Previous version - Standard 621.19 - Standards Obstruction Markings - 2000/06/01

Preamble

The Standards Obstruction Markings Manual has been updated and revised to include the specifications governing design requirements and quality assurance tests for any light required under these standards. Accordingly, the Manual was also brought into line with the structure of the Canadian Aviation Regulations (CARs) and related standards.

Although compliance to the Standards Obstruction Markings is voluntary, it is recommended that persons planning to erect a building or structure likely to be hazardous to aviation safety because of its height and location still abide by these standards as the Minister may, by Order, direct the owner or persons in control of such building or structure found to be hazardous to aviation safety, to mark it and light it in accordance with these standards.

For your ease of reference, please note that the text in italics is information in support of the standards.

NOTE:

In the French version of the Standards Obstruction Markings, the terms "marque" and "balise" have the same meaning as "balisage"; while the terms "feu" and "balise lumineuse" have the same meaning as "éclairage". Both terms "balise" and "éclairage" stems from the verbs "baliser" and "éclairer" which are used in CAR 601.19.
(amended 2000/06/01; no previous version)

CHAPTER 1 - INTRODUCTION

1.1 Incorporation by Reference and Authority for Publication

These Standards are incorporated by reference under subsection 5.9(3) of the Aeronautics Act and published under the authority of section  601.19 of the Canadian Aviation Regulations, reproduced below for information purposes only:

Where it is likely that a building, structure or object, including an object of natural growth, is hazardous to aviation safety because of its height and location, the Minister may, by order, direct the owner, or other person in control of the building, structure or hazard, to mark it and light it in accordance with the standards specified in the Standards Obstruction Markings Manual.

1.2 Responsibilities

1.2.1 Responsibility of the Minister

It is the responsibility of the Minister to assess individual obstructions, namely buildings, structures or objects, to determine if they are likely to constitute a hazard to air navigation and consequently require marking and/or lighting in accordance with the standards identified as such in this publication.

NOTE:

If it has been determined that a planned construction might create an obstruction to air navigation for a Department of National Defence (DND) aerodrome, the appropriate DND authorities are to be advised.

1.2.2 Responsibility of Owners of Structures

Persons planning to erect an obstruction, namely a building, structure or object, including a moored balloon, either permanently or temporarily, should contact the appropriate regional Civil Aviation authority, as specified in Appendix A, as early as possible and provide the following information on the planned obstruction, using the Aeronautical Obstruction Clearance Form (#26-0427) as shown in Appendix C:

  1. (a) location;

    1. (i) latitude and longitude (indicate if NAD 27 or NAD 83 datum is used),

    2. (ii) indicated on a 8 1/2" x 11" portion of 1:50,000 scale map;

  2. (b) overall height in metres and feet above sea-level;

  3. (c) overall height in metres and feet above ground level;

    1. (i) side view drawing with dimensions,

    2. (ii) shielded objects indicated on side view and location map. Indicate if shielded object marked and lighted;

  4. (d) start and completion dates of construction;

  5. (e) date of proposed removal, if the obstruction is of a temporary nature; and

  6. (f) name, address and telephone number of owner or person in control of obstruction.

1.3 Definitions

Appurtenance - That part of any vertical mast, pole or other appendage added to a building, structure or object that protrudes above the top of the building, structure or object; (servitude)

Beam Spread - The angle between the two directions in the vertical or horizontal plane in which the intensity is equal to 50 percent of the minimum specified peak beam effective intensity; (angle d'ouverture du faisceau)

Catenary - The curved span of overhead wires hung freely between two or more supporting structures, normally with regard to exceptionally long elevated spans over canyons, rivers and deep valleys; (caténaire)

Effective Intensity - The effective intensity of a flashing light is equal to the intensity of a steady-burning (fixed) light of the same color which produces the same visual range under identical conditions of observation; (intensité efficace)

Fixed Light - (see Steady Burning Light) (feu fixe or feu permanent)

Flight Visibility - The average forward horizontal distance from the cockpit of an aircraft in flight, at which prominent unlighted objects may be seen and identified by day and prominent lighted objects may be seen and identified by night; (visibilité en vol)

Lighting - Any light displayed on an obstruction as a means of indicating the presence of the obstruction; (feu or balisage lumineux)

Markers - An object displayed on an obstruction during daytime as a means of indicating the presence of relatively invisible obstructions such as power lines; (balise)

Marking - A symbol, group of symbols, or markers that are displayed on the surface of an obstruction and intended to reduce hazards to aircraft by indicating the presence of the obstruction by day; (marque or marquage)

Meteorological Visibility - The greatest distance, expressed in statute miles, that selected objects (visibility markers) or lights of moderate intensity at night (25 candela) can be seen and identified under specific conditions of observation; (visibilité météorologique)

Painting - Marking applied to the surface of an obstruction and intended to identify the presence of the obstruction by day; (marque de peinture)

Steady Burning Light or Fixed light - A light having constant luminous intensity when observed from a fixed point; (feu permanent or feu fixe)

Units of Light Specification - Refer to Figure 1-1; (unités photométriques)

  1. (a) Lumen - Unit of the luminous flux output from a light fixture.

  2. (b) Candela -Unit of the luminous intensity of light emitted from a light fixture in a specific direction within a solid angle (steradian).

  3. (c) Lux - Unit of illuminance of light falling upon a surface area. May be expressed as lumens per square metre or photons per second per square metre.

NOTE:

Imperial unit of illuminance is "footcandle". Simple approximate conversion factor:
10 lux = 1 footcandle.

Vertical Aiming Angle - The angle formed between the horizontal and a line through the centre of the vertical beam spread; (calage en site)

Figure 1-1 - Units of Measurement of Light

CHAPTER 2 - GENERAL

2.1 Purpose of Standards

The purpose of obstruction marking and lighting is to provide an effective means of indicating the presence of likely hazards to aviation safety.

More specifically, the marking and lighting standards are aimed at ensuring that an obstruction to air navigation remains visible at a range sufficient to permit a pilot to take appropriate action in order to avoid the obstruction by not less than 305 m (1,000 feet) vertically within a horizontal radius of 610 m (2,000 feet) from the obstruction.

2.2 Obstructions Requiring Marking and/or Lighting

Unless otherwise provided for in these standards, the following obstructions should be marked and/or lighted in accordance with the standards specified therein:

  1. (a) any obstruction penetrating an airport Obstacle Limitation Surface as specified in the Aerodrome Standards and Recommended Practices Manual - TP 312;

  2. (b) any obstruction greater than 90 m (300 feet) AGL within 2 nautical miles of the imaginary centre line of a recognised VFR route such as, but not limited to, a valley, a railroad, a transmission line, a pipeline, a river or a highway;

  3. (c) any permanent catenary wire crossing where any portion of the wires or supporting structures exceed 90 m (300 feet) AGL;

  4. (d) any obstructions greater than 150 m (500 feet) AGL; and

  5. (e) any other obstruction to air navigation that is assessed as a likely hazard to aviation safety in accordance with paragraph 2.3.1(a).

2.3 Transport Canada Aeronautical Evaluations

The Minister may perform an Aeronautical Evaluation with respect to the following types of obstructions:

  1. (a) obstructions greater than 90 m (300 feet) AGL, but not exceeding150 m (500 feet) AGL;

  2. (b) catenary wire crossings, including temporary crossings, where the wires or supporting structures do not exceed 90 m (300 feet) AGL;

  3. (c) obstructions less than 90 m (300 feet) AGL; and

  4. (d) any other obstruction specified in these standards.

