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
1 Oct 72 AC 70/7460- 1B
(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 21a(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 Oct 72 AC 70/7460- 1B Appendix 1
DOUBLE OBSTRUCTION
LIGHT FITTING (Fresnel Globe)
SINGLE OBSTRUCTION
LIGHT FITTING (Fresnel Globe) 300 mm ELECTRIC CODE BEACON (Fresnel Lens) 24-Inch Double End 24-Inch Single End 36-Inch Double End ROTATING BEACONS Pace 1
AC 70/7460-1B 1 Oct 72 Appendix i A-More than 150 ft. but not more than 300 fl.
A -Not more than 150 fl.
A-More than 300 ft. but not more than 450 ft.
PAINTING AND LIGHTING OF TOWERS, POLES AND SIMILAR OBSTRUCTIONS Page 2
1 Oct 72 AC 70/7460-1B Appendix i Not less than 5 ft.
nor more than 10 ft.
Not less than 5 ft.
nor more than 10 ft Special double obstruction light
SUSPENSION TYPE
OBSTRUCTION LIGHT
INSTALLATION A-More than 300 ft. but not more than 450 fl.
A-Not more than 150 ft.
PAINTING AND LIGHTING OF SMOKESTACKS AND SIMILAR OBSTRUCTIONS Page 3
AC 70/7460-1B Appendix 1 1 Oct 72
LIGHTING MARKING LIGHTING MARKING A-More than 150 ft. but not more than 300 fl. A and B- 15 ft. A and B-Not more A -5 ft. or more B-Not more than 150 ft. or more than 150 ft. B-Less than 15 ft.
PAINTING AND LIGHTING OF WATER TOWERS AND SIMILAR OBSTRUCTIONS Page 4
1 Oct 72 AC 70/7460-1B Appendix 1
LIGHTING
MARKING A-More than 150 ft. but not more than 300 ft. A and B- 15 ft. or more B-Not more than 150 ft.