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Fleet Reliability - Coding
Air Transport Association of America (ATA) Spec 100 is the industry standard for coding manuals, Service Difficulty reports (SDRs) and maintenance related activities. This coding system can get very specific – as more and more digits are used. For example:
ATA 2100: Air Conditioning
ATA 2110: Cabin Compressor (Packs)
ATA 2120: Air Distribution System
ATA 2130: Cabin Pressurization System
ATA 2131: Cabin Pressure Controller
ATA 2132: Cabin Pressure Indicator
ATA 2133: Cabin Pressure Outflow valve
ATA 2134: Cabin Pressure Sensor
ATA 2140: Heating Systems
ATA 2150: Cooling Systems
ATA 2160: Cabin Temperature Control
ATA 2161: Temperature Controller
ATA 2162: Temperature Indicator
ATA 2163: Temperature Sensor
ATA 2170: Humidity Control System
As you can see, the first two digits correspond to a very general aircraft system. Our example is ATA 21 (Air conditioning). Adding a third digit, we can expand to very specific aircraft systems. Air conditioning is broken down into individual, functional systems (Packs, Distribution, Pressurization, Heating, Cooling, Temperature control and Humidity control). By adding a fourth digit, we can define the various components that make up each system. Our example defines some of the components that make up the Temperature Control System (Controller, Indicator and Sensor).
The most efficient and accurate coding format for an aircraft systems alert program is the three-digit format. For example, if a pilot write-up states that the cabin pressurization system is erratic, you would code this Pirep as ATA 2130. If enough Pireps related to pressurization occur on your fleet, an ATA 2130 Alert will be generated – prompting you to perform a technical analysis of the pressurization system on your fleet.
If you were to use only two digits, you would code all air conditioning system write-ups (Heating, cooling, control, packs, etc) as ATA 21. In this case, if your program alerts ATA 21, you would have to analyze all of the various systems in ATA 21 to determine if a reliability issue exists in any one of them. This is a very inefficient way to identify system problems.
If you were using a four-digit coding system, you would use the code for the component that was replaced to fix the aircraft. For example, if you changed a controller to fix the pressurization system, you would code the write-up as ATA 2131 (Controller). The problem with this system is that you are simply coding component removals – not system problems. Any seasoned maintenance professional knows that not all component replacements fix the aircraft. Therefore, counting component removals is not an efficient way to identify aircraft system reliability problems.
In review, the most effective way to code aircraft problems is by using a 3-digit ATA code to identify the aircraft system that is experiencing a problem. There are some exceptions to this rule, but for the most part – 3 digits are sufficient. The emphasis should be on coding the problem – not the fix. Your technical analysis will determine the actual fixes for each problem.
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