2.3.1 Purpose of Aeronautical Evaluations

Aeronautical Evaluations are used by the Minister:

  1. (a) to determine, for the purposes of section 2.2, whether or not it is likely that an obstruction to air navigation is a likely hazard to aviation safety; or

  2. (b) where expressly provided for in these standards, to specify alternative modes of complying with the obstacle marking and lighting standards while ensuring that the visibility requirement set out in section 2.1 is met.

2.3.2

Subject to any specific limit set out in these standards, an Aeronautical Evaluation conducted under paragraph 2.3.1(b) above may result in the Minister approving alternate:

  1. (a) colour of the obstruction;

  2. (b) dimensions of colour bands or rectangles;

  3. (c) colours and types of lights;

  4. (d) basic signals and intensity of lighting;

  5. (e) night/day lighting combinations;

  6. (f) flashing rate of lights; and

  7. (g) portions of the obstruction to be marked and/or lighted (i.e: the object may be located with respect to other objects or terrain so that a lesser portion of it only needs to be marked and/or lighted).

2.4 Aeronautical Evaluation Guidelines

2.4.1

The following factors are normally considered by the Minister during an Aeronautical Evaluation:

  1. (a) the location of buildings, structures or objects on high terrain;

  2. (b) surrounding topography;

  3. (c) VFR air traffic density;

  4. (d) the presence of atmospheric conditions which would affect ceiling and flight visibility; and

  5. (e) the proximity of obstructions to water aerodromes and heliports.

2.4.2

Attached to these standards as Appendix C is the form normally used to record basic data for the purposes of conducting an Aeronautical Evaluation.

2.5 Shielding

The principle of shielding established below may be employed in an Aeronautical Evaluation when assessing the need to apply the marking and lighting standards to buildings, structures or objects, and accepting the application of lesser obstruction marking and lighting standards.

2.5.1 Principle of Shielding

The principle of shielding may be applied in a way that a dominant permanent building, structure or object which is marked and/or lighted, obviates the need for marking and/or lighting other buildings, structures or objects in the immediate surrounding area, which might otherwise be treated as individual obstructions.

More specifically, the principle of shielding may be applied if the marking and/or lighting of a dominant permanent building, structure or object is assessed as providing sufficient warning to aircraft that, in avoiding the dominant obstruction, they will also avoid the unmarked or unlighted obstructions in the immediate surrounding area without risk of collision.

2.5.2 Two Adjacent Similar Obstructions

Where two similar obstructions of equal height are situated adjacent to each other, one of two obstructions is shielded provided the separations listed in Table 2-1 are not exceeded.

Table 2-1
Height of Obstructions
AGL
Separation
Metres (feet) Metres (feet)
30 to 75 (100 to 249) 15 (50)
76 to 122 (250 to 399) 23 (75)
123 to 198 (400 to 649) 30 (100)
199 to 290 (650 to 949) 45 (150)
291 and higher (950 and higher) 60 (200)
2.5.3 Adjacent Narrow and Large Obstructions

A narrow obstruction is shielded when it is situated with respect to a large obstruction so that an aircraft, whose flight path would avoid the large obstruction would, as a result, also avoid the narrow one.

The effectiveness of the shielding will depend upon the way in which the normal path of the aircraft is orientated in relation to the general orientation of the large and narrow obstructions.

2.5.4 Adjacent Cable Spans

A cable span across a recognized VFR route in a valley or along a watercourse does not require marking and/or lighting where it is shielded by a large obstruction such as a bridge or a higher cable span.

More specifically, a cable span segment is shielded when it is situated within 610 m (2,000 feet) of the dominant obstruction so that it remains below a sloping down surface at a gradient of 5% projected from the adjacent edges of the dominant obstruction. (Refer to Figure 2-1).

If the second cable span is above the gradient, this span is not shielded and should be marked or lighted in accordance with the applicable standards.

2.5.5 Cluster of Structures

Where it is not possible to apply a uniform standard to a cluster of obstructions such as industrial plants, oil refineries, thermal generating stations, and similar structures, they should be assessed on an individual basis to determine whether or not they should be treated as likely hazards to aviation safety or as an extended obstruction, taking into account the structure's location, height and spacing.

When treated as an extended obstruction, sufficient marking and lighting should be provided to ensure that the extent of the obstruction is defined and adequate visual warning, as referred to in section 2.1, is provided from any normal angle of aircraft approach.

Figure 2-1 - Shielding of Cable Spans

CHAPTER 3 - DAY MARKINGS

3.1 Paint Markings - General

3.1.1 Standard Colours of Paint

Alternate sections of international orange (hereafter to be referred to as "orange") and white paint provide maximum visibility of an obstruction by contrast of colours.

Subject to section 3.1.2, where alternate sections of orange and white paint markings are required under these standards, the colours of paint markings should conform with the United States Federal Standard FED-STD-595, namely:

  1. (a) Orange no. 12197; and

  2. (b) White no. 17875.

Specifications describing the technical characteristics of various paints and their application techniques may be obtained from:

GSA - Specification Section
470 L'Enfant Plaza
Suite 8100
Washington, DC 20407
Telephone: (202) 755-0325

3.1.2 Alternative colours

Where the use of orange and white colours required under section 3.1.1 is considered to be aesthetically unacceptable, the Minister may approve:

  1. (a) alternative colour schemes, provided:

    1. (i) the colours conform with the basic visibility criteria of section 2.1; and

    2. (ii) the paint meets the other specifications of section 3.1.1 above, or

  2. (b) the use of plastic wrap pole marking in lieu of painting.

3.1.3 Maintenance of Paint Quality on Obstructions

Subject to section 3.1.4, the surfaces of structures required to be marked with paint should be repainted whenever a colour is changed or whenever its effectiveness is reduced significantly by such factors as scaling, oxidization, chipping, or layers of industrial contamination.

3.1.4 Surfaces Not Requiring Paint

Where the smoothness of a painted surface would create a potential hazard to maintenance personnel, the ladders, decks and walkways of structures are exempt from the painting requirements of section 3.1.3 above, provided that the effectiveness of overall marking on a structure is not significantly reduced.

Paint may also be omitted from other critical surfaces, if it has an adverse effect upon signal transmissions.

3.1.5 Painting Skeletal Structures

Paint markings should be applied to all inner and outer surfaces of skeletal structures. This standard applies to supporting structures of overhead transmission lines, communications towers, and similar skeletal structures.

3.2 Solid Pattern

A structure required to be marked should be coloured a solid orange, if the structure's horizontal and vertical dimensions are less than 3.2 m (10.5 feet) respectively.

3.3 Checkerboard Pattern

Subject to sections 3.3.3 to 3.3.4, alternate rectangles of orange and white should be displayed on the appropriate surfaces of buildings and on the following types of structure:

  1. (a) water, gas, and grain storage tanks; and

  2. (b) large structures of 3.2 m (10.5 feet) or more across, having a horizontal dimension that is equal to or greater than the vertical dimension.

3.3.1 Size of Rectangles

Unless the dimensions and the shape of a structure otherwise dictate, the sides of the checkerboard rectangles should measure not less than 1.5 m (5 feet) and no more than 5 m (20 feet), the angles being as nearly square as possible and the corner surfaces being coloured in orange.

3.3.2 Roofs

Where it is not practical to paint the roof of a structure in a checkerboard pattern, the roof should be coloured solid orange.

3.3.3 Spherical Structures

Where part or all of a spherical structure does not permit exact application of a checkerboard pattern, the shape of the rectangle should be modified to suit the shape of the structure.

3.3.4 Storage Tanks

Where the shape of a storage tank does not permit the use of a checkerboard pattern, the structure should be coloured by alternating bands of orange and white, or a limited checkerboard pattern applied to the upper one-third of the structure. The skeletal framework of certain water, gas and grain storage tanks may be excluded from the checkerboard pattern.
(Refer to Figure 3-1).

3.4 Alternate Bands

Alternate bands of orange and white should be displayed on the following types of structure:

  1. (a) communications towers and supporting structures of overhead transmission lines;

  2. (b) poles;

  3. (c) chimneys;

  4. (d) skeletal framework of storage tanks and similar structures;

  5. (e) structures that appear narrow from a side view, that are 3.2 m (10.5 feet) or more across, and the horizontal dimension is less than the vertical dimension;

  6. (f) buildings with horizontal siding; and

  7. (g) wind turbine towers and rotor blades.

3.4.1 Characteristics of Bands

The width of bands on structures 3.2 m (10.5 feet) to 150 m (500 feet) in height should be equal, provided that each band has a width not less than 0.5 m (1.5 feet) nor more than 30 m (100 feet). The bands should be perpendicular to the vertical axis, and those at the top and bottom coloured orange. There should be an odd number of bands on the structure. Each band should be approximately 1/7 of the height of the structure up to 213.5 m (700 feet) and 30.5 m (100 feet) in width for structures over 213.5 m (700 feet). The width of all bands should be equal and in proportion to the structure's height. If the top of the structure has a cover or roof, the highest orange band should be continued to cover the entire top of the structure.

To simplify painting of individual structural members or complete structure sections, they may be painted prior to final assembly. In order to accommodate approximations in proportionate band widths, the pre-painting of individual standard length structural sections should be completed in 3.2 m (10 feet) or 7.5 m (20 feet) incremental sections with application as detailed in Figure 3-4.

3.4.2 Wind Turbine Rotor Blades

Wind turbine rotor blades should be marked, front and back, with three bands of orange and white paint beginning with an orange band at each tip, the bands being approximately the same width as those on the supporting tower, as indicated in Figure 3-5.

The remaining inner blade area may be any colour.

3.5 Marking of Power Lines

3.5.1 Support Structures

Support structures of power lines should be painted in alternate bands of orange and white in accordance with section 3.4, and be clear of trees and brush insofar as practicable so as to be clearly visible in each direction from which an aircraft is likely to approach.

3.5.2 Shore and Tower Base Markers

Where according to an Aeronautical Evaluation the markings of support structures would not clearly indicate the presence of aerial wire and cables, the shore and tower base markers, as indicated in Figure 3-3, should be painted orange and white, and be either of the panel or pole type.

3.5.3 Aerial Cable Markers

Where according to an Aeronautical Evaluation other methods of marking are inadequate or not practicable, aircraft warning markers should be displayed on aerial wires and cables, as indicated in Figure 3-3 and specified below:

  1. (a) Dimensions - Cable spherical markers should be 50 cm (20 inches), 75 cm (2.5 feet) or 150 cm (5.0 feet ±15 cm (0.5 feet)) in diameter.

    Other dimensions may be acceptable as determined by an Aeronautical Evaluation as providing adequate visibility. Refer to section 2.1.

  2. (b) Spacing - The 50 cm (20 inch) diameter spherical markers should be spaced at intervals of approximately 30 m (100 feet). The 75 cm (2.5 feet) diameter spherical markers and conical markers should be spaced at intervals of approximately 45 m (150 feet). The 150 cm (5 feet) diameter spherical markers should be spaced at intervals of 90 m (300 feet) to 120 m (400 feet). Where the associated span is relatively short, not less than two markers should be used. The markers should be displayed on the highest wire or by other means at the same height.

  3. (c) Staggered Installation - Where there is more than one wire at the highest level, the spheres may be installed alternately along each wire, as indicated in Figure 3-3, as long as the distance between adjacent markers meets the spacing standard. This method will allow the weight and wind loading factors to be distributed.

  4. (d) Pattern - Overhead wires should be marked by alternating solid colour spheres of orange and white. An orange sphere should be placed at each end of the overhead wire and spacing adjusted to accommodate the rest of the spheres. When less than four spheres are needed, they should be orange.

    An alternating colour scheme is the most conspicuous pattern against all backgrounds.

3.5.4 Lighting for Day Marking

Where support structures or a power line crossing are assessed in an Aeronautical Evaluation as likely to be inadequately marked by painting and markers, the support structures should be lighted for day marking by the use of medium or high intensity white flashing obstruction lighting in accordance with the standards specified in Chapter 6 or 7, as the case may be.

Figure 3-1 - Day Marking - Checkerboard Pattern

Figure 3-2 - Day Marking - Alternate Bands

Figure 3-3 - Day Marking - Markers for Cable Spans

Figure 3-4 - Day Marking - Pre-painting of Skeletal Structures - Acceptable Approximations of Band Widths  Download PDF

Figure 3-5 - Wind Turbines Day Marking - Alternate Bands

CHAPTER 4 - DAY/NIGHT LIGHTING

4.1 Lighting Systems

Lighting is primarily installed on obstructions in order to warn pilots of a potential collision during nighttime operations. If the lighting is of sufficient intensity, however, it may also serve to give warning during daytime operations and may be approved, by way of an Aeronautical Evaluation, in lieu of other means of day marking.

Any light required under these Standards to be used for day or night obstruction lighting should comply with the specifications of Appendix B governing design requirements and quality assurance tests.

Obstruction lighting displayed on structures consists of one of the systems described in the following provisions.

4.1.1 Red Obstruction Lighting System

Subject to section 4.1.2, a red obstruction lighting system should be used for night marking on structures 150 m (500 feet) AGL or less, and consists of steady burning aviation red lights as illustrated in Figure 5-1(a) and flashing aviation red beacons as illustrated in Figure 5-1(b), when orange and white paint is required to be used for day marking.

4.1.2 Medium Intensity White Flashing Obstruction Lighting System

A medium intensity white flashing obstruction lighting system should have an omnidirectional photometric output and automatically selected intensity modes of day/twilight (20,000 effective candela) and night (2,000 effective candela).

  1. (a) Medium intensity white flashing obstruction lighting systems may be used instead of a red obstruction lighting system and in place of high intensity white flashing obstruction lighting systems, including those required for the supporting structures of catenary wires, where an Aeronautical Evaluation assesses such substitution as acceptable. When used on supporting structures of catenary wires, reference to the standards specified in Chapter 8 with the exception of intensity and beam spread, should be made.

  2. (b) Where a medium intensity white flashing obstruction lighting system is operated 24 hours a day on obstructions 150 m (500 feet) AGL or less, daytime marking standards do not apply.

  3. (c) A medium intensity white flashing obstruction lighting system may be used on structures exceeding 150 m (500 feet) AGL only if daytime marking is also used.

