Human factors research and development investigates the capabilities and limitations of the human within a system. Of the many variables affecting human performance in the aviation maintenance system, training is among the most important. The advent of advanced technology hardware and software has created intelligent training simulations. This paper describes one advanced technology training system under development for the Federal Aviation Administration

Johnson, William B.

Norton, Jeffrey E.

English

NASA Technical Reports Server

N92-30126 
Using Intelligent Simulation to Enhance Human Performance in Aircraft Maintenance I 
William B. Johnson 
Jeffrey E. Norton 
Galaxy Scientific Corporation 
2310 Parklake Drive, Suite 200 
Atlanta, GA 30345 
ABSTRACT 
Human Factors research and development investigates the capabilities and limitations of the 
human within a system. Of the many variables affecting human performance in the aviation 
maintenance system, training is among the most important. The advent of advanced technology 
hardware and software has created intelligent training simulations. This paper describes one 
advanced technology training system under development for the Federal Aviation Administration. 
1.0 INTRODUCTION/BACKGROUND 
A myriad of human factors challenges associated with aircraft maintenance exist. 
Maintenance and inspection are essential to ensure continuing airworthiness on the aging fleet. New 
advanced technology procedures for aircraft further complicate the aviation maintenance system. 
The human is a critical component of the maintenance -system. Therefore, research and development 
must address a variety of issues affecting the human in maintenance. Figure 1 depicts a few of the 
factors that can affect human performance in the maintenance system. 
Figure 1. The Human in the Maintenance System 
BMalatenance Equipment . : ... 5"... 
Data Sources 
This paper was prepared under Cunding by the Federal Aviation Administration. Office of Aviation Medicine. Contrac\ Number DTFA03-89-C-00043. 
The authors acknowledge Dr. William T. Shepherd, Office oC Aviation Medicine, Delta Air Lines, and Clayton State College. 
305 
https://ntrs.nasa.gov/search.jsp?R=19920020883 2020-03-17T11:27:59+00:00Z
The "work environment" includes not only physical characteristics such as noise, 
temperature, and illumination levels, but also less tangible measures associated with management-
labor communications, corporate goal setting and attainment, and individual decision making by 
maintenance personnel. "Data sources" include the variety of technical information that a technician 
must access to perform and record maintenance actions. "Training" includes the many activities that 
prepare the human to perform a given maintenance task. Training must also help the human 
maintain an appropriate level of technical proficiency for safe, efficient, and effective job 
performance. 
Human factors research and development is recognized as a critical component of aviation 
safety. The Aviation Safety Act of 1988 (PLlOO-59I) (ref.I) mandates that research attention be 
devoted to a variety of human performance issues including aircraft maintenance and inspection. 
Similarly, The Aviation Security Improvement Act of 1990 (PLlOI-604) (ref. 2) states that the FAA 
"shall review issues relating to human performance in the aviation security system with the goal of 
maximizing such performance." The National Plan for Aviation Human Factors (ref. 3) is but 
another official recognition that the human is a most critical factor in aviation safety. 
The Biomedical and Behavioral Sciences Division of the FAA Office of Aviation Medicine 
is engaged in a research program entitled "Human Factors in Aviation Maintenance." The program 
is conducting research in the areas listed in Table 1. 
• Advanced Technology Training Systems 
• Advanced Technology Information Systems 
• Analysis of Human Error in Maintenance and Inspection 
• Communications in Maintenance Environments 
• Development of Human Factors Guide for Maintenance 
• Human Factors Work Site Evaluations 
Table 1. Human Factors in Aviation Maintenance Research Topics 
The comprehensive research program is described elsewhere (ref. 4). This paper will 
describe only the research and developmerif task associated with advanced technology training 
systems. 
2.0 TRAINING TECHNOLOGY 
Demographic data (ref. 5) indicates that there will be a distinct shortage of qualified aviation 
maintenance technicians (AMTs) by the year 2000. The obvious solution is to create methods that 
permit less qualified personnel to conduct maintenance and inspection by using advanced technology 
job aiding equipment (Le., make the tools smarter and the job easier). A second way would be to 
devise new methods that will train, efficiently and effectively, more personnel as AMTs (Le., make 
the human smarter). Of course, a hybrid of these two approaches would be to create job aids that 
also train (Le., smarter tools and smarter people). 
306 -
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The suggested hybrid approach requires research and development on the use of artificial 
intelligence technology for both training and job aiding systems. The research must address issues 
associated with interface design and software optimization for portable computer systems. The 
advanced technology training system is called an "intelligent simulation". It is "intelligent" because 
it contains software components that provide extensive modeling and feedback that approach what 
might be provided by a human simulation instructor. 
The advanced technology training project reports the current status of maintenance training, 
develops a prototype training system, and evaluates the system in maintenance training environments 
(ref. 6). The training is described in the following sections. 
3.0 Environmental Control System (ECS) Trainer 
The ECS Trainer (Figure 2) permits the student to interact with a simulation of the Boeing 
