14-11
Types of Errors
Unintentional
An unintentional error is an unintentional wandering or
deviation from accuracy. This can include an error in
your action (a slip), opinion, or judgment caused by poor
reasoning, carelessness, or insufficient knowledge (a
mistake). For example, an AMT reads the torque values from
a job card and unintentionally transposed the number 26 to 62.
He or she did not mean to make that error but unknowingly
and unintentionally did. An example of an unintentional
mistake would be selecting the wrong work card to conduct
a specic repair or task. Again, not an intentional mistake
but a mistake nonetheless.
Intentional
In aviation maintenance, an intentional error should really be
considered a violation. If someone knowingly or intentionally
chooses to do something wrong, it is a violation, which
means that one has deviated from safe practices, procedures,
standards, or regulations.
Kinds of Errors
Active and Latent
An active error is the specic individual activity that is an
obvious event. A latent error is the company issues that lead
up to the event. For example, an AMT climbs up a ladder to
do a repair knowing that the ladder is broken. In this example,
the active error was falling from the ladder. The latent error
was the broken ladder that someone should have replaced.
The “Dirty Dozen”
Due to a large number of maintenance-related aviation
accidents and incidents that occurred in the late 1980s and
early 1990s, Transport Canada identied twelve human
factors that degrade people’s ability to perform effectively
and safely, which could lead to maintenance errors. These
twelve factors, known as the “dirty dozen,” were eventually
adopted by the aviation industry as a straight forward means
to discuss human error in maintenance. It is important to
know the dirty dozen, how to recognize their symptoms,
and most importantly, know how to avoid or contain errors
produced by the dirty dozen. Understanding the interaction
between organizational, work group, and individual factors
that may lead to errors and accidents, AMTs can learn to
prevent or manage them proactively in the future.
Lack of Communication
Lack of communication is a key human factor that can
result in suboptimal, incorrect, or faulty maintenance.
[Figure 14-16] Communication occurs between the AMT
and many people (i.e., management, pilots, parts suppliers,
aircraft servicers). Each exchange holds the potential
for misunderstanding or omission. But communication
between AMTs may be the most important of all. Lack
of communication between technicians could lead to a
maintenance error and result in an aircraft accident. This
is especially true during procedures where more than one
technician performs the work on the aircraft. It is critical
that accurate, complete information be exchanged to ensure
that all work is completed without any step being omitted.
Knowledge and speculation about a task must be claried and
not confused. Each step of the maintenance procedure must
be performed according to approved instructions as though
only a single technician did the work.
A common scenario where communication is critical and a
lack thereof can cause problems, is during shift change in an
airline or xed base operator (FBO) operation. A partially
completed job is transferred from the technician nishing
his or her workday to the technician coming on duty. Many
steps in a maintenance procedure are not able to be seen or
veried once completed due to the installation of components
hiding the work. No steps in the procedure can be omitted
and some steps still to be performed may be contingent on
the work already completed. The departing technician must
thoroughly explain what has occurred so that the arriving
technician can correctly complete the job. A recounting of
critical steps and any difculties encountered gives insight.
A lack of communication at this juncture could result in the
work being continued without certain required operations
having been performed.
The approved steps of a maintenance procedure must be
signed off by the technician doing the work as it is performed.
Continuing a job that has been started by someone else should
only occur after a face-to-face meeting of technicians. The
applicable paperwork should be reviewed, the completed
work discussed, and attention for the next step should be
drawn. Absence of either a written or oral turnover serves
as warning that an error could occur.
It is vital that work not be continued on a project without
both oral and written communication between the technician
who started the job and the technician continuing it. Work
should always be done in accordance with the approved
written procedure and all of the performed steps should
bear the signature of the technician who accomplishes the
work. If necessary, a phone call can be made to obtain an
oral turnover when technicians cannot meet face-to-face
at the work area. In general, the technician must see his or
her role as part of a greater system focused on safe aircraft
operation and must communicate well with all in that system
to be effective.