  4. (d) Because of possible distracting or disabling glare to motorists, vessel operators, and pilots on approach to an airport, a medium or high intensity white flashing obstruction lighting system should not be installed at heights less than 60 m (200 feet) AGL, unless assessed as acceptable in an Aeronautical Evaluation.

  5. (e) Where the height of a structure necessitates the installation of a high intensity white flashing obstruction lighting system, a medium intensity white flashing obstruction lighting system may be used to mark its appurtenances, in accordance with the standards specified in Chapter 7.

4.1.3 High Intensity White Flashing Obstruction Lighting System

Subject to section 4.1.2, a high intensity white flashing obstruction lighting system should have a unidirectional photometric output and automatically selected operational modes for day (200,000 effective candela or 100,000 effective candela for support structures of catenary lines), twilight (20,000 effective candela) and for night (2,000 effective candela).

  1. (a) A high intensity white flashing obstruction lighting system should be used only for the lighting of a structure exceeding 150 m (500 feet) AGL in height, unless assessed as necessary for a lower structure in an Aeronautical Evaluation. When this system is operated 24 hours a day, daytime marking standards do not apply.

  2. (b) A high intensity white flashing obstruction lighting system should be either of two types:

    1. (i) Simultaneously flashing levels of lights - Where there is an appurtenance greater than 12 m (40 feet) above a structure requiring high intensity white flashing lighting, a medium intensity omnidirectional white flashing light unit should be installed on top of the appurtenance and flash in unison with the levels of high intensity obstruction lights as specified in Chapter 7; or

    2. (ii) Sequentially flashing levels of lights installed on the support structures of an extensive span of transmission lines (catenary) over rivers, canyons and deep valleys - The lights should be controlled in a fashion such that there is a unique system display to indicate the top of the support structures and lowest elevation of the catenary, as specified in Chapter 8.

4.1.4 Dual Lighting

Where, due to glare problems, it is not practical to install medium or high intensity white flashing obstruction lighting systems for nighttime marking, a dual lighting system consisting of red obstruction lighting for nighttime marking and the applicable white flashing obstruction lighting for daytime marking should be installed. Subject to the paragraphs 4.1.2(b) and (c), when this type of dual lighting system is used, daytime obstruction marking standards do not apply.

4.2 General Provisions

4.2.1 Temporary Obstruction Lights
  1. (a) When a likely hazard to aviation safety is present during the construction of a structure, at least two obstruction lights should be installed at the uppermost part of the structure so as to permit unobstructed viewing of at least one light.

  2. (b) Wherever an Aeronautical Evaluation assesses the type of obstruction lighting system that would be the permanent installation for the completed structure, the temporary lighting should be of the same type. In addition, as the height of the structure exceeds each level at which permanent obstruction lights will be required, two or more similar lights should be installed at that level. The lights should be positioned so as to ensure unobstructed viewing of at least one light at each level by a pilot on a potential collision course.

  3. (c) Except for periods when they would interfere with construction, temporary red lights should be operated during periods of darkness and reduced flight visibility. Temporary high or medium intensity white lights should be operated 24 hours a day or until all of the permanent obstruction lights are in operation. If practicable, the permanent obstruction lights should be installed and operated at each level as construction progresses.

    1. (i) Aviation Red Obstruction Lights - Each steady burning temporary light should emit at least 32.5 candela of aviation red light in all horizontal directions.

    2. (ii) White Obstruction Lights - Each temporary light should conform to the standards specified in Chapters 7 and 8, as applicable. The flashes of various fixtures on a structure do not have to be simultaneous.

  4. (d) When the installation of temporary lights is not possible, floodlighting may be used.

4.2.2 Temporary Construction Equipment

Since there is such a variance in construction cranes, derricks, oil and other drilling rigs, it is recommended to consider each case individually.

4.2.3 Floodlighting

A moored balloon, chimney, church steeple or similar obstruction not exceeding 150 m (500 feet) AGL may be floodlit by means of fixed search light projectors that should be installed at three or more equidistant points about the base of the obstruction and provide an average illumination of 150 lux over the top one-third of the obstruction.

4.2.4 Group of Obstructions

If individual objects within a group of obstructions are not the same height and are spaced more than 45 m (150 feet) apart, the prominent objects within the group should be lighted in accordance with the standards for individual obstructions of a corresponding height. In addition, at least one flashing red beacon or medium intensity white light should be installed at the top of a prominent centre obstruction.

However, if there is no prominent centre obstruction, then an Aeronautical Evaluation will be performed to assess the location of the applicable beacons.

4.2.5 Modified Ground Level

The elevation of the tops of the buildings in congested areas should be used as the equivalent of the ground level when determining the proper number of light levels required to adequately light an obstruction.

4.2.6 Monitoring of Obstruction Lighting

Although some obstruction lighting systems have redundant features, close monitoring by visual or automatic means remains an essential aviation safety feature. Hence, the following standard.

Obstruction lighting systems should be closely monitored by visual or automatic means as follows:

  1. (a) obstruction lighting without automatic monitoring should be visually monitored once every 24 hours;

  2. (b) where obstruction lighting is not accessible for visual monitoring, a properly maintained automatic monitor should be used to provide indication that the system or portion thereof is not functioning properly. The monitor should be designed to register the malfunction of any light on the obstruction regardless of its position;

  3. (c) the monitor output should be located in an area generally occupied by authorized personnel. Both red and white light systems should be monitored;

  4. (d) all obstruction lighting should be visually inspected on a regular basis. Lamps should be replaced after being operated for not more than 75 percent of their rated life. Flashtubes are exempted from this replacement standard; and

  5. (e) the owner/operator of the obstruction should advise the nearest regional Civil Aviation authority as specified in Appendix A, as soon as possible, of any obstruction lighting unserviceabilities so that an appropriate NOTAM action can be initiated.

4.2.7 Glare from Flashing Obstruction Lights
  1. (a) Where obstruction lighting is likely to distract operators of aircraft, railway trains, surface vessels, and other vehicles, or if the lighting will be in a congested residential area, a suitable shield should be installed on the appropriate lights to minimize the adverse effects of the light.

  2. (b) In the proximity of navigable waterways or along coastal regions, the installation of an obstruction lighting system should be coordinated with marine authorities in order to avoid interference with marine navigation.

4.2.8 Photometric Specification

White flashing obstruction lighting should conform to the specifications of photometric output of light fixtures as shown in Tables 6-1, 7-1 and 8-1 which specify the requirements for effective intensity in the horizontal and vertical beam spreads. The effective intensity should be determined by standard integration formulas for strobe-type lights.

CHAPTER 5 - RED OBSTRUCTION LIGHTING SYSTEMS

5.1 Characteristics of Red Obstruction Lighting

Unless otherwise specified in these standards, a red obstruction lighting system should consist of a combination of steady burning aviation red lights and flashing red beacons.

5.1.1 Maintenance

To ensure the proper light output of a flashing red beacon or steady burning red light, the operating voltage provided at the lamp socket should not vary by more than 3 percent from the rated voltage of the lamp. This voltage should be measured during the hours of normal operation. When the lamp is replaced, the same lamp or an approved alternate should be used.

5.1.2 Operation of Red Obstruction Lights

A red obstruction lighting system should be operated continuously or turned on and off by means of an acceptable automatic photoelectric control device having an on/off setting between 300 lux and 600 lux of northern sky illuminance.

