Reference for vertical locations

Aviation Mechanic General (AMG) practice question 3 of 15 on Aircraft Drawings. ACS element AM.I.B.K3 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic General (AMG) practice mode.

Question bank updated 2026-09-22

QUESTIONVertical locations on an aircraft drawing are given by reference to the

Abuttock line.
Bfuselage station.
Cwaterline.

Show the answer and explanation

Correct answer: C. waterline.

A — incorrect The buttock line is the reference for locations left and right of the aircraft's longitudinal axis, called butt stations.
B — incorrect Fuselage stations give forward and aft locations measured from the datum, not vertical positions.
C — correct The handbook states that vertical locations on aircraft are made in reference to the waterline.

BACKGROUND

Aircraft drawings locate points along three references. Forward and aft locations are made by reference to the datum and expressed as fuselage stations. Locations left and right of the aircraft's longitudinal axis are made by reference to the buttock line and are called butt stations. Vertical locations are made in reference to the waterline. Drawings show these as FS, WL, and right and left buttock line (RBL and LBL) values.

STUDY TIP

Link each axis to its reference: fore-aft to fuselage station, left-right to buttock line, up-down to waterline.

KEY POINTS

Vertical locations are referenced to the waterline.
Left and right locations are referenced to the buttock line (butt stations).
Forward and aft locations are fuselage stations measured from the datum.

SOURCES

FAA-H-8083-30B ch04 "Station Numbers & Location Identification on Aircraft"

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