As nearly two-third of air crashes are caused by flight-crew (cockpit crew) error, error occurred in the cockpit hence have attracted greatest attention by safety investigations. Flightcrew error can be operationally defined as “crew action or inaction that leads to deviation from crew or organisational intentions or expectations” (Helmreich, Klinect &Wilhelm, 1999, p.3).
The definition of flightcrew error can be classified into five error types (Helmreich et al, 1999).
1) Intentional noncompliance errors are caused by the crew’s behaviours which consciously/intentionally violate the Standards Operation Procedures (SOPs) or regulations. For example, a flight-crew shortcuts or ignore the necessary briefings or checklist. The possibility of violations could be caused by pilot’s complacency or poorly designed and inadequate procedures themselves.
2) Procedural errors refer to the slips, lapses, or mistakes occurred in the implementing of procedure and regulations, in which the flight-crew intends to follow the procedures, but they makes an error in execution. One implication of procedure errors could be the deficient design of SOPs; another possibility is failure to conduct basic Crew Resources Management (CRM) behaviours, such as unconsciously omitting items on checklists.
3) Communication errors occur when information is incorrectly transmitted or interpreted. For example, the Air Traffic Control (ATC) transmits the incorrect readback to flight-crew; or the information is incorrectly interpreted within the flight crew.
4) Proficiency errors are reflected in which one or more of flight-crew members lack the knowledge to complete a needed aircraft operation, such as lack of required stick and rudder skill of properly operating airplane. Proficiency error emphasize that pilot must be given extensive and strict training before they are released to the line.
5) Operational decision errors are that flight-crew make a discretionary decision not covered by SOPs which may create the unnecessarily additional risks. For example, due to excessively rely on automation, crews make an arbitrary decision without consideration or re-evaluation of threat in operational environment, such as choosing to fly into bad weather. Operational decision errors reflect the deviations from the policy in cases where there is inadequate CRM.
During 1997 and 1998, the University of Texas Team Research Project had completed a data collection from Line Operations Safety Audits (LOSA), which conducted three airlines with an aggregated sample of 184 flight-crew on 314 segments. The aggregated LOSA results showed that the intentional non-compliance errors were the most frequent type of errors (54%); followed by Procedural (29%); Communications (6%); Proficiency (5%); and Operational decision making (6%); the distribution of error types are presented in Table 1 (Klinect, Wilhelm & Helmreich, 1999).
|Type of Error||Percentage of All Errors|
|Operational decision making||6%|
Table 1. the Distributions of Error Types (Klinect et al, 1999, p.4)
There are three types of responses to crew error (Helmreich et al, 1999):
1) Trap – the error is founded and managed before it leads to additional error or inconsequential outcome.
2) Exacerbate – the error is detected, but the crew’s inappropriate action or inaction cause a negative consequences.
3) Fail to respond – as the error is not detected or is ignored, the crew hence fail to take any reaction to deal with the error.
LOSA results show that 53% of the error responses were a failure to respond; and 36% of the unintentional errors would result in a condition of undesired aircraft state, in which the flight-crew need take action to avoid the potential consequences of an undesired state, such as execution of effective error management strategies. The distribution of flight crew response to unintentional error is shown in Table 2 (Klinect et al, 1999).
|Error response||Percentage of unintentional errors|
Table 2 the Distribution of Flight-crew Responses to unintentional Error (Klinect et al, 1999, p.5)
After the error occurs and the crew responds, there are three possible outcomes (Helmreich et al, 1999):
1) Inconsequential – the error has no adverse influence in safe completion of the flight, or is successfully excluded by crew error management. This is the modal outcome, a fact demonstrates that the robust performance of aviation system.
2) Undesirable aircraft state - is a condition where the aircraft is unnecessarily put into a condition which increases risk to safety. It includes deviations from desired navigational path or altitude, low fuel state, unstable approach, improper landing e.g. long landing, landing in the wrong runway or in wrong country, etc.
3) Additional error – the response to error can lead to a subsequent error (additional error), in which flight-crew can start the cycle of response over again.
The LOSA results indicates that 85% of the flight-crew errors resulted in inconsequential outcome; nevertheless, 15% of the errors observed would lead to an additional error or undesired aircraft state, the distribution of flight-crew error outcomes are shown in Table 3 (Klinect et al, 1999).
|Error Outcome||Percentage of Outcomes|
|Undesired Aircraft State||12%|
Table 3 - Distribution of Flightcrew Error Outcomes (Klinect et al, 1999, p.5)
Undesired Sate Responses
After entering an undesired aircraft state, 1) the condition can be mitigated by the crew response that corrects the error. For instance, if a crew becomes uncertain of position on navigation, a timely decision of performing a ‘lost procedure’ may mitigate this situation; 2) besides, the condition of undesired aircraft state can become worse, if the crew’s response exacerbates the severity by resulting in another error. For example, a crew’s error response may increase the level of risk; 3) another possibility is that flight-crew can fail to respond (Helmreich et al, 1999) .
Undesired Sate Outcomes
There are three possible outcomes after the undesired aircraft state (Helmreich et al, 1999):
1) Recovery – this outcome indicates that the risk has been successfully excluded.
2) Additional error – this resolution shows that a crew’s actions lead to another round of error and management.
3) Crew-based incident or accident.
The Model of Flightcrew Error Management
The model of flight-crew error management can effectively promote the comprehensive analysis of error, response and outcome, and also can facilitate the evaluation of failure or success of act of defence. The classification of error definition not only can assist organisations (e.g. airlines, aviation school, air force) to make proper response, but also can be used as scenarios for flight-crew training purpose. The model of flight-crew error management is shown in Figure 1.
Figure 1. the Model of Flight-crew Error Management (Helmreich et al, 1999, p.3)
- Helmreich, R.L., Klinect, J.R., & Wilhelm, J.A. (1999). Models of threat, error, and CRM in flight operations. Proceedings of the Tenth International Symposium on Aviation Psychology. Retrieved from the Google Scholar: http://scholar.google.co.nz/scholar
- Klinect, J.R., Wilhelm, J.A., & Helmreich, R.L. (1999). Threat and error management: Data from line operations safety audits. Proceedings of the Tenth International Symposium on Aviation Psychology. Retrieved from the Google Scholar:http://scholar.google.co.nz/scholar
Contributors to this page
Authors / Editors