204. FOUR LEVELS OF VISUAL INSPECTION.
a. Inspection Tasks. Visual inspection tasks are divided into four categories relating to their difficulty and degree of effectiveness as follows:
• Walkaround Inspection.
General Visual Inspection.
• Detailed Visual Inspection.
• Special Detailed Visual Inspection.
b. Additional Special NDI. An additional category may be used when visual inspection is supplemented by specialized NDI equipment.
05. ACCEPTABLE PRACTICE FOR VISUAL INSPECTION. Acceptable prac ice for the four levels of visual inspection is defined in the following paragraphs. For each level, the practice is divided into the four parts of the inspection procedure described in Table 2-1. Details of the inspection procedures will vary for different types of operators and aircraft; for example, the walkaround for a general aviation aircraft and a commercial jet will have major differences. It is important however, that the procedure for each aircraft type in a given service be carried out with the same care and detail every time the aircraft is inspected. Also, in all inspections described herein, the inspector should have available and be familiar with the documentation and reporting forms and the ground rules mandating the inspection. Refer to Appendices A through F for sample visual inspection procedures and equipment.
Level 1. Walkaround. The walkaround inspection is a general check conducted from ground level to detect discrepancies and to determine general condition and security.
NOTE: This is the only one of the four inspections that may be accomplished by either flight or maintenance personnel. The focus and perspective will vary based on the relation of the inspection to flight or maintenance operations.
Basis for Inspection. Most maintenance instructions mandate walkaround inspections on a periodic basis. The overall purpose is to serve as a quick check to determine if detectable inconsistencies exist which would affect the performance of the aircraft.
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Preparation for the Inspection. Aircraft history should be used to gain information useful in inspecting the aircraft (e.g., are there recurring problems or have there been hard landings?). In addition the aircraft should be clean enough for an effective inspection to take place, the necessary tools and equipment should be available (e.g., flashlight, rag, notebook), and other aids, tools, and procedures may be necessary (e.g., inspection of some aircraft is easier if already on jacks, but this is not always necessary).
(3) Implementation. Beginning the inspection at the nose, the inspector should approach the inspection from the perspective of the pilot and mechanic by, first, determining general condition and, second, identifying maintenance items. A good rule is to check for items affecting safety, legality, efficiency, and comfort. The following paragraphs give a partial listing of things to look for. Each aircraft will be different, but a surprising number of different aircraft have similar struc-
• Observe left and right side of fuselage and left and right wings. (Does the aircraft list?) Work to your left. Check general condition of paint.
Check exterior surface components within reach.
Check windows. Check engine, propellers or fan blades, exhaust area, and pylons. Check leading edges everywhere. Check control surfaces for slop, wear, and security. Check each gear well. Check all entry and exit points to the aircraft.
static dischargers. Observe surfaces at different angles using available light to enhance surface evaluation.
• Examine according to what the standard condition (Question the existence of any unusual condition.) Look for anything different from one side to another. (It is important to shake, push, pull, listen, and feel when possible.) Run your hand over skin junction areas or composite surfaces.
• Walk around twice. (Observations during the first cursory walkaround the aircraft should be used to determine the general condition. On the second time around revisit the areas noted on the initial walk and look for other discrepancies that may be revealed through closer scrutiny of a specific This is when specific locations should be observed.)
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• Are there major dents or intrusions in the skin?
Look for evidence of flexing parts, waves in the skin, weave or bubble in fiber glass or composite components, eroded fairings, and bulging or flattened seals. Are any external components bent?
there evidence of damage? Check windows for crazing, dirt, and pitting.
• Rivet characteristics should be noted. Observe rivets for damage. Look for loose broken or missing rivets. Localized chipping of paint, cracked paint on sealant, or fretting corrosion are indicative of movement. Look for smoked or stained riv-
• Check all venting for leaks. Check all input tubing to insure it is clear. Check all antennas for chipping and strikes. Check for obstructions in pitot tubes, static and engine pressure orifices, and temperature venturies.
