CS 27.1381  Instrument lights

ED Decision 2003/15/RM

The instrument lights must:

(a) Make each instrument, switch, and other devices for which they are provided easily readable; and

(b) Be installed so that:

(1) Their direct rays are shielded from the pilot’s eyes; and

(2) No objectionable reflections are visible to the pilot.

CS 27.1383  Landing lights

ED Decision 2003/15/RM

(a) Each required landing or hovering light must be approved.

(b) Each landing light must be installed so that:

(1) No objectionable glare is visible to the pilot;

(2) The pilot is not adversely affected by halation; and

(3) It provides enough light for night operation, including hovering and landing.

(c) At least one separate switch must be provided, as applicable:

(1) For each separately installed landing light; and

(2) For each group of landing lights installed at a common location.

CS 27.1385  Position light system installation

ED Decision 2003/15/RM

(a) General. Each part of each position light system must meet the applicable requirements of this paragraph, and each system as a whole must meet the requirements of CS 27.1387 to 27.1397.

(b) Forward position lights. Forward position lights must consist of a red and a green light spaced laterally as far apart as practicable and installed forward on the rotorcraft so that, with the rotorcraft in the normal flying position, the red light is on the left side and the green light is on the right side. Each light must be approved.

(c) Rear position light. The rear position light must be a white light mounted as far aft as practicable, and must be approved.

(d) Circuit. The two forward position lights and the rear position light must make a single circuit.

(e) Light covers and colour filters. Each light cover or colour filter must be at least flame resistant and may not change colour or shape or lose any appreciable light transmission during normal use.

CS 27.1387  Position light system dihedral angles

ED Decision 2003/15/RM

(a) Except as provided in sub-paragraph (e), each forward and rear position light must, as installed, show unbroken light within the dihedral angles described in this paragraph.

(b) Dihedral angle L (left) is formed by two intersecting vertical planes, the first parallel to the longitudinal axis of the rotorcraft, and the other at 110° to the left of the first, as viewed when looking forward along the longitudinal axis.

(c) Dihedral angle R (right) is formed by two intersecting vertical planes, the first parallel to the longitudinal axis of the rotorcraft, and the other at 110° to the right of the first, as viewed when looking forward along the longitudinal axis.

(d) Dihedral angle A (aft) is formed by two intersecting vertical planes making angles of 70° to the right and to the left, respectively, to a vertical plane passing through the longitudinal axis, as viewed when looking aft along the longitudinal axis.

(e) If the rear position light, when mounted as far aft as practicable in accordance with 27.1385(c), cannot show unbroken light within dihedral angle A (as defined in sub-paragraph (d)), a solid angle or angles of obstructed visibility totalling not more than 0.04 steradians is allowable within that dihedral angle, if such solid angle is within a cone whose apex is at the rear position light and whose elements make an angle of 30° with a vertical line passing through the rear position light.

CS 27.1389  Position light distribution and intensities

ED Decision 2003/15/RM

(a) General. The intensities prescribed in this paragraph must be provided by new equipment with light covers and colour filters in place. Intensities must be determined with the light source operating at a steady value equal to the average luminous output of the source at the normal operating voltage of the rotorcraft. The light distribution and intensity of each position light must meet the requirements of sub-paragraph (b).

(b) Forward and rear position lights. The light distribution and intensities of forward and rear position lights must be expressed in terms of minimum intensities in the horizontal plane, minimum intensities in any vertical plane, and maximum intensities in overlapping beams, within dihedral angles L, R, and A, and must meet the following requirements:

(1) Intensities in the horizontal plane. Each intensity in the horizontal plane (the plane containing the longitudinal axis of the rotorcraft and perpendicular to the plane of symmetry of the rotorcraft) must equal or exceed the values in CS 27.1391.

(2) Intensities in any vertical plane. Each intensity in any vertical plane (the plane perpendicular to the horizontal plane) must equal or exceed the appropriate value in CS 27.1393, where I is the minimum intensity prescribed in CS 27.1391 for the corresponding angles in the horizontal plane.

