AC 70/7460-1A 1 Jan 72
(3) More than 300 feet but not more than 450 feet:
(a) At the top apply 18a(1).
(b) At approximately two-thirds and one-third of the overall height apply 18b(2).
f. Group of Structural Hazards. Towers, poles, tanks, smokestacks, accordance with the following specifications: common potential hazard to air navigation should be lighted in and similar obstructions which are so grouped as to present a
(1) This specification applies to a group of closely spaced towers, Obstructions." Section C. tures does not exceed 150 feet. an extensive obstruction and lighted in accordance with poles, tanks, smokestacks, or similar obstruction of approxi- mately the same overall height above ground, or water if so situated, in which the spacing between the individual struc- ¿'Prominent Buildings and Similar Extensive The group may be considered
(2) This specification applies to a group of closely spaced towers, between the individual structures is not in all cases equal to poles, tanks, smokestacks, and similar obstructions which may or may not be of the same overall height, in which the spacing similar obstructions of a corresponding overall height above prescribed in the section for individual towers, poles and ground, or water if so situated. or less than 150 feet. Each prominent object within the group should be lighted in accordance with the specifications
(a) In addition, there should be installed at the top of a least one rotating beacon producing aviation red flashes. located near the center of the group of obstructions, at prominent center obstruction or on a special tower
(b) The rotating beacon should be of the type described in Chapter 5 of this circular.
Page 36 Chap. 6 Par. 19
1 Jan 72 AC 70/7460-1A
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. 6 Par. 19 Page 37 (and 38)
1 Jan 72 AC 70/7460-1A * 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, except transmission lines and their support structures. These standards do not require modification of existing marking and lighting; however, he 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 struc-
Structures and Transmission Line Support Structures).
There should be installed at the top (or near the top if a smokestack) of the obstruction, a light or lights in a manner to 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.
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.
(3) 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.
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.
Par. 20 Page 39
AC 70/7460-1A 1 Jan 72 * b. Antenna Towers and Similar Open Structures, Not applicable to these types of structures at this time.
22. SPECIFICATIONS.
a. High Intensity White Obstruction Lighting on Smokestacks and facilitate lamp replacements. readily accessible to enable cleaning when necessary and to point of the structure. It is important that these lights be deposits generally in evidence from this type of structure, the top lights should be installed from 5 to 10 feet below the highest Similar Obstructions. To avoid the obscurant effect of the
(1) When the height of the particular obstruction above ground or water, if so situated, is:
Not more than 300 feet: At a near top level apply 21a(1).
(b) More than 300 feet but not more than 600 feet:
ž 1 At a near top level apply 21a(1). At a point equal to approximately one-half of the overall height apply 21a(3).
More than 600 feet but not more than 1000 feet: 1 At a near top level apply 2la(1). 2 At approximately two-thirds and one-third of the ance with 2la(3). overall height, apply two additional levels in accord-
(d) More than 1000 feet but not more than 1400 feet: I At approximately three-fourths, one-half and one- 1 At a near top level apply 21a(1). levels in accordance with 21a(3). fourth of the overall height apply three additional More than 1400 feet but not more than 1800 feet: 1 At a near top level apply 21a(1).
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 Jan 72 AC 70/7460-1A (£) More than 1800 feet but not more than 2100 feet:
1 At a near top level apply 21a(1).
2 At approximately five-sixths, two-thirds, one-half, one-third, and one-sixth of the overall height apply six additional levels in accordance with 2la(3).
Transmission lines.
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.
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. The 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.
The middle light should flash first, the top light should flash second and the bottom light should flash last. The 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 70/7460-1A . 1 Jan 72 *
(e) The effective intensity 1/ for 180 degrees horizontal, five percent due to environmental circumstances is al- Lowed. 500 2/ to 1,000 2/ candelas during the night. The peak than 100,000 2/ candelas during the day and between the center of the beam. A tolerance of plus or minus of the effective intensity should be approximately at centered on the transmission line, should be no less
(f) The horizontal beam spread, centered on the transmission line, should be 180 degrees.
(g) The vertical beam spread, to 50 percent of the effective intensity, should be no less than three degrees, and to ten percent of effective intensity, should be no less than six degrees.
The lights should flash white and may be made up of one horizontal spread). All lights operated in the same direction should provide the required sequential opera- tion in that direction. lamps may be joined to produce 180 degrees total the specified horizontal spread, (i.e., two 90 degree or more light fixtures at each level in order to obtain ployed to prevent blinding a pilot. The lights should be adjustable and shielded so that and beam adjustment of the lights should also be em- cated within the approach area of a runway, shielding the ground. In the case of a transmission line(s) lo- prevent glare from the light from distrubing persons on the beam peak can be tilted up above the horizon to
(j) A light sensitive control device, an automatic time control, or a manual switch should be provided to sunset to sunrise and vice versa. change the intensity of the light for operation from New York 10017). Intensity of Flashing Signal Lights, published in Illuminating Illuminating Engineering Society, 345 East 47th Street, New York, Engineering, Vol. LIX., p. 747 (Nov. 1964) (available from the The effective intensity of the light should be determined from the Illuminating Engineering Society, Guide for Calculating the Effective Intensity sufficient to be adequately visible in the day and night at three miles in three miles meteorological visibility is desired. * Page 42 Chap. 7 Par. 22
1 Jan 72 AC 70/7460-1A * (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.
(3) 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. 7 Par. 22 Page 43
AC 70/7460-1A
- Jan 72 * NAVIGATION CHAPTER 8. STANDARDS FOR DUAL LIGHTING SYSTEMS ON OBSTRUCTIONS TO AIR
23. PURPOSE. To provide the specifications for dual obstruction lighting systems to be placed on obstructions to air navigation.
24. structure, that would come within the scope of these standards, be modified if that structure is altered or replaced by a similar structure. APPLICATION. The general specifications which follow apply to the obstruction lighting of buildings, smokestacks and similar obstructions, the FAA may recommend that marking and lighting displayed on an existing except transmission lines and their support structures. These standards do not require modification of existing marking and lighting; however,
25. SPECIFICATIONS.
a. Dual Obstruction Lighting Systems on Smokestacks and Similar intensity white obstruction lighting systems are to be used for night and day obstruction lighting respectively, the obstruction lights should be installed as follows: Obstructions. Where both the red obstruction lighting and high
(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 2la(1).
(3) Structures more than 300 feet but not more than 450 feet:
(a) Red lights, apply 19b (2) (c). (b) White lights, I At approximately two-thirds of the overall height 1 At a near top level apply 2la(1). 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 21a(1).
At approximately one-half of the overall height apply 21a(2).
* Page 44 Chap. 8 Par. 23
1 Jan 72 AC 70/7460-1A * (5) Structures more than 600 feet but not more than 750 feet:
Red lights, apply 19b(2) (e).
White lights, 1 At a near top level apply 2la(1).
I 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 21a(1).
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:
(b) (a) White lights, Red lights, apply 19b (2) (8).
1 At a near top level apply 2la(1).
. 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 2la(1).
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 2la(1).
2 At approximately three-fourths, one-half, and onefourth of the overall height apply 2la(3).
(10) Structures more than 1200 feet but not more than 1350 feet:
(a) Red lights, apply 19b(2) (1).
(b) White lights, 1 At a near top level apply 21a(1).
At approximately seven-ninths, four-ninths, and twoninths of the overall height apply 2la(3). * Chap. 8 Par. 25 Page 45
AC 70/7460-1A 1 Jan 72 * (11) Structures more than 1350 but not more than 1400 feet:
(a) (b) White lights, Red lights, apply 19b(2) (j).
1 At a near top level apply 2la(1).
2 At approximately four-fifths, one-half, and one- fifth of the overall height apply 2la(3).
(12) Structures more than 1400 feet but not more than 1500 feet:
(a) Red lights, apply 19b(2) (j).
(b) White lights, 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:
(a) Red lights, apply 19b(2) (k).
(b) White lights, . At a near top level apply 21a(1).
2 At approximately nine-elevenths, seven-elevenths, tour-elevenths, and two-elevenths of the overall height apply 21a(3).
(14) Structures more than 1650 feet but not more than 1800 feet:
(a) Red lights, apply 19b(2) (1).
(b) White lights, 1 At a near top level apply 2la(1).
2 At approximately five-sixths, seven-twelfths, five- 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 2la(3). six-thirteenths, four-thirteenths, and two-thirteenths Page 46 Chap. 8 Par. 25
1 Jan 72 AC 70/7460-1A
(16) Structures more than 1950 feet but not more than 2100 feet:
(a) Red lights, apply 19b(2) (n).
(b) White lights, 1 At a near top level apply 2la(1).
- At approximately six-sevenths, nine-fourteenths, onehalf, five-fourteenths, and one-seventh of the overall height apply 2la(3).
b. Antenna Towers and Similar Open Structures. Not applicable to these types of structures at this time.
Chap. 8 Par. 25 Page 47 (and 48)
1 Jan 72 AC 70/7460-1A Appendix 1
DOUBLE OBSTRUCTION
LIGHT FITTING (Fresnel Globe)
ONILL HOTT (Fresnel Globe) 300 mm ELECTRIC CODE BEACON (Fresnel Lens) 24-Inch Double End 24-Inch Single End 36-Inch Double End ROTATING BEACONS Page 1