human factors

Aviation Maintenance 26-11
of the instructor and trainee are included in the software. Thus, in addition to system logic and
data, the program for instruction contains person-models that allow more appropriate feedback
and branching. An ITS was developed for the environmental control system of a Boeing-767-300
(Johnson et al., 1992), usable both as a job aid and a training device. An evaluation of this
system, using 20 AMTs, compared the ITS with the instructor-led instruction, by comparing the
performance on a posttraining examination (Johnson, 1990). No significant performance differences
were found, showing that the system was at least as effective as the much more expensive
instructor-led training.
With the evolution of technology allowing the use of portable computer systems at the work
point, the basic logic and interface of such an ITS can become a useful job aid. Particularly, when
interfaced with the central maintenance computer of a modern aircraft, it can support improved
diagnosis techniques. Indeed, in the military, Johnson (1990) showed that a diagnosis task is dramatically
improved in speed and accuracy with the use of a portable-computer-based job aid.
Aircraft are now designed with on-board maintenance computer systems, so that the hardware
support for such tasks is in place. However, human factors in design of the interface and logic are
still required to ensure usability.
An additional project (Jones & Jackson, 1992) applied many of the intelligent tutoring systems
developed for airline maintenance to an airways facilities environment. This advanced technology
training system used the MITT Tutor (from Galaxy Scientific Corporation) to develop a troubleshooting
training program for the air-traffic control beacon interrogator (ATCBI-4). The trainee
was able to interact with a model of the ABI-4 and solve problems using various diagnostic procedures.
The program allowed access to flow diagrams and oscilloscope traces, while monitoring
trainee progress and errors.
18. International differences in inspection. The organization of the inspection/repair/ buyback process
is different in the United States and the United Kingdom. A study of these differences (Drury &
Lock, 1992) showed that integration between inspection and repair was emphasized in the United
Kingdom, while organizational separation of these functions was considered desirable in the
United States. Recent work (parallel to the preceding program) at an airline (Scoble, 1994) showed
that it is possible to better integrate the repair and buyback functions with the inspection process
within the existing United States context.
26.5 Future Challenges for Human Factors
in Maintenance and Inspection
The function- and task-based approach detailed in this chapter was introduced to put human actions,
and particularly human error, into a systems context of ensuring continuing airworthiness. In this
way, the potential for human-factors interventions can be seen, alongside those of the physicists and
engineers who specify the inspection intervals and who design the equipment for defect detection and
repairs. The need for human-factors effort is clear, as it continues to be in flight operations. Maintenance
and inspection error shows itself in spectacular system failures with depressing regularity.
As will be clear from the review of both system-level studies and function-specific interventions in
the previous section, many valid studies have been carried out to bring human-factors techniques into
a domain neglected for far too long. These are not the only efforts, but just those for which specific
references can be cited. In a number of airlines, human factors has been introduced: Error-reporting,
human-factors audits, new forms of work organization, and particularly, MRM training in almost all.
In addition, aviation regulatory authorities, beyond the FAA and CAA already mentioned, are analyzing
maintenance human factors in aircraft accidents. ICAO’s concept of a human-factors model (the
SHELL model) has moved from the cockpit into the hangar. ICAO has already mandated human-factors
training for all maintenance personnel.