A cloud that trails an aircraft and is formed by the ejected water from the exhaust of the aircraft engines. It mixes with and saturates, or slightly supersaturates, the air in the wake of the aircraft. The duration of the trails is dependent on the prevailing temperature and relative humidity. Exhaust trails are more common and longer than aerodynamic trails. For the trails to be formed, the temperature ordinarily must be below the critical value as indicated by a line marked MINTRA on a tephigram. A tephigram is an aerological map on which temperatures and potential temperatures (pot) are marked along X- and Y-axes, respectively, and used to ascertain the stability of the atmosphere. MINTRA is a flight level below which exhaust trails will not form positively and above which they may or may not do so. Also called contrails. See also tephigram.
An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved