i. A red radial line, which means, “Do not exceed the parameter beyond this.”
ii. A green arc, indicating the normal operating range.
iii. A yellow arc, which indicates the caution zone.
iv. A blue radial line, which is used only in an ASI (air-speed indicator), shows the best single-engine-rate-of-climb speed.
v. A white arc, which also is used only in an ASI, shows the flap-operating speed.
An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved