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.
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:
- B738, Perth Australia, 2008 (On 9 May 2008, a Boeing 737-800 made a low go around at Perth in good daylight visibility after not approaching with regard to the temporarily displaced runway threshold. A second approach was similarly flown and, having observed a likely landing on the closed runway section, ATC instructed a go around. However, instead, the aircraft flew level at a low height over the closed runway section before eventually touching down just beyond the displaced threshold. The Investigation found that runway closure markings required in Australia were contrary to ICAO Recommendations and not conducive to easy recognition when on final approach.)
- B738, vicinity Denpasar Bali Indonesia, 2013 (On 13 April 2013, a Lion Air Boeing 737-800 flew a day non precision approach to runway 09 at Bali (Denpasar) and continued when the required visual reference was lost below MDA. Despite continued absence of visual reference, the approach was continued until the EGPWS annunciation 'TWENTY', when the aircraft commander called a go around. Almost immediately, the aircraft hit the sea surface to the right of the undershoot area and broke up. All 108 occupants were rescued with only four sustaining serious injury. The Investigation attributed the accident entirely to the actions and inactions of the two pilots.)
- 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.)
- RJ85, vicinity Medellín International (Rionegro) Colombia, 2016 (On 29 November 2016, a BAe Avro RJ85 failed to complete its night charter flight to Medellín (Rionegro) when all engines stopped due to fuel exhaustion and it crashed in mountainous terrain 10 nm from its intended destination killing almost all occupants. The Investigation noted the complete disregard by the aircraft commander of procedures essential for safe flight by knowingly departing with significantly less fuel onboard than required for the intended flight and with no apparent intention to refuel en route. It found that this situation arose in a context of a generally unsafe operation subject to inadequate regulatory oversight.)
- A320, Harstad/Narvik Norway 2004 (On 25 November 2004, a MyTravel Airways Airbus A320 departed the side of the runway at Harstad, Norway at a low speed after loss of directional control when thrust was applied for a night take off on a runway with below normal surface friction characteristics. It was found that the crew had failed to follow an SOP designed to ensure that any accumulated fan ice was shed prior to take off and also failed to apply take off thrust as prescribed, thus delaying their appreciation of the uneven thrust produced.)
- 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.