5.2 Flashing Red Beacons

A flashing red beacon used in a red obstruction lighting system should:

  1. (a) produce aviation red light;

  2. (b) produce red light flashes having each a peak effective intensity of at least 1,500 candela, measured at any horizontal azimuth angle;

  3. (c) have a flashing mechanism that does not permit more than 40 nor fewer than 20 flashes per minute; and

  4. (d) be lighted from one-half to two-thirds of the total on/off cycle.

5.3 Steady Burning Red Lights

The intensity of light emitted by each lamp within a steady burning red light unit should not be less than 32.5 candela in aviation red colour, with distribution of light as indicated in Table 5-1 (refer to Figure 5-1).

Table 5-1
Angle
(degrees above horizontal)
Intensity
(percentage of total intensity)
-15 to 0 5
0 to 2.5 40
2.5 to 12.5 100
12.5 to 15 40
15 to 30 15
30 to 90 5
5.3.1 Mandatory Use of Dual Steady Obstruction Lights

For the purposes of this Chapter, a "single light unit" means a light unit containing a single lamp only, and a "dual light unit" means a light unit containing two lamps.

The provision of two lamps under this standard is for reason of redundancy.

Subject to section 5.3.2, dual light units containing at least two lamps, each enclosed within an aviation red globe should be used as follows:

  1. (a) a red obstruction dual light unit should be installed as a top light unit, at each end of a row of single light units at the top level, in areas or locations where the failure of a lamp would cause the obstruction to be totally unlighted when viewed by the pilot of an approaching aircraft;

  2. (b) the top level of a structure 45 m (150 feet) AGL or less, should have one or more dual lights units installed at the highest point and operated simultaneously; and

  3. (c) when a malfunction of a single light unit could create an unsafe condition, and in remote areas where maintenance cannot be performed within a reasonable period of time, at least two dual light units should be installed at each intermediate level on a structure. Both light units should be operated simultaneously or a transfer relay may be used to switch to the spare light should the active side fail.

5.3.2 Permitted Use of Single Red Obstruction Light Units

Where more than one steady burning red light is required to be installed either horizontally or vertically for red obstruction lighting, a single red light unit may be used:

  1. (a) on the top level of structures such as airport electronic navigational aid buildings and horizontal structures such as building roof outlines; and

  2. (b) on intermediate levels of skeletal and solid structure having more than one level of lighting and more than one single light unit on each level;

provided that maintenance for lamp replacement or repair can be accomplished within a reasonable period of time.

5.4 Appurtenances

5.4.1

The location of the light levels to be installed on a red obstruction lighting system should be a function of the combined height of the main structure and any appurtenance.

5.4.2

Where an appurtenance is less than 12 m (40 feet), the determined location of intermediate light levels should be maintained, but the top light may be placed at the base of the appurtenance. If such placement does not allow unobstructed viewing of the top light by the pilot, additional lights should be installed.

5.4.3

Where the appurtenance is more than 12 m (40 feet), the top light should be installed on the top of the appurtenance. If the appurtenance is not capable of carrying the light unit, the light may be mounted on the top of an adjacent mast.

5.5 Poles, Towers and Similar Skeletal Structures

The following standards apply to communications towers, supporting structures or overhead transmission lines, and similar skeletal structures.

5.5.1 Top Mounted Obstruction Light
  1. (a) On structures 45 m (150 feet) AGL or less, two or more steady burning lights should be installed.

  2. (b) On structures exceeding 45 m (150 feet) AGL, at least one red flashing beacon should be installed.

5.5.2 Lights Mounted at Intermediate Levels

The number of levels of lights should be in accordance with Figure 5-2. The number of lights at each level should be determined by the shape and height of the structure. The lights should be installed so as to provide an unobstructed view of at least one light by a pilot on a potential collision course. More specifically:

  1. (a) in the case of steady burning red lights,

    1. (i) for structures 107 m (350 feet) AGL or less, two or more steady burning red lights should be installed on diagonally or diametrically opposite positions,

    2. (ii) for triangular shaped structures 107 m (350 feet) AGL or less, two red light units, single or double, should be installed provided that at least one can be viewed unobstructed from any normal angle of approach. If this is not possible, then three red light units should be installed, one on each apex of the triangular cross-section, and

    3. (iii) for structures exceeding 107 m (350 feet) AGL, steady burning red lights should be installed on each outside corner at each level; and

  2. (b) in the case of flashing red beacons on structures exceeding 107 m (350 feet) AGL but not exceeding 150 m (500 feet) AGL, a red flashing beacon should be installed within the structure proper, except that if the structural members impair the viewing of the beacon, then two flashing red beacons should be installed on the outside of diagonally or diametrically opposite positions at each level.

5.6 Chimneys, Flare Stacks and Similar Solid Structures

5.6.1 Top Mounted Red Obstruction Lights

Red Obstructions lights mounted at the top of chimneys, flare stacks or similar solid structures should meet the following requirements:

  1. (a) on structures 45 m (150 feet) AGL or less, at least three steady burning red obstruction lights should be installed at regular intervals on the horizontal plane at or near the top, in a manner to ensure an unobstructed view by the pilot of an approaching aircraft;

  2. (b) on structures exceeding 45 m (150 feet) AGL, two or more flashing red beacons should be installed in a manner to ensure an unobstructed view by the pilot of an approaching aircraft; and

  3. (c) on chimneys, red lights may be displayed as low as 6 m (20 feet) below the tops of chimneys in order to avoid the obscuring effect of the deposits generally emitted by this type of structure. These lights should be readily accessible for cleaning and lamp replacement.

5.6.2 Mounting at Intermediate Levels
  1. (a) In the case of steady burning lights, at least three lights should be mounted on each intermediate level to ensure an unobstructed view of at least two lights on each level by the pilot of an approaching aircraft.

    The recommended number of light levels is contained in Figure 5-2.

  2. (b) In the case of flashing beacons, the required number of beacon levels should be in accordance with Figure 5-2. Where the structure exceeds 107 m (350 feet) AGL, two or more flashing beacons should be installed on each level to allow an unobstructed view of at least one beacon by the pilot of an approaching aircraft.

5.7 Prominent Buildings and Similar Extensive Structures

Individual obstructions having a similar height above ground and located not more than 45 m (150 feet) apart within a group of obstructions may be considered as an extensive obstruction for lighting purposes, in which case they should display steady burning red lights to indicate the extent of the obstruction as specified from section 5.7.1 to section 5.7.3 inclusively.

5.7.1 Structures 45 m (150 feet) or Less in Both Horizontal Dimensions

If the extensive obstruction is 45 m (150 feet) or less in both horizontal dimensions, at least one steady burning obstruction light should be displayed on the highest point at each end of the major axis of the obstruction. If this method of lighting is impractical because of the shape of the obstruction, then a double obstruction red light may be displayed in the centre of the highest point (refer to Figure 5-4).

5.7.2 Structures Exceeding 45 m (150 feet) in any Horizontal Dimension

If the extensive obstruction exceeds 45 m (150 feet) AGL in any horizontal dimension, at least one steady burning obstruction light should be displayed for each 45 m (150 feet) 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 at each end of the obstruction. Additional lights should be displayed on the highest points along the 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 (refer to Figure 5-4).

