AMC 25.812(b)(1) Emergency lighting

ED Decision 2017/015/R

General Requirements

Emergency exit signs should consist of a consistent type throughout the aeroplane. They may be letter based or symbolic, as outlined below.

Letter based emergency exit signs should use letters with a height to stroke width ratio of not more than 7:1 nor less than 6:1.

Symbolic emergency exit signs should be white and green in compliance with European Standard (EN) ISO 7010:2012, Graphical symbols, safety colours and safety signs, registered safety signs. The green area of the sign should constitute at least half of the total area of the sign.

In determining the area of an emergency exit sign, no part of the sign outside of the white background (text signs) or green element (symbolic signs), for instance a surrounding contrasting border, should be included.

Minimum size - emergency exit signs required by CS 25.811(d)(1) or (d)(3)

For each emergency exit sign required by CS 25.811(d)(1), and for each emergency exit sign required on each bulkhead or divider by CS 25.811(d)(3), at each point along any possible aeroplane egress path, the next closest required emergency exit sign visible at each point along the egress path should be sized and located such that it is no farther away from the escapee than its maximum allowable viewing distance calculated as below.

Egress paths to be assessed should be:

(1)     any possible path from a passenger seat that can be occupied during taxiing, take-off, and landing to any passenger emergency exit; and

(2)     any possible path from a point adjacent to any passenger emergency exit to any other passenger emergency exit.

Calculation of maximum viewing distance

For an emergency exit sign required by CS 25.811(d)(1) and for an emergency exit sign required on each bulkhead or divider by CS 25.811(d)(3), the following formulae, as modified by the notes below, apply for calculating a maximum viewing distance. The maximum allowable viewing distance for a sign is in each case the lower of the two values D1 and D2:

where:

1.       Z is the distance factor obtained from Table 1 below;

2.       h_letter is the overall height of each letter – which should be at least of 25 mm (1 inch) high;

3.       h_symbol is the overall height of the white symbolic element incorporating the green ‘running man’ – which should be at least 40 mm (1.6 inches) high;

4.       x_sign is the overall area of the sign; and

5.       D₁, D₂, h_letter and h_symbol have the same units, and x_sign is in the same squared units as D₁, D₂, h_letter and h_symbol.

Note 1: In the case of dual-language text based emergency exit signs, only the English text is to be considered when selecting h_letter for use in the above formula. However, in determining the area of the sign (x_sign) for use in the above formula, the actual area may be used

Examples of acceptable designs of symbolic exit signs

Table 1: Z factor to be used for text based and symbolic emergency exit signs

Minimum size - emergency exit signs required by CS 25.811(d)(2)

For an emergency exit sign required by CS 25.811(d)(2), any sign using English letters of at least 25 mm (1 inch) height, or a white symbolic element (i.e. that part incorporating the green ‘running man’) of at least 40 mm (1.6 inches), with an overall area of at least 64.5 cm² (10 square inches) will be acceptable.

Supplementary directional arrows

The inclusion of an arrow or arrows in any of the signs discussed above, in order to increase the comprehension of the sign, is encouraged. The possibility to improve comprehension and the appropriate orientation of the arrows will depend on the particular installation. If arrows indicate a movement other than straight ahead, in the case of a symbolic sign, the depicted movement direction of the ‘running man’ (to the right/to the left) should be chosen to be compatible with the orientation of the arrow(s). There may be other reasons to choose a particular movement direction of the ‘running man’, for instance where a sign required by CS 25.811(d)(2) is placed to the left or right of the emergency exit. In this case, the ‘running man’ should not suggest movement away from the emergency exit.

In the case of symbolic signs, the arrows should be in accordance with the style defined in European Standard (EN) ISO 7010:2012, i.e. type D of ISO 3864-3. The ratio of overall length of an arrow to the width of its tail should be not more than 7:1 nor less than 5.5:1.

[Amdt 25/3]

[Amdt 25/19]