Definition
An imaginary line extending outward from the end of a runway along the intended departure path, used as a reference for measuring obstacle clearance and the climb performance required during takeoff.
Plain English
A pretend straight line drawn out from the end of the runway in the direction the aircraft will fly after takeoff. It is used as a starting point to check whether the aircraft can climb high enough to clear anything in its path.
Context Anchor
Seen in takeoff, departure procedure, and obstacle-clearance discussions.
Why Pilots Care
Provides a reliable visual reference to maintain the correct initial track, ensuring obstacle clearance and compliance with published departure instructions.
Analogy
Think of it like the starting line on a track, except it is placed at the end of the runway and used for the climb after takeoff.
Intuition Check
Do not assume this is a painted line on the runway. It is usually an imaginary reference line used for planning and measurement.
Example Sentence 1
The required climb gradient is measured from the departure reference line at the end of the runway.
Example Sentence 2
During the briefing, the instructor pointed out the departure reference line to show where the first turn would begin.