767-300 air conditioning portion of the ECS. The system is designed to train for troubleshooting -
the most complex of maintenance tasks. The student can operate the system under normal or 
malfunction conditions. 
To troubleshoot the malfunction, the student looks at displays, manipulates controls and 
switches, and tests, inspects and replaces components. While troubleshooting, the student has access 
to operational information for the equipment. The student may also ask for advice on how to solve 
the problem most effectively. 
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Figure 2. Environmental Control System Trainer 
The following sections of the paper will familiarize the reader with the ECS Trainer from 
several different viewpoints. First, the interface design is discussed. Then, the general instructional 
design is addressed. Finally, the implications and possible future directions of the system are 
discussed. 
307 
3.1 Interface Design 
Figure 3 shows the primary (Overview) display used by the student. The system was 
designed so that the majority of relevant troubleshooting infonnation is only one display away from 
the primary display. This design prevents the student from getting "lost" while in the Trainer. 
8-767-300 
ECS Overview 
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Figure 3. Primary ECS Display 
From the Primary ECS display the student may access the displays, controls, and components 
that are required to troubleshoot a malfunction. For example, if the student selects the overhead 
panel there are two modes of operation. The first mode, shown in Figure 4, will provide basic 
instruction on how the equipment operates. The second mode, shown in Figure 5, provides a 
simulation of the system which the student can use for real-time operational practice. An expert 
system, embedded in the simulation, advises the student on system operation as needed or requested. 
ECS OYfJdlead Panel.' Equipment Infonnahon 
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Figure 4. Equipment Infonnation 
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ECS Overhead Panel 
Figure S. Equipment Operation 
From the Primary ECS display the student can access the Fault Isolation Manual (FIM). The 
FIM, shown in Figure 6, is taken directly from the airline's training documentation. In the training 
system the FIM becomes a dynamic troubleshooting display that provides advice and feedback. 
rII.·· .• •· .• · •.·· 
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Figure 6. Page from Fault Isolation Manual 
: FAULT CDDEI 
: LOCATION 
The student can also select "Help" from the Primary ECS display. The "Help" button 
provides three kinds of assistance. Help on the "current screen" describes how to use the features 
that are specific to the current display. The "advice" option provides hints to the student on how to 
troubleshoot a malfunction. The advice is based on the information contained in the FIM. The "how 
to use the system" option describes how to use the features that are common to all displays. 
3.2 Instructional Design 
The ECS intelligent simulation is designed with the instructional philosophy that "adult 
learners learn best by doing". The instructional design, therefore, permits the learner to operate the 
equipment in any way. The student can ask for help and advice at any time and is provided advice 
when it is badly needed. The intelligent simulation does not force the learner to follow any specific 
order. Essentially, the system adapts to the needs and learning characteristics of the student. This 
type of training system is not like a book, which must be accessed in a linear fashion, page after 
page. Instead, it is like having an airplane and an instructor for each student. 
The general design used to develop the ECS Trainer is shown in Figure 7. The system is 
designed to include an instructional environment, a student model, an expert model, and an instructor 
model. This general architecture is called an Intelligent Tutoring System (ITS). The ITS monitors 
student performance (through the student model) and compares these actions to the subject matter 
expert actions (the expert model). Based on the difference between the student and expert actions, 
the ITS provides remediation and instruction accordingly (the instructor model). When the ITS 
309 
technology is combined with the simulation-based instructional environment the power of the 
instruction is very high. It is similar to providing each learner with a full-time simulator instructor. 
STLOENT 
IoIOOEL 
Figure 7. Intelligent Tutoring System 
The remainder of this section will explain each of the components of an ITS and how each is 
implemented for the ECS Trainer. 
3.2.1 Instructional Environment 
The instructional environment in which the student operates is an interactive simulation of 
the ECS. The mOdel of the ECS is based on changes in inputs to the system. For example, as the 
demand on the cooling pack changes, the change is propagated from componenf to component and 
reflected on the equipment displays. This simulation gives the student the look and feel of the real 
maintemmceenvironment. 
The student is allowed to manipulate the displays, test equipment, and control panels in any 
order. When parts are replaced, the simulation will change accordingly. As in the "real world", the 
student must observe current indications to determine whether the malfunction has been eliminated. 
310 
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3.2.2 Student Model 
The student model tracks student perfonnance (ref. 7) within the instructional environment. 
The student model logs infonnation about what the student has seen and what actions the student 
has taken for each malfunction. Also, the student model records the amount of time and/or dollars 
expended to correct a malfunction and the number of errors made. 
Some of the types of infonnation stored in the student model are the types of tests 
perfonned, which parts were inspected, which parts were replaced and which errors were made. 
