25 May 2005
controller with the lateral alignment and angle of descent of an aircraft on approach to a
runway. Landing instructions are given to the pilot by voice communications.
Electronic NAVAID Requirements
Project Scope. The operational category of the existing runway system
will establish the electronic NAVAID requirement. The operational categories of new
runways, changes in operational categories, the required NAVAIDS, and the type of
NAVAID (i.e., ILS or PAR) will be established by USAC-TSC, Air Force MAJCOM, or
NAVAID Design and Installation. Table A17.1 in UFC 3-260-01,
Attachment 17, includes a list of design documents governing NAVAIDS and the agency
from which siting and design information can be obtained for each type of electronic
AIRFIELD ELECTRICAL SYSTEMS
General. Airfield electrical facilities for visual NAVAIDS are almost
universally series circuit with power supplied by constant-current regulators with engine-
generator standby power, all housed in airfield lighting vaults.
The power supply for electronic NAVAIDS is alternating current transformed to the
appropriate voltage, with standby power supplied by engine-generators and/or batteries.
Power Source. Power for NAVAIDS can be supplied by the air base or by
commercial utility sources. In addition to the primary power source, all airfield visual
NAVAIDS listed as required in UFC 3-535-01 need an emergency back-up power
source that is automatically activated in case of a primary power source outage. Older
visual NAVAID systems were, and are, based on a 2,400-volt (V) power source. Newer
installations generally feed the vault equipment with 480V power, although 240V is
sometimes used for small installations.
Standby Power. Emergency back-up power is typically provided by an
engine-generator (E/G). E/G installations require a separate room or shelter with
independent ventilation. Fuel storage capacity for 72 hours of operation is required.
Automatic starting and transfer switching is required with the E/G to be on-line within 15
seconds of a primary power failure except where Category II operations are conducted.
During Category II operations, a one-second power transfer is required.
Constant Current Regulators (CCR). Power to airfield series lighting
circuits is controlled by CCRs that convert constant voltage regulator input to a constant
current output. The CCR output provides either 6.6 or 20.0-ampere current output to
power the lighting circuits, with the voltage varying with the number of connected lights.