A threat is a condition generated in the operating environment that affects or complicates the performance of a task or a crew’s compliance with applicable standards. Interruptions and distractions are frequent threats facing flight crews and have been shown to lead to significant safety problems.
Interruptions (e.g., due to ATC communications) and distractions (e.g., due to a conversation among others on the flight deck) occur frequently during flight. Some cannot be avoided and therefore must be coped with by the flight crew. Others can be minimized or eliminated through training, adoption of effective procedures, discipline and the use of good judgment. If the number of interruptions and distractions is not minimized or the impact of residual interruptions and distractions is not controlled, flight safety can be affected. In particular, when a flight crew is disturbed while monitoring or controlling the aircraft, errors can occur and go undetected.
This Briefing Note discusses the causes and consequences of interruptions and distractions and describes techniques for reducing and dealing with them. The focus in this material is on actions for both individual flight crew members and their companies.
The omission of a required action or an inappropriate action is the most frequent causal factor in incidents and accidents as illustrated by Table 1. These omissions or errors are often the result of an interruption or distraction. Also, the US Aviation Safety Action Program (ASAP) reveals that 14 percent of crew reports include references to an interruption or distraction (Source: US ASAP - 2000-2001).
Table 1: Effects of Distractions and Interruptions in Approach-and-Landing Accidents
|% of Events
|Omission of action or inappropriate action
|Inadequate crew coordination, cross-check and backup
|Insufficient or loss of lateral or vertical situational awareness
|Inadequate or insufficient understanding of prevailing conditions
|Slow or delayed action
|Incorrect or incomplete pilot/controller communications
Source: Flight Safety Foundation - ALAR - 1998-1999
Factors Involved in Interruptions and Distractions
Interruptions and distractions in the cockpit may be subtle and momentary or intrusive, obvious and continuing, but all can be disruptive to the flight crew. A study by the NASA Aviation Safety Reporting System (Aviation Safety Reporting System (ASRS)) in 1998 indicated that there are four primary factors that generate interruptions or distractions:
- receiving the final weights while taxiing
- a flight attendant entering the cockpit
- calls from ATC or on company radio
- Head-down activity
- Responding to an abnormal condition or unanticipated situation
- system malfunction
- weather or environmental threat
- Searching for traffic after a Airborne Collision Avoidance System (ACAS)/ACAS alert.
Over time, the ASRS database has been used to estimate the respective contributions of these four sources to interruptions and distractions. These estimates are shown in Table 2.
Table 2: Factors Involved in Interruptions and Distractions
|% of Events
|50 to 68%
|16 to 22%
|Response to abnormal condition/unanticipated situation
|14 to 19%
|Searching for traffic after a TCAS/ACAS Alert
|8 to 11%
Sources: NASA - ASRS
The four factors shown in Table 2 are behaviours of the flightcrew. A variety of other contributing factors can make these and other flight events more likely to result in interruptions and distractions. These include:
- Poor flight-deck ergonomics
- High flight-deck noise levels
- Inadequate language proficiency (pilots and controllers)
- Poor airport infrastructure (e.g., unclear markings)
- Flight crew fatigue.
It is also important to note that interruptions and distractions need not be large or of long duration to result in a safety problem. Even minor disruptions (e.g., a non-threatening equipment malfunction) can turn a routine flight into a challenging event, particularly for a crew at the end of a long, tiring day of flying.
Effect of Interruptions or Distractions
The primary effect of interruptions or distractions is to break the flow of ongoing cockpit activities which, in turn, can lead to errors and associated safety problems. An error may occur if the attention of the flight crew is diverted while crewmembers are engaged in safety-critical tasks such as:
An interruption/distraction often leaves the flight crew with a feeling of being rushed and faced with competing tasks of varying priority. This can result in an increase in workload even when the actual task load is reasonable and steady. As a result, a crew faced with concurrent task demands will typically focus on one or a few tasks while ignoring all others. This response is typical of most people when dealing with excessive workload.
Unless mitigated by effective compensatory techniques, a disruption leading to a lapse of attention can result in:
- Failure to monitor the flight path, possibly leading to an altitude or course deviation or even Controlled Flight Into Terrain (CFIT).
- Missing or misinterpreting an ATC instruction leading to a traffic conflict or runway incursion.
- Omitting an action and failing to detect and correct the resulting abnormal condition or configuration.
- Being “behind the aircraft” because of a task overload due to the combination of flying duties and attention to the interruption or distraction.
The following are examples of unsafe situations resulting from interruptions and distractions:
- Taxiway or runway incursion
- Incorrect aircraft configuration for takeoff
- Late landing gear retraction
- Premature or delayed slats/flaps retraction
- Flaps placard-speed (VFE) exceedance
- Late response to ATC instructions
- Failure to select engine anti-ice when required
- Altitude/flight level “bust” in climb or descent
- Inadequate fuel management (e.g., late detection of fuel imbalance)
- Speed below minimum during descent
- Failure to reset altimeter
- Altitude deviation or stall during holding pattern
- Late aircraft configuration for landing
- Failure to capture (or monitor capture of) localizer or glide slope
- Descent below MDA
- Taxiway excursion
- Failure to set parking brake on arrival at gate or parking stand.
Reducing Interruptions and Distractions
In order to reduce interruptions and distractions, actions are required at both the company and personal levels. Company policies and procedures should be designed with full knowledge of the sources and effects of interruptions and distractions. Likewise, the training for both flight and cabin crews should include information on interruptions and distractions and advice on how to decide when an interruption is warranted.
