UFC 3-535-01
17 November 2005
manholes and handholes, light bases and cans. See the following paragraphs for
providing a counterpoise system for lightning protection.
12-1.6
Counterpoise Lightning Protection System
Provide a continuous counterpoise of number 4 (minimum) AWG bare, stranded copper
wire over the entire length of all primary circuits supplying airfield lighting: outside
pavements, with a minimum 2.4 meter (8 foot) ground rod installed at least every 300
meters (1,000 feet). Do not connect counterpoise system to the light bases.
12-1.6.1
Counterpoise Criteria
Along runway/taxiway or apron shoulders, install the counterpoise halfway between the
pavement and at approximately half the depth of the duct (or cable, if direct buried) if at
all possible. If this is not practical, install counterpoise 10-15 centimeters (4-6 inches)
above the duct or direct-buried cable. Route the counterpoise around each light base or
unit, at a distance of about 0.6 meters (2 feet) from the unit; do not connect to the unit.
For duct not along a shoulder or for duct bank, lay the counterpoise 10-15 centimeters
(4-6 inches) above the uppermost layer of direct buried ducts, or on the top of the
concrete envelope of an encased duct bank. Provide only one counterpoise wire for
cables for the same duct bank. Connect all counterpoise wires leading to a duct bank to
the single counterpoise wire for the duct bank. Lay the counterpoise at least 0.3 meters
(12 inches) from any light cans or in routing counterpoise around manholes or
handholes. Do not connect the counterpoise to the lighting vault power grounding
system. Use brazing or thermoweld for all connections. The counterpoise resistance to
ground must not exceed 25 ohms at any point using the drop of potential method.
12-1.7
Frangibility and Accident-Avoidance Construction
In the areas around the runway, including the approach zone, all above-grade
structures must be lightweight and of a frangible or low impact resistant construction
using breakaway sections to minimize hazards to aircraft. Concrete foundation or
mounting slabs must not extend above the finished grade of the surrounding surface.
12-1.7.1
ALSF Frangibility
A slight trade-off in frangibility can result in significant savings in energy. Older ALSF
systems use 300 watt lamps in the outer 600 meters (2,000 feet) to satisfy the
photometric requirements, which can actually be met with newer 200 watt lamps.
However, the 200-watt lamps are rated at 6.6 amps rather than 20 amps and their use
would require a change in isolation transformers. This would not be difficult in major
renovations or new installations except that eight additional wires must be installed in
low impact resistant and semi-frangible light supports. The major command may accept
the slight loss of frangibility in order to achieve the energy savings.
12-1.8
Airfield Lighting Vault
Vaults house the regulator and control equipment, emergency generator and power
transfer switch, and other electrical equipment needed for operation of the airfield
lighting system. The vault may be a separate building or structure, or an enclosure
within a larger structure, as appropriate. Vaults must be of concrete or masonry
construction meeting all building codes for the type of structure. Vaults constructed in
the past generally had a primary service of 4160/2400 volt, 3 phase, 60 hertz power. All
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