AC 70/7460-1B 1 Oct 72 1 In lieu of installing the obstruction lights on the obstruction, a pole or poles of height slightly greater than the overall height of the obstruction may be installed on or adjacent to the obstruction and lighted in accordance with the specifications prescribed in Section 19a.
2 It is important that those towers, poles, or similar structures be installed in such a manner as to indicate the general definition and extent of the obstruction.
(c) In the event early or special warning is considered necessary to provide adequate protection for aircraft, the top lights on each obstruction as required under Section 19c(1) and 19c(2) above, should be replaced with described in Section 18a. one or more flashing 300 m electric code beacons as
(d) Where obstructions are extensive as in the case of a line of trees or hills, and the use of the fixed obstruction lights would be impracticable or inadequate, flashing or rotating hazard beacons may be used as an alternate to the fixed obstruction lights. Such beacons should be obstruction at intervals not exceedirg 3,000 feet, pro- vided at least three beacons are placed on any one side located on the highest points or edges of the extended or edge of the extensive obstruction to indicate a line of lights. The flashing or rotating beacons should be of the type described in Chapter 5 of this circular,
d. Bridges. accordance with the following specifications. However, where the bridge structure is over navigable water, approval of the lighting installation must be obtained from the Commandant of the United States Coast Guard to avoid interference with marine navigation. The superstructure of a bridge should be lighted in
(1) When the bridge Superstructure is not more than 1,50 feet in overall length: There should be installed at the approximate center of the highest point of the superstructure at least two lights, each light consisting of a lamp of at least 100 watts, enclosed in aviation red obstruction light globes, two lights should burn simultaneously and should be positioned The so as to insure unobstructed visibility of at least one of the lights from aircraft at any normal angle of approach, Page 34 Chap. 6 Par, 19
1 Oct 72 AC 70/7460-1B
(2) length: When the bridge superstructure is more than 150 feet in overall
(a) There should be installed for each 150 feet, or fraction thereof, of the overall length of the bridge superstructure one or more lights, each light consisting of a lamp i at least 100 watts, enclosed in aviation red obstructior light globes. These lights should be installed on the highest points of the superstructures at approximately equal intervals not exceeding 150 feet in a manner to indicate the general definition and extent of the obstruction, and to insure unobstructed visibility of the lights from aircraft at any normal angle of approach, The distance between these top lights may be increased to a distance not exceeding 600 feet when the particular bridge is located more than 15,000 feet from the reference point of any landing area.
(b) Where the bridge superstructure exceeds 150 feet in overall length and the use of the above described obstruction lights would be impracticable or inadequate, flashing or rotating hazard beacons should be used as an alternate to the fixed obstruction lights. Such beacons should be located on the highest points or edge of the bridge superstructure at intervals not exceeding 3,000 feet, provided at least three beacons are installed to indicate the extent of the obstruction. The flashing or rotating beacons should be of the type described in Chapter 5 of
e. Water Towers, Grain Elevators, Gas Holders, and Similar Obstructions.
should be lighted in accordance with the following specifications, Water towers, grain elevators, gas holders, and similar obstructions when the particular obstruction is:
Not more than 150 feet in overall height above ground, or water if so situated:
(a) At the top apply 18b(2).
(2) More than 150 feet but not more than 300 feet:
(a) At the top apply 18a(2).
(b) At the approximate midpoint of the overall height (as equidistant between the ground and the top of the structure as the shape of the obstruction will permit) apply 18b(2).
Chap. 6 Par. 19 Page 35
AC 70/7460-1B 1 Oct 72
(3) More than 300 feet but not more than 450 feet:
(a) At the top apply 18a(2).
(Б) At approximately two-thirds and one-third of the overall height apply 18b (2).
f. Group of Structural Hazards. Towers, poles, tanks, smokestacks, and similar obstructions which are so grouped as to present a common potential hazard to air navigation should be lighted in accordance
(1) This specification applies to a group of closely spaced towers, poles, tanks, smokestacks, or similar obstruction of approximately the same overall height above ground, or water it so situated, in which the spacing between the individual structures does not exceed 150 feet. The group may be considered an extensive obstruction and lighted in accordance with Section C.
"Prominent Buildings and Similar Extensive Obstructions."
This specification applies to a group of closely spaced towers, poles, tanks, smokestacks, and similar obstructions which may or may not be of the same overall height, in which the spacing between the individual structures is not in all cases equal to or less than 150 feet. Each prominent object within the group should be lighted in accordance with the specifications preobstructions of a corresponding overall height above ground, or water if so situated. scribed in the section for individual towers, poles and similar In addition, there 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, at least one rotating beacon producing aviation red flashes.
