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Centerline dash pattern

Aviation Mechanic General (AMG) practice question 6 of 15 on Aircraft Drawings. ACS element AM.I.B.K1 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic General (AMG) practice mode.

Question bank updated 2026-09-22

QUESTIONOn an aircraft drawing, how is a centerline drawn?

  1. AA series of short, evenly spaced dashes
  2. BOne long dash followed by two short dashes
  3. CAlternate long and short dashes
Show the answer and explanation

Correct answer: C. Alternate long and short dashes

  • A — incorrect Short, evenly spaced dashes are hidden lines, which show invisible edges or contours, not centers.
  • B — incorrect One long and two short evenly spaced dashes make up a phantom line, which shows an alternate or missing-part position.
  • C — correct The handbook states that centerlines are made up of alternate long and short dashes and indicate the center of an object or part of an object.

BACKGROUND

Every drawing is composed of lines, and standardized line types let a mechanic tell boundaries, hidden surfaces, dimensions and centers apart. A centerline is drawn as alternate long and short dashes and marks the center of an object or of a feature such as a hole. Where centerlines cross, the short dashes intersect symmetrically, and for very small circles the centerline may be shown unbroken. Hidden lines (short dashes) and phantom lines (one long, two short) look similar but carry different meanings.

STUDY TIP

Memorize the three dashed patterns as a set: long-short is center, all short is hidden, long-short-short is phantom.

KEY POINTS

  • Centerlines use alternate long and short dashes.
  • They mark the center of an object or feature.
  • Short dashes alone are hidden lines; long-short-short is a phantom line.

SOURCES

  • FAA-H-8083-30B ch04 "Centerlines"
  • FAA-H-8083-30B ch04 "Hidden Lines"
  • FAA-H-8083-30B ch04 "Phantom Lines"
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MORE ON AIRCRAFT DRAWINGS

SkyDrill is not affiliated with the FAA. This is an original practice item based on FAA-H-8083-30B Aviation Maintenance Technician Handbook – General, 14 CFR part 43 and part 65. Regulations and handbooks are revised; confirm details against the current edition.