BS EN 4705:2020 pdf download.Aerospace series —Measurement methods regarding the lifetime behaviour of light units ina standardized aircraft-related environment.
5 Failure mode Identification
5.1 General
This document refers to failure modes as given in 4.1 b) and 4.1 c)only.
The behaviour of light units regarding lifetime shall be evaluated by testing. To minimize test duration an appropriate extrapolation model shall be applied.
Unless otherwise specified predictions according to this document shalt be made with a confidence level of 95 %.
5.2 BrIghtness degradation calculation selection
The brightness degradation can be approximated by different fitting functions depending on the technology of the light unit. The selected method and the achieved accuracy shall be indicated by the manufacturer. One recommended method based on testeng and extrapolation is described In
IES LM 80/TM 21,
5.3 Colour degradation
The major contributor regarding colour degradation is operation time, hut other parameters, namely temperature, operational current and specified colour, may have an impact.
Under the given preconditions, i.e. specified target chromaticity and a tolerance defined by the radii of the associated MacAdam ellipse, the following shall be considered as failure case.
End of life is reached when the chromaticity shift curve intersects the borderline of the corresponding MacAdam ellipse, see Figure 2.
5.1 General
This document refers to failure modes as given in 4.1 b) and 4.1 c)only.
The behaviour of light units regarding lifetime shall be evaluated by testing. To minimize test duration an appropriate extrapolation model shall be applied.
Unless otherwise specified predictions according to this document shalt be made with a confidence level of 95 %.
5.2 BrIghtness degradation calculation selection
The brightness degradation can be approximated by different fitting functions depending on the technology of the light unit. The selected method and the achieved accuracy shall be indicated by the manufacturer. One recommended method based on testeng and extrapolation is described In
IES LM 80/TM 21,
5.3 Colour degradation
The major contributor regarding colour degradation is operation time, hut other parameters, namely temperature, operational current and specified colour, may have an impact.
Under the given preconditions, i.e. specified target chromaticity and a tolerance defined by the radii of the associated MacAdam ellipse, the following shall be considered as failure case.
End of life is reached when the chromaticity shift curve intersects the borderline of the corresponding MacAdam ellipse, see Figure 2.
