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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:
- CRJ7, Lorient France, 2012 (On 16 October 2012, a Brit Air Bombardier CRJ 700 landed long on a wet runway at Lorient and overran the runway. The aircraft sustained significant damage but none of the occupants were injured. The Investigation attributed the accident to poor decision making by the crew whilst shoeing signs of complacency and fatigue and failing to maintain a sterile flight deck or go around when the approach became unstable. A context of deficiencies at the airport and at the Operator was also detailed and it was concluded that aquaplaning had occurred.)
- C56X, Port Harcourt Nigeria, 2013 (On 14 July 2011, the crew of a Cessna Citation intentionally continued a night ILS approach at Port Harcourt below the applicable DA without having any visual reference with the runway and a crash landing and lateral runway excursion which severely damaged the aircraft followed. The Investigation did not establish any reason for the violation of minima but noted the complications which had arisen in respect of CRM because of two-Captain flight crew. Absence of two-way radio communications between the fire trucks and both ATC and the AFS Watch Room was noted to have delayed discovery of the crashed aircraft.)
- B739, Yogyakarta Indonesia, 2015 (On 6 November 2015, a Boeing 737-900 overran the 2,200 metre-long landing runway at Yogyakarta after a tailwind approach with airspeed significantly above the applicable Vref followed by a long landing on a wet runway without optimum use of deceleration devices. The flight crew management of the situation once the aircraft had come to a stop was contrary to procedures in a number of important respects. The aircraft operator took extensive action to improve crew performance following the event. The Investigation found significant fault with the airport operator's awareness of runway surface condition and an absence of related significant risk management.)
- MA60, vicinity Kaimana West Papua Indonesia, 2011 (On 7 May 2011, the crew of a Xian MA60 lost control of their aircraft during an attempted go around at Kaimana after failing to obtain sufficient visual reference to complete the approach despite a significant violation of the minima for the required visual-only approach. The aircraft was destroyed by the high speed impact and all occupants were killed. The Investigation found that the crew had comprehensively failed to conduct the go around procedure as prescribed and it was suspected that the new-to-type Captain may have reverted to procedures for his previous jet aircraft type after ineffective type conversion training.)
- SF34, vicinity Newcastle New South Wales Australia, 2012 (On 8 November 2012, the crew of a Saab 340 advised destination ATC at Newcastle in daylight hours that they were 'visual' and were so cleared. The aircraft was then observed to turn towards the lights of an industrial complex 6nm from the airport and descend and ATC intervened to provide guidance to final approach. Investigation found that the experienced Captain was guiding the First Officer, who had gained his professional licence 10 months earlier, towards what he had mistaken for the runway. Descent, perceived by the Captain as on 'finals', continued to 680 feet agl before a climb commenced.)
- B742 / B741, Tenerife Canary Islands Spain, 1977 (On 27 March 1977, a KLM Boeing 747-200 began its low visibility take-off at Tenerife without requesting or receiving take-off clearance and a collision with a Boeing 747-100 backtracking the same runway subsequently occurred. Both aircraft were destroyed by the impact and consequential fire and 583 people died. The Investigation attributed the crash primarily to the actions and inactions of the KLM Captain, who was the Operator's Chief Flying Instructor. Safety Recommendations made emphasised the importance of standard phraseology in all normal radio communications and avoidance of the phrase "take-off" in ATC Departure Clearances.)
- DH8A, Nuuk Greenland, 2011 (On 4 March 2011, an aircraft left the runway during a mishandled landing at Nuuk, Greenland which resulted in the collapse of the right main landing gear due to excessive 'g' loading. The landing followed an unstabilised VMC approach in challenging weather conditions. The Investigation concluded that the crew had become focussed solely on landing and that task saturation had mentally blocked any decision to go around. The aircraft commander had less than 50 hours experience on the aircraft type and had only been released from supervised line training 6 days earlier.)
- A333, Kathmandu Nepal, 2015 (On 4 March 2015, the crew of a Turkish Airlines A333 continued an automatic non precision RNAV approach below the prescribed minimum descent altitude without having obtained any element of visual reference and when this was acquired a few seconds before the attempted landing, the aircraft was not aligned with the runway centreline and during a 2.7g low-pitch landing, the left main gear touched down on the grass. The aircraft then left the runway completely before stopping with a collapsed nose gear and sufficient damage to be assessed a hull loss. None of 235 occupants sustained serious injury.)
- SW4, Cork Ireland, 2011 (On 10 February 2011, control of a Spanish-operated Fairchild SA227 operating a scheduled passenger flight from Belfast UK to Cork, Ireland was lost during an attempt to commence a third go around due to fog from 100 feet below the approach minimum height. The Investigation identified contributory causes including serial non-compliance with many operational procedures and inadequate regulatory oversight of the Operator. Complex relationships were found to prevail between the Operator and other parties, including “Manx2”, an Isle of Man-based Ticket Seller under whose visible identity the aircraft operated. Most resultant Safety Recommendations concerned systemic improvement in regulatory oversight effectiveness.)
- SW4, Sanikiluaq Nunavut Canada, 2012 (On 22 December 2012, the crew of a Swearingen SA227 attempting a landing, following an unstabilised non-precision approach at Sanikiluaq at night with questionable alternate availability in marginal weather conditions, ignored GPWS PULL UP Warnings, then failed in their attempt to transition into a low go around and the aircraft crashed into terrain beyond the runway. One occupant – an unrestrained infant – was killed and the aircraft was destroyed. The Investigation faulted crew performance, the operator and the regulator and reiterated that lap-held infants were vulnerable in crash impacts.)
- B735, vicinity Kazan Russia, 2013 (On 17 November 2013, the crew of a Boeing 737-500 failed to establish on the ILS at Kazan after not following the promulgated intermediate approach track due to late awareness of LNAV map shift. A go around was eventually initiated from the unstabilised approach but the crew appeared not to recognise that the autopilot used to fly the approach would automatically disconnect. Non-control followed by inappropriate control led to a high speed descent into terrain less than a minute after go around commencement. The Investigation found that the pilots had not received appropriate training for all-engine go arounds or upset recovery.)
- A332, vicinity Perth Australia, 2014 (On 9 June 2014, a 'burning odour' of undetermined origin became evident in the rear galley of an Airbus A330 as soon as the aircraft powered up for take off. Initially, it was dismissed as not uncommon and likely to soon dissipate, but it continued and affected cabin crew were unable to continue their normal duties and received oxygen to assist recovery. En route diversion was considered but flight completion chosen. It was found that the rear pressure bulkhead insulation had not been correctly refitted following maintenance and had collapsed into and came into contact with APU bleed air duct.)
- … further results
- 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.