(4) Findings. Initial findings should be recorded in a personal notebook as soon as discrepancies are discovered. Do not rely on memory: Findings should be transferred to the aircraft log or official record of discrepancy as soon as possible.
Recommendations for action will depend on whether the inspection precedes flight operations or maintenance and whether the discrepancy is safety or flight critical.
b. Level 2. General. A general inspection is made of an exterior with selected hatches and openings open or an interior, when called for, to detect damage, failure, or irregularity.
(1) Basis for Inspection. When a specific problem is suspected, the general inspection is carried out to identify, if possible, the difficulty. General inspections are also routinely used when panels are open for normal maintenance.
(2) Preparation for the Inspection. Ensure cleanliness of the aircraft. The necessary tools and equipment required may include flashlight, mirror, notebook, droplight, rolling stool, tools for removal of panels, ladders stands, or platforms. Other aids such as jacking of the aircraft may or may not be discretionary; knowledge of a specific aircraft may be essential; and common problems may require information, even if not on the inspection card.
Implementation. General looking is not enough. As this pictures, You should continually ask Be inquisitive. Question whether you have seen "What is wrond with chap 2 Par 205 Page 49
this betore. Move, shake, pull, twist, and push all parts possible. Apply weight to load bearing components. Compare one side to the other if applicable. Be aware of other systems in the inspection area. Look for abnormalities in the area, even if not related to this inspection. Adjusting the source of illumination, view items under inspection from different angles. Is the area pressurized? If so, does this affect any part of the in- spection? inspect all structural components, all moveablę partsa all attach points, and brackets. Check all cables, conduits, hoses for condition and clearance. Check condition and security of load and stress points. Look for chafing and fretting corrosion. Observe proximity of one part to another. Look for loose or missing fasteners, use of proper sealants, noticeable cracks, indications of corrosion, and debris in closed areas. Observe that cables, conduits, and hoses are properly routed. Observe that there is sufficient strain relief. Observe rivets for dam- (localized chipping of paint, cracked paint on sealant, or fret- Look for smoked rivets and discoloration of paint.
ting corrosion are indicative of movement.)
(4) Findings. Transfer all information relating to discrepancies from your notebook. . Record discrepancies as a work order. Discoveries during the inspection may indicate the need for a more detailed inspection. Depending on the findings, this may be either a Level 3 or Level 4.
c. Level 3. Detailed. A detailed visual inspection is an intensive visual examination of a specific area, system, or assembly to detect damage failure or irregularity. Available inspection aids should be used. Surface preparation and elaborate access procedures may be required.
(1) Basis for Inspection. A detailed inspection is called for when a specific problem is suspected and the general inspection dictates additional inspection. Or, if the inspection is otherwise mandated, a detailed visual inspection is carried out to identify, if possible, the difficulty. Detailed inspections are also periodically called for on damage-tolerant aircraft to ensure the airworthiness of the critical structure.
(2) Preparation for the Inspection. Tools and equipment will vary, but may include a prism, supplemental lighting, mirror, magnifying glass, flashlight, dye penetrant, notebook, droplight, rolling stool, and standard and specialized hand tools.
Documentation required is specific to the procedures outlined by steps on work cards. Also review the SBs, ADS, aircraft history, and accident reports. Other aids such as knowledge of a specific aircraft and common problems may be essential even if not on the inspection card.
(3) Implementation. The reasoning that originally dictated the inspection should be considered. If it was because Chap 2 Page 50 Par 205
some corrosion was found, then a more in-depth examination is required. If the inspection is in response to an AD for a crack, carefully inspect the surrounding area to rule out additional occurrences or stress induced because of the crack. In a detailed inspection, you are usually searching for failure, damage, or irregularity. Check the condition and security of lockwires and the load and stress points. Look for fretting corrosion. Observe proximity of one part to another. Look for loose or missing fasteners, use of proper sealants, obvious cracks, indications of corrosion, and debris in closed areas. Observe that cables, conduits, and hoses are properly routed. Observe that there is sufficient strain relief. Look to see if any chafing has occurred.
