Air India A321 tail strike offers valuable lessons on psychology of surprise
The captain entered a dilemma zone where, to avoid collision with a vehicle on the runway, the brain chose to take the decision of flight
On February 15, 2020, an Airbus A321 aircraft of Air India was rolling down the runway at Pune for takeoff when the captain of the flight suddenly noticed a vehicle on the runway. As per the investigation report, the vehicle was about 1,000 m away, but at a speed of over 100 kts (185.2 kmph), 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 A321 at a speed 24 kts (44.44 kmph) 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 important to analyse for understanding why such reactions are permitted by the brain. It is not possible to train a pilot for every possible scenario.
Read the final investigation report here.
There are two points worth discussing that the investigators failed to highlight.
1. What caused the captain to rotate the aircraft way below the rotation speed?
2. What if the captain hadn’t rotated to attempt an early lift-off?
In aviation terminology, rotation means applying back pressure to a control device, such as a yoke, side stick or centre stick, to lift the plane's nose wheel off the ground during takeoff.
Startle and surprise effects can influence pilot performance in many detrimental ways. These effects serve as distractions that can disrupt normal operations 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 are discarded and 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 and Viravanh 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.
An Air India Airbus A321. Image courtesy: Wikimedia Commons/Flickr/Aeroprints.com
This contrasts with startle because startle is always triggered by a sudden, highly intense 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 the 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 what was expected happened, or because something happened while it was not expected, or because something that was 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 100 kts, she entered the high-speed regime. The consequences of a stop or go decision will be higher as compared to when the aircraft is at a 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 with a high degree of reasonableness the distance of the vehicle from the aircraft closing in.
Dual cognitive system
Cognitive systems involve two mental processes:
System 1 -- The 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 -- The 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.
Dual Cognitive System
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' to save their mental resources, they enter as little as possible into higher modes of coupling, while remaining sufficiently effective and reliable. To achieve this in a reliable way, they incorporate in their mental representation a model of themselves as controllers.
Surprise and disruption
In 2005, the National Aeronautics and Space Administration (NASA) issued a report on the challenges of emergency and abnormal situations in aviation. According to the report, "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% of "textbook emergencies" (those emergencies for which a checklist exists) were handled well by flight crews, while only about 7% 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 minimise their impact."
The stress response is a very archaic inheritance in the development of species, which allows a forced and fast readaptation 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 optimisation of the physical capacities and maximises 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 reinterpreting 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 8,59,000 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 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, or VMU (Velocity of Minimum Unstick) 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 is reached by pulling the side stick or control column full-back. This has to be demonstrated with all the 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 the 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 1% of the scheduled takeoff distance. Thus, the abuse tests should not result in field lengths of more than 101% of the takeoff field lengths calculated in accordance with the applicable requirements of part 25 for presentation in the AFM.
The pilot in command (PIC) at the controls of the A321 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 and 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 147 kts (272.24 kmph) was closer as the aircraft accelerated as compared to a full stop which would have entailed losing 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 123 kts (227.79) kmph, the pilot rotated the aircraft in an attempt to get airborne.
Digital Flight Data Recorder (DFDR) readout showing the side stick input and airborne stages
The captain’s naturalistic decision to avoid an unpleasant situation and pulling the stick fully back did not change the distance that the aircraft travelled before getting airborne. However, it's that split second in an emotional state of surprise in which such decisions are taken.
The duration of surprise is normally longer which explains why TOGA (takeoff/go-around) was not immediately selected to increase thrust to the maximum. There can be an innumerable combination of circumstances that could present themselves that the crew would not have practised in the simulator during training. The training on unexpected events during Line-oriented Flight Training (LOFT) scenarios is the key to be prepared for such events.
Captain Amit Singh is a training and safety expert with over 30 years of experience in the commercial air transport industry. He has been associated with two startup low-cost carriers and has hands-on experience with their needs and challenges. He has been a part of the senior management at IndiGo and Air Asia India. Captain Singh has been speaking at international fora on training and safety. He is also the author of mindFly the Human Factors blog.
(This article first appeared in safetymatters.co.in)