Aircraft Drawings
What is the purpose of an extension line on an aircraft drawing?
Answer
To extend the line showing a side or edge of a figure so a dimension can be placed to that side or edge
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 to a feature is the job of a leader line, alternate position is shown by a phantom 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 part number from the text to the feature it describes
- To indicate the surface that must be machined or otherwise finished
- To show the alternate position of a moving part
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