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Error prone?

Garnet Ridgway: Human factors (HF) as a contributory cause of air accidents is as old as aviation itself, although admittedly it gained its moniker only relatively recently. It can therefore be argued that the ‘recent trend’ of HF-related accidents is, in fact, simply the continuation of a problem that has never been fully understood.

During World War I, the British Royal Flying Corps concluded that 90% of fatalities among pilots were caused by “their own deficiencies”. Today, the majority of this percentage would certainly be classified as HF-related (insufficient training, fatigue, excessive workload), giving a proportion comparable to that of modern aviation accidents.

In the period following World War I, efforts were made to improve the accommodation of human physiology into military aircraft in the hope of reducing accident rates. While some progress was made (the advent of closed cockpits, for example), the psychological aspects of HF were still poorly understood. By way of demonstration of this lack of understanding, consider the world’s first widely adopted flight simulator, the Link Trainer.

Despite its name, the Link Trainer was actually envisaged as a device for the selection of pilots “most suitable for instrument flying”. This backward approach of attempting to tailor the users to the requirements of the machine, rather than vice versa, is indicative of the attitude prevalent for much of the 20th century, and lingers to this day. Additionally, causes of accidents resulting from these psychological subtleties are far more difficult to identify after the event; this resulted in further misidentification of HF-related accidents as “pilot error” or other such catch-all phrases.

So, what is the way forward? Ironically, the most effective (and often final) layer of mitigation for HF errors in design or maintenance is a human operator – an ability to cope well with sudden, unexpected changes has been instilled by millennia of evolution. However, this must be facilitated by good, user-centric system design and comprehensive HF assessment at the test and evaluation phase. Finally, there must be an acceptance that HF is, in fact, a real issue that causes fatal air accidents. 

Garnet Ridgway has a PhD from the University of Liverpool. He has designed cockpit instruments for Airbus and currently works for a leading UK-based aircraft test and evaluation organization.


Sophie Robinson: The role that the human element can play in air safety has recently been put in to sharp focus by a spate of accidents caused by HF – Virgin Galactic, TransAsia Flight 235 and the Lynx Mk9A crash in Afghanistan being just a few examples from recent months.

What could be causing this apparent surge of human-induced accidents? The increased maturity of all areas of aircraft design is partly to blame; engines are more reliable, airframes stronger and materials more durable, meaning accidents resulting from mechanical or manufacturing failures are becoming rarer.

As a result, the proportion of HF-related accidents has increased. While technological advances have improved safety in some areas, advances in other areas have created new safety issues. For example, as the sophistication of avionic systems (autopilots, navigation, radios, and so on) in aircraft has increased, so too has the cognitive effort required to fly modern aircraft. This can result in a dangerously high workload for the pilots, and combined with the high-pressure nature of aviation jobs, can lead to mistakes being made that can have deadly consequences. This was not the case for the relatively simple aircraft and relaxed duty cycles of yesteryear.

The increasingly automated cockpit environment can also lead to low crew arousal: according to a 2013 survey by the British Airline Pilots’ Association, more than half of pilots have fallen asleep in the cockpit. The poll showed that of the 56% who admitted to taking an impromptu nap, 29% said they had awoken to find the other pilot asleep. This certainly wouldn’t happen if piloting an aircraft required the full attention of the crew for the duration of the flight!

As aircraft continue to become more complex, and testing schedules remain tight, HF issues have the potential to be missed during the design, manufacturing and testing stages of the product lifecycle. As the proportion of accidents attributed to HF continues to increase, it is logical to increase proportionally the attention paid to HF-related issues during aircraft evaluation. While HF can never be eradicated, there certainly remains scope for improvement.

Sophie Robinson works at the front line of aerospace testing as a rotary-wing performance and flying qualities engineer for a leading UK-based aircraft test organization. She also holds a PhD in aerospace engineering from the University of Liverpool, UK.



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