From SKYbrary Wiki
Plan Continuation Bias
(Plan) Continuation Bias is the unconscious cognitive bias to continue with the original plan in spite of changing conditions.
The following explanation of continuation bias is derived from a Transport Safety Board of Canada accident report.
To make decisions effectively, a pilot or controller needs an accurate understanding of the situation and an appreciation of the implications of the situation, then to formulate a plan and contingencies, and to implement the best course of action. Equally important is the ability to recognize changes in the situation and to reinitiate the decision-making process to ensure that changes are accounted for and plans modified accordingly. If the potential implications of the situation are not adequately considered during the decision-making process, there is an increased risk that the decision and its associated action will result in an adverse outcome that leads to an undesired aircraft state.
A number of different factors can adversely impact a pilot's decision-making process. For example, increased workload can adversely impact a pilot's ability to perceive and evaluate cues from the environment and may result in attentional narrowing. In many cases, this attentional narrowing can lead to Confirmation Bias, which causes people to seek out cues that support the desired course of action, to the possible exclusion of critical cues that may support an alternate, less desirable hypothesis. The danger this presents is that potentially serious outcomes may not be given the appropriate level of consideration when attempting to determine the best possible course of action.
One specific form of confirmation bias is (plan) continuation bias, or plan continuation error. Once a plan is made and committed to, it becomes increasingly difficult for stimuli or conditions in the environment to be recognized as necessitating a change to the plan. Often, as workload increases, the stimuli or conditions will appear obvious to people external to the situation; however, it can be very difficult for a pilot caught up in the plan to recognize the saliency of the cues and the need to alter the plan.
When continuation bias interferes with the pilot's ability to detect important cues, or if the pilot fails to recognize the implications of those cues, breakdowns in situational awareness (SA) occur. These breakdowns in SA can result in non-optimal decisions being made, which could compromise safety.
In a U.S. National Aeronautics and Space Administration (NASA) and Ames Research Center review of 37 accidents investigated by the National Transportation Safety Board, it was determined that almost 75% of the tactical decision errors involved in the 37 accidents were related to decisions to continue on the original plan of action despite the presence of cues suggesting an alternative course of action. Dekker (2006) suggests that continuation bias occurs when the cues used to formulate the initial plan are considered to be very strong. For example, if the plan seems like a great plan, based on the information available at the time, subsequent cues that indicate otherwise may not be viewed in an equal light, in terms of decision making.
Therefore, it is important to realize that continuation bias can occur, and it is important for pilots to remain cognizant of the risks of not carefully analyzing changes in the situation, and considering the implications of those changes, to determine whether or not a more appropriate revised course of action is appropriate. As workload increases, particularly in a single-pilot scenario, less and less mental capacity is available to process these changes, and to consider the potential impact that they may have on the original plan.
Accidents and Incidents
SKYbrary includes the following reports relating to events where continuation bias was considered to be a factor:
- A332, Caracas Venezuela, 2013 (On 13 April 2013, an Air France Airbus A330-200 was damaged during a hard (2.74 G) landing at Caracas after the aircraft commander continued despite the aircraft becoming unstabilised below 500 feet agl with an EGPWS ‘SINK RATE’ activation beginning in the flare. Following a superficial inspection, maintenance personnel determined that no action was required and released the aircraft to service. After take off, it was impossible to retract the landing gear and the aircraft returned. Considerable damage from the earlier landing was then found to both fuselage and landing gear which had rendered the aircraft unfit to fly.)
- L410, vicinity Lukla Nepal, 2017 (On 27 May 2017, a Let 410 attempting to complete a visual approach to Lukla in rapidly deteriorating visibility descended below threshold altitude and impacted terrain close to the runway after stalling when attempting to climb in landing configuration. The aircraft was destroyed by the impact and two of the three occupants fatally injured. The Investigation concluded that the Captain had lost situational awareness at a critical time and had been slow to respond to the First Officer’s alert that the aircraft was too low. Safety Recommendations included the establishment of an independent and permanent Air Accident Investigation Agency.)
- A320, vicinity Sochi Russia, 2006 (On 3 May 2006, an Airbus 320 crew failed to correctly fly a night IMC go around at Sochi and the aircraft crashed into the sea and was destroyed. The Investigation found that the crew failed to reconfigure the aircraft for the go around and, after having difficulties with the performance of an auto go-around, had disconnected the autopilot. Inappropriate control inputs, including simultaneous (summed) sidestick inputs by both pilots were followed by an EGPWS PULL UP Warning. There was no recovery and about a minute into the go around, a steep descent into the sea at 285 knots occurred.)
- B737, Fort Nelson BC Canada, 2012 (On 9 January 2012, an Enerjet Boeing 737-700 overran the landing runway 03 at Fort Nelson by approximately 70 metres after the newly promoted Captain continued an unstabilised approach to a mis-managed late-touchdown landing. The subsequent Investigation attributed the accident to poor crew performance in the presence of a fatigued aircraft commander.)
- E145, en-route, near London ON Canada, 2014 (On 5 September 2014, the crew of an Embraer 145 encountered a more continuous area of convective activity en-route than expected. When it became impossible to see a way to continue through it, the aircraft commander requested, received and actioned flight path advice from the Company flight-following function. This led to the penetration of a mature thunderstorm and several minutes of severe turbulence with aircraft control lost and only regained upon exit from the storm. The Investigation found that the weather avoidance advice was based on an inappropriate source and that following it was an inappropriate command decision.)
- TSB. Air Transportation Safety Investigation Report A18P0031 Loss of Control and Collision with Terrain. 14 August 2019.
- The “Barn Door” Effect by C. West, Ph.D., NOAA - a paper about pilots’ propensity to continue approaches to land when closer to convective weather than they would wish to get while en route.