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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:
- AS32 / B734, Aberdeen UK, 2000 (For reasons that were not established, a Super Puma helicopter being air tested and in the hover at about 30 feet agl near the active runway at Aberdeen assumed that the departure clearance given by GND was a take off clearance and moved into the hover over the opposite end of the runway at the same time as a Boeing 737 was taking off. The 737 saw the helicopter ahead and made a high speed rejected take off, stopping approximately 100 metres before reaching the position of the helicopter which had by then moved off the runway still hovering.)
- BN2A, vicinity Bonaire Netherlands Antilles, 2009 (On 22 October 2009, a BN2 Islander suspected to have been overloaded experienced an engine failure shortly after departure from Curaçao. Rather than return, the Pilot chose to continue the flight to the intended destination but had to carry out a ditching when it proved impossible to maintain height. All passengers survived but the Pilot died. The cause of the engine failure could not be established but the Investigation found a context for the accident which had constituted systemic failure by the Operator to deliver operational safety which had been ignored by an inadequate regulatory oversight regime.)
- B732, vicinity Islamabad Pakistan, 2012 (On 20 April 2012, the crew of a Boeing 737-200 encountered negative wind shear during an ILS final approach at night in lMC and failed to respond with the appropriate recovery actions. The aircraft impacted the ground approximately 4 nm from the threshold of the intended landing runway. The Investigation attributed the accident to the decision to continue to destination in the presence of adverse convective weather and generally ineffective flight deck management and noted that neither pilot had received training specific to the semi-automated variant of the 200 series 737 being flown and had no comparable prior experience.)
- FA50 / Vehicle, Moscow Vnukovo Russia, 2014 (On 20 October 2014 a Dassault Falcon 50 taking off at night from Moscow Vnukovo collided with a snow plough which had entered the same runway without clearance shortly after rotation. Control was lost and all occupants died when it was destroyed by impact forces and post crash fire. The uninjured snow plough driver was subsequently discovered to be under the influence of alcohol. The Investigation found that the A-SMGCS effective for over a year prior to the collision had not been properly configured nor had controllers been adequately trained on its use, especially its conflict alerting functions.)
- AT72, Helsinki Finland, 2012 (On 19 August 2012, the crew of a Flybe Finland ATR 72-200 approaching Helsinki failed to respond appropriately to a fault which limited rudder travel and were then unable to maintain directional control after touchdown with a veer off the runway then following. It was concluded that as well as prioritising a continued approach over properly dealing with the annunciated caution, crew technical knowledge in respect of the fault encountered had been poor and related training inadequate. Deficiencies found in relevant aircraft manufacturer operating documentation were considered to have been a significant factor and Safety Recommendations were made accordingly.)
- 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.