(b) The rotating beacon should be of the type described in Chapter 5 of this circular.
Page 36 Chap. 6 Par. 19
1 Oct 72 AC 70/7460-1B
g. Trees. A line of trees, with the individual trees located less than 150 feet apart, or a tree-covered area should be lighted as an extensive obstruction as specified in Paragraph 19c, Prominent Buildings and Similar Extensive Obstructions, with the obstruction lights mounted on poles or towers, of a height slightly greater than the height of the outstanding trees. Individual trees and widelyspaced trees should be lighted in accordance with the following specification: Poles of a height slightly greater than the height of the outstanding tree(s) should be installed adjacent to the tree(s) and lighted in accordance with Section 19a.
h. 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.
chap • • ar. is Page 37 (and 38)
1 Oct 72 AC 70/7460-1B * CHAPTER 7. STANDARDS FOR LIGHTING OBSTRUCTIONS TO AIR NAVIGATION WITH
HIGH INTENSITY WHITE OBSTRUCTION LIGHTS
20. PURPOSE. To provide the specifications for high intensity white obstruction lights to be placed on obstructions to air navigation.
21. APPLICATION, The general specifications which follow apply to the obstruction lighting of buildings, smokestacks and similar obstructions, she a may re odent that. except transmission lines and their support structures. These standards do not require modification of existing marking and lighting; however, the FAA may recommend that marking and lighting displayed on an existing structure, that would come within the scope of these standards, be modified if that structure is altered or replaced by a similar structure.
a. For Smokestacks and Similar Obstructions (Excluding Antenna Structures and Transmission Line Support Structures).
(1) There should be installed at the top (or near the top if a smokestack) of the obstruction, a light or lights in a manner o insure unobstructed visibility of at least one light from aircraft at any normal angle of approach. If the obstruction is solid by nature, such as a smokestack, there should be installed four such lights placed at regular intervals on the horizontal plane.
(2) For smokestacks and similar obstructions more than 300 feet but not more than 600 feet in overall height there should be installed one additional level of lights, (other than the top level), in such a position on the obstruction to insure unobstructed visibility of them from aircraft at any normal angle of approach.
For smokestacks and similar obstructions more than 600 feet in overall height there should be installed one additional level of lights (other than the top level) for each additional 400 feet, or fraction thereof, of total structure height.
(4) The angular adjustment of the beam peak above the horizon should be determined during the FAA aeronautical study to insure minimum effect on people residing near the structure and the greatest safety to airmen. The angular adjustment of the lights should be such that the beams of all lights do not strike the ground closer than three statute miles from the structure.
* Chap. 7 Par. 20 Page 39
AC 70/7460-1B 1 Oct 72
b. Antenna Towers and Similar Open Structures. Not applicable to these types of structures at this time.
22. SPECIFICATIONS.
High Intensity White Obstruction Lighting on Smokestacks and Similar Obstructions. To avoid the obscurant effect of the deposits generally in evidence from this type of structure, the top lights should be installed from 5 to 10 feet below the highest point of the structure. It is important that these lights be readily accessible to enable cleaning when necessary and to facilitate lamp replacements.
(1) When the height of the particular obstruction above ground or water, if so situated, is:
(a) Not more than 300 feet: At a near top level apply 2la(1).
(b) More than 300 feet but not more than 600 feet:
1 At a near top level apply 21a(1).
2 At a point equal to approximately one-half of the overall height apply 2la(2).
(c) More than 600 feet but not more than 1000 feet:
At a near top level apply 2la(1).
2 At approximately two-thirds and one-third of the overall height, apply two additional levels in accordance with 2la(3).
(d) More than 1000 feet but not more than 1400 feet:
1 At a near top level apply 21a(1).
2 At approximately three-fourths, one-half and one-fourth of the overall height apply three additional levels in accordance with 21a(3).
(e) More than 1400 feet but not more than 1800 feet:
1 At a near top level apply 2la(1).
2 At approximately four-fifths, three-fifths, two-fifths and one-fifth of the overall height apply four additional levels in accordance with 2la(3).
Page 40 Chap. 7 Par. 21
1 Oct 72 AC 70/7460-1B (E) More than 1800 feet but not more than 2100 feet:
At a near top level apply 21a(1).
