NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: course, heading, track
From: Paul Hirose
Date: 2002 Feb 7, 12:40 -0800
From: Paul Hirose
Date: 2002 Feb 7, 12:40 -0800
Trevor Kenchington wrote: > > So, if I understand that correctly, U.S. aviation terminology does not > distinguish between what we surface-bound types call "heading" and > "course". Are aircraft so stable in yaw that the distinction is not needed? American fliers use "course" for intended path over ground, and "heading" for the direction to point the aircraft nose to make good that path. If both directions are measured from the same reference (e.g., true), their difference is the "wind correction angle". It's assumed aircraft movement through the air is identical to the direction its nose is pointing. Airplanes have an advantage over sailing vessels in this respect. They have a yaw indicator and a control surface (rudder) dedicated to yaw. Since an airplane turns by banking, the rudder's job is simply to control yaw, usually to minimize it, but sometimes (as when making a crosswind landing) to intentionally yaw the plane. Actually, in aviation all three terms are commonly used with two different meanings. The line from Point A to Point B is called a course, but the word is also used for the direction of that line in degrees. Similarly, we speak of accident investigators reconstructing the track of an airplane, but when an inertial navigation system displays TRK 340, it's understood to be the instantaneous direction of movement over the ground. Heading is the predicted direction needed to make good the course, and is also the direction the plane is pointed at a given instant. I've never found these double meanings confusing, since the intended one is obvious from context. Maybe it's the mother duck syndrome, but I think the aviation terms are easier to keep straight. -- paulhirose@earthlink.net (Paul Hirose)