SEE & AVOID - A SOUND COLLISION AVOIDANCE STRATEGY?

ICAO standards and consequently most regulatory jurisdictions state that pilots have an obligation to be ‘vigilant’ so as to see and avoid other aircraft – here is an example:

US FAA Regulation 14 CFR Part 91.113 (b) states:

…vigilance shall be maintained by each person operating an aircraft so as to see and avoid other aircraft

In many ways this has come to be seen as the last line of defence in collision prevention but we know that it fails. We need to understand why this is – what are the limitations to see and avoid?

Firstly, there are significant physical obstructions to a pilot’s line of sight, in the shape of the aircraft’s own structure. In fact a pilot’s field of view as permitted by the size and shape of the cockpit windows, only constitutes a small portion of the total sphere of airspace around him or her. In some aircraft the wings may also present a further external obstruction to their view. Moving one’s head may help mitigate for things like window posts but nothing will permit observations below, above or behind the aircraft. Pilots must understand that these are effectively blind spots to any see and avoid strategy.

We are well aware from eyesight tests that human vision varies substantially from one person to another. It is also true that an individual’s own visual acuity can vary with time of day, fatigue, light conditions etc. Those of us of a certain age also know that our eyesight deteriorates with the passing years… The likelihood of actually seeing a conflicting aircraft, even if it is within the field of view, is highly dependent upon the visual acuity of the observer and there is no consistent means to predict that.

We also know that the sensitivity of the retina varies across its surface. The point at which the lens focuses the image, the Fovea, is the most sensitive to colour and definition but this diminishes as distance from the Fovea increases. Our peripheral vision, what we see ‘out of the corner of the eye’ is relatively insensitive and is actually best at detecting motion across the arc of vision. This is recognised in the design of road traffic signals, which use not only a change of colour but a change of light source position to attract our attention – rather like the wig-wag lights on taxiways.

Another inherent visual factor is empty field myopia. At rest or in the absence of something to focus on, our eyes focus at approximately half a metre distance. This means that when looking at an empty sky, we may inadvertently be focused much too close and thereby compromise the ability to see another aircraft in the distance. Other effects like dirt on the windscreen can ‘trap’ the focus of the eye. It may be necessary to deliberately choose objects in the distance to draw the focus out to where the targets might be.

Pilots will be familiar with the effects of glare from a low bright sun – it is quite simply impossible to look in that direction let alone search for aircraft. Fighter pilots have always taken advantage of this to attack ‘out of the sun’. To make it worse pilots may be tempted to use sun visors or even charts and newspapers to block out the glare, thereby increasing the area physically blocked from view. Glare may also interact with atmospheric effects like dust, haze, mist and precipitation to increase their effect on the prevailing visibility. Whilst we know that VFR includes 5 kilometres of visibility, this can vary dramatically in different directions with the atmosphere and the light. 

See and avoid may not be so hard if all we had to do was look out of the window. Unfortunately, or perhaps fortunately, pilots have many other things to do and cockpit workload often increases in the same places that traffic density increases. This allows less and less time for looking for aircraft precisely when there may be more to see. As with all cockpit activities pilots must be careful not to become so absorbed with one task as to forget to carry out another task, such as looking out.

There are a number of techniques recommended for more effective visual scanning. As well as moving the head, pilots can divide the field of view up into segments and scan each in turn in a systematic fashion. In the case of 2 pilots they might choose to search their ‘half’ of the sky. Focusing on objects in the distance may help avoid empty field myopia. Operators should research the various scan techniques and train the ones most suited to their operation and environment.

Finally let’s look at a couple of characteristics of distant visual targets. Firstly, the diagram on the left demonstrates that geometrically an aircraft on a collision course will maintain the same position in the field of view as it gets closer. This means that there will be no angular movement of the target across the field of view and therefore our peripheral vision will be less likely to detect it until it is very close. The aircraft that is going to hit you may be the hardest to see.