This information is then passed along to the expert and instructor models. 
3.2.3 Expert Model 
As the student troubleshoots a malfunction, the student's actions are compared against those 
of an ECS expert. This expertise is contained in the expert model. The ECS expert model knows 
the procedural and/or logical steps that are required to troubleshoot the system. This knowledge is 
represented in the fonn of component connectivity diagrams, fault trees, and operational procedures. 
3.2.4 Instructor Model 
When the student's actions are compared against the expert's actions, the instructor model 
gauges the difference between these two set of actions and decides how to act upon the difference. 
For example, the student may respond to a Warning light on the ECS Overhead Panel incorrectly. 
The instructor model must decide whether to let the student make this error and continue, or let the 
student know of the error immediately. The way that the instructor model responds is usually 
dependent on the severity and consequences of the inappropriate action. 
The instructor model also is responsible for problem selection. The instructor model will 
analyze the historical information about the problems already completed by the student. The 
instructor model looks for deficiencies on previous malfunctions to detennine which malfunction to 
present to the student next. 
4.0 Future Considerations of Advanced Technology for Aviation Maintenance 
4.1 AMT Schoolhouse Training and Testing 
Advanced technology is becoming more widely available for aviation maintenance training. 
Planned changes to Federal Aviation Regulation (FAR) Part 147, Aviation Maintenance Technician 
Schools, will pennit the use of educational technology in the classroom and laboratory. It is 
reasonable to expect that computer simulations may supplant requirements to operate certain turbine 
engines. Such a substitution is critical for schools located in the heart of a city. The use of 
computer simulations will also be critical in controlling equipment costs for all FAR Part 147 
schools. 
311 
Technical instructors always customize their materials to meet the needs of their students. 
Advanced Technology training must be capable of such modification if it is to gain wide acceptance. 
Most AMT instructors are not computer programmers or computer-based training developers. 
Therefore tools, usually called authoring systems, must be designed so that AMT instructors can 
make changes to the advanced technology software. A U.S. Air Force research program called 
Microcomputer Intelligence for Technical Training (ref. 7) has shown that such authoring systems 
are possible. 
As AMT certification procedures (FAR Part 65) evolve with the new training technology, it 
is likely that some practical testing may also use computer simulation. Many portions of the 
General, Airframe, and Powerplant practical exam present the examinee with system troubleshooting 
problems. Computer simulation is an ideal method to evaluate an individual's system understanding 
through troubleshooting. 
4.2 Training and Job Aiding 
This paper has focused on the application of advanced technology to maintenance training. 
The same technologies can be applied to intelligent job aids. The development of the expert system 
knowledge base, for training or for aiding, is labor intensive; therefore, it is very expensive. By 
designing systems that can be used in training environments and on the job, the cost can be easier to 
justify. When students became familiar with the system for training, they are more likely to use the 
system when in the job environment. 
4.3 More Technology - Not the Only Answer 
This paper has discussed advanced technology from the standpoint of what it can do to 
enhance human performance in maintenance and inspection. The focus has been on function more 
than on form. Hardware systems such as digital video interactive, CD-ROM storage, notebook color 
computers, voice input/output devices, and other such devices have not been discussed. Hardware 
technology is very important. However, attention to software design and interface design, combined 
with a knowledge of the capabilities of the human maintainer, are the key ingredients to effective 
advanced technology applications. Human factors research and development will ensure important 
attention to the human as advanced technology is introduced to the maintenance system. 
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5.0 REFERENCES 
1. The Aviation Safety Research Act of 1988, Pub.L.No.100-592, 102 Stat. 3011 (1988). 
2. The Aviation Security Improvement Act of 1990, Pub.L.No.101-604, 104 Stat. 3066 (1990). 
3. Federal Aviation Administration. (1991). The National Plan for Aviation Human Factors. 
Washington, DC: The Federal Aviation Administration. 
4. Federal Aviation Administration, Office of Aviation Medicine. (1991). Human factors in aviation 
maintenance: Phase one progress report. Washington, DC: Department of Transportation. 
5. Shepherd, W.T. and Parker, J.P. (1991). Future availability of aircraft maintenance personnel. 
Proceedings of the 35th Annual Meeting of the Human Factors Society. San Francisco, CA: The 
Human Factors Society, 33-36. 
6. Johnson, W.B. (1990). Advanced technology for aviation maintenance training. Proceedings of 
Human Factors in Aviation Maintenance and Inspection. Washington, DC: Office of Aviation 
Medicine, 115-130; also in Proceedings of the FAA Training Technology Symposium. 
Washington, DC: FAA Office of Training and Higher Education, 81-97. 
7. Johnson, W.B. and Norton, lE. (1992). Modeling student performance in diagnostic tasks: a decade 
of evolution. In J. Wes Regian and Valerie J. Shute (Eds.). Cognitive Approaches to Automated 
Instruction. Hillsdale, NJ: Lawrence Erlbaum Associates, Inc. Publishers. 
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Using Intelligent Simulation to Enhance Human Performance in Aircraft Maintenance

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