FAA Aviation Mechanic Airframe (AMA)Airframe StructuresEasy
A technician is reviewing a structural repair drawing that specifies work at 'Fuselage Station (FS) 320.' What does this number represent?
- AThe distance in inches from the wing root along the wing span
- BThe distance in inches aft of a zero reference datum along the longitudinal axis
- CThe distance in inches from the aircraft centerline
- DThe distance in inches above or below a horizontal reference plane
Show answer & explanationAnswer & explanation
Correct answer: B. The distance in inches aft of a zero reference datum along the longitudinal axis
Fuselage Station (FS) numbers measure distance aft (or forward, if negative) of a fixed zero datum point along the aircraft's longitudinal axis. This is different from Buttline (distance from centerline) or Waterline (vertical distance).
Why the other options are wrong
- A. This describes a wing station, not a fuselage station.
- C. This describes Buttline (BL), not Fuselage Station.
- D. This describes Waterline (WL), a vertical measurement.
Fuselage Station (FS)
A dimensional reference system that measures distance in inches aft of a zero datum point along the aircraft's longitudinal axis, used to precisely locate structure and equipment.
- Datum is a fixed reference point, often the nose or a point ahead of it.
- Works together with Buttline (lateral) and Waterline (vertical) systems.
- Used in maintenance manuals to pinpoint repair or inspection locations.
Memory trick: 'Station' = distance down the runway of the fuselage (fore-aft)