(4) Findings. Recommendations (discoveries during this inspection may indicate the need for a more detailed inspection, such as a Level 4).
d. Level 4. Special Detailed. A special detailed inspection is an intensive examination of a specific item, installation, or assembly to detect damage, failure, or irregularity.
is likely to make use of specialized techniques and equipment.
Intricate disassembly and cleaning may be required.
(1) Basis for Inspection. As systems and structures have become more complex, special inspections using extraordinary techniques and equipment have evolved to ensure airworthiness.
These are covered in instructions for special detailed inspections. Special detailed inspections are also periodically called for on damage-tolerant aircraft to ensure the airworthiness of the critical structure. This level of inspection may also be invoked based on recommendations from a lower level.
(2) Preparation for the Inspection. Tools and equipment vill vary but may include a ilashlight, mirror, video borescopes, special aids and tooling, Dremel, rolling stool, image enhancement and recording devices, supplemental lighting, magnifying glass, dye penetrant, notebook, and standard and specialized hanc tools. Documentation required is specific to the procedures outlined by steps on work cards; review of SBs, ADS, and aircraft history; and reference to the original or referred discrepancy, if any. Another aid is the discrepancy report from the contracting NDI company.
Implementation. Procedures are defined in detail by the specific instruction procedure, but they are limited to the scope of visual inspection. The locations to be inspected will vary greatly, but may include portions of the aircraft that are inaccessible without major disassembly, such as the interior surface of the wing skin, pylon butt Joints, and lap joints.
some of these cases the objective of the inspection may be best Chap 2 Par 205 Page 51
served both practically and economically through the use of NDI techniques.
(4) Findings. Satisfy documentation that specified this level of inspection. Documentation will be both internal and external and may include work cards, ADs and SBs. Recommendations should include recommendations for correction of the discrepancy and follow-up inspection.
206.-299. RESERVED.
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CHAPTER 3. VISUAL INSPECTION AIDS
300. GENERAL. The two indispensable aids to visual inspection are illumination and optical aids of various types. Illumination and lighting are crucial to all forms of visual inspection and can vastly affect the inspection outcome. In the following sections these two elements of the inspection process will be discussed. In the lighting section, all the aspects of lighting in the inspection environment are discussed. In the section covering visual aids, most optical devices which have found utility in aircraft inspection are described.
TOOLS. It should be emphasized that eye-mirrorflashlight is an indispensable combination for visual inspection.
Aircraft structure and components requiring inspection are frequently located beneath skin, cables, tubing, control rods, pumps, and actuators. Therefore, good secondary access by reflection is often essential. Visual inspection aids usually consist of a strong flashlight, a mirror with a ball joint, and a 2- to 5-power simple magnifier. The mirror should be of adequate size (except for very awkward access situations) with reflecting surface free of dirt, cracks, and worn coating; and the swivel joint should be tight enough to maintain its setting. A magnifying mirror may be useful in some situations. A 10-power magnifier is recommended for positive identification of suspected cracks; however, other NDI techniques, such as dye penetrant, magnetic particle, or eddy current can also be used to verify indications. Visual inspection of some areas can only be accomplished with the use of remote viewing devices, such as borescopes and video imaging systems.
b. Special Techniques. Visual inspection is a ubiquitous process used in many locations and involves numerous special techniques. Each will have an optimum lighting environment and its own types of visual and optical enhancements. It is up to the inspector to select the appropriate illumination and optical aid for the inspection at hand.
01. LIGHTING AND ILLUMINATION. Federal Aviation Requlation, section 145.35 (g) dealing with facilities recuires that lightinc should be adequate for the work being performed and should not adversely affect the quality of the work. Such lighting can be provided by a combination of general background and supplemental illumination and will vary with practice and be task dependent.