5.7.3 Structures Exceeding 45 m (150 feet) AGL

Steady burning obstruction lights should be installed at the top of an obstruction as specified in sections 5.5.1 and 5.5.2. At intermediate levels, steady burning lights should be displayed for each 45 m (150 feet) 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 the outside corner on each level with the remaining lights evenly spaced between the corner lights (Refer to Figure 5-4).

5.8 Bridges

Obstruction lighting for bridges that are assessed as likely hazards to aviation safety are subject to an Aeronautical Evaluation.

Red obstruction lighting or medium/high intensity white flashing obstruction lighting, as applicable, should be installed on bridges as shown in Figure 5-5.

5.9 Wind Turbines

A wind turbine should have a flashing red beacon mounted on the highest practical point of the turbine as indicated in Figure 5-6.

Figure 5-1 - Red Obstruction Lighting Light Units

Figure 5-2 - Red Obstruction Lighting Light Levels

Figure 5-3 - Red Obstruction Lighting Towers, Poles And Similar Structures

Figure 5-4 - Red Obstruction Lighting Prominent Buildings

Figure 5-5 - Obstruction Lighting Bridges

Figure 5-6 - Wind Turbines

CHAPTER 6 - MEDIUM INTENSITY WHITE FLASHING OMNIDIRECTIONAL OBSTRUCTION LIGHTS

6.1 Application

The standards contained in this Chapter govern the use of medium intensity lighting.

Refer to Chapter 8 for additional standards applicable to catenaries.

6.2 Characteristics

6.2.1 Photometric Output

A medium intensity white flashing system should provide white flashing output with the photometric characteristics specified in Table 6-1.

Table 6-1
Operation
Mode
Minimum
Effective
Intensity
(candelas)
Peak
Effective
Intensity
(candelas)
Minimum
Beam Spread
(degrees)
Horizontal - Vertical
day/twilight
night
7500
750
20,000 (1)
2,000 (1)
360 (2) 3 (3)
360 (2) 3 (3)

NOTE (1): Tolerance of plus or minus 25%.

NOTE (2): Multiple light units may be required to achieve horizontal coverage where the structure would partially shield a single unit.

NOTE (3): Refer to paragraph 6.3.3.

6.2.2 Flash Rate

The flash rate of a medium intensity white flashing system should be 40 flashes per minute, plus or minus 5 percent.

6.2.3 Flash Duration

The flash duration of a medium intensity white flashing system should be 0.1 to 0.25 seconds for the night intensity only. When the effective flash duration is achieved by a group of short flashes, the short flashes should be emitted at a rate of not less than 30 per second.

6.2.4 Intensity Control

The medium intensity white flashing system should be controlled so as to provide day, twilight and night modes of operation, in conformity with the values of Northern sky illuminance specified in Table 6-2.

Table 6-2
Mode Illuminance Change
(lux)
day to twilight
twilight to night
night to twilight
twilight to day
between 300 and 600
between 20 and 50
between 20 and 50
between 300 and 600

6.3 Use of Medium Intensity Lighting

6.3.1 Alternative to Red Obstruction Lighting

The medium intensity white flashing obstruction lighting system may be used as an alternative to the red obstruction lighting system. Refer to Chapter 5.

6.3.2 Appurtenances

A medium intensity white flashing omnidirectional light unit should be used for top indication of appurtenances higher than 12 m (40 feet) where the main structure is required under these standards to have high intensity white flashing obstruction lighting.

6.3.3 Vertical Aiming

The actual beam spread of manufactured light units may be in excess of the minimum requirement of Table  6-1 .

For installation, the lower limit of the beam should be set between minus 1 degree and plus 0.5 degrees of the horizontal, the lower limit being the point at which the beam intensity exceeds the minimum requirements.

6.3.4 Levels of Light Units

The levels of light units for medium intensity white flashing obstruction lighting should meet the specifications of Figure 6-2.

This figure is similar to Figure 5-2 for red obstruction lighting, except that the lowest mounting height normally is limited to 60 m (200 feet) AGL. Refer to paragraph 4.1.2(c).

6.4 Supporting Structures of Catenary Wires

Medium intensity white flashing obstruction lighting may be used to warn the pilot of an approaching aircraft of the presence of supporting structures of catenary wires, provided that no portion of the obstruction exceeds 150 m (500 feet) AGL, and provided that an Aeronautical Evaluation assesses it as acceptable. In such instances the light units should be mounted and operated sequentially as specified in Chapter 8.

6.5 Flashtube Replacement

The flashtubes in a light unit should be replaced upon failure, when the peak effective intensity falls below 15,000 effective candela (20,000 candela minus 25 percent), or at the manufacturer's recommended intervals, whichever occurs first.

Figure 6-1 - Medium Intensity White Flashing Obstruction Lighting Typical Light Unit

Figure 6-2 - Medium Intensity White Flashing Obstruction Lighting Mounting Levels

CHAPTER 7 - HIGH INTENSITY WHITE FLASHING OBSTRUCTION LIGHTS - GENERAL

7.1 Application

The standards contained in this Chapter govern the use of high intensity lighting. In addition, Chapter 8 contains specific lighting standards applicable to the support structures of catenary wire crossings.

7.2 Characteristics

7.2.1 Typical Light Units

In a high intensity white flashing obstruction lighting system, a minimum of three light units should be installed at each mounting level in order to provide 360 degree coverage.

This standard stems from the fact that individual light units in a high intensity white flashing system are not omnidirectional.

7.2.2 Photometric Output

A high intensity white flashing obstruction lighting system should provide white flashing output with the photometric characteristics specified in Table 7-1.

Table 7-1
Operation
Mode
Minimum
Effective
Intensity
(candelas)
Peak
Effective
Intensity
(candelas)
Minimum
Beam Spread
(degrees)
Horizontal - Vertical
day
twilight
night
100,000
7500
750
200,000 (1)
20,000 (2)
2,000 (2)
360 (3) 3 to 7
360 (3) 3 to 7
360 (3) 3 to 7

NOTE (1): Minimum.

NOTE (2): Tolerance of plus or minus 25%.

NOTE (3): Effective beam coverage.

7.2.3 Beam Spread

A relatively narrow vertical beam spread should be emitted as specified in Table 7-1 to provide full light intensity at possible collision altitudes with the structure so that persons on the ground or at altitudes sufficiently above the structure receive only minimum light. The actual horizontal beam spread of manufactured light units should be either 90 or 120 degrees, such that either 3 or 4 lights are needed to provide the 360 degree effective coverage at each level.

7.2.4 Flash Rate

All light units should flash simultaneously at 40 flashes per minute, plus or minus 5 percent.

7.2.5 Flash Duration

The flash duration of a high intensity white flashing system should be 0.1 to 0.25 seconds for the night intensity only. When the effective flash duration is achieved by a group of short flashes, the short flashes should be emitted at a rate of not less than 30 per second.

7.2.6 Intensity Control

The high intensity white flashing obstruction lighting should be controlled in a manner to provide day, twilight and night modes of operation. Control should be such that the operation for a particular mode occurs for the values of Northern sky illuminance specified in Table 7-2.

Table 7-2
Mode Illuminance Change
(lux)
day to twilight
twilight to night
night to twilight
twilight to day
between 300 and 600
between 20 and 50
between 20 and 50
between 300 and 600

7.3 Vertical Aiming

7.3.1 Installation

The top light should be set at zero degrees to the horizontal and all other lights should be installed in accordance with the specifications of Table 7-3.

