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.
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.
Well designed and diligently applied Standard Operating Procedures (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.
- 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.
- Review and if necessary improveSOPs
- 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:
On 7 September 2019, the crew of a Boeing 737-800 completed a circling approach to runway 18R by making their final approach to and a landing on runway 18L contrary to their clearance. The Investigation found that during the turn onto final approach, the Captain flying the approach had not appropriately balanced aircraft control by reference to flight instruments with the essential visual reference despite familiarity with both the aircraft and the procedure involved.It was concluded that the monitoring of runway alignment provided by the relatively low experienced first officer had been inadequate and was considered indicative or insufficient CRM between the two pilots.
On 16 June 2021, a Boeing 737-400 was taxiing for departure at night after push back from stand when the ground crew who completed the push back arrived back at their base in the tug and realised that the tow bar they had used was not attached to it. The aircraft was prevented from taking off and it was then found that it had taxied over the unseen towbar and sustained damage to both nose gear tyres such that replacement was necessary. The Investigation concluded neither ground crew had checked that the area immediately ahead of the aircraft was clear.
On 3 January 2019, prescribed vertical separation was lost between a Bombardier DHC8-400 and a Piaggio P180 on converging cruise tracks at FL 220 and only restored after a resulting TCAS RA was followed. The Investigation found both aircraft were being flown in accordance with their clearances and that the controller involved had not been aware of corresponding traffic and conflict alerting system activations. A specific traffic display fault which arose from failure to follow a routine software upgrade procedure correctly and the shift supervisor failing to recognise the need to act as controller when workload increased were assessed contributory.
On 7 November 2018, a Boeing 747-400F overran wet landing runway 14 at Halifax at night and was sufficiently damaged as a result of exceeding the available RESA to render it a hull loss. The Investigation attributed the overrun to a combination of factors including use of un-factored landing distance, momentary mishandling of the thrust levers just after touchdown, a pilot-caused lateral deviation diverting attention from deceleration, inadequate braking and late recognition of an approach tailwind component. Poor NOTAM presentation of runway availability also led the crew to believe that the longer and more suitable runway 25 was not available.
On 2 September 2016, an ATR72-600 cleared to join the ILS for runway 28 at Dublin continued 800 feet below cleared altitude triggering an ATC safe altitude alert which then led to a go around from around 1000 feet when still over 5nm from the landing runway threshold. The Investigation attributed the event broadly to the Captain’s inadequate familiarity with this EFIS-equipped variant of the type after considerable experience on other older analogue-instrumented variants, noting that although the operator had provided simulator differences training, the -600 was not classified by the certification authority as a type variant.
On 15 November 2018, a Bombardier DHC8-300 made a main gear only touchdown at Stephenville with only minor damage after diverting there when the nose landing gear only partially extended when routinely selected on approach at the originally intended destination. The Investigation found that the cause was incorrect nose gear assembly which had allowed hydraulic fluid to leak and eventually led to it jamming. There was some concern at the way the flight was conducted following the problem which involved continuous smartphone communications with the operator and an overspeed which it was considered constituted an avoidable risk to safety.
On 27 April 2020, an ATR 72-200 freighter crew attempted a night takeoff in good visibility aligned with the edge of runway 06 and did not begin rejecting it until within 20 knots of the applicable V1 despite hearing persistent regular noises which they did not recognise as edge light impacts and so completed the rejection on the same alignment. The Investigation noted both pilots’ familiarity with the airport and their regular work together and attributed their error to their low attention level and a minor distraction during the turnround after backtracking.
On 2 February 2019, a Bombardier CRJ200 narrowly avoided collision with part of a convoy of snowplough vehicles which had entered the landing runway without clearance less than 10 seconds before touchdown and begun to position on the centreline. The Investigation found that despite the prompt initiation of a go-around on sighting the vehicles, the aircraft was likely to have cleared them by less than 100 feet. A number of opportunities for improved ground vehicle movement procedures were identified and the incursion was seen as indicative of a general need to more effectively address this risk at Canadian airports.
On 24 November 2019, as an Airbus A321 taking off from the 2665 metre-long runway 05 at Glasgow approached the calculated V1 with the flex thrust they had set, the aircraft was not accelerating as expected and they applied TOGA thrust. This resulted in the aircraft becoming airborne with less than 400 metres of runway remaining. The Investigation confirmed what the crew had subsequently discovered for themselves - that they had both made an identical error in their independent EFB performance calculations which the subsequent standard procedures and checks had not detected. The operator is reviewing its related checking procedures.
On 28 April 2018, a Boeing 737-800 exited the landing runway at Perth and without clearance crossed a lit red stop bar protecting the other active runway as another 737 was accelerating for takeoff. This aircraft was instructed to stop due to a runway incursion ahead and passed 15 metres clear of the incursion aircraft which by then had also stopped. The Investigation concluded that, after failing to refer to the aerodrome chart, the Captain had mixed up two landing runway exits of which only one involved subsequently crossing the other active runway and decided the stop bar was inapplicable.
On 19 January 2010, PSA Airlines CRJ 200 began take off from Charleston with an incorrect flap setting. After late crew recognition, a rejected take off was commenced at V1+13KIAS and an overrun into the EMAS bed at approximately 50knots followed. It was noted that had the overrun occurred prior to installation of the EMAS bed, the aircraft would probably have run down the steep slope immediately after the then-available RESA. The flap setting error was attributed non-adherence to a sterile flight deck. The late reject decision to an initial attempt to correct the flap error during the take off.
On 24 May 2010 the crew of a Regional Embraer 145 operating for Air France continued an unstable visual approach at Ljubljana despite breaching mandatory go-around SOPs and ignoring a continuous EGPWS PULL UP Warning. The subsequent touchdown was bounced and involved ground contact estimated to have been at 1300fpm with a resultant vertical acceleration of 4g. Substantial damage was caused to the landing gear and adjacent fuselage. It was concluded that the type-experienced crew had mis-judged a visual approach and then continued an unstabilised approach to a touchdown with the aircraft not properly under control.
On 29 March 2010, a Raytheon 390 operating a passenger charter flight failed to follow acknowledged taxi instructions in normal visibility at night and entered the departure runway at an intermediate intersection and turned to backtrack against an opposite direction CRJ200 which had just started its take off roll. There was no ATC intervention but the CRJ crew saw the aircraft ahead and were able to stop before reaching it. The Raytheon flight crew stated that they had “encountered considerable difficulties finding out where they were while taxiing” and ended up on the departure runway “without realising it”.
On 20 December 2009 a Blue Line McDonnell Douglas MD-83 almost stalled at high altitude after the crew attempted to continue climbing beyond the maximum available altitude at the prevailing aircraft weight. The Investigation found that failure to cross check data input to the Performance Management System prior to take off had allowed a gross data entry error made prior to departure - use of the Zero Fuel Weight in place of Gross Weight - to go undetected.
On 20 August 2011, a First Air Boeing 737-200 making an ILS approach to Resolute Bay struck a hill east of the designated landing runway in IMC and was destroyed. An off-track approach was attributed to the aircraft commander s failure to recognise the effects of his inadvertent interference with the AP ILS capture mode and the subsequent loss of shared situational awareness on the flight deck. The approach was also continued when unstabilised and the Investigation concluded that the poor CRM and SOP compliance demonstrated on the accident flight were representative of a wider problem at the operator.
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