Page 335 - Planning and Design of Airports

Airport Lighting, Marking, and Signage 293

The Airport Beacon
Beacons are lighted to mark an airport. They are designed to produce
a narrow horizontal and vertical beam of high-intensity light which is
rotated about a vertical axis so as to produce approximately 12 flashes
per minute for civil airports and 18 flashes per minute for military
airports [28]. The flashes with a clearly visible duration of at least 0.15 s
are arranged in a white-green sequence for land airports and a white-
yellow sequence for landing areas on water. Military airports use a
double white flash followed by a longer green or yellow flash to dif-
ferentiate them from civil airfields. The beacons are mounted on top
of the control tower or similar high structure in the immediate vicinity
of the airport.

Obstruction Lighting
Obstructions are identified by fixed, flashing, or rotating red lights or
beacons. All structures that constitute a hazard to aircraft in flight or
during landing or takeoff are marked by obstruction lights having a
horizontally uniform intensity duration and a vertical distribution
design to give maximum range at the lower angles (1.5° to 8°) from
which a colliding approach would most likely come. The criteria for
determining which structures need to be lighted are published by the
FAA [18, 19].

The Aircraft Landing Operation
An aircraft approaching a runway in a landing operation may be
visualized as a sequence of operations involving a transient body
suspended in a three-dimensional grid that is approaching a fixed
two-dimensional grid. While in the air, the aircraft can be considered
as a point mass in a three-dimensional orthogonal coordinate system
in which it may have translation along three coordinate directions
and rotation about three axes. If the three coordinate axes are aligned
horizontal, vertical, and parallel to the end of the runway, the direc-
tions of motion can be described as lateral, vertical, and forward. The
rotations are normally called pitch, yaw, and roll, for the horizontal,
vertical, and parallel axes, respectively. During a landing operation,
pilots must control and coordinate all six degrees of freedom of the
aircraft so as to bring the aircraft into coincidence with the desired
approach or reference path to the touchdown point on the runway.
In order to do this, pilots need translation information regarding
the aircraft’s alignment, height, and distance, rotation information
regarding pitch, yaw, and roll, and information concerning the rate of
descent and the rate of closure with the desired path. The glide path,
height, time, and distance relationships during a typical landing are
shown in Fig. 8-1.