Consultation expired with comments. The proposed Equivalent Safety Finding (ESF) has been editorially updated based on the comments received, and the corresponding Comment-Response Document (CRD) has been completed by EASA.
Details
Identification of issue
CS 29.811(d) requires that: “Each passenger emergency exit marking and each locating sign must have white letters on a red background or a universal emergency exit symbol, of adequate size. These signs must be self or electrically illuminated, and have a minimum luminescence (brightness) of at least 0.51 candela/m2 (160 microlamberts). The colours of a text-based sign may be reversed if this will increase the emergency illumination of the passenger compartment.”
Also, in accordance with CS 29.812(e): “The energy supply to each emergency lighting unit must provide the required level of illumination for at least 10 minutes at the critical ambient conditions after an emergency landing.”
Photoluminescence technology does not fully comply with certain parts of CS 29.811(d) and CS 29.812(e).
The non-compliances can be summarised as follows:
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CS 29.811(d) requires that some of the areas of the sign be white.
The colour of photoluminescent signs appears pale yellow in normal ambient light levels and appears glowing pale green in low ambient light levels.
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CS 29.811(d) requires that the sign must be self or electrically illuminated.
Photoluminescent is neither self nor electrically illuminated. The photoluminescent material must first be charged by another light source before emitting light.
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CS 29.811(d) requires that the illuminated sign has a minimum luminescence (brightness) of at least 0.51 candela/m2 (160 microlamberts).
The initial brightness of fully charged photoluminescent material meets this requirement. However, the initial brightness is dependent on cabin light intensity and charging duration. The brightness level of photoluminescent material will decrease when left in darkness, and therefore the minimum luminescent of 0.51 candela/m2 is not guaranteed for a long time.
Also, for the universal symbol signs, the green areas are opaque (no light is emitted by the sign). Similarly, for the language-based signs the red areas are opaque.
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CS 29.812(e) requires that the “energy supply” to the sign “must provide the required level of illumination for at least 10 minutes at the critical ambient conditions after an emergency landing”.
Compliance with this requirement is not obvious for a photoluminescent sign that shows a varying brightness level over time.
