CS 25.1389 Position light distribution and intensities

• ED Decision 2003/2/RM found in: CS-25 Amdt 27 - Large Aeroplanes (Jan 2023)

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](#_DxCrossRefBm1709821694). (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](#_DxCrossRefBm1709821695), where I is the minimum intensity prescribed in [CS 25.1391](#_DxCrossRefBm1709821694) 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](#_DxCrossRefBm1709821693), except that higher intensities in overlaps may be used with main beam intensities substantially greater than the minima specified in [CS 25.1391](#_DxCrossRefBm1709821694) 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](#_DxCrossRefBm1709821693) 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.