The manufacturing specifications provide for the peak intensity of the light beam to be adjusted from zero to 8 degrees above the horizon.

Table 7-3
Height of Light Unit
in Metres (feet) AGL
Degrees of
Elevation
exceeding 150 (500)
122 to 150 (401 to 500)
90 to 122 (301 to 400)
less than 90 (300)
0
1
2
3
7.3.2 Higher Aiming

Where terrain, nearby residential areas or other situations dictate, the light beam should be elevated further above the horizon. The main beam of light at the lowest level should not strike the ground closer than 5 kilometres (3 miles) from the structure. If additional adjustments are necessary, the lights should be individually adjusted upward, in one degree increments, starting at the bottom.

Caution: Higher elevation angles may reduce conspicuity by raising the beam above the collision course flight path. This adjustment should not derogate from the intended purpose of the lighting system.

7.3.3 Special Cases

Where a high intensity white flashing lighting system is installed on a structure located near highways, waterways, airport approach areas and similar sensitive areas, shielding or an adjustment to the vertical or horizontal aiming may be approved through an Aeronautical Evaluation to ensure that the lights do not distract or otherwise cause a hazard to motorists, vessel operators, or to pilots on an approach to an airport.

Caution: This adjustment should not derogate from the intended purpose of the lighting system.

7.4 Number of Light Units per Level

At least three lights should be installed on the outside diameter of the structure. The light units should be installed on each level in a manner to ensure an unobstructed view of the system by a pilot.

The number of light units recommended per level (except for the supporting structures of catenary wires of cable spans and buildings) is dependent upon the horizontal coverage from each light unit and is further dependent upon the average outside diameter of the specific structure and the horizontal beam width of the light unit. The number of light units indicated in Table 7- 4 are the minimum.

Table 7-4
Structure Diameter
Metres (feet)
Light Units per Level
less than 6 (20)

6 to 30 (20 to 100)

31 to 60 (101 to 200)

more than 60 (200)
3

4

6

8

7.5 Relocation or Omission of Light Units

Light units should be installed on a structure in such a manner that the light distribution and intensity is not disrupted by the structure.

  1. (a) Lowest Level of Lights: The lowest level of light units may be installed at a higher elevation than normal on a structure if the surrounding terrain, trees or adjacent buildings would obscure the lights. In exceptional circumstances, the lowest level of lights may be assessed through an Aeronautical Evaluation as not being necessary.

  2. (b) Two Adjacent Structures: When two structures are situated 150 m (500 feet) or less from each other and the light units are installed at the same levels, the sides of the structures facing each other need not be lighted; therefore, the inboard lights may be omitted, provided that all lights on both structures flash simultaneously. Minor adjustments in the vertical placement of the lights to either or both of the structure's intermediate levels of lights may be approved through an Aeronautical Evaluation in order to place the lights on the same horizontal plane. Where one structure is higher than the other, one or more complete level of lights should be installed on that part of the higher structure which extends above the lower structure. If the structures are of such height that the levels of lights cannot be placed in identical horizontal planes, then the light units should be placed in such a way that the centre of the horizontal beam patterns of each structure does 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 Northeast/Southwest and Northwest/Southeast orientation.

7.6 Three or More Adjacent Structures

The feasibility of treating three or more adjacent structures as an individual structure or as a complex of structures is normally assessed through an Aeronautical Evaluation that will take into consideration the location, height and spacing of structures in relation to one another.

7.7 Chimneys, Flare Stacks and Similar Structures

7.7.1 Number of Light Levels

The number of levels of light depends upon the height of the structure and should meet the specifications of Figure 7-4.

7.7.2 Location of Top Level Lights

The top level of light units should be installed on the highest point of the structure, except in the case of chimneys, where they may be installed as low as 6 m (20 feet) below the top of the chimney, in order to minimize the deposit build-up due to the emission from this type of structure.

7.8 Radio and Television Towers and Similar Structures

7.8.1 Number of Light Levels

The number of light levels required on radio and television towers and similar structures depends upon the height of the structure, excluding antennas and similar appurtenances, and should meet the specifications of Figure 7-4.

7.8.2 Use of Ice Shields

Where icing is likely to occur, metal grates or similar protective ice shields should be installed directly over each light unit to prevent accumulations of ice or falling ice from damaging the light units, provided that no light is obscured from view to pilots of approaching aircraft.

7.8.3 Top Level of Lights

One level of lights should be installed at the highest point of the structure. If the highest point is a rod or antenna incapable of supporting a lighting system, the top level of lights should be installed at the highest portion of the main skeletal structure. Due to the type of construction of some towers, however, where the guy wires come together at the top, this level of lights may be installed as low as 3 m (10 feet) below the top. If the rod, antenna or similar appurtenance exceeds 12 m (40 feet) above the main structure, a medium intensity white flashing obstruction light should be mounted on the top of this appurtenance. If the appurtenance, such as a whip antenna, cannot support a medium intensity white flashing obstruction light, one or more of these lights may be installed on a pole adjacent to the appurtenance so as to provide an unobstructed view of at least one light.

7.9 Prominent Buildings and Similar Extensive Structures

Light units should be installed on the top of prominent buildings and similar extensive structures, in a manner so as to provide an effective 360 degree protective coverage.

The number of light units depends upon the side dimensions of the structure as well as the actual beam spread of the light units, as specified below.

7.9.1 Obstructions 60 m (200 feet) or Less in Both Horizontal Dimensions

At least three light units should be installed at the highest portion of the structure in a manner to ensure that at least one light is visible to the pilot of an approaching aircraft. The light units may be mounted on a single pedestal at or near the centre of the obstruction. If the light units are placed more than 3 m (10 feet) from the centre point, a minimum of four light units should be used.

7.9.2 Obstructions Exceeding 60 m (200 feet) in One Horizontal Dimension

Two light units should be placed on each of the shorter sides. These light units may either be installed adjacent to each other at the midpoint of the edge of the obstruction or near each corner and directed horizontally in a manner to give 180 degrees of coverage to each end of the obstruction. One or more light units should be installed along the overall length of the major axis at approximately equal intervals not exceeding 30 m (100 feet) from the corners or from each other, as specified in Figure 7-6.

7.9.3 Obstructions Exceeding 60 m (200 feet) in Both Horizontal Dimensions

Light units should be equally spaced along the overall perimeter of the obstruction at intervals of 30 m (100 feet) or fraction thereof.

7.10 Flashtube Replacement

The flashtubes in the light units should be replaced upon failure, or when the effective daytime intensity falls below the minimum 200,000 candela (or 100,000 candela in the case of systems installed on the supporting structures of overhead catenary wires), or at the manufacturer's recommended intervals, whichever occurs first.

Figure 7-1 - High Intensity White Flashing Obstruction Lighting Typical Light Unit

Figure 7-2 - High Intensity White Flashing Obstruction Lighting

Figure 7-3 - High Intensity White Flashing Obstruction Lighting Location/Omission Of Lighting For Chimneys

Figure 7-4 - High Intensity White Flashing Obstruction Lighting

Figure 7-5 - High Intensity White Flashing Obstruction Lighting

Figure 7-6 - High Intensity White Flashing Obstruction Lighting Lighting On Prominent Buildings (Top Level)

CHAPTER 8 - HIGH INTENSITY WHITE FLASHING OBSTRUCTION LIGHTING FOR SUPPORTING STRUCTURES OF CATENARY WIRES

8.1 Purpose

The purpose of lighting the supporting structures of catenary wires with a unique sequentially flashing lighting system is to warn pilots of the presence of the supporting structures themselves as well as to alert them that the structures support one or more catenary wires.

