This is a very good question. Prior to starting a job in the maintenance publications (library) department of an airline I had no idea what this data meant. However, now I am very familiar with it. In the last 2 weeks I have been updating/creating Airplane Flight Manuals for our aircraft fleet and the planes we are leasing. Each aircraft "variant" has a different AFM based on the specs of that specific model (-8Q82). For example, all of our aircraft are 737-800s but we have about 5-6 different sub-variants. I haven't examined each AFM closely but they are ever so different (weights, performance, etc).
Think of it like this, the 2010 North American-spec Toyota Corolla CE
, LE, SE
are all the same car in terms of size/body but there are packages you can add (A, B, C, D package). The A,B,C,D part would correspond to the last few digits of the exact aircraft model and correspond to the specifications of that exact aircraft model based on what was ordered when the plane was first built for an airline and/or leasing company.
It is also interesting to note that the documents that are sent for each aircraft (IPC, Wiring Diagram Manual) are different based on the owner/leasing company. All of the ILFC planes have their own documents, all of the GE Capital Leasing planes have their own documents. The documents are all for 737-600/700/800 but because each leasing company owns different variants, the documentation is different. For example, if we do not have an aircraft owned by ILFC, we cannot give mechanics a Wiring Diagram Manual CD which is published for GE Capital Leasing aircraft. I'm sure the info isn't much different, however it is not acceptable. Some documents are interchangeable but most are specific to the leasing company/aircraft owners. The funny thing is each original CD looks the same (it's distributed by Boeing) but the document number is different. Close attention to detail is CRITICAL in the job that I do as many documents look the same except for small differences in numbers/codes on the front page.[Edited 2011-10-14 18:37:12]
[Edited 2011-10-14 18:46:47]