CHAPTER 3. EQUIPMENT REQUIREMENTS.
3.1 General.
This section addresses environmental, design, and photometric requirements for obstruction light equipment. Criteria for selecting the proper obstruction lighting equipment, installation tolerances, and administrative information are in AC 70/7460-1, Obstruction Marking and Lighting.
3.2 Environmental Requirements.
Obstruction lighting equipment must be designed for continuous operation under the following conditions:
a. Temperature. Storage/shipping: -67 degrees Fahrenheit (F) (-55 degrees Celsius (C)) to 130 degrees F (55 degrees C). Operating: -40 degrees F (-40 degrees C) to 130 degrees F (55 degrees C).
b. Humidity. 95 percent relative humidity.
c. Wind. Wind speeds up to 150 miles per hour (mph) (240 kilometeres per hour (kmph)).
d. Wind-blown Rain. Exposure to wind-blown rain from any direction.
e. Salt Fog. Exposure to salt-laden atmosphere.
f. Sunshine. Exposure to solar radiation.
3.3 Design Requirements.
3.3.1 Light Unit.
The light unit must be lightweight and designed for easy servicing and lamp (or flashtube) replacement. Materials used within the light unit must be selected for compatibility with their environment. All plastic lens parts (including gaskets), that are exposed to ultraviolet radiation or ozone gas must not change color, crack, check, disintegrate, or be otherwise degraded (photometry must remain compliant) and meet the equipment warranty requirements of AC 150/5345-53, Appendix 2. Each light unit must be an independent unit and must flash at the specified intensity or at its highest intensity when control signals are absent.
3.3.2 Light Covers.
Light-transmitting covers for light units must be per the requirements in MIL-C-7989. In addition, if plastic covers are used, they must be resistant to checking, crazing, or color changes caused by ultraviolet radiation or ozone gas exposure.
3.3.3 Light Colors.
The aviation red must be per ICAO Annex 14, Volume 1, Appendix 1, Colours for Aeronautical Ground Lights, at operating temperature within the following chromaticity boundaries:
purple boundary y = 0.980 - x
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yellow boundary y = 0.335
x + y + z = 1
Xenon flashtube emission or a color temperature range from 4,000 to 8,000 degrees Kelvin is acceptable for white obstruction lights. See Engineering Brief #67 for additional information about lamp chromaticity requirements.
3.3.3.1 Light Color During Daytime.
Means must be provided on all L-810 obstruction lights to indicate the specified non-powered color during daytime viewing. See Engineering Brief #67 for additional information.
3.3.4 Aiming (for L-856 and L-857).
Light units must have a method for adjustment of the vertical aiming angle between 0 and +8 degrees. A spirit level or other device must be provided as part of each light unit for setting the vertical aiming angle of the light beam with an accuracy of one degree.
3.3.5 Control Unit.
3.3.5.1 Flashing White Obstruction Lighting Systems.
The control unit must set the system's flash rate, intensity and sequence and must be capable of controlling light units up to a distance of 2,500 feet (ft) (762 meters (m)). If the control unit or control wiring fails, the light units must continue to flash per Table 4 flash rate. Failure of an intensity step change circuit must cause all light units to remain operating at their proper intensity or alternatively to operate at the high intensity step.
3.3.5.1.1 Monitoring.
Each light unit must be monitored for FLASH/FAIL status. FAIL status is defined as either of the following conditions: unit misses four or more consecutive flashes; unit flashes at wrong intensity step during day operation. Monitoring must be fail safe (i.e., active signals for FLASH and absence of signals for FAIL). There must be a provision to permit connection to a remote alarm device, (supplied by others or as an option), to indicate the system and individual light unit FLASH/FAIL status.
NOTE: See Engineering Brief #67 for additional information regarding the failure requirements for multiple alternative lighting devices (ALDs).
3.3.5.1.2 Placement.
The control and monitor functions may be consolidated in a light unit or in a single enclosure for remote mounting or they may be distributed into several light units.
