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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:
- 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.)
- B738, vicinity Christchurch New Zealand, 2011 (On 29 October 2011, a Boeing 737-800 on approach to Christchurch during the 68 year-old aircraft commander's annual route check as 'Pilot Flying' continued significantly below the applicable ILS minima without any intervention by the other pilots present before the approach lights became visible and an uneventful touchdown occurred. The Investigation concluded that the commander had compromised the safety of the flight but found no evidence to suggest that age was a factor in his performance. A Safety Recommendation was made to the Regulator concerning the importance of effective management of pilot check flights.)
- 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.)
- 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.)
- AS3B, vicinity Sumburgh Airport Shetland Islands UK, 2013 (On 23 August 2013, the crew of a Eurocopter AS332 L2 Super Puma helicopter making a non-precision approach to runway 09 at Sumburgh with the AP engaged in 3-axes mode descended below MDA without visual reference and after exposing the helicopter to vortex ring conditions were unable to prevent a sudden onset high rate of descent followed by sea surface impact and rapid inversion of the floating helicopter. Four of the 18 occupants died and three were seriously injured. The Investigation found no evidence of contributory technical failure and attributed the accident to inappropriate flight path control by the crew.)
- C500, vicinity Santiago Spain, 2012 (On 2 August 2012, a Cessna 500 positioning back to base after completing an emergency medical team transfer operation earlier in the night crashed one mile short of the runway at Santiago in landing configuration after being cleared to make an ILS approach. The Investigation concluded that the approach was unstabilised, had been flown without following the ILS GS and that the crew had used DME distance from the VOR near the crash position rather than the ILS DME. Fog was present in and around the airport.)
- B738, Kingston Jamaica, 2009 (On 22 December 2009, the flight crew of an American Airlines’ Boeing 737-800 made a long landing at Kingston at night in heavy rain and with a significant tailwind component and their aircraft overran the end of the runway at speed and was destroyed beyond repair. There was no post-crash fire and no fatalities, but serious injuries were sustained by 14 of the 154 occupants. The accident was attributed almost entirely to various actions and inactions of the crew. Damage to the aircraft after the overrun was exacerbated by the absence of a RESA.)
- 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.)
- 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.)
- B738/B738, vicinity Oslo Norway, 2012 (On 31 October 2012, a Norwegian Air Shuttle Boeing 737-800 on go around after delaying the breaking off of a fast and high unstable ILS approach at Oslo lost separation in IMC against another aircraft of the same type and Operator which had just taken off from the same runway as the landing was intended to be made on. The situation was aggravated by both aircraft responding to a de-confliction turn given to the aircraft on go around. Minimum separation was 0.2nm horizontally when 500 feet apart vertically, both climbing. Standard missed approach and departure tracks were the same.)
- A320/B738, vicinity Delhi India, 2013 (On 2 September 2013, a B737 crew were not instructed to go around from their approach by ATC as it became increasingly obvious that an A320 departing the same runway would not be airborne in time for a landing clearance to be issued. They initiated a go around over the threshold and then twice came into conflict with the A320 as both climbed on similar tracks without ATC de-confliction, initially below the height where TCAS RAs are functional. Investigation attributed the conflict to ATC but the failure to effectively deal with the consequences jointly to ATC and both aircraft crews.)
- A342, Perth Australia, 2005 (On 24 April 2005, an Airbus A340-200 landed short of the temporarily displaced runway threshold at Perth in good daylight visibility despite their prior awareness that there was such a displacement. The Investigation concluded that the crew had failed to correctly identify the applicable threshold markings because the markings provided were insufficiently clear to them and probably also because of the inappropriately low intensity setting of the temporary PAPI. No other Serious Incidents were reported during the same period of runway works.)
- … 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.