The amount of light needed to perform the variety of seeing tasks in visual inspection of aircraft and related components depends not only on the task itself, but also on the vision and the age of the worker (vision may need correcting with glasses and older chap Par 300 Page 63
eyes require more light), the importance of the task (how critical or expensive is a mistake), and the reflectance of the task background (the greater the difference between task and background, the easier it is to see).
a. General Considerations for Lighting Aircraft Maintenance Areas. The following factors should be considered as allimportant requirements of good planning for aircraft maintenance lighting systems:
(1) Safety of Personnel. Determine the quantity, quality, and type of illumination desirable for safety of personnel, the maintenance processes, and the environment.
(2) Selection of Lighting Equipment. Select lighting equipment that will provide the quantity and quality requirements by examining luminance characteristics and performance that will meet installation, operating, and actual maintenance conditions.
Equipment Maintenance. Select and arrange lighting equipment so that it will be easy and practical to maintain.
Energy Management. Energy management considerations and economic factors, including initial operating and maintenance costs versus the quantity and quality requirements for optimum visual performance, should be balanced (reference IES handbooks on lighting, also see Appendix G in this document). Whenever possible, the use of daylight should be considered for maintenance areas. Due consideration should be given to the National Energy Policy Act of 1992 covering the use of energy efficient illumination.
b. Illuminance Values. The IES has provided a range of illuminance values and illuminance categories to be used for generic types of interior activities when specific recommendations are not available (see Table 3-1).
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TABLE 3-1. ILLUMINANCE VALUES
ILLUMINANCE CATEGORIES AND ILLUMINANCE VALUES FOR GENERIC
TYPES OF ACTIVITIES
RANGE OF
ILLUMINANCE ILLUMINANCES REFERENCE
TYPE OF ACTIVITY CATEGORY (FOOTCANDLES) WORK- PLANE Public spaces with 2-3-5 dark surroundings Simple orientation 5-7.5-10 General for short temporary lighting visits throughout spaces Working spaces 10-15-20 where visual tasks are only occasionally performed Performance of vis- D 20-30-50 ual tasks of high contrast or small size Performance of vis- E 50-75-100 Illuminance ual tasks of medium on task contrast or small size Performance of vis- F 100-150-200 ual tasks of low contrast or very small size Performance of vis- G 200-300-500 ual tasks of low contrast or very small size over a prolonged period Performance of very H 500-750-1000 Illumination prolonged and ex- of task obacting visual task tained by a combination of general and local (supplementa ry lighting) Performance of very I 1000-1500-200 special visual tasks of extremely low contrast and small size The IES has also established a procedure (range approach) for selecting illuminance values from the ranges listed in Table 3-1 by Chap 3 Par 301 Page 65
using a weighting-factor guidance system, reflecting lightingperformance trends found in research (see Table 3-2). It was established to accommodate a need for flexibility in determining illuminances so that lighting designers could design lighting systems to meet specific needs. Such flexibility requires that additional information be available to effectively use the range approach. To use the range approach, a lighting task should be considered to be composed of the following elements:
TABLE 3-2. WEIGHTING FACTORS TO BE CONSIDERED IN SELECTING
SPECIFIC ILLUMINANCE WITHIN RANGES OF VALUES FOR
EACH ILLUMINANCE CATEGORY For Illuminance Categories A through C Room and Occupant Characteristics Weighting Factor
- 1 + 1 Occupants' ages Under 40 40-55 Over 55 Room surface re- Greater than 30 to 70 Less than 30 flectances* 70 percent percent percent
b. For Illuminance Categories D through I Task and Worker Characteristics Weighting Factor -1 + 1 Workers' ages Under 40 40-55 Over 55 Speed and/or accu- Not Important Important Critical racy** Reflectance of Greater than 30 to 70 Less than 30 task background*** 70 percent percent percent Average weighted surface reflectances including wall, floor and ceiling reflectances if they encompass a large portion of the task area or visual surroundings. For instance in an aircraft hanger where the ceiling height is 25 feet, neither the task nor the visual surroundings encompass the ceiling, so only the floor and wall reflectances would be considered.
In determining whether speed and/or accuracy is not important, important, or critical, the following questions need to be answered: What are the time limitations?
produce an unsafe condition or product? Will errors reduce productivity and be costly?
