The results of brand-new research indicate that experience is no protection against the risk of a ‘mid-air’.

The Massey University research, Mid-air collisions in uncontrolled airspace: Common factors and ways forward, analysed four general aviation accident reports from New Zealand, and 150 more from Australia, Canada, and the US, from 1999 through to 2022.

The research extracted findings and recommendations from the accident reports, to identify the common factors in mid-air collisions in uncontrolled airspace, and how future accidents might be prevented.

Most of the collisions happened between fixed-wing aircraft, on daylight recreational flights, and in VMC conditions. Nearly half of the accidents occurred in the vicinity of an aerodrome.

More than half of the accident report recommendations were directed at pilots, about one in six were aimed at regulators, and one in ten at operators.

The research, by Dr Isaac Henderson and Claire Walton, of Massey’s School of Aviation, has lessons for all pilots, no matter how experienced, on the ‘basics’ – consistent use of ‘see and avoid’ techniques, making good use of the radio, and effective preflight planning.

The link between poor planning and collision risk

The researchers found that the cause of more than half of the accidents related to pilot judgement and decision-making. The most common instances were a lack of vigilance (such as pilots not maintaining adequate lookout), pilots failing to maintain separation, making procedural errors (for example, conducting a nonstandard circuit join), and failing to give way.

Claire, a commercial pilot of more than 25 years’ experience, says this result was surprising, because there’s a common assumption that collisions generally start and end with loss of situational awareness.

One in every six accidents did have a lack of situational awareness as a finding – for instance, loss of awareness of other aircraft, failing to recognise the risk of a collision, being preoccupied with other tasks, and incorrect assumptions about the other aircraft’s intentions.

“But we found that the biggest precursor to collisions was poor judgement and decision-making,” Claire says.

“For example, in failing to maintain adequate visual lookout, the pilot has already decided there isn’t sufficient risk of a collision, and possibly also that there’s no need to provide accurate position reports.”

Claire says, as a pilot, her biggest lesson from the research was the importance of preparation.

“On a broad level, it’s vital to continue my learning between biennial flight reviews.

“But on a more immediate level, it’s important for me to think ahead about join procedures and give way rules.

“What do I need to know about the airspace I’m going into? What are the radio calls I’ll need to make?”

These were questions that some of the pilots who would later be part of a mid-air collision did not ask themselves, nor prepare for, during what should have been the planning phase of their flight – before their aircraft even left the ground.

The contribution of visual limitations

Visual limitations contributed to half of the accidents in the study. Of these, the limitations of see and avoid were the most common. For Isaac, the lead researcher, this finding confirmed the importance of understanding what limits the ability of pilots to undertake an effective visual scan and sight other traffic.¹

Isaac highlights that many pilots don’t understand the limitations of the see and avoid technique, and how to manage those limitations.

“The main limitation of see and avoid is that you won’t see an aircraft you’re on a collision course with unless you look directly at it. This is because there can be no relative movement between the aircraft – the angle between the two aircraft stays constant, and the conflicting aircraft will simply appear bigger and bigger in exactly the same spot on the windshield.

“That poses a problem for the human eye, because peripheral vision – where we don’t see what we’re directly looking at, but around it – only detects movement.

“That’s why we need to look directly at a conflicting aircraft.”

Isaac also believes that pilots need to move from unaided see and avoid to aided see and avoid, such as making and listening to radio calls to know where to visually scan.

How poor radio work plays a part

Poor communication was a factor in one in every four accidents. Of these, failing to make appropriate radio calls was the most common finding (for instance, not broadcasting intentions to enter a circuit).

Broadcasting on the wrong frequency was also a recurring factor, as was failing to hear and interpret radio calls, and failing to monitor radio frequencies.

“It seems obvious, but my recommendation, based on this research, is to use the radio so everyone else knows exactly where you are. And then listen properly to other radio calls, so you know where they are,” says Isaac.

