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Interruption or Distraction

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Article Information
Category: Human Behaviour Human Behaviour
Content source: SKYbrary About SKYbrary
Content control: SKYbrary About SKYbrary

Description

Pilots and ATCOs perform lengthy and complex procedures in the course of their duties. An interruption breaks the thread of these procedures and can have undesirable consequences. Distractions can make it difficult for the pilot or ATCO to concentrate on the task in hand.

Types of Interruption

Interruption on the flight deck may result from causes within the aircraft, e.g. the occupant(s) of (the) flight deck supernumary crew seat (s), the activation of an caution or warning, the activation of a cabin crew call alert, unexpected information from ATC or the operating Company.

Interruption may also occur in the control room, e.g due to a telephone call, a message from a colleague or detection of a potential airspace infringement or level bust.

Types of Distraction

Examples of circumstances where distraction may occur on the flight deck include non-relevant conversation, equipment malfunction and adverse weather.

For the ATCO, distraction may result from extraneous noise, e.g. loud conversation between colleagues, or from an uncomfortable or inconvenient position.

Effects

On the flight deck, the interruption of a procedure may result in missing a vital checklist action or failing to follow correctly a prescribed procedure.

In the control room, interruption may cause an ATCO to fail to take an intended action.

Distraction on the flight deck or in the control room may make it difficult for the pilot or ATCO to concentrate on his/her task, possibly resulting in error or omission.

Defences

Well designed and diligently applied SOPs should minimise the prevalence of, or significant effect from, interruptions and distractions. For example, the sterile flight deck procedure implemented by many airlines below FL100 reduces distractions and interruptions during a period which can be expected to result in relatively high-workload situations during most flights. However, these same arrangements are often not applied to critical elements of the pre flight process. As an example, departure performance calculations made by the crew prior to engine start are done at a time when the risk of interruption or distraction within, or external to, the crew is routinely high.

Typical Scenarios

  • A flight deck checklist is interrupted by an interphone call from the cabin crew; the checklist is subsequently resumed but an important action is omitted.
  • A discussion of non-relevant matters is carried out on the flight deck and none of the crew members present notice that they have entered an active runway without clearance.
  • Cross checking of take off performance calculations being made in the flight deck prior to engine start is interrupted by the arrival of the dispatcher.
  • An ATCO misses an important message due to a radio playing in the control room.

Contributory Factors

Solutions

  • Review and if necessary improve SOPs
  • Insist that SOPs are followed
  • Review and if necessary improve the design of the ATCO’s position
  • Review and if necessary improve CRM and TRM training provisions

Accidents & Incidents

Events on the SKYbrary Accident and Incident Database where the Official Investigation included reference to Distraction as an element in causation:

  • A139 / A30B, Ottawa Canada, 2014 (On 5 June 2014, an AW139 about to depart from its Ottawa home base on a positioning flight exceeded its clearance limit and began to hover taxi towards the main runway as an A300 was about to touch down on it. The TWR controller immediately instructed the helicopter to stop which it did, just clear of the runway. The A300 reached taxi speed just prior to the intersection. The Investigation attributed the error to a combination of distraction and expectancy and noted that the AW139 pilot had not checked actual or imminent runway occupancy prior to passing his clearance limit.)
  • A306, vicinity Birmingham AL USA, 2013 (On 14 August 2013, a UPS Airbus A300-600 crashed short of the runway at Birmingham Alabama on a night IMC non-precision approach after the crew failed to go around at 1000ft aal when unstabilised and then continued descent below MDA until terrain impact. The Investigation attributed the accident to the individually poor performance of both pilots, to performance deficiencies previously-exhibited in recurrent training by the Captain and to the First Officer's failure to call in fatigued and unfit to fly after mis-managing her off duty time. A Video was produced by NTSB to further highlight human factors aspects.)
  • A319 / PRM1, en-route, near Fribourg Switzerland, 2011 (On 10 June 2011 an ATC error put a German Wings A319 and a Hahn Air Raytheon 390 on conflicting tracks over Switzerland and a co-ordinated TCAS RA followed. The aircraft subsequently passed in very close proximity without either sighting the other after the Hahn Air crew, contrary to Company procedures, followed an ATC descent clearance issued during their TCAS ‘Climb’ RA rather than continuing to fly the RA. The Investigation could find no explanation for this action by the experienced crew - both Hahn Air management pilots. The recorded CPA was 0.6 nm horizontally at 50 feet vertically.)
  • A319 / UNKN, Stockholm Arlanda Sweden, 2011 (On 5 February 2011, an Airbus A319-100 being operated by Air Berlin on a passenger flight departing Stockholm inadvertently proceeded beyond the given clearance limit for runway 19R and although it subsequently stopped before runway entry had occurred, it was by then closer to high speed departing traffic than it should have been. There was no abrupt stop and none of the 103 occupants were injured.)
  • A319, Casablanca Morocco, 2011 (On 8 August 2011 an Air France Airbus A319 crew failed to correctly identify the runway on which they were cleared to land off a visual approach at Casablanca and instead landed on the parallel runway. ATC, who had already cleared another aircraft to cross the same runway, did not notice until this other aircraft crew, who had noticed the apparently abnormal position of the approaching aircraft and remained clear of the runway as a precaution, advised what had happened. Investigation was hindered by the stated perception of the Air France PIC that the occurrence was not a Serious Incident.)
  • A319, Las Vegas NV USA, 2006 (On 30 January 2006 the Captain of an Airbus A319 inadvertently lined up and commenced a night rolling take off from Las Vegas on the runway shoulder instead of the runway centreline despite the existence of an illuminated lead on line to the centre of the runway from the taxiway access used. The aircraft was realigned at speed and the take off was completed. ATC were not advised and broken edge light debris presented a potential hazard to other aircraft until eventually found. The Investigation found that other similar events on the same runway had not been reported at all.)
  • A319/A319, en-route, South west of Basle-Mulhouse France, 2010 (On 29 June 2010, an Easyjet Switzerland Airbus A319 inbound to Basle-Mulhouse and an Air France Airbus A319 outbound from Basle-Mulhouse lost separation after an error made by a trainee APP controller under OJTI supervision during procedural service. The outcome was made worse by the excessive rate of climb of the Air France aircraft approaching its cleared level and both an inappropriate response to an initial preventive TCAS RA and a change of track during the ensuing short sequence of RAs by the Training Captain in command of and flying the Easyjet aircraft attributed by him to his situational ‘anxiety’.)
  • A319/B733, en-route, near Moutiers France, 2010 (On 8 July 2010 an Easyjet Airbus A319 on which line training was being conducted mis-set a descent level despite correctly reading it back and, after subsequently failing to notice an ATC re-iteration of the same cleared level, continued descent to 1000 feet below it in day VMC and into conflict with crossing traffic at that level, a Boeing 737. The 737 received and actioned a TCAS RA ‘CLIMB’ and the A319, which received on a TCAS TA, was given an emergency turn by ATC. The recorded CPA was 2.2 nm and 125 feet.)
  • A320 / A346, en-route, Eastern Indian Ocean, 2012 (On 18 January 2012, ATC error resulted in two aircraft on procedural clearances in oceanic airspace crossing the same waypoint within an estimated 2 minutes of each other without the prescribed 1000 feet vertical separation when the prescribed minimum separation was 15 minutes unless that vertical separation existed. By the time ATC identified the loss of separation and sent a CPDLC message to the A340 to descend in order to restore separation, the crew advised that such action was already being taken. The Investigation identified various organisational deficiencies relating to the provision of procedural service by the ANSP concerned.)
  • A320 / B738, vicinity Dubai UAE, 2012 (On 22 April 2012, an Airbus A320 and a Boeing 737 came into close proximity near Dubai whilst on the same ATC frequency and correctly following their ATC clearances shortly after they had departed at night from Sharjah and Dubai respectively. The Investigation found that correct response by both aircraft to coordinated TCAS RAs eliminated any risk of collision. The fact that the controller involved had only just taken over the radar position involved and was only working the two aircraft in conflict was noted, as was the absence of STCA at the unit due to set up difficulties.)
  • A320, Basel-Mulhouse-Freiburg France, 2014 (On 6 October 2014, an A320 crew requested, accepted and continued with an intersection take off but failed to correct the takeoff performance data previously entered for a full length take off which would have given 65% more TODA. Recognition of the error and application of TOGA enabled completion of the take-off but the Investigation concluded that a rejected take off from high speed would have resulted in an overrun. It also concluded that despite change after a similar event involving the same operator a year earlier, relevant crew procedures were conducive to error.)
  • A320, Cochin India, 2011 (On 29 August 2011, a Gulf Air Airbus A320 deviated from the extended centreline of the landing runway below 200 feet aal but continued to a night touchdown which occurred on the edge of the 3400 metre runway and was followed by exit from the side onto soft ground before eventually coming to a stop adjacent to the runway about a third of the way along it. The subsequent investigation attributed the event to poor crew performance.)
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