Codes and Standards

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 contained in AC 70/7460-1, Obstruction Marking and Lighting.

3.2 Environmental Requirements. Obstruction lighting equipment shall be designed for continuous operation under the following conditions:

a. Temperature. -67°F (-55° C) to +130°F (+55°C).
b. Humidity. 95 percent relative humidity.
c. Wind. Wind speeds up to 150 mph (240 kin).
d. Wind-blown Rain. Exposure to wind-blown rain from any direction.
e. Salt Fog. Exposure to salt-laden atmosphere.

3.3 Design Requirements.

3.3.1 Light Unit. The light unit shall be lightweight and designed for easy servicing and lamp (flashmbe) replacement. Materials used within the light unit shall be selected for compatibility with their environment. Each light unit shall be an independent unit and will 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 shall conform to the requirements of MIL-C-7989.

3.3.3 Light Colors. The aviation red shall be in accordance with ICAO (ANNEX 14, July 1990: Volume 1, Appendix 1, Fig. 1.1) colors for aeronautical ground lights at operating temperature within the following chromaticity boundaries:

purple boundary y = 0.980 - x
yellow boundary y = 0.335

x+y+z=l

Xenon flashtube emission is acceptable for white obstruction lights.

3.3.4 Aiming (for L-856 and L-857). Light units shall have a method for adjustment of the vertical aiming angle between 0 and + 8 degrees. A spirit level or other device shall be provided as part of each light unit for setting the vertical aiming angle of the light beam with an accuracy of 1 degree.

3.3.5 Control Unit.

3.3.5.1 Flashing White Obstruction Lighting Systems. The control unit shall set the system's flash rate, intensity and sequence. It shall be capable of controlling light units up to a distance of 2,500 feet (762m). If the control unit or control wiring falls, the light units shall continue to flash in accordance with Table 4 flash rate. Failure of an intensity, step change circuit shall 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 shall 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 shall be fail safe (i.e., active signals for FLASH and absence of signals for FAIL). There shall be a provision to permit connection to a remote alarm device, (supplied by others or as an option), to indicate system and individual light unit FLASH/FAIL status.

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 shall display the status of each light unit. An intensity control override switch shall also be mounted in the enclosure to manually control light intensity during maintenance or in the event of a photoelectric control malfunction.

3.3.5.2 Red Obstruction Lights. The control unit shall set the system flash rate and flash sequence. Failure of the flashing circuit shall cause the light units to come "on" steady burning for incandescent lights. An override switch shall 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 shall 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 shall set the operating mode for each light unit in the system. Outage of one of two lamps in the uppermost red beacon (L-864 incandescent unit) or outage of any uppermost red strobe shall 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 shall 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 shall 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 shall be fail safe (i.e., active signals for FLASH and absence of signals for FAIL). There shall be a provision to permit connection to a remote alarm device, (supplied by others or as an option) to indicate FLASH/FAIL status.

3.3.6 Input Voltage. The obstruction lio~ting equipment shall be designed to operate from the specified input voltage ± 10 percent. (Note) incandescent lamps must be operated to within 3% of the rated lamp voltage to provide proper light output..

3.3.7 Transient Protection. The power input, control and monitor interface circuitry (if any) shall be designed to withstand and/or include separate surge protection devices which have tested against defined waveforms detailed in ANSI/IEEE C62.41-1991, namely, 3000 Amp, 8/20~s - short circuit current pulse and 6000 Volt, 1.2/50[xs - open circuit voltage pulse.

3.3.8 Warning Labels. All enclosures which contain voltages, exceeding 150 volts dc or ac (rms) shall have high voltage warning label(s) placed at a conspicuous location(s). Also, a visual indicator shall be included within the enclosure to indicate that greater than 150 vdc is present on the high voltage capacitors.

3.3.9 Interlock Switches. Interlock switches shall be incorporated in each power supply and optionally in each flashhead so that opening either unit shall (1) interrupt incoming power and (2) discharge all high voltage capacitors within that enclosure to 50 volts or less within 30 seconds.

3.3.10 Nameplate. A nameplate, with the following information, shall be permanently attached to each unit, e.g.

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 AWG -- conductors. (Item e shall be 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 shall include nominal input voltage, number of phases, frequency, and peak volt-ampere (VA) rating.

3.3.11 Component Ratings.

3.3.11.1 Discharge Lighting Equipment. All components in discharge lighting equipment except the flashtube, shall be designed for ease of servicing and to meet performance requirements for a minimum of 1 year without maintenance. Flashtube or flashtUbes shall have a minimum rated life of 2 years without maintenance or loss of light output below minimum specified candela.

3.3.11.1.1 Component Separation Rating. If the light unit's power supply and optical head are separate components, the manufacturer shall rate each light unit for maximum and minimum separation at a given AWG wire size. The manufacturer shall include this rating on the nameplate per section 3.3.10. The rating certifies that the unit meets all requirements within the rated distances. The manufacturer shall maintain records of test results which support the stated separation rating.

3.3.11.2 Incandescent Light Equipment. All components in incandescent lighting equipment, except lamps, shall be designed to meet performance requirements for a minimum of 1 year without maintenance Lamps shall have a minimum rated life of 2,000 hours at rated voltage.

3.3.12 Leakage Current. Ail obstruction lighting equipment classified in section 1.2 shall be designed to withstand application of 1000 volts AC or 1414 volts DC between the input power leads and equipment chassis for 10 seconds during which the leakage current shall not exceed 10 micro amperes at ambient room temperature and humidity.

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3.4 Performance Requirements.

3.4.1 Photometric.

3.4.1.1 General. The effective intensity for flashing lights shall be calculated in accordance with the following formula by the method described for "Flashing Light Signals" in the IES Handbook, 1993 Reference and Application Volume 8th Edition, Page 96 and 97:

For discharge flashing lights, the equipment shall 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.

The effective intensity for multiple pulse flashes as used in strobe lights during nighttime operation shall be calculated by:

The frequency of the pulses shall not be less than 100 Hz and the interval tA- tz shill 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 shall lie between +4 and +20 degrees. With a minimum vertical beam spread of l0 degrees and at all radials throughout the omnidirectional 360 degrees, there shall be a minimum intensity of 32.5 candela. Mechanical interface for installation shall be 3/4 or 1 inch NPT side and bottom.

3.4.1.3 L-856 Light Unit. The beam spread and effective intensity shall be in accordance with Table 1.

NOTES: (1) Multiple light units may be used to achieve a horizontal coverage of 360 degrees.

(2) When the light unit is leveled the intensity at zero degrees elevation angle (horizontal) shall be at least as great as the minimum specified beam peak intensity. The light unit must produce at least 1/2 the minimum allowable peak intensity at -1.0 degree. For Stray light, the intensity at 10 degrees below horizontal, at any radial, shall 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

NOTES: (1) Multiple light units may be used to achieve a horizontal coverage of 360 degrees.

(2) When the light unit is leveled the intensity at zero degrees elevation angle (horizontal) shall be at least as great as the minimum specified beam peak intensity. The light unit must produce at least 1/2 the minimum allowable peak intensity at -1.0 degree. For stray light, the intensity at 10 degrees below horizontal, at any radial, shall 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 shall be a peak effective intensity of 2,000 ± 25% candela. There shall also be a minimm effective intensity of 750 candela throughout a minimum vertical beam spread of 3 degrees.

3.4.1.5.1 Beam Adjustment. When the light unit is leveled the intensity at zero degrees elevation angle (horizontal) shall be at least as great as the minimum specified beam peak intensity. The light unit must produce at least 1/2 the minimum allowable peak intensity at -1.0 degree.

3.4.1.6 L-865 Light Unit. Photometric requirements are defined in Table 3.

Table 3. L-865 Intensity Requirements

NOTES: (1) Multiple light units may be used to achieve a horizontal coverage of 360 degrees.

(2) When the light unit is leveled, the intensity at zero degrees elevation angle (horizontal) shall be at least as great as the minimum specified beam peak intensity. The light unit must produce at least 1/2 the minimum allowable peak intensity at -1.0 degree. For stray light, the intensity at 10 degrees below horizontal, at any radial, shall 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 shall be 60 FPM.

3.4.1.8 L-885 Light Unit. The requirements are the same as the L-864 light unit, except the flash rate shall be 60 FPM.

3.4.2 Flash Rate and Duration.

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 shall be emitted at a rate of not less than 100 Hz.

(3) The light intensity during the "off" period shall be less than 10 percent of the peak effective intensity. The "off" period shall 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 shall flash within 1/60 of a second of each other.

3.4.3.2 Sequenced Flashing Systems. Catenary support structure systems composed of L-857, L-866, or L-885 light units shall have a sequenced flashing characteristic. 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. The flash sequence shall be middle, top, and bottom. The interval between top and bottom flashes shall be about twice the interval between middle and top flashes. The interval between the end of one sequence and the beginning of the next shall be about 10 times the interval between middle and top flashes. The time for the completion of one cycle shall be 1 second (4- 5 percent).

3.4.4 Intensity Step Changing.

3.4.4.1 White Obstruction Lights. The light unit intensity shall be controlled by a photocell facing the northern (,polar) sky. White obstruction lights shall automatically change intensity steps when the ambient light changes as follows:

a. From day intensity to twilight intensity when the illumination decreases below 60 footcandles but before it reaches 35 foot-candles.

b. From twilight intensity to night intensity when the illumination decreases below 5 footcandles but before it reaches 2 foot-candles.

c. From night intensity to twilight intensity when the illumination increases above 2 footcandles but before it reaches 5 foot-candles.

d. From twilight intensity to day intensity when the illumination increases above 35 footcandles but before it reaches 60 foot-candles.

3.4.4.2 Red Obstruction Lights. If automatic control is utilized, the light unit shall mm on when the ambient light decreases to not less than 35 foot-candles and mm off when the ambient light increases to not more than 60 foot-candles. 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 shall mm off and red obstruction lights shall mm on when ambient light changes from twilight to night as specified in paragraph 3.4.4.1 .b. Red obstruction lights shall turn off and white obstruction lights shall mm on when ambient light changes from night to twilight as specified in paragraph 3.4.4.1.c.

3.5 Instruction Manual. An instruction manual containing the following information shall be furnished with all obstruction lighting equipment.

a. Complete system schematic and wiring diagrams showing all components cross-indexed to the parts list.

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 levelir;g and aiming of light units.

d. Maintenance instructions, including lamp (fiashtube) 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 should be provided in the text. A discussion should be included about mixing light units as replacements with other manufacturer's units with emphasis on assuring system design of obstruction lighting is not degraded.

e. Operating instructions.

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