AC 70/7460-1F 9/27/78 (Б) side fail. with these units to switch light sources should one reasonable time period. A transfer relay may be used Intermediate Level. Double units should be installed at intermediate levels when a malfunction of a single unit could create an unsafe condition, and in remote areas where maintenance cannot be performed within a C. Rated Lamp Voltage. To ensure the proper lumen output, the normal operation. the lamp socket with the lamp operating during the hours of should not be more than plus or minus 3 percent of the rated voltage of the lamp. operating voltage provided to the recommended obstruction lamp The input voltage should be measured at
d. Operation of Red Lights. Red obstruction lights should be operated if practical, face the north sky. the lights may remain on continuously. The sensing device should, rises to a level of not less than 58 footcandles (624.3 lux), or be turned on during daytime when a prominent unlighted object device should turn off the lights when the north sky illuminance cannot be seen from a distance of three statute miles. The control visibility is restricted. In Alaska, however, the lights should They should also be turned on during daytime when the flight surface to a level of not less than 35 footcandles (376.7 lux). by a satisfactory control device adjusted so the lights will be turned on when the north sky illuminance falls on a vertical e • Availability of Specifications.
(I) See Chapter 9. FAA. FAA Specifications CAA 446 and AC 150/5345-2 (L-810) are available free of charge fron the Department of Transportation.
(2) Forms Center. See Chapter 9.
f. Poles, Towers, and Similar Skeletal Structures. The following standards apply to radio and television towers, supporting struc- tures for overhead transmission lines and similar lacy structures.
(1) Top Mounted Obstruction Light.
(a) Structures Not More Than 150 Feet (46m) AGL. Two or more an aircraft at any normal angle of approach. steady burning lights should be installed in a manner to ensure unobstructed visibility of one or more lights from Page 18 Chap. 5 Par. 16
9/27/78 AC 70/7460-1F
(b) Structures Exceeding 150 Feet (46m). AGL. At least one 300mm flashing beacon should be installed in a manner to normal angle of approach. ensure unobstructed visibility from an aircraft at any
(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 should be installed two such beacons properly positioned on top of at least one beacon. of the main structure to permit unobstructed viewing
2. Appurtenances Exceeding 20 Feet (6m)• If a rod, (6m) in height is incapable of supporting a beacon, a supporting mast with one or more beacons should be antenna or other appurtenance greater than 20 feet height within 20 feet (6m) of the tip of the installed adjacent to the appurtenance and to a at least one beacon. appurtenance so as to permit unobscured viewing of
(2) and height of the structure. These lights should be mounted 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 from any normal angle of approach. so as to ensure unobstructed viewing of at least one light
(a) Steady Burning Lights.
Structures Not More Than 450 feet (137m) AGL. Two on diagonally or diametrically opposite positions. or more steady burning lights should be installed Structures Exceeding 450 Feet (137m) AGL. Install level. steady burning lights on each outside corner of each
(b) Flashing Beacons.
Structures Not More Than 450 Feet (137m) AGL. These of flashing beacons. structures normally do not require intermediate levels Par. 16 Page 19
AC 70/7460-1F 9/27/78 Structures More Than 450 feet (137n) AGL. 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 outof each level. side of diagonally or diàmetrically opposite positions
g. Chimneys, Flare Stacks and Similar Solid Structures.
(1) Top Mounted Obstruction Lights.
Structures Not More Than 150 Feet (46m) 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 approach. least two lights from aircraft at any normal angle of
(b) Structures Exceeding 150 Feet (46m) AGL. 300mm flashing beacons should be installed in a Two or more 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 facili- tate lamp replacements.
(2) Mounting Intermediate Levels.
(a) 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.
(b) Flashing Beacons. The number of beacon levels may be obtained from Appendix 2, Figs. 1-3.
1• Structures Not More Than 450 Feet (137m) AGL. These structures normally do not need intermediate levels of flashing beacons.
2. Structures Exceeding 450 Feet (137m) AGL. 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.
Page 20 Chap. 5 Par. 16
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 (46m) apart, the group of obstructions may be considered an extensive obstruction. Prominent buildings and similar extensive obstructions should display steady burning obstruction lights in a manner to indicate the extent of the obstruction as Structures Not More Than 150 Feet (46m) in Either Horizontal Direction. If the structure/extensive obstruction is not more than 150 feet (46m) 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.
Structures More Than 150 Feet (46m) in at Least One Horizontal Direction. If the structure/extensive obstruction is more than 150 feet (46m) in either or both horizontal dimensions, at least one steady burning obstruction light should be displayed for each 150 feet (46m), 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 (46m) 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 near a landing area, the edge nearest the landing area should be lighted.
(3) Special Warning. Flashing or rotating beacons may be used in lieu of steady burning obstruction lights in the event early or special warning is considered necessary. Such beacons should be displayed on the highest points of an extensive obstruction at intervals not exceeding 3,000 feet (915m). At least three beacons should be displayed on one side of the extensive obstruction to indicate a line of lights.
Group of Obstructions. If individual objects within a group of obstruction are not the same height and are spaced more than 150 feet (46m) 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.
Chap. 5 Par. 16 Page 21
AC 70/7460-1F 9/27/78
(5) Obstructions More Than 150 Feet (46m) AGL. Steady burning obstructions 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 (46m), 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.
í• 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 obstruction and installed on or adjacent to the structure.
Chap. 5 Page 22 Par. 16
9/27/78 AC 70/7460-1F CHAPTER 6. HIGH INTENSITY OBSTRUCTION LIGHTING STANDARDS
17. 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 However, the overall height of the main structure excluding all appur- in accordance with FAR, Part 77, Objects Affecting the Navigable Airspace.
tenances, 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 20m 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
a. High Intensity Obstruction Light. The lighting systems referred to sions of the latest issuance of FAA Advisory Circular 150/5345-43, in the following standards should conform with the applicable provi- FAA/DOD Specification I-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 lights units are unique in the case of supporting structures of overhead transmission lines. (See paragraph 17.j.)
(1) Effective Intensity. Day Mode - no less than 200,000 candelas (100,000 candelas for transmission line supporting structures);
approximately 4,000 candelas. twilight mode - approxinately 20,000 candelas; night mode -
(2) Intensity Step Changing. The systems should automatically vertical surface is as follows: change intensity steps when the north sky illumination on a
(a) Pium Tion drops Day-to-Twilight. This should not occur before the 11lumination drops to 60 footcandles (645.8 lux), but should occur before its drops below 30 footcandles (322.9 lux). The 11luminance sensing device should, if practical, face the north sky.
(b) Twilight-to-Night. This should not occur before the 1llumination drops to five footcandles (53.8 lux), but 1ux) • should occur before it drops below two footcandles (21.5 Chap. 6 Par. 17 Page 23
AC 70/7460-1F 9/27/78
(c) Night to Day• above should be reversed in transitioning from the night to day mode. The intensity changes listed in (a) and (b)
(3) Flash Rate. All light units should flash simultaneously at 40 unique sequencing of catenary systems.) pulses per minute. (See paragraph 17.j. for flash rate and
(5) 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 in synchronism with the high intensity lighting system, be of approximately the same intensity as the twilight mode during appurtenances• directional white light, similar in size to the 300mm red flashing beacon, for installation on top of antennas or similar the high intensity lighting system provide for a small omni- Antenna or Similar Appurtenance Light. The specifications for fied to provide full light intensity at possible collision altitudes above the structure will receive only stray light. altitudes with the structure while persons on the ground or at Beam Spread. A relatively narrow vertical beam spread is speci- This light should operate 24 hours a day, flash
d. to the horizontal. at the bottom. The top light should normally remain at zero degrees each light may be adjusted upward, in one degree increments, starting zontal) as shown below. If additional adjustments are necessary, dents. Should elevating the light beam be necessary, it is recommended that the beam be elevated (in degrees above the hori- miles (5km) from the structure to prevent irritation to nearby resi- the light beam above the horizontal. The beam of the light at the lower level should not strike the ground closer than three statute situations dictate, it may be desirable to use louvers and/or elevate degrees elevation. Where terrain, nearby residential areas or other installation would be for all light units to be installed at zero ment from zero to eight degrees above the horizontal. The normal Installation Guidance. The manufacturing specifications provide for the peak intensity of the light beam to be capable of angular adjust- Flashtube Replacements. The flashtubes in a light unit should be supporting structures of overhead transmission lines). 200,000 candelas (100,000 candelas for systems installed on the replaced when the peak effective daytime intensity falls below Page 24 Chap. 6 Par. 17
Level of Number of Levels of Lights Installed Light 2 Top 5 4
- 1
- 2 2 1 2 2 2 BOTTOM - 2 2 3 3 Figures indicate degrees of elevation above the horizontal.
