What's This 'A' Check, 'C' Check Stuff?
Aircraft inspections defined
By Jack Hessburg
Last month, I discussed the derivation of Maintenance Review Board (MRB) tasks. Let's now examine how they are grouped into efficient work packages.
Packages are constructed by dividing the maintenance tasks into convenient, bite-size chunks to minimize the time the airplane is out of service, to keep the maintenance workload level, and to maximize the use of maintenance facilities.
Scheduled maintenance tasks are grouped into work packages known as blocks. The complete package is sometimes referred to as a complete overhaul cycle. The concept is called block maintenance or sometimes progressive maintenance.
The following groupings typically illustrate the concept, and Figure 1 shows how they all interact.
This check travels under several common names and post-flight, maintenance pre-flight, service check, and overnight to name a few. It is the lowest scheduled check. Walk around inspection by flight crew is not normally a part of a maintenance program. A daily check is a cursory inspection of the aircraft to look for obvious damage and deterioration. It checks for "general condition and security" and reviews the aircraft log for discrepancies and corrective action. The accomplishment of the daily check requires little in the way of specific equipment, tools, or facilities.
A basic requirement is that the airplane remains airworthy. Usually, a daily check is accomplished every 24 to 60 hours of accumulated flight time. Examples of daily check items include:
• Visually inspect ta il skid shock strut pop-up indicator
• Check fluid levels
• Check general security and cleanliness of the flight deck
• Check that emergency equipment is installed
This is the next higher level of scheduled maintenance. It is normally accomplished at a designated maintenance station in the route structure and includes the opening of access panels to check and service certain items. Some limited special tooling, servicing, and test equipment is required. The 'A' check includes the lower check, i.e. Daily check.
Examples of 'A' check items include:
• General external visual inspection of aircraft structure for evidence of damage, deformation, corrosion, missing parts
• Check crew oxygen system pressure
• Operationally check emergency lights
• Lubricate nose gear retract actuator
• Check parking brake accumulator pressure
• Perform Built-in Test Equipment (BITE) test of Flap/Slat Electronics Unit
This is a slightly more detailed check of components and systems. Special equipment and tests may be required. It does not involve, however, detailed disassembly or removal of components.
Contemporary maintenance programs do not use the 'B' check interval. For a number of reasons, the tasks formerly defined for this interval have, for many airplanes, been distributed between the 'A' and 'C' check.
The following two checks are traditionally known as heavy checks. They are normally accomplished at the main maintenance base of the airline where specialized manpower, materials, tooling, and hangar facilities are available.
'C' check: This is an extensive check of individual systems and components for serviceability and function. It requires a thorough visual inspection of specified areas, components and systems as well as operational or functional checks. It is a high-level check that involves extensive tooling, test equipment, and special skill levels. 'C' checks remove the airplane from the revenue schedule for 3 to 5 days. The 'C' check includes the lower checks, i.e. 'A,' 'B,' and Daily checks.
Examples of 'C' check items:
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