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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:

  • A320 / A139 vicinity Zurich Switzerland, 2012 (On 29 May 2012, a British Airways Airbus A320 departing Zürich and in accordance with its SID in a climbing turn received and promptly and correctly actioned a TCAS RA 'CLIMB'. The conflict which caused this was with an AW 139 also departing Zürich IFR in accordance with a SID but, as this aircraft was only equipped with a TAS to TCAS 1 standard, the crew independently determined from their TA that they should descend and did so. The conflict, in Class 'C' airspace, was attributed to inappropriate clearance issue by the TWR controller and their inappropriate separation monitoring thereafter.)
  • B732, vicinity Resolute Bay Canada, 2011 (On 20 August 2011, a First Air Boeing 737-200 making an ILS approach to Resolute Bay struck a hill east of the designated landing runway in IMC and was destroyed. An off-track approach was attributed to the aircraft commander’s failure to recognise the effects of his inadvertent interference with the AP ILS capture mode and the subsequent loss of shared situational awareness on the flight deck. The approach was also continued when unstabilised and the Investigation concluded that the poor CRM and SOP compliance demonstrated on the accident flight were representative of a wider problem at the operator.)
  • SH36, vicinity Oshawa ON Canada, 2004 (On 16 December 2004, an Air Cargo Carriers Shorts SD3-60 attempted to land at Oshawa at night on a runway covered with 12.5mm of wet snow which did not offer the required landing distance. After unexpectedly poor deceleration despite selection of reverse propeller pitch, full power was applied and actions for a go around were taken. Although the aircraft then became airborne in ground effect, it subsequently failed to achieve sufficient airspeed to sustain a climb and an aerodynamic stall was followed by impact with terrain and trees beyond the end of the runway. The aircraft was substantially damaged and both pilots sustained serious injuries but there was no post-crash fire)
  • B738, vicinity Eindhoven Netherlands, 2013 (On 31 May 2013, a Boeing 737-800 (EI-ENL) being operated by Ryanair on a scheduled international passenger flight from Palma del Mallorca to Eindhoven as FR3531 was established on the ILS LOC in day IMC with the AP and A/T engaged and APP mode selected but above the GS, when the aircraft suddenly pitched up and stick shaker activation occurred. After a sudden loss of airspeed, the crew recovered control manually and the subsequent approach was completed without further event.)
  • CRJ1, Kinshasa Democratic Republic of Congo, 2011 (On 4 April 2011, the crew of a Georgian Airways Bombardier CRJ100 operating a domestic flight for the United Nations lost control of their aircraft as they commenced a go around from below the MDA for the non precision approach flown due to an absence of visual reference with the runway. They were aware from their weather radar of severe convective weather in the vicinity of the airport although the METAR passed by ATC did not indicate this. The aircraft crashed alongside the runway and was destroyed. All occupants except one who was seriously injured were killed.)

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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.