Station Number: A term used in aviation to refer to the location of an object in an aicraft along the fore to aft axis. Also referred to as Frame Station. Often abbreviated as STA or FS. Derived from the actual location of the frames that carry the stringers which in turn support the aluminum skin of the fuselage.
In some models of aircraft where a new model has been developed by adding fuselage sections to an existing aircraft model in order to lengthen an aircraft, the new frame stations will keep the same numbers but add a letter after them to distiguish them as added sections. For instance, in an aircraft where the frames are 20 inches apart, instead of going from FS 340 to 360 as would normally be done, it would go to FS 340A, 340B, etc. until eventually returning to the previously designed FS 360. In these instances station numbers in these areas are designated by showing an addition at the end of the FS callout, i.e. something located 10.25 inches aft of FS 340B would be called out as located at FS 340B + 10.25.
Example: That bulkhead is too far aft. It was supposed to be located at station number 433.00 but instead it's at station number 435.00.