Is the Glass Half Empty or Half Full?
By Fred Workley
April 1999
For maintenance professionals, like you and me, who spend hours "looking" at airplanes, here is a question -- Do we look to confirm that there is a crack or do we look to confirm that there is no crack? Either way, we still look. Federal Aviation Regulations Part 1 tell us that inspection is maintenance.
In the process of doing a study on Human Factors for future articles, I came across the final report of the Third Federal Aviation Administration meeting on Human Factors Issues in Aircraft Maintenance and Inspection Training Issues, November 1990. In an article titled Training for Visual Inspection, by Drury and Gramopadhye, it is pointed out that the basic training principle is to determine whether the activity is indeed trainable. How did you receive your training for visual inspection?
Maintenance personnel have to look and see at the same time. We spend hours looking, but are we good at seeing? Here is where the human role in inspection is important. It is the human that makes the difference because we can interpret what we see and make a decision whether we can keep the aircraft flying. There are differences between maintenance personnel with respect to their abilities to inspect. The important thing is that no matter who does the inspection and their level of training or experience, the end result should be consistency in the performance with respect to findings.
The task of inspection has two parts that include manual tasks, such as initiate, access, and respond; and cognitive (thinking) tasks, such as search and decision making?
How do we inspect? We initiate by reading a checklist or work card and understanding the area to be inspected. Access is gained and we locate the specific area and get into a position to look and see. We then search visually with our eyes. We may use several methods. One is to look at the whole area for obvious discrepancies and then look in greater detail. Another way is to move the eyes systematically over the area pausing to really look at each small area until a particular zone is completed, then reverse the pattern while looking at the same small areas from different angles while eliminating any shadows. Once an indication of a discrepancy has been found, we mark it and clearly define its location.
For example, let's consider an area of suspected metal corrosion. You think you see corrosion. Now you have a decision to make. You must now examine the indication against your knowledge of corrosion and the standards that you remember or can quickly reference. You get out your red rag and your scribe to go in for a closer look. What your mind said at first was corrosion turns out to be dirt and surface paint with poor adhesion to the primer. You respond by either marking the defect, then writing it up for repair, or by deciding it is not a defect. If it is not a defect, then you return to your search.
If the area was repaired, it is likely that it will be visually inspected for a final time by either the person who made the repair or a buy-back inspection of the marked area.
The manual tasks of inspecting are just as important as the cognitive tasks. The manual tasks do require training. Access is the necessary step to find symptoms that on further diagnosis may indicate problems. It is generally believed that the cognitive skills of search and decision making are improved with experience and training. We can't leave to chance the finding of particular defect in an aircraft being inspected. Uncontrolled training in the cognitive skills will not be productive. Also, on-the-job training doesn't really help the trainee see for him or herself. They may instead pick up the bad habits of other inspectors. Believe it or not, research has shown that inspector's performance improves with training, but not necessarily with practice.
Practice may improve speed and accuracy. However, search and decision making will only be improved by training. This training should be performed off-line in a controlled setting. Often, the on-the-job environment at the aircraft is in a production setting. The inspector has to be prepared to search and make decisions well before the search process begins. Good decision making can not be left to trial and error in an uncontrolled environment. With the inspector's training controlled, it is likely that the repeatability of finding the same discrepancies by different inspectors is good. This works the same way when you are trying to confirm that there are no discrepancies.
The experience level of the aviation maintenance professional does have some influence on finding discrepancies. If we ever found any discrepancy during a zonal inspection, many of us remember, we will look for it again. However, as the inspection of aging aircraft has taught us, over time there can be a whole new set of discrepancies. This is why every time we start a visual inspection it is possible that we may find a discrepancy that hasn't shown up before in the life of the aircraft -- even if it is twenty years old. More important to confirm without a doubt that the aircraft has no discrepancies. It is a tough thing to look, and search, and not find anything time after time. But, isn't that really what we are doing during visual inspections? That's how we keep em' flying.
