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Continuation Bias

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Plan Continuation Bias

Article Information
Category: Human Behaviour Human Behaviour
Content source: SKYbrary About SKYbrary
Content control: SKYbrary About SKYbrary

Definition

(Plan) Continuation Bias is the unconscious cognitive bias to continue with the original plan in spite of changing conditions.

Discussion

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:

  • A109, vicinity London Heliport London UK, 2013 (On 16 January 2013, an Augusta 109E helicopter positioning by day on an implied (due to adverse weather conditions) SVFR clearance collided with a crane attached to a tall building under construction. It and associated debris fell to street level and the pilot and a pedestrian were killed and several others on the ground injured. It was concluded that the pilot had not seen the crane or seen it too late to avoid whilst flying by visual reference in conditions which had become increasingly challenging. The Investigation recommended improvements in the regulatory context in which the accident had occurred.)
  • FA20, vicinity Narsarsuaq Greenland, 2001 (On 5 August 2001, a Dassault Falcon 20 with an inoperative GPWS making a night approach to Narsarsuaq by visual reference impacted terrain 4.5 nm from the aerodrome. The Investigation noted the original crew intention to fly a non-precision instrument approach and attributed the accident to the failure of the crew to follow applicable procedures or engage in meaningful CRM as well as to deficiencies in the Operator's required procedures which had combined to leave the crew vulnerable to a 'black hole' effect. The effects of fatigue were considered likely to have been contributory.)
  • B738/A321, Prague Czech Republic, 2010 (On 18 June 2010 a Sun Express Boeing 737-800 taxiing for a full length daylight departure from runway 06 at Prague was in collision with an Airbus 321 which was waiting on a link taxiway leading to an intermediate take off position on the same runway. The aircraft sustained damage to their right winglet and left horizontal stabiliser respectively and both needed subsequent repair before being released to service.)
  • C501, vicinity Trier-Fohren Germany, 2014 (On 12 January 2014, the crew of a Cessna 501 on a private business flight with a two-pilot crew attempted to make an unofficial GPS-based VNAV approach in IMC to the fog-bound VFR-only uncontrolled aerodrome at Trier-Fohren. However, after apparently mis-programming the 'descend-to' altitude and deviating from the extended centre, the aircraft emerged from the fog very close to the ground and after pulling up collided with obstructions, caught fire and crashed killing all occupants. The Investigation noted an apparent absence of pre-flight weather awareness beyond the intended destination and that there was a suitable fog-free diversion.)
  • B732, vicinity Abuja Nigeria, 2006 (On 29 October 2006, an ADC Airlines’ Boeing 737-200 encountered wind shear almost immediately taking off from Abuja into adverse weather associated with a very rapidly developing convective storm. Unseen from the apron or ATC TWR it stalled, crashed and burned after just over one minute airborne killing 96 of the 105 occupants. The Investigation concluded that loss of control during the wind shear encounter was not inevitable but was a consequence of inappropriate crew response. Concerns about the quality of crew training and competency validation were also raised.)

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Related Articles

Further Reading

  • 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.