On 15th Feb 2020, an A 321 aircraft was rolling down the runway for takeoff when the Captain of the flight suddenly noticed a vehicle on the runway. As per the investigation report, the vehicle was about 1000m away but at a speed of over 100kts, the pilot could not probably accurately assess the distance of the vehicle from the aircraft. The Captain pulled back at the side stick of the A-321 at a speed 24kts below the calculated rotation speed. After a few seconds of struggle with the side stick moving back and forth the aircraft got airborne at the calculated rotation speed. The tail of the aircraft scraped the runway.
An analysis would show that even by attempting to get airborne early, just the aircraft’s nose lifted causing the tail to scrape the runway and the aircraft got airborne close to the calculated rotation speed. The psychology of the decision is also important to understand why such reactions are permitted by the brain and it is not possible to train a pilot for every possible scenario.
There are two points worth discussing that the investigators failed to highlight.
- What caused the Captain to rotate the aircraft way below the rotation speed?
- What if the Captain hadn’t rotated to attempt an early lift-off?
Startle and surprise effects can influence pilot performance in many detrimental ways. These effects serve as a distraction that can disrupt the normal operation and erode safety margins. On a more critical level, they can lead to inappropriate intuitive actions or hasty decision making. Well learned procedures and skills can be discarded and are substituted by the first thing that comes to mind.
Psychology of Surprise
The psychology of surprise is about how people respond to unexpected events. Studies have been carried out like the “Human capability to cope with unexpected events by Jean Paries & Viravahn Somvang. Surprise results from a disparity between a person’s expectations and what is actually perceived. This implies that surprise can be elicited by the presence, but also by the absence of stimuli. This contrasts with startle because startle is always triggered by a sudden highly intensive stimulus and cannot be triggered by the absence of a stimulus. The effects of surprise are in part comparable to those of startle. Physiological responses to surprise include increased heart rate and blood pressure, cognitive responses include confusion and loss of situational awareness, and may involve the inability to remember the current operating procedures.
The duration of the surprise response is typically longer than that of the startle reflex. The discrepancy between expected and actual circumstances requires the person experiencing the surprise to reevaluate the situation to continue with the task. Larger discrepancies usually require more time for reevaluation than smaller discrepancies. Furthermore, the surprise also takes more time when the discrepancy requires an update of the expectations of the person experiencing the surprise (Horstmann, 2006).
The ‘unexpected’ is a mismatch appearing between perceived reality and expectations, not immediately manageable through comprehension and/or action. Such gap may be perceived for example because something happened differently (sooner, later, stronger, weaker, etc.) from what was expected, or because something else than expected happened, or because something happened while it was not expected, or because something expected did not happen.
Categorisation of Crisis
A crisis can simply be differentiated into two main categories: complexity, and urgency. In this situation, as the aircraft speed increased beyond 100kts, she entered the high-speed regime. The consequences of a stop or go decision will be higher as compared to slow speed. Since the aircraft was accelerating, a decision had to be taken intuitively without time for deliberation. There was no time to discuss the scenario and it was difficult to judge the distance of the vehicle from the closing in aircraft with a high degree of reasonableness.
Dual Cognitive System
The cognitive processes involve two mental processes.
System 1’ reasoning is fast, automatic, and mostly unconscious; it relies on ‘fast and frugal’ heuristics offering seemingly
effortless conclusions that are generally appropriate in most settings, but maybe faulty, for instance in experimental situations devised to test the limits of human reasoning abilities.
‘System 2’ reasoning is slow, deliberative, and consciously controlled and effortful, but makes it possible to follow normative rules and to overcome the shortcomings of system 1.
Depending on the problem, the context, and the person either system 1 or system 2 reasoning is more likely to be activated, with different consequences for people’s ability to reach the normatively correct solution. The two systems can even compete: system 1 suggests an intuitively appealing response while system 2 tries to inhibit this response and to impose its own norm-guided one.
Humans permanently manage a “cognitive trade-off” in order to save their mental resources, they enter as little as possible into
higher modes of coupling, while remaining sufficiently effective and reliable. In order to achieve this in a reliable way, they incorporate in their mental representation a model of themselves as controllers.
Surprise & Disruption
In 2005, NASA issued a report on the challenges of emergency and abnormal situations in aviation. Quote: ‘some situations may be
so dire and time-critical or may unfold so quickly’ that pilots must focus all of their efforts on the basics of aviation—flying and landing the airplane—with little time to consult emergency checklists’. The report indicated that, although pilots are trained for emergency and abnormal situations, ‘it is not possible to train for all possible contingencies’.