At apped are stay thee overal it apply six additional levels in accordance with 2la(3).
b. Transmission lines.
(1) The catenary of transmission lines or similar obstructions should be identified in accordance with the following specifica- The towers, poles, or similar structures supporting such a line should be lighted in accordance with appropriate specifications in Paragraph 19a except as noted below:
(a) A system of three sequentially flashing white lights should be installed on each transmission line supporting structure (or adjacent terrain).
(b) Each light should flash at 60 flashes per minute. A plus or minus five percent tolerance due to environmental circumstances is allowed.
(c) One light should be at the top of the structure, one light should be at the height above ground or water of the lowest point in the catenary, and one light should be approximately midway between the other two lights.
middle light should normally be a minimum of 50 feet from the other two lights. The vertical and horizontal arrangements of the lights may be subject to the structural limits of the towers and/or adjacent terrain and a tolerance of 20 percent from uniform spacing of the bottom and middle light is allowed. If the base of the supporting tower (s) is higher than the lowest point in the catenary, such as a canyon crossing, one or more lights shall be installed on the adjacent terrain at the level of the lowest point of the span.
(d) The middle light should flash first, the top light should flash second and the bottom light should flash last.
OFF interval between the second and third light should be about twice as long as between the first and second light.
The interval between the end of one sequence and beginning of the next should be about ten times the interval between the first and second light. The ON time of any flash normally should not be less than 20 microseconds or more than 50 milliseconds. The ON time is the time when the instantaneous intensity exceeds the effective intensity. * Chap. 7 Par. 22 Page 41
AC 70/7460-1B 1 Oct 72
(e) The effective intensity 1/ for 180 degrees horizontal, centered on the transmission line, should be no less than 100,000 2/ candelas during the day and between 500 2/ to 1,000 2/ candelas during the night. The peak of the effective intensity should be approximately at the center of the beam. A tolerance of plus or minus five percent due to environmental circumstances is al-
(f) The horizontal beam spread, centered on the transmission line, should be 180 degrees.
(8) The vertical beam spread, to 50 percent of the effective intensity, should be no less than three degrees, and to than six degrees. ten percent of effective intensity, should be no less
(h) The lights should flash white and may be made up of one or more light fixtures at each level in order to obtain the specified horizontal spread, (i.e., two 90 degree lamps may be joined to produce 180 degrees total horizontal spread). All lights operated in the same direction should provide the required sequential operation in that direction.
(i) The lights should be adjustable and shielded so that the beam peak can be tilted up above the horizon to prevent glare from the light from disturbing persons on the ground. In the case of a transmission line(s) located within the approach area of a runway, shieiding and beam adjustment of the lights should also be employed to prevent blinding a pilot.
(i) A light sensitive control device control, or a manual switch should be provided time change the intensity of the light for operation from sunset to sunrise and vice versa.
1/ The effective intensity of the light should be determined from the Illuminating Engineering Society, Guide for Calculating the Effective Intensity of Flashing Signal Lights, published in Illuminating Engineering, Vol. LIX., p. 747 (Nov. 1964) (available from the New York 10017). Illuminating Engineering Society, 345 East 47th Street, New York, 21 Intensity sufficient to be adequately visible in the day and night at three miles in three miles meteorological visibility is desired.
Page 42 Chap. 4 Par. 22
1 Oct 72 AC 70/7460-18
(2) The area in the immediate vicinity of the base of the supporting structures should be cleared of all structures and objects of natural growth that could interfere with the line of sight between a pilot and the lights.
When this complete lighting system is employed, the following marking and lighting is not required:
(a) Spherical markers (Chapter 3, paragraph 8b);
(b) The marking of the supporting structures (Chapter 3, paragraphs 8 and 9), for the surface area having the same exposure covered by this lighting system; and,
(c) The installation of obstruction lights on the supporting structures (Chapter 6, paragraph 19), designed to serve the same exposure covered by this lighting system.
(4) The precise final adjustments of the system for each installation are subject to study by FAA field offices to insure the best optimum adjustments for residents and pilots.
Chap.
Par.
AC 70/7460-1B 1 Oct 72 CHAPTER 8. STANDARDS FOR DUAL LIGHTING SYSTEMS ON OBSTRUCIIONS TO AIR NAVIGATION
23. PURPOSE. To provide the specifications for dual obstruction lighting systems to be placed on obstructions to air navigation.
