-300 (N818NW). Photo: Alberto Cucini/Airways

Runway Overruns

Runway excursions continue to be a significant threat to the industry. Given that the maneuver of landing an aircraft is still performed manually, with the exception of extremely poor visibility, human vulnerability continues to be challenged.

My recent feature on how pilots calculate landing performance, mentioned how the industry has been working hard in recent years to emphasize the importance of prior planning rather than simply relying on ‘this usually works at this airport.’

Prior to landing, pilots can always fly a go-around, which is when an approach is discontinued and a climb is performed away from the runway. It is also known as a missed approach or an overshoot. This alternative maneuver is still available in many aircraft until the reverse thrust is selected after touchdown. You could be forgiven for thinking that taking off after the landing gear has already touched down on the runway is unusual.

On the other hand, consider whether it is a choice between climbing away from the runway or landing at the incorrect speed and/or position. On reflection, it’s perhaps not such a strange concept after all and this is what is termed as a balked landing.

According to flight tracking data, the KE crew attempted two go-arounds before the third approach, which led to the accident. Thus, the crew successfully flew two missed approaches and was clearly not afraid to go around when it was previously needed.

Weather reports on the day of the accident paint a stormy picture, with cumulonimbus clouds, reported being near CEB at the time. These clouds can pose a great threat to aircraft because they are associated with the formation of thunder and lightning.

Furthermore, they are frequently located close to areas with heavy rain and gusty and unpredictable winds. Pilots must adhere to strict airspeed tolerances during final approach. In more volatile conditions, such winds can make it nearly impossible to keep the airspeed within the limits of what is permitted.

plane landing on runway
Photo by Nguyen Hung on

Practice Makes Perfect

Go-arounds are rarely flown in practice, but they almost always appear at some point in recurrent simulator training. Even if the action of flying a missed approach is a byproduct of another rehearsed maneuver.

Despite this regular training, there is still an uncomfortable number of approaches continuing to a landing, when a go-around would have been a safer option. Factors such as landing at a familiar airport or crew fatigue can sometimes contribute to pilots continuing to land in unsuitable situations.

Another factor that can influence a pilot’s decision-making is the amount of fuel remaining. In good weather, some airlines allow their crews to carry less or no diversion fuel at all, or for this fuel to be consumed in flight if needed, providing the probability of landing at the destination is very high.

Given the inclement weather around CEB at the time, the crew in this situation should have planned to have enough fuel to divert to another airport. Despite this, some crews still feel under pressure when the runway is so close after descending to a very low altitude on the approach, and the alternative of diverting appears very unappealing in comparison.

Flight crews are well-versed in operating in a controlled environment where strict procedures and stringent legislation work together to provide crews with a clear framework of what is safe and permissible and what is not. Despite the fact that this framework is binary because compliance is either achieved or not, we still see situations where suboptimal decisions are made on the flight deck, contributing to landings occurring when it would have been safer not to.

Photo: LCY London City Airport runway. Photo: Iain Marshall/Airways

Mental Hurdles

When an approach does not meet the prescribed tolerances for the descent profile and aircraft configuration, the industry classifies it as ‘unstable’. It should come as no surprise that the number of unstable approaches can be measured in terms of percentage points.

What may surprise you is that, of the small number of unstable approaches, the vast majority continue to a landing rather than opting for the safer option of a go-around. Unraveling why this happens leads us to a far more complicated, yet fascinating subject.

A number of airlines, and, more recently, the business aviation sector, have recognized in recent years that understanding the science behind pilot psychology and decision-making is at the heart of why many approach and landing accidents occur.

The Presage Group is a Canadian firm that identifies and implements solutions to reduce human-induced error in procedurally driven workplaces. The firm’s work is so highly respected that airlines frequently benefit from insurance cost savings as a result of the Presage Group delving deeply into an airline’s inner workings and culture and then offering bespoke solutions for reducing operational risk.

Such studies are broad in scope, and the outcomes are frequently far-reaching.

In addition to improving safety and procedural compliance during the approach and landing phases, substantially increased efficiency in other stages of the flight can often be found as well. One example is that the intervals between changing wheel brake components can extend, due to pilots adopting a more structured and methodical approach to energy management.

Photo: Qatar Airways

Culture Clash

This article would be incomplete if we did not discuss the impact that culture can have on the effectiveness of how a team of pilots works together. While the Captain is legally responsible for the safe conduct of the flight, the vulnerability of the human being requires a constant flow of cross-checking and monitoring from both pilots, irrespective of their experience.

However, in some countries, co-pilots who speak up when something goes wrong are considered disrespectful to their more senior colleague.

Of course, whether such a factor played a role in this accident remains to be seen, but observing cultural niceties at the expense of flight safety is a trait that the National Transportation Safety Board (NTSB) identified as a significant factor in the tragic crash of KE801 on approach to Guam (GUM) in 1997.

Among the somber headlines that deliver the news of another aircraft accident, a silver lining can sometimes still be found. Those are the lessons that can be shared and learned to make the industry safer for us all.

The size of the silver cloud is, of course, determined by the thoroughness and transparency of the subsequent accident investigation.

Featured image: Salt Lake City (SLC) Airport overview with snow. Photo: Michael Rodeback/Airways

Aviation author and commercial pilot based in the UK, with close to twenty years in the industry.

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