High Intensity Light Units. The high intensity capacitor discharge light units known to date which meet the FAA/DOD Specification L-856 are not omidirectional, except for the light used on antennas or for 360 degrees of coverage about a structure to ensure that the than one light unit is required in order to obtain 200,000 candelas similar appurtenances. See paragraph 17 b.(5). Therefore, more system is visible from aircraft at any normal angle of approach.
(1) Numbers 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 similar solid structures. On structures having an antenna levels indicated in Appendix 2, Figs. 4-6, for chimneys and 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, Figs. 7-9. The light levels reommended for other structures, i,e., cooling towers, supporting structures of catenaries and buildings, may be found under the appropriate
(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 Par. 17 Page 25
AC 70/7460-1F 9/27/78
(b) Structures Exceeding 20 Feet (6m) But Not More Than 100 Feet (31m)• Four light units per level.
(c) Structures Exceeding 100 Feet (31m) But Not More Than 200 Feet (61m). Six light units per level.
(₫) Structures Exceeding 200 Feet (61m). 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 elevation, would be lower than surrounding terrain, trees or adjacent building(s). See Appendix 1, Fig. 7. In certain instances, as determined by an FAA aeronautical study, the elimination of the lowest level may be permissible.
Two Adjacent Structures. Where two structures are situated within 200 feet (61m) of each other and the light units will be installed at the same levels, the sides of the structures facing each other need not be lighted; therefore, the inboard lights may be eliminated. However, all lights on both structures must flash in synchronism. Minor adjustments in the vertical placement of the lights to either or both of the structure's intermediate 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 1dentical 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 individual structures or a complex will be spacing between structures. determined by the FAA as the result of an aeronautical study, taking into consideration the structure's location, heights and Page 26 Chap. 6 Par. 17
9/27/78 AC 70/7460-1F level of lights may be installed from five (1.5m) to 10 feet (3m) Normally, the top level of light units are installed on the highest deposits generally emitted by this type structure. below the top. This is to avoid the obscurant effects of the point of a structure. However, in the case of chimneys, the top viewing of the system from aircraft at any normal angle of approach. Chimneys, Flare Stacks and Similar Solid Structures. The number of The light units should be installed in a manner to ensure unobstructed units recommended for each level is dependent on the outside dia- meter of the structure but should in no case be less than three. levels of lights recommended depends on the height of the structure and may be obtained from Appendix 2, Figs. 4-6. The amount of light h• Radio and Television Towers and Similar Skeletal Structures.
in a manner to ensure unobstructed viewing from aircraft at any normal angle of approach. Mounting of Lights. The number of levels recommended depends on the height of the structure, excluding antennas and similar At least three lights should be installed on each level and mounted so that the effective intensity over the full beam is not impaired by the structural members, They should be mounted appurtenances, and may be obtained from Appendix 2, Figs. 7-9.
(2) the light units. Ice Shields. Where climatic conditions dictate, metal grates or similar protective ice shields should be installed directly over each light unit to prevent falling ice accumulation from damaging
(3) Top Level of Lights. One level of lights should be installed at unobscured viewing of at least one beacon, be installed adjacent to the appurtenance and to a height within 20 feet (6m) of the tip of the appurtenance so as to permit If the appurtenance (such as a whip antenna) is incapable of supporting the omnidirectional light, one or more beacons should 20 feet (6m) above the main structure, a white capacitor discharge omnidirectional light should be mounted on the highest point. the main skeletal structure. If the rod or antenna is more than
(4) shown in Appendix 2, Figs. 7-9. Intermediate Levels of Lights. The intermediate levels of lights should be installed at approximately the same heights
1. Hyperbolic Cooling Towers.
(1) Mounting of Obstruction Lights. The light units should be Chap. 6 least two lights from aircraft at any normal angle of approach. installed in a manner to ensure unobstructed visibility of at Par. 17 Page 27
AC 70/7460-1F 9/27/78 More than one light unit should be visible to provide the required intensity about the structure and to indicate to pilots the magnitude of the structure.
(2) Top Level of Obstruction Lights. The number of light units recommended depends on the diameter of the structure at the top• See paragraph 17.e.(2).
(3) Structures Exceeding 600 Feet (183m) AGL. Structures greater than 600 feet (183m) AGL should have one additional level of light units installed approximately mid-point on the structure and in line with the top level of lights.
j. Supporting Structures of Overhead Transmission (Catenary) Lines.
(1) Purpose. The purpose of marking the supporting structures of overhead transmission lines with a unique, sequentially flashing lighting system is to warn pilots of the presence of the support catenary line. structures themselves and to alert pilots that they support a
(2) Mounting of Obstruction Lights. A system of three levels of sequentially flashing light units should be installed on each supporting structure (or adjacent terrain) of an overhead transmission line. One level should be installed at the top of the structure, one at the height of the lowest point in the catenary, and one level at approximately midway between the other two lights. The middle level should normally be a minimum of 50 feet (15m) from the other two levels. If the installation of the top level of lights presents a potential danger to maintenance personnel, or is necessary for lightning protection, such lights may be mounted from five (1.5m) to 10 feet (3m) below the highest point of the structure.
(a) Flash Sequence. The flash sequence should be middle level, top level and bottom level with all lights on the same level flashing simultaneously. The time delay between flashes of the levels is designed to present a unique system display similar to a flash of lightning.
(Б) Flash Rate. Each series of flashes is repeated 60 times every minute.
(o) rest de not Synchronization. Although desirable, the corresponding light levels on associated supporting towers of a catenary crossing need not flash simultaneously.
Page 28 Chap. 6 Far. 17
9/27/78 AC 70/7460-1F Horizontal Coverage. Two or more light units should be on the transmission line. Where a catenary crossing is plane such as to provide 180 degrees of coverage centered installed at each light level and directed on a horizontal transmission lines. vide the most effective light coverage to warn pilots approaching from either direction of the presence of the situated near a bend in a river, canyon, etc., the direction of the horizontal beam pattern should be directed to pro- Variation. The vertical and horizontal arrangments of in the span. is higher than the lowest point in the catenary, such as on the adjacent terrain at the level of the lowest point a canyon crossing, one or more lights should be installed 20 percent from uniform spacing of the bottom and middle light is allowed. If the base of the supporting structure(s) the lights may be subject to the structural limits of the towers and/or adjacent terrain and a tolerance of Special Cases. Where lighting systems are installed on sup- should not derogate the intended purpose of the lighting horizontal light direction may be necessary. This adjustment In these cases, shielding or an adjustment to the vertical or vessel operators or pilots on an approach to an airport. airport approach areas, etc., caution should be exercised to ensure that the lights do not cause a hazard to motorists, porting structures located near vehicular bridges, waterways, So section lagre Area Surrounding Support Structures. The area in the immediate could interfere with the line-of-sight between a pilot and vicinity of the base of the supporting structures should be cleared of all structures and objects of natural growth that Omission of Standard Marking. When the high intensity obstruc- tion lighting system is used to identify a catenary line crossing, the following marking and lighting may be omitted:
(a) Markers. Spherical markers on the lines.
(b) Paint. The marking of the supporting structures for the system. surface area having the same exposure covered by this lighting chap. 6 Red Obstruction Lights. The installation of red obstruction lights on the supporting structures serving the same exposure covered by the high intensity obstruction lighting system.
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