You’re not necessarily protected by experience

The research sample comprised 361 pilots, the majority of whom held a CPL or ATPL. The research indicated that the actions of pilots with significant flying hours were just as likely to show up in findings and recommendations, as were less experienced pilots.

While this was surprising, Claire says, it confirms that no one is exempt.

“You could be an A-cat instructor or a senior airline captain and still be at risk of a mid-air collision.”

The only rider to that was that higher total flight hours made a pilot less likely to fall victim to their own visual limitations.

And generally, pilots who held any rating, such as an instructor or instrument rating, were less likely to have findings and recommendations about judgement and decision-making, personal limitations, their competence, or violations of rules.

Recommendations of the investigation reports

One in every four accident reports recommended that pilots improve their knowledge about traffic procedures.

Of those, the most common recommendations were for pilots to make themselves familiar with give way rules in uncontrolled airspace, and to be familiar with traffic pattern entry practices at unattended aerodromes.

Similarly, one in every four accident reports recommended improved practice for managing ‘visual limitations’. Of those, pilots maintaining effective lookout was the most frequent recommendation.

Isaac says this finding illustrates the need for pilots to understand the limitations of see and avoid, consciously scan their field-of-view, and help their see and avoid with other information to build situational awareness (for instance, listening to position reports).

Lack of vigilance figured in one in four accidents, communications failures in one in five, and faulty aircraft equipment was a factor in one in six.

“Simply put, if pilots aren’t vigilant for collision risk, they won’t look for other aircraft or listen to radio broadcasts in a way that will aid their situational awareness and their ability to avoid other aircraft,” Isaac explains.

The recommendations for improving communications practice were simple – broadcast your intentions, listen to radio calls, and follow best practice (for example, using standard phraseology, and making calls at the right time).

“The number of mid-air collisions where these things did not happen should be testament to the importance of getting the basics right,” says Claire.

Aircraft equipment, where fitted, can also improve situational awareness of other aircraft – airborne collision avoidance systems (ACAS), lighting, and fitting transponders all come up as recommendations.

Flying near aerodromes

As noted earlier, just under half of the accidents occurred in the vicinity of an aerodrome. The research found two big factors in these accidents were poor communications, and poor field-of-view (for instance, if you’re in a lowwing aircraft, you have poor downward field-of-view and should fix that by doing a couple of quick turns to move the wings and see if any traffic is present).

Recommendations for safer flying near aerodromes were predominantly directed at pilots – practise to build your flying competency, follow communications best practice, and be aware of your visual limitations.

Questions for the future

The researchers say there are other areas needing further consideration and research.

The first is whether human factors training needs to be re-thought.

“Even though I’d had two decades in commercial operations, I was really surprised with how much I learned when I began my university studies,” Claire says.

“Understanding human factors in a more thorough way helped explain many of my experiences, and challenged some of my long-held assumptions about safe flying.”

Claire also believes new training devices to help build core competencies, such as communications, will help future pilots avoid collisions in uncontrolled airspace.

“With new technologies like virtual reality and artificial intelligence, we have new opportunities to improve pilot training and better support student pilots as they learn.”

Both authors highlight how important it is to keep the spotlight on safety in uncontrolled airspace.

“It’s been great to see the Civil Aviation Authority’s initiatives, such as the Plane Talking and Circuit Certainty seminars, and the Work Together, Stay Apart campaign,” says Claire.

“But we need to keep up the momentum to prevent future accidents in uncontrolled airspace.”

“Every one of the 308 flights in our sample set off as usual, and in the course of their flight, collided with another aircraft in uncontrolled airspace,” says Isaac.

“It highlights our fallibility as humans and the possibility that this could happen to anyone.

“The whole aviation sector needs to continue to work together to prevent future mid-air collisions in uncontrolled airspace.

“We hope our research will play a small role in contributing to that.”

More information

Vector Online: Things that jeopardise your lookout

 

---

Footnotes

¹ In some instances, a pilot did see the other aircraft but there wasn’t enough time to respond – this figured in about one in 10 accidents.

Main photo: iStock.com/Gerrit Rautenbach