Definition
Centerline (CL) is the imaginary line running lengthwise down the middle of a runway, taxiway, helipad, or final approach course. On instrument approach charts and in operations specifications, CL refers to the published course or alignment that an aircraft is expected to track to or from a landing area.
Plain English
The middle line of a runway, taxiway, or approach path that pilots aim to fly along or land on.
Context Anchor
Seen in helicopter instrument procedure diagrams and operations-specification discussions, especially where the approved path and obstacle-clearance area are being described.
Derivation
From 'center' (middle) plus 'line.' The two-letter abbreviation CL is used on charts and in regulatory text where space is tight.
Why Pilots Care
Maintaining alignment on the centerline ensures safe touchdown and prevents runway excursions, especially critical in low-visibility helicopter operations.
Intuition Check
Do not read CL here as a classroom course, a clearance limit, or a command to climb. In this context, it means the intended path line for the procedure.
Example Sentence 1
The approach plate showed the final approach course aligned with the runway CL.
Example Sentence 2
Ops specs require demonstrated ability to track the CL within specified tolerances during IFR landings.