On the right is a diagram that shows the visual arc described by an aircraft closing head on. This model is based on a closing speed of 600 knots but even if we halve that, it indicates that a target may only describe an arc of half a degree in our vision, when only 6 seconds from impact. It is still only 1 degree at 3 seconds, when the ‘avoid’ part is out of the question.

PILOT TRAINING - ARE WE GETTING IT RIGHT?

The steering wheel of my old Reliant Scimitar motor car once came off in my hands while I was driving. That was certainly unexpected and the people who sold it to me would probably have said it couldn’t happen. But it did, and I had to figure out how to steer the vehicle while stopping in a safe (ish) place. I got lucky I suppose.

My thanks to Skybrary for https://bit.ly/2ImYXYY - a summary of the Preliminary Report on the investigation into the crash of B737 MAX 8 on 10 March 2019.

The way I read this summary (and I’m sure I’ll be corrected if I’m wrong), the aircraft was technically flyable, although not in a way the pilots had ever seen before and certainly not in a way they had trained for. In fact, they did manage to fly it for a while, overcoming the efforts of the automation to pitch the aircraft down into a suicidal dive, by nose-up elevator and electric stabiliser trim inputs. But eventually it won…

If we go back 10 years to AF447, the pilots were also presented with something they had never seen and had never trained for. The aircraft was technically flyable and operated to design but they couldn’t work out what was happening and correct it. The Air Asia A320 that crashed in 2014 was flyable, although the captain’s well-intentioned actions had caused the flight control systems to revert to ‘alternate law’. The pilots would have seen alternate law in the simulator but never with a sudden and unexpected onset.

I would be prepared to stake a substantial bet that each of these crews could have easily and competently managed an engine failure on the preceding take-off (and any other take-off). That’s what we have trained them for. But these other random, unexpected and potentially startling conditions are not trained and are therefore far more difficult to manage, just like my steering wheel incident.

So perhaps it is time be a bit more imaginative and a bit less optimistic when designing flight training profiles and show pilots some more extreme and unusual flight conditions.

A380 WAKE TURBULENCE AND CHALLENGER BIZJET UPSET

A British national daily among other media outlets has been running with a story that a Bombardier Challenger business jet encountered wake turbulence from an Airbus A380 over the Indian Ocean. The story says that the encounter was so severe that the bizjet was rolled inverted and lost 10,000 feet in altitude. Photos of the cabin interior show total devastation and when the aircraft was diverted to Muscat, Oman, some passengers were taken to hospital.

But wait a minute, the A380 has been in service for over 10 years and there are now more than 200 of them criss-crossing the skies every day. Much of the world's upper airpsace is operated on reduced vertical separation minima (RVSM), meaning that vertical separation between opposite direction aircraft is 1,000 feet.

So why hasn't this happened before? We know that the A380 has a higher wake turbulence category but if it was dragging around vortices capable of inverting a sizeable business jet, surely there would have been more severe wake turbulence reports by now?

Or perhaps there is something we don't know...

COGNITIVE DISSONANCE - a factor in 'Pressonitis'?

Firstly I should make it clear that I am not a psychologist, nor in the truest sense of the word am I a scientist, although as an aviator I have a broad understanding of a lot of science. My knowledge of this topic in particular comes from extensive research into why pilots were flying approaches to land - the ‘approach’ being the last part of the flight descending towards the runway - when all of the available evidence indicated that the landing could not be achieved either safely or in compliance with operating procedures. The approach trajectory was either too steep or too shallow, the aircraft was too fast or too slow or the landing gear and flaps were not in the correct configuration. Pilots’ standard operating procedures required them to execute a ‘go-around’ in such circumstances, to abandon the approach, climb away safely and start again but some were simply not complying. This ‘unstable approach’ phenomenon as it is known, has been one of the most common contributory factors in commercial aviation accidents over the last 30 years or more but the tendency to press on in spite of the evidence is not unique to pilots.