3.3.5.1.2.1 Remote Mounting.
In addition to the above, if placed in a remote mounted enclosure, the control unit must display the status of each light unit. An intensity control override switch must also be mounted in the enclosure to manually control light intensity during maintenance or in the event of a photoelectric control malfunction.
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3.3.5.2 Flashing Red Obstruction Lights.
The control unit must set the system flash rate and flash sequence. Failure of the flashing circuit must cause the light units to energize and operate as steady burning lights. An override switch must be mounted on the control unit to manually control the lights during maintenance or in the event of a lack of a photoelectric control signal. To insure proper operation, all flashing red obstruction lights, inclusive of any associated system steady burning red lights, must be certified with a control unit whether internal or external to the lighting unit.
3.3.5.2.1 Dual Lighting Systems.
The control unit may be a separate unit or incorporated as part of either the white or red obstruction light control unit. The control unit must set the operating mode for each light unit in the system. Outage of one of two lamps, or any failure in the device that causes a reduction in intensity of the horizontal beam or results in an outage in the uppermost red beacon (L-864 unit) or outage of any uppermost red strobe, must cause the white obstruction light system to operate in its specified "night" step intensity. At no time should both red and white systems be on simultaneously. An override switch must be mounted on the control unit to manually control the operating mode of the system during maintenance or in the event of a lack of a photoelectric control signal.
3.3.5.2.2 Monitoring.
Each separate L-864 light unit and each tier of L-810 light units must be monitored for FLASH/FAIL status. FAIL is defined as outage of any lamp in an L-864 light unit, outage of any one lamp in a tier of L-810 light units, or failure of a flasher (steady on and/or total) for an L-864 light unit. Monitor signals must be fail safe (i.e., active signals for FLASH and absence of signals for FAIL). There must be a provision to permit connection to a remote alarm device, (supplied by others or as an option) to indicate FLASH/FAIL status.
NOTE: See Engineering Brief #67 for additional information regarding the failure requirements for multiple alternative lighting devices (ALDs).
3.3.6 Input Voltage.
The obstruction lighting equipment must be designed to operate from the specified input voltage ±10 percent. Incandescent lamps must be operated to within ±3 percent of the rated lamp voltage to provide proper light output.
3.3.7 Performance Criteria.
Manufacturers are required to publish performance criteria for all light generating devices (see Engineering Brief #67).
3.3.8 Transient Protection.
Equipment with solid state devices must be designed to withstand and/or include separate surge protection devices that are tested against defined waveforms per IEEE C62.41-1991, Table 4, Location Category C1, for single phase modes (line to ground, line to neutral, line and neutral to ground).
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3.3.9 Radiated Emissions.
NOTE: Optional only. No equipment qualification is required.
a. Obstruction lighting that uses electronic circuitry to power the light source must be classified as an incidental radiator (47 CFR §15.13). This applies to equipment that does not intentionally generate any radio frequency energy, but may create such energy as an incidental part of its intended operations.
b. Obstruction light systems must employ sound engineering practices to minimize the risk of harmful interference.
3.3.10 Warning Labels.
All enclosures that contain voltages exceeding 150 volts direct current (VDC) or alternating current (AC) root mean square (rms) must have high voltage warning label(s) placed at a conspicuous location(s). Also, a visual indicator must be included within the enclosure to indicate that greater than 150 VDC is present on the high voltage capacitors.
3.3.11 Interlock Switches.
Interlock switches must be incorporated in each power supply and optionally in each flashhead so that opening either unit must (1) interrupt incoming power and (2) discharge all high voltage capacitors within the enclosure to 50 volts or less within 30 seconds.
