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Twin parallel lines or bars between which an instrument needle is to be aligned. Tramlines are also guidance lines on the flight deck for a V/STOL (vertical/short takeoff and landing) aircraft proceeding on its own power. The tramlines in airborne radar are the reference lines within which the target must be brought for a successful lock-on.
An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved