Visual Inspection and Complex Systems (9.6.3-4) PDF

Visual Inspection and Complex Systems (9.6.3-4) Learning Objectives 9.6.3.1 Recall human and external aspects that are necessary to facilitate accurate visual inspection (Level 1). 9.6.3.2 State the importance of reference information (Level 1). 9.6.3.3 Recall steps in the conduct...

Visual Inspection and Complex Systems (9.6.3-4) Learning Objectives 9.6.3.1 Recall human and external aspects that are necessary to facilitate accurate visual inspection (Level 1). 9.6.3.2 State the importance of reference information (Level 1). 9.6.3.3 Recall steps in the conduct of a successful visual inspection (Level 1). 9.6.4.1 State the typical sequence of information processing in a complex system (Level 1). 9.6.4.2 Recall the importance of procedures, data and reference material (Level 1). 2023-01-12 B-09 Human Factors Page 211 of 340 CASA Part 66 - Training Materials Only  Visual Inspection Eyesight Visual inspection is one of the primary methods employed during maintenance to ensure the aircraft remains in an airworthy condition. Visual inspection can be described as the process of using the eye, alone or in conjunction with various aids, to examine and evaluate the condition of systems or components of an aircraft. Good eyesight is of prime importance in visual inspection. Glasses or contact lenses are to be used where prescribed. Regular eyesight checks should be made. Visual inspection is often the principal method used to identify defects in systems or components of aircraft. Although the engineer’s vision is important, they must also make judgments about what they see. To do this, training, experience and common sense are required. Thus, reliable visual inspection requires that the engineer rst sees the defect and then actually recognises that it is a defect. Of course, experience comes with practice, but tell-tale signs to look for can be passed on by more experienced colleagues. Visual Aids AMEs may use magni ers and borescopes to enhance their visual capabilities. Borescopes enhance the engineers visual capabilities 2023-01-12 B-09 Human Factors Page 212 of 340 CASA Part 66 - Training Materials Only  Other Senses to Assist Visual Inspection The engineer may supplement their visual inspection by examining the element using his other senses (touch, hearing, smell, etc.). They may also manipulate the element being inspected to make further judgments about its condition. For instance, they might feel a surface for unevenness, or push against it to look for any unanticipated movement. 2023-01-12 B-09 Human Factors Page 213 of 340 CASA Part 66 - Training Materials Only  Reference Information Introduction Information such as approved maintenance data including technical bulletins are important when carrying out inspections. Typically, it informs the inspector of known and potential defects and problems that could be encountered during the inspection. It provide information about where to look (the correct area, component or system) and what to look for (for example, what other operators have found) when conducting the inspection. Flight Safety Foundation Approved maintenance data in the from of electronic Maintenance Manual 2023-01-12 B-09 Human Factors Page 214 of 340 CASA Part 66 - Training Materials Only  Conducting the Visual Inspection A number of techniques and steps can be helpful when conducting visual inspections. These include preparation, conducting a systematic inspection, including minimising distractions, and nishing/recording the ndings of the inspection. Conducting visual a inspection using a black light 2023-01-12 B-09 Human Factors Page 215 of 340 CASA Part 66 - Training Materials Only  Preparation Various steps that an engineer can take to carry out a reliable visual inspection. The engineer should: Ensure that they understand the area, component or system to be inspected (e.g., as speci ed on the work card). Locate the corresponding area, component or system on the aircraft itself. Make sure the environment allows the visual inspection task (considering factors such as lighting, access, etc.). Virgin An engineer should always understand the area, component or system they are inspecting 2023-01-12 B-09 Human Factors Page 216 of 340 CASA Part 66 - Training Materials Only  Systematic Inspection Conduct a systematic visual search, moving eyes carefully in a set pattern so that all surfaces and interfaces are inspected. Examine thoroughly any potential degradation or defect that is seen and use judgement and reference data to decide whether it constitutes a problem. Finish Record any problem that is found. If interrupted, continue the inspection a few steps prior to where it was left off. Image by SpaceX on Pexels SpaceX engine inspection 2023-01-12 B-09 Human Factors Page 217 of 340 CASA Part 66 - Training Materials Only  Concentration for Visual Inspection Visual inspection requires a considerable amount of concentration. Long spells of continuous inspection can be tedious and result in low arousal. An engineer’s low arousal or lack of motivation can contribute to a failure to spot a potential problem or a failure to recognise a defect. The effects are potentially worse when an inspector has a very low expectation of nding a defect, e.g., on a new aircraft. Engineers may nd it bene cial to take short breaks between discrete visual inspection tasks, such as at a particular system component, frame, lap