Detail Considerations - Performing an Effective Aircraft Maintenance Inspection
Presentation by SofemaOnline (SOL) - www.sofemaonline.com
Visual inspection is an essential part of airplane maintenance.
The visual inspection component of NDI requires trained and experienced inspection personnel, using validated procedures and appropriate calibration standards with effective, well-maintained equipment in a well-managed maintenance environment.
Visual inspection is defined as the process of using the eye, alone or in conjunction with various aids, as the sensing mechanism from which judgments may be made about the condition of a unit to be inspected.
BASIS FOR INSPECTION
The first step is to understand the reason for the Inspection, for example, is it part of a zonal Inspection, or is it related to another document? If so are you familiar with this document?
What is the periodicity of the inspection, for example, if you are looking at an item or area as part of a 6000-hour inspection, then you are basically saying that everything is good for another 6000 hours?
How long will 6000 hours take to accumulate? – It could be 18 months on a low-cost operation that is doing more than 4000 hours each year, conversely, it could be 10 years or more on an aircraft that is only achieving 400 to 600 hours each year.
REVIEW IN DETAIL THE SOURCE DOCUMENTS
The task may have originated as part of the Maintenance Review Board (MRB) process undertaken using MSG 3 methodology.
Or it may have originated as part of the System Safety Assessment SSA which is driven by the Type Certificate Holders (TCH) Certification Process.
Relevant documents may include FAA Advisory Circulars, FAA or EASA Airworthiness Directives, Other Service Bulletin, or Alert Service Bulletin issued by the TCH or Original Equipment Manufacturer (OEM) Inspection related information may also be found with the Standard Practices Manuals and Non-Destructive Testing (NDT) Manuals.
FULL UNDERSTANDING OF THE CONTROLLING DATES FOR THE TASK
What is the effective date of the inspection, (means the date before which the inspection should be accomplished)?
NOTE - That this may be referenced in a number of ways as calendar time, airframe hours, airframe cycles, engine hours, or number landings as applicable.
Have you reviewed the applicability related to the aircraft, engine, or part number?
Ease of access to the inspection area is important in obtaining reliable visual inspection results. Access consists of the act of getting into an inspection position (primary access) and performing the visual inspection
(secondary access). Unusual positions (i.e., crouching, lying on the back, and overhead reaching) constitute examples of difficult access.
Impact on Inspection. The necessity to get both hands into the aircraft structure while holding a flashlight or mirror or reaching into awkward openings can affect the inspector's motivation, attitude, decision-making, and ability to interpret what is seen.
Staging equipment (e.g., platforms, ladders, stools) used to permit access to the airframe and engines should be used safely, i.e., secured manually or brake engaged to prevent slips and falls. Protection should be provided to prevent potential injury from sharp edges and shifts in heavyweights.
Adequate protection from falls should be provided wherever possible, such as railings and harnesses and lanyards on high-working platforms.
Lighting. Adequate quality and intensity of illuminance and elimination of direct glare, reflected glare, and harsh shadows all enhance the identification of defects.
Conversely, excessive visual fatigue and the delayed eye adaptation experienced when moving from bright surroundings into dark ones and vice versa could reduce effective detection of defects.
Illumination should be provided during the occupancy of spaces that possess limited access. In those areas which do not have fixed lighting, portable and vehicle-mounted lighting equipment should be used.
Uncontrolled large differences of illumination and excessive glare should be avoided.
Lighting and Safety. Some accidents which have been attributed to an individual's carelessness could have been partially due to poor lighting.
Special conditions may require different illuminance levels. In some cases, higher levels may be required.
PREPARATION
What preparation and or cleaning of the item being inspected is required? Is this sufficient for you to be able to perform the inspection (Never forget that you MUST satisfy yourself that the area is ready for you?
Are there any special requirements related to the inspection which need to be considered? such as unusual surface preparation (etching, paint removal) or the temperature range over which the inspection is effective.
It is necessary for parts to be inspected to be free from dirt, contamination, or anything which would tend to obscure detection of important defects. It is also important during cleaning not to remove or obscure evidence of a defect.
For example, cracks may become hidden by abrasive treatment and rendered invisible.
Working Environment. Excessive temperature, wind, rain, and other climactic factors tend to adversely affect inspections.
Excessive noise tends to reduce concentration, create tension, and prevent effective communication.
These conditions increase the likelihood of errors, degrade reliability, and potentially impact personnel safety.
Safety hazards that could cause injury to the inspector or prevent the identification of defects should be eliminated or minimized.
The operating safety instructions of the manufacturers of the inspection systems and materials should be followed. The eye can be harmed by intense lighting and lasers
The various materials used for cleaning in preparation for visual inspection may contain chemicals which, if improperly used, can be hazardous to the health and safety of operators.
Safe handling of cleaning materials should be ensured and Flammable or combustible cleaners and chemicals should be kept in approved safety containers and only in minimum quantities.
Some cleaners and chemicals may have an adverse effect on the skin, eyes, and respiratory tract.
Manufacturers' warning labels and current safety directives should be observed.
Cleaners and chemicals should be used only in authorized areas. Soiled flammable or combustible cloths should be discarded into covered metal containers.
PERFORMING THE INSPECTION
To conduct an effective visual observation, inspection personnel should not only look at an object but examine it based on their knowledge of it and established rules.
Effective inspectors look at specific targets rather than scan an area.
The eye is functionally blind when it is moving between observation points. Accordingly, a procedure of step-scanning is used. Lookouts spotting objects on the horizon are taught to step-scan with binoculars.
Those who are proficient can detect approaching objects long before they are otherwise visible. Similarly, when observing dim objects against a dark background, observers are taught to focus to one side or above the object viewed.
They are then able to see details that are not otherwise visible. These and other types of methods can be used by inspectors to look for target defects in all parts of the aircraft.
Another useful technique for the inspector is to imagine what type of action would cause a particular defect. This thought process may provide a clue as to what the defect will look like.
It is necessary not only to know how to examine but were to examine when inspecting details for defects with which one is familiar from past inspections.
The flashlight and the mirror are standard tools that should accompany the inspector on all inspections. The inspector should become skillful in using these tools.
It may be necessary to remove corrosion to assess the condition of the underlying material.
It is important not to destroy the surface finish, or remove protective coatings which would be difficult to replace, such as the “cladding” found on the skin surface of major transports.
Inspection after Maintenance. After a component has been serviced, repaired, or otherwise maintained, it should be inspected for abnormalities. A similar inspection of the surroundings should be carried out when a component or accessory is reinstalled in the aircraft. Look for loose material, missing coatings, other damage, etc.
Also, magnifiers should be readily at hand for some types of inspections.
Magnifiers are invaluable for defining the extent and character of cracks and problems in riveted assemblies.
What would be the typical description of the defect to be detected, preferably with an illustration of a sample defect.
EVALUATION
Consider the applicable procedures for establishing inspection reliability. Reporting procedures and requirements.
RETURNING TO NORMAL CONFIGURATION
Are there any post-inspection cleaning or restoration tasks applicable?
NEXT STEPS
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