This brought me to the work of Bluma Zeigarnik, a psychologist and psychiatrist born in Lithuania at the turn of the last century. She is probably best known for studies inspired by her Professor’s observation that a waiter appeared to have a much better recollection for orders that had yet to be paid for, than those which had already been settled. The waiter’s workflow involved taking the order, delivering the food and drinks and finally taking the money, at which point the workflow would be finished. He stored the order in his memory until the customer had paid and then subconsciously dumped it. In other words an incomplete pattern of work held a much higher priority for retention in the memory than one which was effectively completed.

Zeigarnik went on to study school children learning in class and found that those who were interrupted in the course of their work remembered more, and more accurately, than those who were allowed to finish without interruption. In isolation that is interesting but doesn’t tell us a great deal. However, Zeigarnik and her successors have shown that the increased memory retention is attributable to a heightened level of cognitive arousal whilst a task is being conducted, which is replaced by a more satisfied lower arousal once the task is successfully completed. The heightened cognitive arousal was in turn attributed to a degree of discomfort that the goal may fail, discomfort that could only be assuaged by success. Nowadays we know this as the ‘Zeigarnik Effect’. To take it one step further, research suggested that humans remember bad things more clearly than they remember the good things; perhaps from a survival perspective this makes sense – we remember what has done us harm so that we can avoid it in future.

So finally, the outcome of this ‘cognitive dissonance’, the disparity between aspiration and reality during the conduct of a task, is that we humans harbour a compelling desire to complete a task once we have commenced it. This can be so compelling that we may press on although all of the indications, our instincts and maybe even our own colleagues are telling us to stop and rethink the strategy. This is what we found with the ‘unstable approaches’ continued to landing – pilots had become so focused on achieving the goal that they were able to ignore the evidence that it was failing – and it probably applies to many other aspects of professional and personal life.

AIR CRASHES - 3 DIFFERENT THINGS – BUT ARE THEY CONNECTED?

The first of these three things I have mentioned in this blog before. I spend a lot of time taking apart fatal aviation accidents, looking for the influences and factors which came together in the unique combination that allowed each ‘accident’ to happen. In recent years one of the most common precursors to a crash is procedural non-compliance – deviation from standard operating procedures by one or more of those involved. The reasons that pilots and other professionals deviate in this way are many and often related to complex human behavioural conditions; it is worth looking at Abraham Maslow’s hierarchy of human needs for insight into some of them. Whatever the underlying reasons, prior to a crash the captain will frequently decide to do something contrary to their training and procedures, that will eventually lead to their own demise. Sadly their co-pilots often look on, aware that all is not well but saying nothing.

The second thing is ‘risk denial’; maybe I have raised it in earlier posts. This is a condition that arises when we are regularly exposed to a particular, perhaps severe, hazard but it never actually does us any harm. Over time we may subconsciously adopt a mind-set that whilst the severity could be very high, the probability or likelihood is so low that it can be disregarded. Imagine passing a heavy truck in the opposite direction on a narrow lane – the obvious action would be to slow down and pull in to the side of the road to let it pass safely but every time you have passed a truck no harm has come of it. So you are able to ‘deny’ the risk, despite its blatancy, and drive on as normal with a metre or less between you and death.

So here is the final thing and I wonder if there is a connection between the three? Modern movies, TV shows and most significantly computer games allow us to experience horrifically dangerous and deadly situations without suffering any (other than perhaps psychological) harm. Could that have led to a general conditioning of westernised humanity (including pilots) to be able to subconsciously ignore hazards and adopt risky behaviours on the assumption that we will come to no harm however bad things look? After all, passengers now routinely collect their baggage before evacuating an aircraft, despite the high risk of fire and explosion. I don’t know…

WHY NOT DEBRIEF?

After every mission military pilots and their crew will hold a debrief to discuss want went well and what could have been done better. This is an opportunity for those involved in the task to recognise superior performance and to learn by addressing any deficiencies – makes sense right?