A good first step in a prevention program involves assessing the exposure of both the company and flight crew personnel to interruptions and distractions. Strategies can then be developed to prevent or deal with the identified problems.
It is important to:
- Maintain a high level of interaction and communication among flight crew members and between the flight and cabin crews without simultaneously increasing interruptions and distractions. Effective communication involves a two-way transfer of information, not just a simple one-way consultation
- Schedule actions that can be controlled (e.g., initiation of normal checklists) during periods that are less prone to disruption in order to prevent interference with actions that cannot be controlled (e.g., ATC communications)
- Recognize the range of potential sources of interruptions and distractions and to understand their effect on the flow of cockpit duties
- Reduce interruptions and distractions by adopting appropriate policies and rules
- Acknowledge that the flight crew does not have control over all sources of interruptions/distractions and, thus, mitigation is needed as well as prevention
- Develop prevention strategies and lines-of-defense to minimize the exposure to interruptions and distractions
- Develop or adopt specific techniques to lessen the effects of interruptions and distractions.
Good rules to follow
There are no absolute methods to prevent or control interruptions and distractions. The effectiveness of efforts will depend to some extent on factors such as an airline’s operating environment, prevailing rules and the cultural background of the crewmembers. Nevertheless, there are some good general rules to follow including:
- Adhere to the Sterile Cockpit Rule (U.S. FAR - Part 121.542) as an integral part of SOPs because it has the potential to reduce interruptions and distractions. The Sterile Cockpit Rule limits unnecessary conversations and communications during taxi, takeoff, landing and below 10,000 feet
- Include the Sterile Cockpit Rule in preflight briefings and in Crew Resource Management training with the cabin crew
- Avoid the most frequent causes of interruptions and distractions including:
- Non-flight-related conversations
- Distractions by cabin crewmembers
- Non-flight-related radio calls
- Non-essential public-address (PA) announcements.
Specific approaches for each major factor
There are specific ways to help control each of the major factors that promote interruptions and distractions discussed earlier. These include:
- Brief all jump-seat riders on the Sterile Cockpit Rule
- Put headsets on during critical phases of flight (e.g., for any operations below 10,000 ft)
- Plan PA announcements for low workload periods
- Keep intracockpit communications brief, clear and concise
- Pause or end conversations in advance of approaching the next defined target or the next altitude restriction/constraint.
- Head-down activity
- Define an SOP for task sharing when programming or reprogramming the FMS depending on the level of automation being used and the flight phase
- Plan extended head-down tasks for low workload periods
- Announce when you are going “head down.”
- Responding to an abnormal condition or to an unanticipated situation
- Keep the autopilot engaged to decrease workload unless otherwise required
- Adhere to PF/PNF task sharing for abnormal/emergency conditions (e.g., PNF should maintain situational awareness, monitor and back up the PF)
- Pay particular attention to the proper completion of normal checklists. Handling an abnormal condition has a tendency to disrupt the normal flow of actions as specified in SOPs. When there is an interruption or distraction, the “trigger” event for an SOP or checklist may go unnoticed, resulting in the omission of the associated actions or verifications.
- Search for Traffic
- Express a clear and loud “I fly, you watch” call when required to search for traffic by a TCAS alert or a call from ATC.
Managing/Mitigating Interruptions and Distractions
Some interruptions and distractions are subtle and potentially difficult to detect. The first priority, therefore, must be to recognize that a disruption has, in fact, occurred. Once you are aware that the normal flow of activities has been interrupted, the second priority is to re-establish situational awareness. This is accomplished through the following steps:
- Identify - What was I doing?
- Ask - Where was I interrupted?
- Decide/Act - What decision or action shall I take to get “back on track?”
When deciding on an action:
- Use the clear guidelines in operations golden rules - “fly, navigate, communicate and manage systems, in that order”
- Plan all activities. Be willing to postpone some actions until time and conditions are more conducive
- Ask for more time (e.g., from the ATC or from the other crewmember) to prevent being rushed. “Take time to make time”
- Follow SOPs to verify that any postponed action(s) have been accomplished
- If a disruption interrupts the course of any checklist, an explicit hold should be verbalized to mark the pause in the checklist, and an explicit command should be used for resuming the checklist.
Summary of Key Points
- Interruptions and distractions usually result from the following factors:
- Pilot/controller, intracockpit or cockpit/cabin communications
- Head-down activity
- Responding to an abnormal condition or unanticipated situation
- Searching for traffic
- Prevention strategies and lines-of-defense should be developed to minimize interruptions and distractions and to lessen their effects
- The most effective company prevention strategies and personal lines-of-defense involve strict adherence to:
- Operations golden rules
- Standard calls
- Sterile cockpit rule
- Recovery techniques such as:
- “Identify - Ask - Decide - Act”
- “Prioritize - Plan - Verify.”
Associated Flight Operations Briefing Notes
ALAR Briefing Notes:
Other OGHFA Briefing Notes:
- ICAO - Preparation of an Operations Manual (Doc 9376).
- ICAO - Human Factors Training Manual (Doc 9683).
- ICAO - Human Factors Digest No 8 - Human Factors in Air Traffic Control (Circular 241).
- FAR 121.406, 121.419, 121.421 or 121.422 - CRM Training.
- FAR 121.542 - Sterile Cockpit Rule.
- JAR-OPS 1.945, 1.955 or 1.965 - CRM Training.
- JAR-OPS 1.085(d)(8) - Sterile Cockpit.