(3) Intensities in overlaps between adjacent signals. No intensity in any overlap between adjacent signals may exceed the values in CS 27.1395, except that higher intensities in overlaps may be used with main beam intensities substantially greater than the minima specified in CS 27.1391 and 27.1393, if the overlap intensities in relation to the main beam intensities do not adversely affect signal clarity. When the peak intensity of the forward position lights is greater than 100 candelas, the maximum overlap intensities between them may exceed the values in CS 27.1395 if the overlap intensity in Area A is not more than 10% of peak position light intensity and the overlap intensity in Area B is not more than 2.5% of peak position light intensity.

CS 27.1391  Minimum intensities in the horizontal plane of forward and rear position lights

ED Decision 2003/15/RM

Each position light intensity must equal or exceed the applicable values in the following table:

CS 27.1393  Minimum intensities in any vertical plane of forward and rear position lights

ED Decision 2003/15/RM

Each position light intensity must equal or exceed the applicable values in the following table:

CS 27.1395  Maximum intensities in overlapping beams of forward and rear position lights

ED Decision 2003/15/RM

No position light intensity may exceed the applicable values in the following table, except as provided in CS 27.1389(b)(3):

Where:

(a) Area A includes all directions in the adjacent dihedral angle that pass through the light source and intersect the common boundary plane at more than 10° but less than 20°; and

(b) Area B includes all directions in the adjacent dihedral angle that pass through the light source and intersect the common boundary plane at more than 20°.

CS 27.1397  Colour specifications

ED Decision 2003/15/RM

Each position light colour must have the applicable International Commission on Illumination chromaticity co-ordinates as follows:

(a) Aviation red: ‘y’ is not greater than 0.335; and

‘z’ is not greater than 0.002.

(b) Aviation green:

‘x’ is not greater than 0.440–0.320y;

‘x’ is not greater than y–0.170; and

‘y’ is not less than 0.390–0.170x.

(c) Aviation white:

‘x’ is not less than 0.300 and not greater than 0.540;

‘y’ is not less than ‘x–0.040’ or ‘y_o–0.010’, whichever is the smaller; and

‘y’ is not greater than ‘x + 0.020’ nor ‘0.636–0.400x’;

Where ‘y_o’ is the ‘y’ co-ordinate of the Planckian radiator for the value of ‘x’ considered.

CS 27.1399  Riding light

ED Decision 2003/15/RM

(a) Each riding light required for water operation must be installed so that it can:

(1) Show a white light for at least 3.7 km (two nautical miles) at night under clear atmospheric conditions; and

(2) Show a maximum practicable unbroken light with the rotorcraft on the water.

(b) Externally hung lights may be used.

CS 27.1401  Anti-collision light system

ED Decision 2003/15/RM

(a) General. If certification for night operation is requested, the rotorcraft must have an anti-collision light system that:

(1) Consists of one or more approved anti-collision lights located so that their emitted light will not impair the crew’s vision or detract from the conspicuity of the position lights; and

(2) Meets the requirements of sub-paragraphs (b) to (f).

(b) Field of coverage. The system must consist of enough lights to illuminate the vital areas around the rotorcraft, considering the physical configuration and flight characteristics of the rotorcraft. The field of coverage must extend in each direction within at least 30° above and 30° below the horizontal plane of the rotorcraft, except that there may be solid angles of obstructed visibility totalling not more than 0.5 steradians.

(c) Flashing characteristics. The arrangement of the system, that is, the number of light sources, beam width, speed of rotation, and other characteristics, must give an effective flash frequency of not less than 40, nor more than 100, cycles per minute. The effective flash frequency is the frequency at which the rotorcraft’s complete anti-collision light system is observed from a distance, and applies to each sector of light including any overlaps that exist when the system consists of more than one light source. In overlaps, flash frequencies may exceed 100, but not 180, cycles per minute.

(d) Colour. Each anti-collision light must be aviation red and must meet the applicable requirements of CS 27.1397.

(e) Light intensity. The minimum light intensities in any vertical plane, measured with the red filter (if used) and expressed in terms of ‘effective’ intensities, must meet the requirements of sub-paragraph (f). The following relation must be assumed:

where:

I_e   =   effective intensity (candelas).

I(t)  =  instantaneous intensity as a function of time.

t₂–t₁ =  flash time interval (seconds).

Normally, the maximum value of effective intensity is obtained when t₂ and t₁ are chosen so that the effective intensity is equal to the instantaneous intensity at t₂ and t₁.

(f) Minimum effective intensities for anticollision light. Each anti-collision light effective intensity must equal or exceed the applicable values in the following table: