AC 70/7460-1D 4/18/75 levels of lights. on the highest point. The top level of lights should be installed High Intensity Lighting Systems. The overall height of the mine the number of levels of lights. The top level of lights main structure, excluding all appurtenences, is used to deter- should be installed on the highest portion of the main struc- In addition, a white omnidirectional beacon should be tenance supported by the main structure. displayed on the highest portion of any antenna or other appur- C. Adjacent Structures. The elevation of the tops of the buildings in closely built up areas may be used as the equivalent of the ground level when determining the proper number of lights necessary to adequately mark an obstruction.
Shielded Lights. If any light is shielded by an adjacent object, additional lights should be mounted on that object to retain the of the obstruction. lights may be omitted if they do not contribute to the definition general definition of the obstruction, However, the additional
e. Temporary Warning Lights. When an obstruction to air navigation is be installed at the uppermost point of the structure. presented during construction of a structure, temporary lights should as the height of the structure progresses above the level at which In addition, lights are in operation. The lights should be positioned so as to permanent lights should be installed at such levels. Temporary lights should be displayed from sunset to sunrise until all of the permanent permanent obstruction lights will be required, either temporary or from aircraft at any normal angle of approach. ensure unobstructed visibility of at least one light at each level * Nonstandard Lights. Obstruction lighting other than those specified herein may be utilized provided such lighting installations offer equal or greater light intensity in all angles of azimuth and elevation equal or greater dependability of operation, possess the color characteristics prescribed in Chapter 9, and flash as required. than that specified for standard obstruction light assemblies, afford Chimneys and similar obstructions may be floodlighted by fixed search- provide an average illumination of at least 15 foo‡candles over the top one-third of the obstruction. light projectors installed at three or more equidistant points around the base of each obstruction. The searchlight projectors should Hazard Areas, An area in which a visible or invisible hazard exists or is proposed should be lighted as prescribed by FAA. This lighting would be in addition to such lighting as may be necessary on any natural or man-made obstruction located within the area.
Page 12 Chap. 4 Par. 15
h. Monitoring of Obstruction Lighting. visually observed at least once each 24 hours. In the event obstruc- Obstruction lighting should be tion lighting is not readily accessible for visual observation, a properly maintained automatic visual or audible alarm indicator should be installed and operated to provide an indication that such lights are functioning properly as required. This alarm indicator should be designed to register any malfunction of any light on the obstruction regardless of its position. The automatic monitoring alarm indicator should be located in an area generally occupied by facility personnel. In some cases, this may require relocating the monitor to a remote control station.
Cleaning. All lights, and particularly the top level, should be readily accessible to enable cleaning when necessary and to facilitate lamp/flashtube replacement. The lights should be kept clean to prevent a reduction in light output. They should be cleaned on a scheduled basis to prevent residue from accumulating on the face of the light unit and to prevent crusting due to the lamp heat.
* j• Lamp Types. Only lamps of the type supplied with FAA approved equipment or those recommended by the manufacturer as original or replacement lamps, should be used in the light fixtures. * Notification of Light Failure. Any observed or otherwise known extinguishment or improper functioning of any top steady burning light or any flashing obstruction light, regardless of its position on should be immediately reported. Such reports should be made by a natural or man-made obstruction, which will last more than 30 minutes, telephone or telegraph to the nearest flight service station or office of the FAA and should set forth the condition of the light, or lights, the circumstances which caused the failure and the probable date the operation of the light, or lights. or telegraph should be given immediately upon resumption of normal normal operation will be resumed. Further notification by telephone
1. Interference. Where obstruction lights might present a problem to the safe operation of aircraft (landing or departing), railway trains, motor vehicles and surface vessels, or if the lights might be a source of irritation to residents, consideration should be given to mitigating or eliminating the adverse effects of the lights.
Shielding of lights should be considered, steady burning lights may be made to flash, or the lower level of lights may be extinguished provided the hazard to air navigation is not increased. The FAA Regional Director or his designee is responsible for assuring that such obstruction lighting installations are fully coordinated with all parties concerned and that proper corrective measures are placed in effect. In the case of a navigable waterway, the light installation must be coordinated with the Commandant, U. S. Coast Guard, to avoid interference with marine navigation.
Chap. 4 Far. 15 Page 13
AC 70/7460-1D 4/18/75
m. Manufacturers. The names of qualified manufacturers and a description of their equipment are listed in the FAA Advisory Circular 150/5345-1, Approved Airport Lighting Equipment. See Chapter 9.
* Lighting Equipment. The standards outlined in this advisory circular ere predicated upon the use of lighting units that meet specified intensities, beam patterns, color and flash rates (if appropriate).
Therefore, only equipment having been approved by the Airports Service of the Federal Aviation Administration or nonstandards lights in accordance with paragraph 15.f. above, should be used, O • Lighting Systems) Designation. A method of designating the specific type of lighting system to be employed on a structure, and previously used to designate the number of levels and type of red obstruction lights to be used, has been expanded to cover the high intensity lighting system configurations. (See Appendix 2, Figures 1-12).
(1) Type of lighting system.
(a) A - Red obstruction lighting system
(b) B - High intensity obstruction lighting system C - High intensity obstruction lighting system with an appurtenance extending above the top of the structure.
(d) D - Dual lighting system
(2) Number of levels. The numerical designator immediately following the letter designator, identifies the number of levels of lights. * Page 14 chap. .
Par. 1.
4/18/75 AC 70/7460-1D CHAPTER 5. RED OBSTRUCTION LIGHTING STANDARDS TION LIGHTS. STANDARDS FOR LIGHTING OBSTRUCTIONS TO AIR NAVIGATION WITH RED OBSTRUC- Flashing Red Beacon. This 300 mm flashing beacon consists of two simultaneously flashing incandescent lamps of at least 620 watts with aviation red color filters. The steady burning intensity should not be less than 2,000 candelas (in red). The flashing mechanism should produce not more than 40 flashés per minute nor less than 12 flashes per minute with a period of darkness equal to approximately one-half the luminous period. If the obstruction is located within 15,000 feet (4,500m) of a landing area, the flashing frequency should be not less than 20 flashes per minute. These Specification I-6273. beacons should conform to FAA Specification CAA 446, or Military Steady Burning Red Obstruction Light. This obstruction light con- sists of one or more steady burning lamps of at least 116 watts (when used in multiple circuit), enclosed in an aviation red obstruction light globe. The intensity should be not less than 32.5 candelas. If the flashing mechanism is installed so as to make it necessary for these lights to flash, the simultaneous flashing of all lights will be permissible. These lights should conform to FAA Specification AC 150/5345-2 (L-810), or Military Specification L-7830.
C. Rated Lamp Voltage. The rated voltage of the lamp should, in each case, be not more than three percent higher than the average voltage during the hours of normal operation. across the lamp measured at the lamp socket with the lamp operating *
1. Operation of Red Lights. Red Obstruction lights should be operated y a satisfactory control device adiusted so the lights will be turned on when the north sky illuminance falls on a vertical surface to a level of not less than 35 footcandles (376.7 lux).
They should also be turned on during daytime when the flight visibility is restricted. In Alaska, however, the lights should be turned on during daytime when a prominent unlighted object cannot be seen of not less than 58 footcandles (624.3 lux), or the lights may from a distance of three statute miles. The control device should turn off the lights when the north sky illuminance rises to a level face the north sky. remain on continuously. The sensing device should, if practical,
e. Availability of Specifications.
(1) FAA Specifications CAA 446 and AC 150/5345-2 (L-810) are See Chapter 9. available free of charge from the Department of Transportation.
Chap. 5 Par. 16 Page 15
AC 70/7460-1D 4/18/75
(2) Military Specifications I-6273 and I-7830 are available free of charge from the Naval Publications and Forms Center. See Chapter 9, *
f. Poles, Towers, and Similar Skeletal Structures. The following standards apply to radio and television towers, supporting structures for overhead transmission lines and similar lacy structures. *
(1) Top Mounted Obstruction Light.
Structures Not More Than 150 Feet (45m) AGL. Two or more steady burning lights should be installed in a manner to ensure unobstructed visibility of one or more lights from an aircraft at any normal angle of approach.
(b) Structures Exceeding 150 Feet (45m) AGL. At least one 300 mm flashing beacon should be installed in a manner to ensure unobstructed visibility from an aircraft at any normal angle of approach.
(c) Special Cases.
Appurtenances Not Exceeding 20 Feet (6m). If a rod, antenna or other appurtenance of not more than 20 feet (6m) in height is incapable of supporting a beacon and it is determined that this appurtenance does not allow „unobstructed viewing of a single 300 mm flashing beacon from any normal angle of approach, there shouid be installed two such beacons properly positioned on top of the main structure to permit unobstructed viewing Appurtenances Exceeding 20 Feet (6m). If a rod, antenna or other appurtenance greater than 20 feet (6m) in height is incapable of supporting a beacon, a supporting mast with one or more beacons should be installed adjacent to the appurtenance and to a height within 20 feet (6m) of the tip of the appurtenance so as to permit unobscured viewing of at least one beacon.
(2) Mounting Intermediate Levels. The number of levels of lights may be obtained from Appendix 2, Figs: 1-3. The number of lights on each level is determined by the shape and height of the structure.
These lights should be mounted so as to ensure unobstructed viewing of at least one light from any normal angle of approach.
(a) Steady Burning Lights.
1. If the structure is not more than 450 feet (135m) in height, two or more steady burning lights should be Chap. 5 Page 16 Par. 16
4/18/75 AC 70/7460-1D installed on diagonally or diametrically opposite positions.
If the structure exceeds 450 feet (135m) in height, steady burning lights should be installed on each.
outside corner of each level.
(b) Flashing Beacons.
1. Normally, structures not more than 450 feet (135m) in height do not require intermediate levels of flashing beacons.
If the structure is more than 450 feet (135m) in height, a flashing beacon should be installed within the structure proper. If the structural members impair the viewing of the beacon, then two beacons should be mounted on the outside of diagonally or diametrically opposite positions of each level.
Chimneys, Flare Stacks and Similar Solid Structures.
(1) Top Mounted Obstruction Lights.
(a) Structures Not More Than 150 Feet (45m) AGL. At least three steady burning obstruction lights should be installed at regular intervals on the horizontal plane at or near the top, in a manner to ensure unobstructed visibility, of at least two lights from aircraft at any normal angle of approach.
(b) Structures Exceeding 150 Feet (45m) AGL. Two or more 300 m flashing beacons should be installed in a manner to ensure unobstructed visibility from an aircraft at any normal angle of approach.
(c) Chimneys. Lights may be displayed from five (1.5m) to 10 feet (3m) below the top of chimneys to avoid the obscurant effect of the deposits generally emitted by this type of structure. It is important that these lights be readily accessible to enable cleaning when necessary and to facilitate lamp replacements.
(2) Mounting Intermediate Levels,
(a) Steady Burning Lights. The number of light levels may be obtained from Appendix 2, Figs. 1-3. At least three lights should be installed on each level. These lights should be mounted so as to ensure unobstructed viewing of at least two lights on each level.
Chap. 5 Par. 16 Page 17
AC 70/7460-1D 4/18/75
(b) Flashing Beacons. The number of beacon levels may be obtained from Appendix 2, Figs, 1-3.
1. Normally, structures not more than 450 feet (135m) in beacons. height do not need intermediate levels of flashing
2. If the structure exceeds 450 feet (135m) two or more flashing beacons should be installed on each level and installed in a manner to allow unobstructed viewing of at least one beacon.
h. Prominent Buildings and Similar Extensive Obstructions. If individual objects within a group of obstructions are approximately the same overall height above ground, or water if so situated, and are located not more than 150 feet (45m) apart, the group of obstructions may be considered an extensive obstruction. Prominent buildings and follows: similar extensive obstructions should display steady burning obstruc- tion lights in a manner to indicate the extent of the obstruction as
(1) Direction. Structures Not More Than 150 Feet (45m) in Either Horizontal If the structure/extensive obstruction is not more than 150 feet (45m) in either horizontal dimension, at least one steady burning obstruction light should be displayed on the highest point of each end of the major axis of the obstruction.
If this method of lighting is impracticable because of the shape of the obstruction, then two lights may be displayed in the center of the highest point.
(2) Structures More Than 150 Feet (45m) in at Least One Horizontal one steady burning obstruction light should be displayed for each 150 feet (45m) in either or both horizontal dimensions, at least Direction. If the structure/extensive obstruction is more than 150 feet (45m), or fraction thereof, of the overall length of the major axis of the obstruction. At least one of these lights should be displayed on the highest point of each end of the obstruction. Additional lights, as required, should be displayed at approximately equal intervals not to exceed 150 feet (45m) on the highest points or edge between the end lights. If there are two or more edges of the same height on an obstruction located lighted. near a landing area, the edge nearest the landing area should be
(3) lieu of steady burning obstruction lights in the event early or Page 18 Chap. 5 Par. 16
displayed on the highest points of an extensive obstruction at intervals not exceeding 3,000 feet (900m). At least three beacons should be displayed on one side of the extensive obstruction to indicate a line of lights.
(4) If individual objects within a group of obstructions are not the same height and are spaced more than 150 feet (45m) apart, the prominent objects within the group should be lighted in accordance with the specifications for individual obstructions of a corresponding height, In addition, at least one rotating beacon should be installed at the top of a prominent center obstruction or on a special tower located near the center of the group of obstructions.
(5) Obstructions More Than 150 Feet (45m) AGL. Steady burning obstruction lights should be installed at the top as specified in paragraphs (1) or (2) above. At selected intermediate levels, steady burning lights should be displayed for each 150 feet (45m), or fraction thereof. The position of these lights on the vertical plane should be equidistant between the top lights and the ground level as the shape and type of obstruction will permit. One such light should be displayed at each outside corner on each level with the remaining lights evenly spaced between the corner lights.
i. Alternate Method of Displaying Obstruction Lights. In lieu of installing lights on the obstruction, lights may be placed on poles of slightly greater height than the obstrućtion and installed on or adjacent to the structure.
Chap. 5 Par. 16 Page 19 (and 20)
4/18/75 AC 70/7460-1D
17. CHAPTER 6. HIGH INTENSITY OBSTRUCTION LIGHTING STANDARDS
STANDARDS FOR LIGHTING OBSTRUCTIONS TO AIR NAVIGATION WITH HIGH INTENSITY WHITE OBSTRUCTION LIGHTS. The general standards which follow apply to the obstruction lighting of structures with capacitor discharge obstruction lighting systems. The overall height of a structure including all appurtenances such as rods, antennas, obstruction lighting, etc., are used to determine whether the object is an obstruction to air navigation in accordance with FAR, Part 77, Objects Affecting the Navigable Airspace.
However, the overall height of the main structure excluding all appurtenances, is used to determine the number of light levels recommended on a structure. In addition, a white omnidirectional beacon should be displayed on the highest portion of any antenna or other appurtenance, exceeding 20 feet (6m) supported by the main structure. These standards do not require modification of the marking and lighting on existing structures; however, the FAA may recommend that marking and lighting displayed on an existing structure be modified if that structure is altered or replaced by a similar structure.
High Intensity Obstruction Light, The lighting systems referred to in the following standards should conform with the applicable provisions of the latest issuance of FAA Advisory Circular 150/5345-43, FAA/DOD Specification L-856, High Intensity Obstruction Lighting Systems.
Light Specifications. The following are the basic recommended standards for high intensity obstruction lighting systems applied to structures. However, the intensity, flash rate, sequence and placement of light units are unique in the case of supporting structures of overhead transmission lines. (See paragraph 17.j.)
Effective Intensity. Day Mode - no less than 200,000 candelas (100,000 candelas for transmission line supporting structures);
twilight mode - approximately 20,000 candelas; night mode - approximately 4,000 candelas.
Intensity Step Changing. The systems should automatically change intensity steps when the north sky illumination on a vertical surface is as follows:
* (a) Day to Twilight. This should not occur before the illumination drops to 60 footcandles (645.8 lux), but should occur before it drops below 30 footcandles (322.9 lux).
The illuminance sensing device should, if practical, face the north sky.
(b) 1wilight to Night. This should not occur before the illumination drops to five footcandles (53.8 lux), but should occur before it drops below two footcandles (21.5 lux). * Chap. 6 Par. 17 Page 21
AC 70/7460-1D 4/18/75
(c) Night to Day. The intensity changes listed in (a) and (b) above should be reversed in transitioning from the night to day mode.
(3) Flash Rate. All light units should flash simultaneously at 40 pulses per minute. (See paragraph 17.j. for flash rate and unique sequencing of catenary systems.)
Beam Spread. A relatively narrow vertical beam spread is specified to provide full light intensity at possible collision altitudes with the structure while persons on the ground or at altitudes above the structure will receive only stray light.
Antenna or Similar Appurtenance Light. The specifications for the high intensity lighting system provide for a small omnidirectional white light, similar in size to the 300 mm red flashing beacon, for installation on top of antennas or similar appurtenances. This light should operate 24 hours a day, flash in synchronism with the high intensity lighting system, be of approximately the same intensity as the twilight mode during daylight and reduce in intensity to the night mode simultaneously with the remainder of the system. This appurtenance light should only be used as an adjunct to the high intensity lighting system.
Flashtube Replacements. The flashtubes in a light unit should be replaced when the peak effective daytime intensity falls below 200,000 candelas (100,000 candelas for systens installed on the supporting structures of overhead transmission lines).
d. Installation Guidance. The manufacturing specifications provide for installation would be for all light units to be installed at zero degrees elevation. Where terrain, nearby residential areas or other situations dictate, it may be desirable to use louvers and/or elevate the light beam above the horizontal, The beam of the light at the lower level should not strike the ground closer than three statute miles (5km) from the structure to prevent irritation to nearby residents. Should elevating the light beam be necessary, it is recommended that the beam be elevated (in degrees above the horizontal) as shown below. If additional adjustments are necessary, each light may be adjusted upward, in one degree increments, starting at the bottom. The top light should normally remain at zero degrees to the horizontal.
Chap. 6 Page 22 Par. 17
Level Number of Levels of Lights Installed of Light 1 2 TOP 5 4 3 1 2 2 1 2 2 2 BOTTOM 2 2 3 3 Figures indicate degrees of elevation above the horizontal. * e • High Intensity Light Units. The high intensity capacitor discharge light units known to date which meet the FAA/DOD specification L-856 are not omnidirectional, except for the light used on antennas or similar appurtenances. See paragraph 17.b.(5). Therefore, more than one light unit is required in order to obtain 200,000 candelas for 360 degrees of coverage about a structure to ensure that the system is visible from aircraft at any normal angle of approach. A light unit may contain one or more flashtubes.
(1) Number of Levels of Lights. The number of levels of lights used is dependent upon the overall height of the structure above ground level. The lights should be installed at the levels indicated in Appendix 2, Figs. 4-6, for chimneys and similar solid structures. On structures having an antenna or similar appurtenance extending more than 20 feet (6m) above the main structure, such as a radio or television antenna, the lights should be installed at the levels indicated in Appendix 2, E188. 7-9. The light levels recommended for other structures,
i.e., cooling towers, supporting structures of catenaries and buildings, may be found under the appropriate subject paragraph.
(2) Number of Light Units Per Level. The number of light units recommended per level (except for the supporting structures of transmission lines and buildings) is dependent upon the average outside diameter of the specific structure:
(a) Structures 20 feet (6m) or less - three light units per level.
Chap. 6 Para. 17 Page 23
AC 70/7460-1D 4/18/75
(b) Structures exceeding 20 feet (6m) but not more than 100 feet (30m) - four light units per level.
(c) Structures exceeding 100 feet (30m) but not more than 200 feet (60m) - six light units per level.
(d) Structures exceeding 200 feet (60m) - eight light units per level.
Relocation or Omission of Light Units. Light units should not be installed in such a manner or elevation on a structure that the intended purpose would be derogated.
(1) Lowest Level, The lowest level of light units may be installed at a higher elevation than normal for the height of the structure if the lights, by installing them at the prescribed eleva- tion, would be lower than surrounding terrain, trees or adjacent building(s). See Appendix 1, Fig. 7. In certain instances, as lowest level may be permissible. determined by an FAA aeronautical study, the elimination of the Iwo Adjacent Structures. Where two structures are situated within 200 feet (60m) of each other and the light units will be installed at the sane levels, the sides of the structures facing each other need not be lighted; therefore, the inboard lights ment of the lights to either or both of the structure's inter- flash in snychronism. Minor adjustments in the vertical place- may be eliminated; however, all lights on both structures must mediate levels of lights may be made in order to place the lights on the same horizontal plane. Where one structure is higher than the other, complete level(s) of lights should be installed on that part of the higher structure which extends above the top of the lower structure. If the structures are of such heights that the levels of lights cannot be placed in identical horizontal planes, then the light units should be placed such that the center of the horizontal beam patterns do not face toward the adjacent structure. For example, structures situated north and south of each other should have the light units on both structures installed on a northwest/ Figs. 6, 7 and 8. southeast and northeast/southwest orientation. See Appendix 1, Three or More Adjacent Structures. The treatment of a cluster of structures as individaul structures or a complex will be spacing between structures. determined by the FAA as the regult of an aeronautical study, taking into consideration the structure's location, heights and Page 24 Chap. 6 Par. 17