joint, etc. This is much better than pausing midway through an inspection. Visual Techniques with Non-destructive Inspection Finally, various Non-destructive Inspection (NDI) techniques include an element of visual inspection. This includes the visual analysis of images and uorescent penetrant for large defects but can include techniques which detect defects below visual thresholds. Various specialist tools are used for this purpose, such as the use of eddy currents and x-ray. Fluorescent Penetrant Inspection (FPI) can also make visible cracks and inconsistencies that are invisible to the unaided eye. Non-destructive Inspection (NDI) techniques include an element of visual inspection 2023-01-12 B-09 Human Factors Page 218 of 340 CASA Part 66 - Training Materials Only  The Physical Environment Can Affect Visual Inspection As speci ed elsewhere in these notes, the environment in which the inspection will take place should have the minimum possible negative impact on the inspector’s performance. These environmental considerations include: Access Lighting Temperature control Cleanliness Space. Image by MAX LIBERTINE on Unsplash The environment in which the inspection will take place should have the minimum possible negative impact on the inspector’s performance 2023-01-12 B-09 Human Factors Page 219 of 340 CASA Part 66 - Training Materials Only  Complex Systems Inputs, Processing, Response and Outputs All large modern aircraft can be described as complex systems. Within these aircraft, there are many separate systems, many of which themselves may be considered complex, e.g., ight controls, landing gear, air conditioning systems and, ight management computers. The table below gives an example of the complexity in one particular aircraft system. Any large or complex system can have a wide variety of inputs. The system typically performs complex modi cations on these inputs, or the inputs trigger complex responses. There may be a single output, or many distributed outputs from the system. The processing or modi cation of the input can range from purely mechanical to fully digital, such as in modern electronic and y-by-wire systems where the inputs, processing, outputs and feedback are all digital signals. TYPE OF NATURE OF SYSTEM AILERON Simple aileron Direct connection from control column to control surface; direct movement. Servo tab Direct connection from control column to servo tab; aerodynamic movement aileron of surface. Connection from control column to servo valve via input; hydraulic movement Powered aileron of surface; feedback mechanism; position indication. Powered aileron As above but with interface to spoiler input system to provide additional roll / roll spoiler capability. No connection from control column to surface. Electrical command signal to Fly-by-wire electro-hydraulic servo valve on actuator; signal modi ed and limited by aileron system intermediate in uence of ight control computer. With a complex system, it should still be clear to an AME what the system’s purpose is. A complex aileron system performs the same basic function as a simple aileron system. However, its components and their function may be harder to understand. To maintain such complex systems, it is likely that the engineer will need to have carried out some form of system-speci c training to understand how it works, how it can fail, what it is made up of, and how components can fail. System-speci c training must achieve the correct balance between detailed system knowledge and analytical troubleshooting skills. 2023-01-12 B-09 Human Factors Page 220 of 340 CASA Part 66 - Training Materials Only  Procedures, Data and Reference Material With complex aircraft systems, simpli ed system overviews, written procedures and reference material become even more important sources of guidance than with simple systems. They will break down the system, describe the relationship of one system to other systems and often provide cautions or bring attention to speci c areas or components, making the system easier to understand and work on. When working with complex systems, it is important that the AME uses, and refers to, the appropriate approved data. It is important to follow approved procedures closely, since deviations from procedures may have unintended implications for other parts of the system. In modern aircraft, it is likely that the expertise to maintain various aspects of a complex system may be distributed among individual engineers. Thus, avionics engineers and mechanical engineers may need to collaborate to completely examine a system that interfaces with the ight crew (such as pressurisation controls and indications). Image by Dan Lohmar on Unsplash It is important that the AME uses, and refers to, the appropriate approved maintenance data A single modern aircraft is complex on its own, but many engineers are quali ed to work on several types and variants of aircraft. This will usually mean they have less opportunity to become very familiar with one type. It makes it even more important to adhere to the prescribed procedures and refer to approved data wherever necessary. There is a particular vulnerability when tasks are very similar between a number of different aircraft types (e.g., spoiler systems on the A320, B757 and B767), and may be more easily confused if AMEs don’t refer to the approved data. 2023-01-12 B-09 Human Factors Page 221 of 340 CASA Part 66 - Training Materials Only