3.3.12 Nameplate.
A nameplate, with the following information, must be permanently attached to each unit:
a. Name of unit (light unit, control unit, etc.).
b. FAA type (e.g., L-856, L-864, etc.).
c. Manufacturer's catalog number.
d. Manufacturer's name and address.
e. Rated separation distance in feet is ____ to _____ between power supply and optical head using American Wire Gage (AWG) ____ conductors. (Item e is required if a unique power supply and its associated optical head are separate components of the lighting system as in the case of some discharge lights.)
In addition to the above, the power supply must include nominal input voltage, number of phases, frequency, and peak VA rating.
3.3.13 Optional Arctic Kit
Light systems may be offered with an optional arctic kit to enable operation in temperatures below -40 degrees F (-40 degrees C).
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3.3.14 Component Ratings.
3.3.14.1 Discharge Type Lighting Equipment.
The flashtube or flashtubes must have a minimum rated life of two years without maintenance or loss of light output below the minimum specified candela.
3.3.14.2 Component Separation Rating.
If the light unit's power supply and optical head are separate components, the manufacturer must rate each light unit for maximum and minimum separation at a given AWG wire size. The manufacturer must include this rating on the nameplate per section 3.3.12. The rating certifies that the unit meets all requirements within the rated distances. The manufacturer must maintain records of test results which support the stated separation rating until the next system re-qualification.
3.3.14.3 Incandescent Light Equipment.
Lamps must have a minimum rated life of 2,000 hours at rated voltage.
3.3.14.4 Alternative Light Source Equipment.
Light sources other than incandescent or xenon (light emitting diodes, cold cathode) must have a minimum rated life of two years without maintenance or loss of light output below the minimum specified intensity (see Engineering Brief #67).
3.3.14.5 Light Equipment Components.
All components used in obstruction lighting equipment, except lamps, must be designed to meet performance requirements for a minimum of one year without maintenance.
3.3.15 Leakage Current.
All obstruction lighting equipment classified in paragraph 1.2 must be designed to withstand application of 1,000 volts AC or 1,414 volts DC between the input power leads and equipment chassis for 10 seconds during which the leakage current must not exceed 10 microamperes at ambient room temperature and humidity.
3.4 Performance Requirements.
3.4.1 Photometric.
3.4.1.1 General.
The effective intensity for flashing lights must be calculated per the following formula by the method described for Flashing Light Signals in the IES Handbook, 1993 Reference and Application Volume 8th Edition, Pages 96 and 97:
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()()122.0/21ttIdtItte?+????????=∫
Where:
Ie = Effective intensity (Candela)
I = Instantaneous intensity (Candela)
t1 , t2 = Times in seconds of the beginning and end of that part of the flash when the value of I exceeds Ie. This choice of the times maximizes the value of Ie.
For discharge type flashing lights, the equipment must provide the specified light output at the specified temperature extremes as the input voltage simultaneously varies by ±10 percent from nominal. The light intensity and beam distribution requirements for obstruction lighting equipment are specified below. All intensities listed are effective intensities (except steady-burning red obstruction lights) measured at the flash rate specified in Table 4. All incandescent lights will be tested as steady burning lights. Additional requirements for ALDs are in Engineering Brief #67.
The effective intensity for multiple pulse flashes as used in strobe lights during nighttime operation must be calculated by: ???????????????+++???????????????++???????????????++???????????????+=∫∫∫∫XZttDEttBCttAttettIdtttIdtttIdtttIdtIzXEDCBA2.0...2.02.02.011
The frequency of the pulses must not be less than 50 Hz and the interval tA- t1 must not vary by more than ±5% from the nominal value from pulse to pulse over the simultaneous extremes of temperature and input voltage.
3.4.1.2 L-810 Light Unit.
The center of the vertical beam spread must be between +4 and +20 degrees. With a minimum vertical beam spread of 10 degrees and at all radials throughout 360 degrees, there must be a minimum intensity of 32.5 candela. Mechanical interface for installation must be 3/4 or 1 inch National Pipe Thread (NPT) side and/or bottom.
3.4.1.3 L-856 Light Unit.
The beam spread and effective intensity must be per Table 1.