However, post-flight debriefs in commercial aviation are quite rare, in spite of the obvious potential value. In many regulatory jurisdictions pilots and cabin crew are only considered to be ‘on duty’ until 30 minutes after ‘on-chocks’ time so there is a limited window of opportunity. Furthermore, the crew for the next scheduled flight will frequently be waiting to get on board to maximise preparation time during the short turnaround period. Perhaps most influential is the fact that it isn’t ‘the way we do things around here’ – it’s not part of the culture.

A pilot would think nothing of remarking on a colleague’s smooth landing in difficult crosswind conditions for example but there is unlikely to be much discussion about it if it went less well. The absence of a debrief effectively implies that the entire flight proceeded satisfactorily and in accordance with standard operating procedures: there were no errors, deviations, distractions and consequently no opportunities to learn. Any pilot knows that is never the case but without a professional conversation immediately afterwards, the implication becomes reinforced.

Pilots are well used to debriefs after training flights so why not after every flight?

APPROACH BELOW MINIMUM IN IMC - DON'T...

Almost 30 years ago I was in the right hand seat of a BAC 1-11 narrow-body twin, on approach to Aberdeen. It was around 10 at night, dark, windy and raining - pretty standard stuff. We were on the last of 3 rotations to Heathrow and quite keen to get back to the hotel for a beer and some rest. And the captain had brought his wife along for the week detachment so she was waiting for him...

He was flying down the non-precision approach, with the landing lights glaring onto the clouds in front of the windscreen and the anti-collision beacon intermittently looming orange. At around 500 feet from touchdown I called 'minimum' as dictated by the SOP and there was certainly nothing like a runway in sight. The captain replied - I forget what he said but we continued descending as before and about a hundred feet later the runway lights appeared through the rain and we touched down uneventfully.

It was only later that it dawned on me what had happened - the captain had pressed on below minimum because he didn't want to divert. I was new to civil airline flying and new to the airline so wondered if that was how things were done around here. Of course I quickly learnt that it wasn't.

This all came back to me last week when I read about an A330 that landed off the side of the runway in Kathmandu. Apparently the pilots had trusted the accuracy of the aircraft's GPS based navigation systems enough to continue below the published approach minimum. Of course they were wrong.

To read about the outcome on Skybrary click HERE

THREE LAYERS OF FLIGHT SAFETY

I have spent a lot of time unpicking aircraft accidents in the course of my consultancy for IATA’s risk reduction programmes and as an expert witness in liability cases. Whilst that does risk becoming desensitised to the frequently unnecessary tragedy of these events, it has given me a keen insight into what causes pilots to crash their aeroplanes. Perhaps more importantly I believe it has helped me to distill some key factors which could have stopped them happening – three in fact, which I will explain below.

Prevention – generally we would all accept that prevention is by far the best means to avoid accidents, in the air or on the ground. We have countless opportunities to prevent accidents every day and in flight operations this activity is formalised into procedures and checklists. If we adhere to these tried and tested action sequences, the overwhelming majority of flights will be uneventful. Therefore, straightforward procedural compliance can deliver accident prevention virtually every time.

Recognition – in today’s highly reliable aircraft, operating in a well-controlled environment, facilitated by real-time weather, traffic and airspace information it is rare for anything out of the ordinary to penetrate the serene world of the commercial pilot. But if something unusual does happen it is vital that the pilots quickly recognise the deviation, picking it out from the backdrop of countless hours of ‘normal’. This ability to recognise the abnormal must be founded upon a comprehensive knowledge of what normal should look like; what is the acceptable range of values for every critical parameter.

Recovery – having recognised that things are not going to plan, pilots must be able to recover to normal, or at least to a new ‘normal’ within the constraints of whatever has occurred. Then and pretty much only then, do the pilots require real skill.

So that’s it; prevention through rigorous compliance, recognition based on comprehensive knowledge and finally recovery requiring piloting skill. Most of the current generation of airline pilots will probably never need more than the first of these (and that’s worth bearing in mind when hiring and training pilots) but how do we deliver and maintain the knowledge and how do we hone the skills when they may never be needed in the course of an entire career?