24. APPLICATION. obstruction lighting of buildings, smokestacks and similar obstructions, except transmission lines and their support structures. These standards do not require modification of existing marking and lighting; however The general specifications which follow apply to the the FAA may recomnend that marking and lighting displayed on an existing structure, that would come within the scope of these standards, be modified if that structure is altered or replaced by a similar structure.
25. SPECIFICATIONS.
a. Dual Obstruction Lighting Systems on Snokestacks and Similar Obstructions. Where both the red obstruction lighting and high intensity white obstruction lighting systems are to be used for night and day obstruction lighting respectively, the obstruction lights should be installed as follows:
(1) Structures not more than 150 feet: At a near top level apply 18b (2).
(2) Structures more than 150 feet but not more than 300 feet:
(a) Red lights, apply 19b(2) (b).
(b) White lights, at a near top level apply 21a(1).
(3) Structures more than 300 feet but not more than 450 feet:
(a) Red lights, apply 19b (2) (c).
(b) White lights, 1 At a near top level apply 2la(1).
At approximately two-thirds of the overall height apply 21a(2).
(4) Structures more than 450 feet but not more than 600 feet:
(a) Red lights, apply 19b(2) (d).
(b) White lights, 1 At a near top level apply 2la(1).
At approximately one-half of the overall height apply 2Ia(2).
Page 44 Chap. 8 Dar 22
1 Oct 72 AC 70/7460-1B
(5) Structures more than 600 feet but not more than 750 feet:
(a) Red lights, apply 19b(2) (e).
(Б) White lights, 1 At a near top level apply 2la(1).
2 At approximately four-fifths and two-fifths of the overall height apply 21a(3).
(6) Structures more than 750 feet but not more than 900 feet:
(a) Red lights, apply 19b(2) (f).
(b) White lights, 1 At a near top level apply 2la(1).
2 At approximately two-thirds and one-third of the overall height apply 2la(3).
(7) Structures more than 900 feet but not more than 1000 feet:
(а) Red lights, apply 19b (2) (g).
(b) White lights, 1 At a near top level apply 2la(1).
2 At approximately five-sevenths and two-sevenths of the overall height apply 21a(3).
(8) Structures more than 1000 feet but not more than 1050 feet:
(a) Red lights, apply 19b(2) (g).
(b) White lights, 1 At a near top level apply 21a(1).
2 At approximately five-sevenths, four-sevenths and two-sevenths of the overall height apply 2la(3).
(9) Structures more than 1050 feet but not more than 1200 feet:
(a) Red lights, apply 19b (2) (h).
(b) white lights, 1 At a near top level apply 21a(1).
At approximately three-fourths, one-half, and onefourth of the overall height apply zia(3).
(10) Structures more than 1200 feet but not more than 1350 feet:
(a) Red lights, apply 19b(2) (i).
White lights, 1 At a near top level apply 2la(1).
2 At approximately seven-ninths, four-ninths, and two-ninths of the overall height apply 2la(3).
Chap. 8 Darn 1.5
AC 70/7460-1B 1 Oct 72 * (11) Structures more than 1350 but not more than 1400 feet:
(a) Red lights, apply 19b(2) (j).
(b) White lights, 2 At approximately four-fifths, one-hall, 1 At a near top level apply 2la(1). fifth of the overall height apply 2la(3). and one-
(12) Structures more than 1400 feet but not more than 1500 feet: (a) Red lights, apply 19b(2)(j). White lights, 1 At a near top level apply 21a(1). At approximately four-fifths, three-fifths, two- 21a(3). fifths, and one-fifth of the overall height apply
(13) Structures more than 1500 feet but not more than 1650 feet:
(b) (a) Red lights, apply 19b (2) (k). White lights, At a near top level apply 2la(1). At approximately nine-elevenths, seven-elevenths, height apply 2la(3). tour-elevenths, and two-elevenths of the overall
(14) Structures more than 1650 feet but not more than 1800 feet: (b) (a) Red lights, apply 19b(2) (1). White lights, I At approximately five-sixths, seven-twelfths, five- 1 At a near top level apply 21a(1). 21a(3). twelfths, and one-sixth of the overall height apply
(15) Structures more than 1800 feet but not more than 1950 feet:
(a) Red lights, apply 19b (2) (m).
(b) White lights, 1 At a near top level apply 2la(1). At approximately eleven-thirteenths, nine-thirteenths, of the overall height apply 21a(3). six-thirteenths, four-thirteenths, and two-thirteenths Page 46 Chap. 8