prEN 4731

• Abstract:

  This document defines a measure for the spectral quality of LED luminaires in terms of the ratio of the amount of visual light emitted by the luminaire versus the amount effective for charging photoluminescent products contained in that spectrum.; Fulfilment of this document by a LED luminaire will ensure general compatibility of the luminaire with photoluminescent marking systems.; This document alone does not provide any means of compliance to fulfil any airworthiness requirements.; For a specific aircraft installation, the spectral power distribution and illuminance at the photoluminescent marking systems are relevant.

• Status: Not Published
• Publication Date: 14-Sep-2027
• ICS: 29.140.99 - Other standards related to lamps
• ICS: 49.095 - Passenger and cabin equipment
• Technical Committee: ASD-STAN - Aerospace
• Drafting Committee: ASD-STAN/D 12/WG 4 - Displays, projection and interior lighting
• Current Stage: 4060 - Closure of enquiry - Enquiry
• Start Date: 16-Jul-2026
• Completion Date: 16-Jul-2026
• Ref Project: oSIST prEN 4731:2026 - Aerospace series - Spectral quality of LED luminaires used with photoluminescent marking systems

• Revises: EN 4731:2018 - Aerospace series - Spectral quality of LED luminaires used with photoluminescent marking systems
• Effective Date: 11-Mar-2026

prEN 4731 is a draft CEN European Standard in the Aerospace series for LED luminaires used with photoluminescent marking systems. It defines a spectral-quality measure, the excitation coefficient Ce, to show how effectively a luminaire can charge photoluminescent products compared with how much of its light is visually useful. The document is aimed at luminaires for aircraft cabin use, where the spectrum matters for charging even when the luminance looks acceptable to the eye.

What does prEN 4731 specify?

prEN 4731 specifies how to assess the spectral quality of LED luminaires for charging photoluminescent marking systems, and how to classify and label that performance. The document links the luminaire spectrum to both human visual response and photoluminescent excitation, so users can compare products on a common basis.

Annex	What it covers
Annex A	Approximated excitation spectrum for typical photoluminescent pigments based on strontium aluminate
Annex B	Examples of different light spectra and their correlated Ce values

The scope also states two important limits. prEN 4731 supports general compatibility with photoluminescent marking systems, but it is not by itself a means of showing airworthiness compliance. For a specific aircraft installation, spectral power distribution and illuminance at the marking system remain relevant.

What are the key requirements of prEN 4731?

prEN 4731 sets out a measurement method, a calculation method, a classification scheme, and a labelling rule.

Measure the spectrum under defined conditions

Clause 4.1 requires the luminaire’s spectral irradiance to be recorded in 1 nm steps in steady state, using a spectrometer over 360 nm to 780 nm with optical bandwidth not greater than 5 nm. In practice, this means the result depends on the measured spectrum, not only on declared LED type or correlated colour temperature.

Use the correct method for the luminaire type

For single colour LED luminaires, Clause 4.1.1 uses the measured spectrum directly. For multiple colour LED luminaires, Clause 4.1.2 first requires definition of a colour setting dedicated to charging photoluminescent products, then measurement in that setting. This matters because a tunable luminaire can have different charging performance in different operating modes.

Calculate two weighted irradiances

Clause 4.1 requires calculation of photometrically weighted irradiance EV using the photopic luminosity function V(λ), and approximated weighted excitation irradiance EA using the approximated excitation spectrum A(λ). EV covers the visual range, while EA focuses on the part of the spectrum that contributes to charging. The reader is expected to determine both, then compare them.

Derive the excitation coefficient Ce

Ce is defined in Clause 3 as the quotient EA/(EA+EV). Clause 4.1 uses that value to express spectral quality as a balance between charging effectiveness and visible light output. A higher Ce means more of the emitted light is useful for charging photoluminescent material relative to the visible-light component.

