Aircraft Maintenance- Associations between Errors and Contributing Factors



This study aims to investigate links between specific errors made during Aircraft Maintenance and contributing factors that led to these errors. The quantitive research for this study was based a self-completed questioner carried out by Licensed Aircraft Maintenance Engineers operating under CASA system in Australia. A total of 619 safety occurrences involving aircraft maintenance were reported with 96% of them being related to the actions of the maintenance personnel. These occurrences were then analyised to determine their errors and the contributing factors of these errors.


A questioner was developed where the respondent was given an opportunity to report a critical incident and comment on a range of safety issues pertinent to aircraft maintenance. To encourage the respondents to report honestly and accurately, the respondents replied anonymously.

Occurrence Analysis and Statistical Procedure

Taxonomy was used to provide a standardized technical description of each occurance, such as “access panel not closed” or “material left in aircraft.” The circumstances leading up to the outcome were then analysed and broken down into sequence of up to 3 events. Each event was coded into one of the following categories;
1. Environmental events- Occurrence resulted from the physical location of the event and could not be changed by the personnel at that time.
2. Hardware Related events- Failure or malfunction of tooling, equipment or component
3. Behavioral events
a. Perceptual error- A failure to detect a sign that the person was attempting to detect.
b. Memory lapse- The omission of an action that the person intended to perform.
c. Slip- The performance of a familiar skill-based action at a time when this action was not intended, or the failure to carry out such an action correctly; this category included fumbles and trips.
d. Rule based error- A failure to correctly invoke familiar rules or procedures, either written or based on experience, when dealing with routine problems or when making decisions in familiar situations.
e. Violation- An intentional deviation from procedures or good practice.
f. Knowledge based error- An error in a situation that was unfamiliar or that presented new problems for the person, for which neither automatic mappings nor rules existed.
g. Mischance- The person adhered to correct procedures, but his or her behavior was nevertheless instrumental in leading to the occurrence.

The contributing factors were then linked with each occurrence again using standardized taxonomy as listed below;
1. Fatigue- Mental or physical fatigue, generally related to a lack of adequate nighttime sleep and/or to night shift work.
2. Pressure- Work was being performed under unusual time pressure or haste
3. Coordination- Inadequate teamwork and communication between workers
4. Training- Factors relating to inadequate training of personnel
5. Supervision- Factors relating to inadequate charge of workers
6. Previous deviation- Incorrect performance of a task at an earlier time, and this error remained latent and was not recorded as an event in the occurrence sequence.
4. Procedures- Poorly designed, poorly documented, or nonexistent procedures, or when a deviation from procedures was routinely accepted by management and/or operational personnel.
5. Equipment- Includes poorly designed or maintained equipment or tools, or a lack of necessary equipment, including aircraft spare parts.
6. Environment- The physical environment in which the work was being performed, which was beyond the control of the worker – for example, darkness, glare, heights, and excessive noise
7. Physiological- The worker’s performance was affected by a medical condition or by sensory or physiological limitations

Statistical Procedure


Role of contributing factors

~Factor Chi-square test * x2(6, N = 641)= Implication
Fatigue *39.5 p < .001
Pressure *18.31 p = .001
Coordination *48.1 p < .001
Training *138.11 p = .003
Supervision *20.24 p= .003
Procedures *19.6 p= .003
Previous deviation *59.59 p < .001
Equipment *29.61 p < .001
Enviroment *11.58 p=.072

1. The most common type was memory lapse and pressure fatigue and environmental factors.
2. Violations most commonly associated with pressure.
3. Slips more often related to equipment failure.
4. Knowledge based errors showed a notable correlation with training.

1. full reference in the following format A. Hobbs and A. Williamson (2003). Associations between Errors and Contributing Factors in Aircraft Maintenance. Reference location, date publication.
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