More interestingly, the NASA report noted that a review of voluntary reports filed on the Aviation Safety Reporting System (ASRS) indicated that over 86 percent of ‘textbook emergencies’ (those emergencies for which a checklist exists) were handled well by flight crews, while only about 7 percent of non-textbook emergencies were handled well by flight crews. In other words, the disruptive potential of the ‘unexpected’ is much more dependent on the absence of anticipation than on the objective severity of the corresponding threat.
The first thing unexpected events do on operators is to trigger unpleasant feelings. As experts put it, “Evidence shows that when something unexpected happens, this is an unpleasant experience. Part of managing the unexpected involves anticipating these feelings of unpleasantness and taking steps to minimize their impact”.
The stress response is a very archaic inheritance in the development of species, which allows a forced and fast re-adaptation to face an emergency situation, in which the balance between the situational demand and the resources of the individual is suddenly broken. However, the stress response mainly generates an optimization of the physical capacities, and maximizes the chances of survival through concealment, escape, or attack (“fight or flight”). This augmented physical response is generally not suited to the requirements of modern emergencies, which rather have a cognitive nature. In this regard, the stress response has rather negative, incapacitating effects.
A sudden encounter with the unexpected introduces a mismatch between the current frame and perceived reality. The resulting state of confusion and discontinuity of the action may then trigger two main types of reactions: i) attempting to keep the ongoing frame, but seeking additional data or re-interpreting the existing ones; ii) attempting to change the frame or to replace it.
Dilemma Zone Problem
Dilemma zone crisis is a major problem, especially at high-speed junctions. A number of studies have been conducted to resolve this dilemma. When clearance intervals are not properly timed, drivers may be forced to choose between abruptly stopping and running the red light. In 2012, for example, the National Highway Traffic Safety Administration estimated that over 2.5 million cars were involved in crashes at intersections with traffic signals, resulting in 859,000 fatalities or injuries.
A RED light is perceived as a negative signal to the brain. In the transition zone of yellow light, the human brain is likely to take a higher risk of speeding through the signal and risk a collision instead of slowing down to stop. The justification is that is a sudden deceleration might not give a vehicle coming from behind enough time to brake. The consequences of the two and the probability are poles apart.
The minimum unstick speed, Vmu is calculated after a demonstration during the certification phase of an aircraft type. The test is also known as an ABUSE test since the aircraft nose is lifted well before the lift-off speed by pulling the side stick or control column full-back. This has to be demonstrated with all engines running and with an engine inoperative. One of the requirements is:
There must not be a “marked increase” in the scheduled takeoff distance when reasonably expected service variations such as early and excessive rotation and out-of-trim conditions are encountered. This has been interpreted as requiring takeoff tests with all engines operating with: (a) An abuse on rotation speed, and (b) Out-of-trim conditions, but with rotation at the scheduled VR speed. NOTE: The expression “marked increase” in the takeoff distance is defined as any amount in excess of one percent of the scheduled takeoff distance. Thus, the abuse tests should not result in field lengths more than 101 percent of the takeoff field lengths calculated in accordance with the applicable requirements of part 25 for presentation in the AFM.
The PIC at the controls of the A-321 encountered an unexpected surprise event, that of a jeep on the runway when the aircraft speed was above 100kts. Unable to accurately judge the distance between the two, the PIC entered a situation where a split-second decision needed to be taken to either stop the takeoff ad jam the brakes to come to a halt before a possible collision with the vehicle on the runway or to continue takeoff normally wherein the possibility of a collision could have been high. The decision had to be an intuitive or a naturalistic one since there was time pressure to act.
The rotation speed of 147kts was closer as the aircraft accelerated as compared to a full stop which would entail loosing energy to come to a full stop. The Captain entered the dilemma zone where, to avoid the collision the brain in combination with the emotion of freeze or flight chose to take the decision of flight and at 123kts, rotated the aircraft in an attempt to get airborne.
The Captain’s naturalistic decision to avoid and unpleasant situation and pulling the stick fully back did not change the distance that the aircraft travelled before getting airborne. However, its that split-second decision in an emotional state of surprise that such decisions are taken. The duration of surprise is normally longer which explains why TOGA was not immediately selected to increase thrust to maximumThere can be an innumerable combination of circumstances that could present themselves that the crew would not have practiced in the simulator during training. The training on unexpected events during LOFT scenarios is the key to be prepared for such events.