CS 25.1381 Instrument lights

ED Decision 2003/2/RM

(a) The instrument lights must –

(1) Provide sufficient illumination to make each instrument, switch and other device necessary for safe operation easily readable unless sufficient illumination is available from another source; and

(2) Be installed so that –

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

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

(b) Unless undimmed instrument lights are satisfactory under each expected flight condition, there must be a means to control the intensity of illumination.

CS 25.1383 Landing lights

ED Decision 2003/2/RM

(a) Each landing light must be approved, and 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 landing.

(b) Except when one switch is used for the lights of a multiple light installation at one location, there must be a separate switch for each light.

(c) There must be a means to indicate to the pilots when the landing lights are extended.

CS 25.1385 Position light system installation

ED Decision 2003/2/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 25.1387 to 25.1397.

(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 aeroplane so that, with the aeroplane 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 on the tail or on each wing tip, and must be approved.

(d) 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 25.1387 Position light system dihedral angles

ED Decision 2003/2/RM

(a) Except as provided in sub-paragraph (e) of this paragraph, 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 aeroplane, 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 aeroplane, 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 ^o 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 CS 25.1385(c), cannot show unbroken light within dihedral angle A (as defined in sub-paragraph (d) of this paragraph), 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 ^o with a vertical line passing through the rear position light.

CS 25.1389 Position light distribution and intensities

ED Decision 2003/2/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 aeroplane. The light distribution and intensity of each position light must meet the requirements of sub-paragraph (b) of this paragraph.

(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 aeroplane and perpendicular to the plane of symmetry of the aeroplane) must equal or exceed the values in CS 25.1391.

(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 25.1393, where I is the minimum intensity prescribed in CS 25.1391 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 given in CS 25.1395, except that higher intensities in overlaps may be used with main beam intensities substantially greater than the minima specified in CS 25.1391 and 25.1393 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 more than 102 cd (100 candles), the maximum overlap intensities between them may exceed the values given in CS 25.1395 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 greater than 2·5% of peak position light intensity.

CS 25.1391 Minimum intensities in the horizontal plane of forward and rear position lights

ED Decision 2003/2/RM

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

CS 25.1393 Minimum intensities in any vertical plane of forward and rear position lights

ED Decision 2003/2/RM

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

CS 25.1395 Maximum intensities in over-lapping beams of forward and rear position lights

ED Decision 2003/2/RM

No position light intensity may exceed the applicable values in the following table, except as provided in CS 25.1389(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 25.1397 Colour specifications

ED Decision 2003/2/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 25.1401 Anti-collision light system

ED Decision 2003/2/RM

(a) General. The aeroplane must have an anticollision light system that –

(1) Consists of one or more approved anti-collision lights located so that their 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) of this paragraph.

(b) Field of coverage. The system must consist of enough light to illuminate the vital areas around the aeroplane considering the physical configuration and flight characteristics of the aeroplane. The field of coverage must extend in each direction within at least 75° above and 75° below the horizontal plane of the aeroplane, except that a solid angle or angles of obstructed visibility totalling not more than 0·03 steradians is allowable within a solid angle equal to 0·15 steradians centred about the longitudinal axis in the rearward direction.

(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 aeroplane’s complete anti-collision light system is observed from a distance, and applies to each section 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 either aviation red or aviation white and must meet the applicable requirements of CS 25.1397.

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

where:

I_e    =  effective intensity (candela (candles)

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 lights. Each anti-collision light effective intensity must equal or exceed the applicable values in the following table:

CS 25.1403 Wing icing detection lights

ED Decision 2015/008/R

(see AMC 25.1403)

Unless operations at night in known or forecast icing conditions are prohibited by an operating limitation, a means must be provided for illuminating or otherwise determining the formation of ice on the parts of the wings that are critical from the standpoint of ice accumulation. Any illumination that is used must be of a type that will not cause glare or reflection that would handicap crewmembers in the performance of their duties.

[Amdt 25/16]

AMC 25.1403 Wing icing detection lights

ED Decision 2016/010/R

Unless operations at night in icing conditions are prohibited by an operating limitation, CS 25.1403 requires that a means be provided, during flight at night, to illuminate or otherwise determine ice formation on parts of the wings that are critical from the standpoint of ice accumulations resulting from Appendix C and Appendix O icing conditions. For showing compliance with the CS-25 certification specifications relative to SLD icing conditions represented by Appendix O, the applicant may use a comparative analysis. AMC 25.1420(f) provides guidance for comparative analysis.

a.  If the flight crew cannot see the wings, one acceptable means of compliance with this regulation would be to install an ice evidence probe in a position where the flight crew can observe ice accumulation. The applicant should substantiate that formation of ice on this device precedes formation of ice on the wings or occurs simultaneously with it. Consideration should be given to the need for illuminating the ice evidence probe.

b.  Wing icing detection lights should be evaluated both in and out of clouds during night flight to determine that the component of interest is adequately illuminated without excessive glare, reflections, or other distractions to the flight crew. These tests may be accomplished during the aeroplane certification flight tests. Typically, aeroplane-mounted illumination has been used to comply with this regulation. Use of a hand-held flashlight has not been considered acceptable because of the associated workload. The appropriate manual should identify the ice characteristics which the flight crew is expected to observe as well as the action the flight crew must perform if such ice is observed.

[Amdt 25/16]

[Amdt 25/18]