What is the fuselage station number?

• A. Distance in inches from the datum, measured along the vertical axis of the fuselage.
• B. Distance in inches from the datum along the fuselage’s longitudinal axis.
• C. The distance in inches from the datum, measured along the longitudinal axis of the fuselage.
• D. Distance in inches from the nose, measured along the longitudinal axis.

Answer: (C)

Fuselage station numbers indicate how far along the length of the fuselage a component is located. The distance is measured in inches from a fixed datum line or point and taken along the fuselage’s longitudinal axis, i.e., from nose to tail. This consistent reference lets mechanics specify exact locations for installation, inspection, or rework. So a value like FS 120 means 120 inches aft of the datum along the fuselage’s length. The other options either measure along the wrong axis or use a different reference point, which is not how fuselage stations are defined.