Classify the luminaire

Clause 4.2.1 assigns Ce to four classes: A Excellent, B Good, C Limited, and D Poor. This gives a simple purchasing or design screen for comparing luminaires that may otherwise look similar in output or colour.

State Ce clearly in product information

Clause 4.2.2 requires the Ce value to appear in the product data sheet with three decimal figures. For multiple colour luminaires, the claimed Ce must be accompanied by the colour-setting parameters it refers to, and multiple claims for different colour settings are allowed. That makes the declared performance traceable to a specific operating mode.

What terms does prEN 4731 define?

• LED - A light-emitting diode, described here as a solid-state p-n junction that emits optical radiation when excited by electric current.
• single colour LED luminaire - A luminaire designed to operate in one colour setting only.
• multiple colour LED luminaire - A luminaire designed to operate in two or more colour settings using LEDs of at least two different primary wavelengths.
• colour setting - The set of parameters that defines the power setting of each primary in a multiple colour LED luminaire to achieve a specific colour output.
• photopic luminosity function V(λ) - The wavelength-dependent human visual sensitivity function used to weight light by perceived brightness.
• photometrically weighted irradiance EV - The integral of the photometrically weighted spectrum over 360 nm to 780 nm, used as the visual-brightness side of the Ce calculation.
• excitation coefficient Ce - The ratio of excitation irradiance to total weighted irradiance, used to express spectral quality for charging photoluminescent products.

Who uses prEN 4731?

prEN 4731 is used by aerospace lighting designers, aircraft cabin equipment suppliers, test laboratories, and quality or compliance teams that need to judge whether an LED luminaire is suitable for photoluminescent marking systems. It is also relevant to buyers and specifiers comparing cabin luminaires, because it gives a common way to state charging-related spectral performance in product data. In practice, it supports product selection, testing, and documentation for cabin lighting packages.

What changed in prEN 4731 from the previous edition?

prEN 4731 will supersede EN 4731:2018. The foreword states three significant technical changes: the new term colour setting replaces colour mode, the definition of photopic luminosity function has been corrected, and Clause 4 is retitled to focus on spectral quality in view of charging photoluminescent products.

Which standards are used with prEN 4731?

The normative reference named in the document is EN 4706, Aerospace series - LED colour and brightness ranking. It is used for the comparison value in Clause 4.2.2, including the S4000 setting. The bibliography also cites CIE 018.2:1983, The basis of physical photometry, which supports the photopic luminosity function V(λ) used in the calculations.

What does the prEN 4731 document contain?

prEN 4731 contains the scope, normative references, terms and definitions, and Clause 4 on spectral quality in view of charging photoluminescent products. Clause 4 gives the measurement method for single colour and multiple colour LED luminaires, the Ce calculation, the classification table, and the labelling rule. Annex A provides a standardized approximated excitation spectrum for strontium aluminate-based photoluminescent pigments, and Annex B gives worked examples of luminaire spectra with their Ce values. The document also includes figures that illustrate the excitation spectrum and example spectra for different luminaire types.

SLOVENSKI STANDARD
01-julij-2026
Aeronavtika - Spektralna kakovost LED-svetilk, ki se uporabljajo s
fotoluminiscenčnimi sistemi označevanja
Aerospace series - Spectral quality of LED luminaires used with photoluminescent
marking systems
Luft- und Raumfahrt - Spektrale Qualität von LED-Leuchten zur Verwendung mit
langnachleuchtenden Markierungssystemen
Ta slovenski standard je istoveten z: prEN 4731
ICS:
29.140.99 Drugi standardi v zvezi z Other standards related to
žarnicami lamps
49.095 Oprema za potnike in Passenger and cabin
oprema kabin equipment
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
EUROPEAN STANDARD
NORME EUROPÉENNE
EUROPÄISCHE NORM
April 2026
ICS 49.095; 29.140.99 Will supersede EN 4731:2018
English Version
Aerospace series - Spectral quality of LED luminaires used
with photoluminescent marking systems
Luft- und Raumfahrt - Spektrale Qualität von LED-
Leuchten zur Verwendung mit langnachleuchtenden
Markierungssystemen
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee ASD-
STAN.
If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations
which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

This draft European Standard was established by CEN in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC
Management Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2026 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 4731:2026 E
worldwide for CEN national Members.

Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms, definitions and abbreviations . 5
4 Spectral quality in view of charging photoluminescent products. 7
4.1 Method for determination of Ce for a luminaire . 7
4.1.1 Single colour LED luminaires . 7
4.1.2 Multiple colour LED luminaires . 8
4.1.3 Examples of different light spectra. 8
4.2 Requirement . 8
4.2.1 Ce classification . 8
4.2.2 Labelling . 9
Annex A (informative) Approximated excitation spectrum . 10
Annex B (informative) Examples of different light spectra . 11
Bibliography. 16

European foreword
This document (prEN 4731:2026) has been prepared by ASD-STAN.
After enquiries and votes carried out in accordance with the rules of this Association, this document has
received the approval of the National Associations and the Official Services of the member countries of
ASD-STAN, prior to its presentation to CEN.
This document is currently submitted to the CEN Enquiry.
This document will supersede EN 4731:2018.
— new term “colour setting” and using it instead of “colour mode”;
— correct the definition of term “photopic luminosity function”;
— change heading of Clause 4 into “Spectral quality in view of charging photoluminescent products”.
Introduction
Photoluminescent marking systems are commonly used in passenger airplanes to provide visual
guidance in emergency events. Those marking systems need to be charged by ambient light during
cabin preparation and/ or aircraft operation as to be operational if, at any phase of a flight, an
emergency occurs.
While the certification regulations require photoluminescent marking system to be sufficiently charged
solely by cabin interior lighting, i.e. without accounting for daylight entering the cabin through
windows, only certain portions of the visual light spectrum emitted by a cabin interior luminaire are
stored by the photoluminescent pigment and thus contribute to charging.
1 Scope
This document defines a measure for the spectral quality of LED luminaires in terms of the ratio of the
amount of visual light emitted by the luminaire versus the amount effective for charging
photoluminescent products contained in that spectrum.
Fulfilment of this document by a LED luminaire will ensure general compatibility of the luminaire with
photoluminescent marking systems.
This document alone does not provide any means of compliance to fulfil any airworthiness
requirements.
For a specific aircraft installation, the spectral power distribution and illuminance at the
photoluminescent marking systems are relevant.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
EN 4706, Aerospace series — LED colour and brightness ranking
3 Terms, definitions and abbreviations
For the purposes of this document, the following terms, definitions and abbreviations apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp
— IEC Electropedia: available at https://www.electropedia.org/
3.1
Light Emitting Diode
LED
solid state device embodying a p-n junction, emitting optical radiation when excited by an electric
current
3.2
single colour LED luminaire
luminaire using one or more LEDs as source of light whereas the luminaire is designed to operate in a
single colour setting only
3.3
multiple colour LED luminaire
luminaire using two or more LEDs as source of light whereas the LEDs are of at least two different
primary wavelengths and the luminaire is designed to operate in two or more colour settings
3.4
colour setting
set of parameters that define the power setting of every primary of a multiple colour LED Luminaire
thus achieving a specific colour output
3.5
spectral irradiance
Eλ(λ)
function that relates the spectral irradiance E𝜆𝜆 of a light source to the wavelength λ
Note 1 to entry: The function’s unit is W/m /nm.
3.6
photopic luminosity function
V(λ)
function that relates the average spectral sensitivity of human visual perception of brightness for
photopic vision to the wavelength 𝜆𝜆
Note 1 to entry: Published by the Commission Internationale de L’Éclairage (CIE) in steps of one nanometer with
document CIE 018.2:1983.
3.7
photom
...