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Table 1. L-856 Intensity Requirements.
Beam Spread
Step
Horizontal (1)
(degrees)
Vertical
(degrees)
Peak Intensity
(candela) (2)
Day
Twilight
Night
90 or 120
90 or 120
90 or 120
3 - 7
3 - 7
3 - 7
270,000 ±25%
20,000 ±25%
2,000 ±25%
NOTES:
(1) Multiple light units may be used to achieve a horizontal coverage of 360 degrees.
(2) When the light unit is installed per the manufacturer's instructions, the intensity at zero degrees elevation angle (horizontal) must be at least as great as the minimum specified beam peak intensity. For stray light, the intensity at 10 degrees below horizontal, at any radial, must not be greater than 3% of the peak intensity at the same radial.
3.4.1.4 L-857 Light Unit.
Photometric requirements are defined in Table 2.
Table 2. L-857 Intensity Requirements.
Beam Spread
Step
Horizontal
(degrees) (1)
Vertical
(degrees)
Peak Intensity
(candela)(2)
Day
Twilight
Night
90 or 120
90 or 120
90 or 120
3 - 7
3 - 7
3 - 7
140,000 ±25%
20,000 ±25%
2,000 ±25%
NOTES:
(1) Multiple light units may be used to achieve a horizontal coverage of 360 degrees.
(2) When the light unit is installed per the manufacturer's instructions, the intensity at zero degrees elevation angle (horizontal) must be at least as great as the minimum specified beam peak intensity. For stray light, the intensity at 10 degrees below horizontal, at any radial, must not be greater than 3% of the peak intensity at the same radial.
3.4.1.5 L-864 Light Unit.
At all radials throughout the omnidirectional 360 degrees, there must be a peak effective intensity of 2,000 ±25 percent candela. There must also be a minimum effective intensity of 750 candela throughout a minimum vertical beam spread of 3 degrees.
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3.4.1.5.1 Beam Adjustment.
When the light unit is installed per the manufacturer's instructions, the intensity at zero degrees elevation angle (horizontal) must be at least as great as the minimum specified beam peak intensity.
3.4.1.6 L-865 Light Unit.
Photometric requirements are defined in Table 3.
Table 3. L-865 Intensity Requirements.
Beam Spread
Step
Horizontal
(degrees) (1)
Vertical
(degrees)
Peak Intensity
(candela)(2)
Day/Twilight
Night
360
360
3 minimum
3 minimum
20,000 ±25%
2,000 ±25%
NOTES:
(1) Multiple light units may be used to achieve a horizontal coverage of 360 degrees.
(2) When the light unit is installed per the manufacturer's instructions, the intensity at zero degrees elevation angle (horizontal) must be at least as great as the minimum specified beam peak intensity. For stray light, the intensity at 10 degrees below horizontal, at any radial, must not be greater than 3% of the peak intensity at the same radial.
3.4.1.7 L-866 Light Unit.
The requirements are the same as the L-865 light unit, except the flash rate must be 60 flashes per minute (FPM).
3.4.1.8 L-885 Light Unit.
The requirements are the same as the L-864 light unit, except the flash rate must be 60 FPM.
3.4.2 Flash Rate and Duration.
Flash characteristics are defined in Table 4.
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Table 4. Flash Characteristics for Obstruction Lights
Type
Intensity Step
Flash Rate (1)
Flash Duration (2)
L-856
Day & Twilight
40 FPM
Less than 100 milliseconds (ms)
L-856
Night
40 FPM
Between 100 and 250 ms inclusive
L-857
Day & Twilight
60 FPM
Less than 100 ms
L-857
Night
60 FPM
Between 100 and 250 ms inclusive
L-864
Single
20-40 FPM
1/2 to 2/3 of flash period if incandescent lighting (3), and between 100 and 2000 ms inclusive if other lighting sources.