For example, in reading for leisure there are no time limitations and it is not important Errors will not be costly and will not be related to safety.
and/or accuracy is not important. If, however, safety notes and process procedures are to be read by NDI personnel, accuracy is critical because errors could produce an unsafe condition, and speed is important for economic reasons.
The task background is that portion of the task against which the meaningful visual display is exhibited. For example, on this page the meaningful visual display includes each letter which combines with other letters The display metask background, is the paper, which has a reflectance of approximately 85 per- Chap 3 Page 66 Par 301
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(1) Lighting Task Elements.
(İ) Visual Display. The visual display is the obdifficulty of observation. ject being viewed, which is presumed to present some inherent factor in the observer's visual performance. (i1) Observer Age. The age of the observer is a speed and/or accuracy distinguishes between casual, important, and critical seeing requirements. (iii) Speed and/or Accuracy. The importance of (background against which the details are seen). The reflectance (iv) Task Reflectance. The reflectance of the task will determine the type of illumination best adapted to the re- flectance characteristics of the visual display.
elements should be considered concurrently to determine the ap- (2) Amount and Type of Light. The above lighting task tional information on using this range approach procedure for se- lecting illuminances is provided by the IES in its handbooks on propriate amount and type of light for the lighting task. Addilighting, and in Appendix G of this document.
c. Industrial Lighting. In addition to generic-activity lighting recommendations, the IES through technical committees and knowledgeable individuals provides lighting recommendations for specific industries. Table 3-3 provides the IES recommended area/activity. illuminance categories for general industrial inspection tions for specific tasks and areas in aircraft maintenance. The IES standards contain lighting recommenda- TABLE 3-3. IES RECOMMENDED ILLUMINANCE CATEGORIES FOR THE
DESIGN AND EVALUATION OF LIGHTING SYSTEMS FOR
INDUSTRIAL INSPECTION AREAS INDUSTRIAL GROUP (*Inspection Area/Activity Only) Area/Activity Illuminance Category** Inspection Simple D Moderately Difficult Difficult Very Difficult Exacting nance categories in the Industrial Group. The IES provides a wide variety of industrial area/activity recommendations for illumi- See Table 3-1.
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d. Seeing Tasks. The seeing tasks required for visual inspection of aircraft tend to be three dimensional and curved, rather than two dimensional and flat like seeing tasks found in an office. The seeing task can be almost any distance from the floor, compared with 30 inches for the typical desk top, and in any position from horizontal to vertical. The seeing task can have extremely fine detail requiring thousands of footcandles or be so large that lower levels will suffice. The finish of the article to be inspected (dull or matte versus shiny or mirrorlike versus brushed) greatly affects the amount and orientation of the lighting needed for good visibility.
Good visual inspection lighting depends not only on providing the right illumination levels, but also on selecting the proper lamp and luminaire and mounting or positioning it in the right location. In fact, the latter can often have far more effect on task visibility than the lighting level. Figures 3-1, through 3-3 show examples of the effects of article finish and lighting orientation on visibility. The shiny and matte finish micrometers, shown in Figure 3-1, typify a range of seeing tasks and the effect of lighting system orientation. The graduations on the barrel of the matte finish micrometer are highly legible under all three lighting conditions: fluorescent parallel to the barrel (Figure 3-1A), fluorescent perpendicular to the barrel (Figure 3- 1B), and high-intensity discharge (HID) downlight (Figure 3-1C).
FIGURE 3-1. EXAMPLE OF THE EFFECT OF SHINY AND MATTE FINISH OF
PARTS AND LIGHTING SYSTEM ORIENTATION ON SEEING TASKS (Courtesy of General Electric Company) The graduations of the shiny micrometer cannot be easily read when the barrel is parallel to the fluorescent lighting (Figure 3-1A) because of lines of glare. when the lighting is perpendicular (Figure 3-1B), the reflections wrap around the surface, Chap 3 Page 68 Par 301