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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:
- B744, vicinity Dubai UAE, 2010 (On 3 September 2010, a UPS Boeing 747-400 freighter flight crew became aware of a main deck cargo fire 22 minutes after take off from Dubai. An emergency was declared and an air turn back commenced but a rapid build up of smoke on the flight deck made it increasingly difficult to see on the flight deck and to control the aircraft. An unsuccessful attempt to land at Dubai was followed by complete loss of flight control authority due to fire damage and terrain impact followed. The fire was attributed to auto-ignition of undeclared Dangerous Goods originally loaded in Hong Kong.)
- DHC6, en-route, Arghakhanchi Western Nepal, 2014 (On 16 February 2014 a Nepal Airlines DHC6 attempting a diversion on a VFR flight which had encountered adverse weather impacted terrain at an altitude of over 7000 feet in a mountainous area after intentionally entering cloud following a decision to divert due to weather incompatible with VFR. The aircraft was destroyed and all 18 occupants were killed. The Investigation attributed the accident to loss of situational awareness by the aircraft commander and inadequate crew co-operation in responding to the prevailing weather conditions.)
- B733, Yogyakarta Indonesia, 2011 (On 20 December 2011, the experienced Captain of a Sriwijaya Air Boeing 737-300 flew an unstabilised non-precision approach to a touchdown at Yogyakarta at excessive speed whilst accompanied by a very inexperienced First Officer. The aircraft overran the end of the 2200 metre-long wet runway by 75 metres . During the approach, the Captain 'noticed' several GPWS PULL UP Warnings but no action was taken. The Investigation attributed the accident entirely to the actions of the flight crew and found that there had been no alert calls from the First Officer in respect of the way the approach was flown.)
- 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.)
- DH8D, Sault Ste. Marie ON Canada, 2013 (On 26 May 2013, a Porter Airlines DHC8-400 sustained substantial damage as a result of a mishandled night landing off a visual approach at Sault Ste. Marie which led to a 3g tail strike. The prior approach was stabilised at 500 feet but then unstabilised below that height. The handling pilot involved was a First Officer with 134 hours experience on the aircraft type, which was his first experience of multi crew transport aircraft after significant experience flying light aircraft. An absence of effective monitoring or intervention by the aircraft commander was identified during the Investigation.)
- 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.