L-865
Day & Twilight
40 FPM
Less than 100 ms
L-865
Night
40 FPM
Between 100 and 1000 ms inclusive
L-866
Day & Twilight
60 FPM
Less than 100 ms
L-866
Night
60-FPM
Between 100 and 250 ms inclusive
L-885
Single
60 FPM
1/2 to 2/3 of flash period if incandescent lighting (3), and between 100 and 670 ms inclusive if other lighting sources.
NOTES:
(1) Flash rates have a tolerance of ±5 percent.
(2) When the effective flash duration is achieved by a group of short flashes, the short flashes must be emitted at a rate of not less than 50 Hz.
(3) The light intensity during the "off" period must be less than 10 percent of the peak effective intensity. The "off" period must be at least 1/3 of the flash period.
3.4.3 System Flashing Requirements.
3.4.3.1 Simultaneous Flashing Systems.
All obstruction lights in systems composed of either L-864 light units or L-856 and/or L-865 light units must flash within 1/60 of a second of each other.
3.4.3.2 Sequenced Flashing Systems.
a. Catenary support structure systems composed of L-857, L-866, or L-885 light units must have a sequenced flashing characteristic.
b. This system consists of three lighting levels on or near each supporting structure. One light level is near the top, one at the bottom or lowest point of the catenary, and one midway between the top and bottom.
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c. The flash sequence must be middle, top, and bottom.
d. The interval between top and bottom flashes must be about twice the interval between middle and top flashes.
e. The interval between the end of one sequence and the beginning of the next must be about 10 times the interval between middle and top flashes.
f. The time for the completion of one cycle must be one second (±5 percent).
3.4.4 Intensity Step Changing.
3.4.4.1 White Obstruction Lights.
The light unit intensity must be controlled by a photocell facing the northern (polar) sky. White obstruction lights must automatically change intensity steps when the ambient light changes as follows:
a. From day intensity to twilight intensity when the illumination decreases below 60 foot-candles (645.8 lux) but before it reaches 35 foot-candles (376.7 lux).
b. From twilight intensity to night intensity when the illumination decreases below 5 foot-candles (53.8 lux) but before it reaches 2 foot-candles (21.5 lux).
c. From night intensity to twilight intensity when the illumination increases above 2 foot-candles (21.5 lux) but before it reaches 5 foot-candles (53.8 lux).
d. From twilight intensity to day intensity when the illumination increases above 35 foot-candles (376.7 lux) but before it reaches 60 foot-candles (645.8 lux).
3.4.4.2 Red Obstruction Lights.
If automatic control is utilized, the light unit must turn on when the ambient light decreases to not less than 35 foot-candles (367.7 lux) and turn off when the ambient light increases to not more than 60 foot-candles (645.8 lux). Single L-810 light units are controlled in a manner compatible with the particular installation.
3.4.4.3 Dual Obstruction Lighting System.
White obstruction lights must turn off and red obstruction lights must turn on when the ambient light changes from twilight to night per paragraph 3.4.4.1b. Red obstruction lights must turn off and white obstruction lights must turn on when the ambient light changes from night to twilight per paragraph 3.4.4.1c.
3.5 Instruction Manual.
An instruction manual containing the following information must be furnished with all obstruction lighting equipment:
a. Complete system schematic and wiring diagrams showing all components cross-indexed to the parts list.
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b. Complete parts list of field replaceable parts with applicable rating and characteristics of each part, and with the component manufacturer's part number as appropriate.
c. Installation instructions, including leveling and aiming of light units.
d. Maintenance instructions, including lamp or flashtube replacement, theory of operation, troubleshooting charts and, as appropriate, conspicuous warnings about alignment and replacement of lamps and light units with other than manufacturer recommended items. Explanation of testing requirements regarding light units with specific lamps must be provided in the text. A discussion must be included about mixing light units as replacements with other manufacturers’ units with emphasis on assuring that system design of obstruction lighting is not degraded.
e. Operating instructions.
