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Plan Continuation Bias
(Plan) Continuation Bias is the unconscious cognitive bias to continue with the original plan in spite of changing conditions.
Unconscious bias in thinking leads to a pilot or controller following the originally-intended course of action. This bias appears to be stronger as the culmination of a task nears, for example during the flying of an approach to land or the maintenance of the planned separation between aircraft sequenced for approach to a particular runway.
Continuation Bias may have the effect of obscuring subtle cues which indicate that original conditions and assumptions have changed. It may also act in combination with other cognitive biases.
Accidents and Incidents
SKYbrary includes the following reports relating to events where continuation bias was considered to be a factor:
- B772, San Francisco CA USA, 2013 (On 6 July 2013, an Asiana Boeing 777-200 descended below the visual glidepath on short finals at San Francisco after the pilots failed to notice that their actions had reduced thrust to idle. Upon late recognition that the aircraft was too low and slow, they were unable to recover before the aircraft hit the sea wall and the tail detached. Control was lost and the fuselage eventually hit the ground. A few occupants were ejected at impact but most managed to evacuate subsequently and before fire took hold. The Probable Cause of the accident was determined to be the mismanagement of the aircraft by the pilots.)
- A320, vicinity Tel Aviv Israel, 2012 (On 3 April 2012, the crew of an Air France Airbus A320 came close to loosing control of their aircraft after accepting, inadequately preparing for and comprehensively mismanaging it during an RNAV VISUAL approach at Tel Aviv and during the subsequent attempt at a missed approach. The Investigation identified significant issues with crew understanding of automation - especially in respect of both the use of FMS modes and operations with the AP off but the A/T on - and highlighted the inadequate provision by the aircraft operator of both procedures and pilot training for this type of approach.)
- B735, Jos Nigeria, 2010 (On 24 August 2010, a Boeing 737-500 made an uncontrolled touchdown on a wet runway at Jos in daylight after the approach was continued despite not being stabilised. A lateral runway excursion onto the grass occurred before the aircraft regained the runway centreline and stopped two-thirds of the way along the 3000 metre-long runway. Substantial damage was caused to the aircraft but none of the occupants were injured. The aircraft commander was the Operator's 737 Fleet Captain and the Investigation concluded that the length of time he had been on duty had led to fatigue which had impaired his performance.)
- DHC6, Jomson Nepal, 2013 (On 16 May 2013, a DHC6-300 on a domestic passenger flight made a tailwind touchdown at excessive speed in the opposite direction of the of 740 metre-long runway to the notified direction in use and, after departing the runway to one side during deceleration, re-entered the runway and attempted to take off. This failed and the aircraft breached the perimeter fence and fell into a river. The Investigation identified inappropriate actions of the aircraft commander in respect of both the initial landing and his response to the subsequent runway excursion and also cited the absence of effective CRM.)
- A332, vicinity Perth Australia, 2014 (On 9 June 2014, a 'burning odour' of undetermined origin became evident in the rear galley of an Airbus A330 as soon as the aircraft powered up for take off. Initially, it was dismissed as not uncommon and likely to soon dissipate, but it continued and affected cabin crew were unable to continue their normal duties and received oxygen to assist recovery. En route diversion was considered but flight completion chosen. It was found that the rear pressure bulkhead insulation had not been correctly refitted following maintenance and had collapsed into and came into contact with APU bleed air duct.)
- 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.