Aircraft Drawings
What is the purpose of an extension line on an aircraft drawing?
Answer
To project a side or edge of a figure outward so a dimension can be placed to it
Extension lines are used to extend the line showing the side or edge of a figure so that a dimension can be placed to that side or edge; they are very narrow and have a short break where they leave the object outline. Carrying a note or part number over to the feature it describes is the job of a leader line, and a machined surface is marked with a finish mark.
Source: FAA-H-8083-30B, Ch. 4 p. 4-17 — 'Lines and Their Meanings: Extension Lines'
Not the answer
- To carry a note or a part number from the written text over to the specific feature it describes on the drawing
- To indicate the surface that must be machined or otherwise finished
Practice this
The FAA Aviation Mechanic General knowledge test is 60 questions and takes 42 correct — 70% — to pass. The app’s page carries a free ten-question test drawn from the same bank, marked as you go.
Take the free practice test