8.2 Characteristics

8.2.1 Photometric Distribution

A high intensity white flashing obstruction lighting system required for catenary wires should have the photometric characteristics specified in Table 8-1.

Table 8-1
Operation
Mode
Minimum
Effective
Intensity
(Candelas)
Peak
Effective
Intensity
(Candelas)
Beam Spread
(Degrees)
  Top - Middle
and Bottom
 
day
twilight
night
50,000
7,500
750
100,000 (1)
20,000 (2)
2,000 (2)
360 - 180
360 - 180
360 - 180
3 to 7
3 to 7
3 to 7

NOTE (1): Minimum

NOTE (2): Tolerance of plus or minus 25%.

8.2.2 Flash Rate

Each series of flashes should be repeated 60 times (plus or minus 5 percent) every minute.

8.2.3 Flash Duration

The duration of each flash should be 0.1 to 0.25 seconds for the night intensity only. When the effective flash duration is achieved by a group of short flashes, the short flashes should be emitted at a rate of not less than 30 per second.

8.2.4 Flash Sequence

The flash sequence between the three levels of light units should be as follows: middle to top, top to bottom and bottom to middle. All lights on the same level should flash simultaneously.

8.2.5 Intervals Between Flashes

The time delay between flashes is designed to present a unique system display.

The off interval between the top level of light units and the bottom level should be twice as long as the interval between the middle level and the top level. The interval between the end of one sequence and the beginning of the next should be approximately 10 times the interval between the middle level and the top level. The middle level of obstruction lights may be omitted where the catenary sag is less than 30 m (100 feet). In such cases, the flash sequence should be from bottom level to top level and the off interval between sequences should be four times as long as the interval between the bottom level and the top level.

8.2.6 Intensity Control

The intensity control should meet the standard specified in Chapter 7, section 7.2.6.

8.2.7 Synchronisation

Although desirable, the corresponding light levels on associated supporting towers of a catenary crossing need not flash simultaneously.

8.2.8 Horizontal Coverage

The top light units should provide 360 degree horizontal coverage. The middle light unit and bottom light unit should be installed so as to provide a minimum of 180 degrees coverage centred along the catenary. Where a catenary crossing is situated near a bend in a river, a canyon or similar geographical feature, or is not perpendicular to the flyway, the horizontal beam pattern should be directed as necessary to provide the most effective light coverage to pilots approaching from either direction of the catenary wires.

8.3 Levels of Light Units - Two Supporting Structures

A system of three levels of sequentially flashing light units should be installed on each supporting structure or adjacent terrain. One level of three light units should be installed at the top of the structure, one light unit at the height of the lowest point of the catenary and one light unit at approximately midway between the other two levels of lights. The middle level should be a minimum of 15 m (50 feet) from the other two levels. The middle light unit may be omitted when the distance between the top and the bottom light levels is less than 30 m (100 feet). If the installation presents a potential danger for maintenance personnel or when it is necessary to protect against lightning, the top level of light units may be mounted as low as 6 m (20 feet) below the highest point of the structure.

8.4 Variation

8.4.1

Where dictated by the structural limits of the towers or by the surrounding terrain, a tolerance of 20 percent from uniform spacing may be applied to the vertical and horizontal arrangements of the lights.

8.4.2

If the base of one or more supporting structures is higher than the lowest point in the catenary, such as in the case of a canyon crossing, one or more light units should be installed on the adjacent terrain at the level of the lowest point in the span, in accordance with the specifications of Figure 8-1.

8.5 Omission of Markings

Where high intensity white flashing obstruction lighting is used on a catenary on a 24 hours basis and provides 360 degree coverage about the supporting structure, the marking standards applicable to that structure may be omitted.

8.6 Levels of Light Units - Three or More Supporting Structures

Where a catenary wire crossing requires three or more supporting structures, the inner structures should be equipped with three or four light units per level to provide a full 360 degrees of coverage, in accordance with the specifications of Table  7-4.

The exact number of light units per level depends upon the beam pattern of the particular light and the area to be covered, as determined by the possible directions of approach and upon the effective diameter of the obstruction at the level.

8.7 Flashtube Replacement

The flashtubes in a light unit should be replaced upon failure, when the effective day peak intensity falls below 100,000 candela or at the manufacturer's recommended intervals, whichever occurs first.

8.8 Area Surrounding Support Structures

The area in the immediate vicinity of the base of the supporting structures should be clear of all items and objects of natural growth that could interfere with the line-of-sight between the pilot and the obstruction lighting.

Figure 8-1 - High Intensity White Flashing Obstruction Lighting Supporting Structures of Catenary Lines

CHAPTER 9 - MARKING AND LIGHTING OF MOORED BALLOONS AND KITES

9.1 Application

This chapter applies to the marking and lighting of any moored balloon 1.8 m (6 feet) in diameter or 3 cubic metres (115 cubic feet) of gas capacity and of any kite weighing more than 2.27 kg (5 lbs.) that are operated at heights greater than 90 m (300 feet) AGL. In exceptional circumstances, as determined by an Aeronautical Evaluation, this Chapter also applies to balloon and kite operations below 90 m (300 feet) AGL.

9.2 Marking Requirements

During daytime, streamers or similar type markers should be attached to mooring lines of balloons and kites to warn airmen of their presence, that are:

  1. (a) displayed at not more than 15 m (50 feet) intervals along the mooring lines beginning at 45 m (150 feet) above the surface of the earth and visible from at least 1.6 km (1 mile);

  2. (b) rectangular in shape, 150 mm (6 inches) wide and 3 m (10 feet) in length; and

  3. (c) of the following colour patterns:

    1. (i) solid orange; or

    2. (ii) alternating orange and white, each colour having triangular shape that combines with the other colour to form a rectangle.

9.3 Lighting Requirements

At night, moored balloons and kites should be equipped with the following lighting devices to warn pilots of their presence:

  1. (a) for operations below 150 m (500 feet) AGL, red or white flashing lights of 32.5 candela on moored balloons and on the mooring lines of both balloons and kites, or floodlighting as specified in Chapter 4, paragraph 4.2.3;

  2. (b) for operations above 150 m (500 feet) AGL, white flashes of 500 effective candela or steady burning white lights of equivalent intensity, on moored balloons and on the mooring lines of both balloons and kites;

  3. (c) flashing red and white lights, as determined under paragraphs (a) and (b) above, on the top, nose section, tail section, and on the mooring line/tether cable approximately 5 m (15 feet) below the balloon or kite, so as to define its shape and size, with additional lights equally spaced along the mooring cable's overall length for each 107 m (350 feet), or fraction thereof, commencing at 90 m (300 feet) AGL; and

  4. (d) have an on and off setting of 300 and 600 lux respectively of Northern sky illuminance.

Appendices:

  • Appendix A - Transport Canada Aviation Regions
  • Appendix B - Obstruction Lighting Specifications
  • Appendix C - Sample form (26-0427)
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