Aerospace series - Unmanned Aircraft Systems - Part 004: Lighting requirements

Luft- und Raumfahrt - Unbemannte Luftfahrzeugsysteme - Teil 004: Anforderungen an die zu führenden Lichter

Série aérospatiale - Aéronefs télépilotés - Partie 004 : Exigences de signalement lumineux

Aeronavtika - Letalski sistemi brez posadke - 004. del: Zahteve za razsvetljavo

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oSIST prEN 4709-004:2021
Aeronavtika - Letalski sistemi brez posadke - 004. del: Zahteve za razsvetljavo
Aerospace series - Unmanned Aircraft Systems - Part 004: Lighting requirements
Luft- und Raumfahrt - Unbemannte Luftfahrzeugsysteme - Teil 004: Anforderungen an
die zu führenden Lichter
Série aérospatiale - Aéronefs télépilotés - Partie 004 : Exigences de signalement
Ta slovenski standard je istoveten z: prEN 4709-004
49.020 Letala in vesoljska vozila na Aircraft and space vehicles in
splošno general
oSIST prEN 4709-004:2021 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN 4709-004:2021

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oSIST prEN 4709-004:2021

prEN 4709-004


December 2020
English Version

Aerospace series - Unmanned Aircraft Systems - Part 004:
Lighting requirements
Série aérospatiale - Aéronefs télépilotés - Partie 004 : Luft- und Raumfahrt - Unbemannte
Exigences de signalement lumineux Luftfahrzeugsysteme - Teil 004: Anforderungen an die
zu führenden Lichter
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee ASD-

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, Turkey 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.



CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2020 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 4709-004:2020 E
worldwide for CEN national Members.

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prEN 4709-004:2020 (E)
Contents Page

European foreword . 3
1 Scope . 4
2 Normative references . 4
3 Terms and definitions . 4
4 Technical specifications . 6
4.1 General . 6
4.2 Add-on lights . 6
4.3 Colours . 6
5 Lights for controllability . 7
5.1 General . 7
5.2 Performance Specification . 7
5.2.1 General . 7
5.2.2 Manual direct piloting control mode . 8
5.2.3 Semi-automatic control Mode . 9
5.3 Test Methods. 9
6 Lights for conspicuity . 9
6.1 General . 9
6.2 Performance Specification . 9
6.2.1 General . 9
6.2.2 Blinking and flashing lights . 10
6.2.3 Alternating lights . 10
6.3 Test Methods. 11
6.3.1 Distance Test . 11
6.3.2 Field of Coverage Test . 11
6.3.3 Cycle rate test . 13
7 Lights for other purposes . 14
7.1 General . 14
7.2 Test Methods. 14
Annex A (informative) Reference implementations . 15
Annex ZA (informative) Relationship between this document and the essential
requirements of Delegated regulation (EU) 2019/945 of 12th March 2019 on
unmanned aircraft systems and on third-country operators of unmanned aircraft
systems aimed to be covered . 21
Bibliography . 22


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prEN 4709-004:2020 (E)
European foreword
This document (prEN 4709-004:2020) has been prepared by the Aerospace and Defence Industries
Association of Europe — Standardization (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 ASD-STAN National Domain Ballot in parallel to the CEN
This document was originally reviewed by the Domain Technical Coordinator of ASD-STAN's
Autonomous flying Domain.
This document has been prepared under a mandate given to CEN by the European Commission and the
European Free Trade Association and supports essential requirements of EU Directive(s).
For relationship with EU Directive(s), see informative Annex ZA, which is an integral part of this

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prEN 4709-004:2020 (E)
1 Scope
This document will provide means of compliance to cover lighting related requirements for Part 2 to 4 of
the Annex to the Commission Delegated Regulation on unmanned aircraft and on third country UAS
The purpose is to be able to verify that an UA is equipped with lights which:
— ensure controllability of the UA.
— ensure conspicuity of the aircraft at night, the design of the light shall allow a person on the ground
to distinguish a UA from a manned aircraft.
This document addresses:
— definition of types, technical requirements, and technical parameters of UA lights (e.g. position of
lights for different UA categories, intensity for different operation modes).
— definition of purpose, test procedures, requirements, and compliance rules to evaluate UA lights.
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.
prEN 4709-001:2019 , Aerospace series — Unmanned Aircraft Systems — Part 001: Product
requirements and verification
EN IEC 62368-1:2020, Audio/video, information and communication technology equipment - Part 1: Safety
requirements (IEC 62368-1:2018)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
• IEC Electropedia: available at
• ISO Online browsing platform: available at
control operational modes
safety control categories for which the UA can be operated: automatic, semi-automatic, manual direct
Note 1 to entry Several flight control modes can be used for each category.

At draft stage.

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automatic control operational mode
control operational mode where the UA attitude, speed and flight path are fully controlled by the flight
control system
Note 1 to entry No pilot input is needed to address flight control and vehicle steering, other than to load or
modify the required flight plan or waypoint parameters. C2 link performance and latency are not an issue for control
stability and guidance, besides situation awareness and collision avoidance issues. Examples of automatic modes
are waypoint path navigation, waypoint holding (hovering/loitering), automatic take-off, automatic landing, follow-
me mode, return to home, etc
semi-automatic control operational mode
control operational mode where the remote pilot commands outer loop parameters such as altitude,
heading and UA speed in given values specified by the UA manufacturer
Note 1 to entry The flight control system operates the UA controls to achieve the commanded outer loop
parameter value. Envelope flight protection and/or control decoupling functions should be in place in this control
operational mode. The flight manual shall clearly specify, for any possible/available control mode that is classified
as semi-automatic, for each degree of freedom, the level of involvement of the pilot to address control stability. For
assisted modes a higher latency on C2 link may be adequate (e.g. < 5 s) but vehicle steering is always pilot direct
responsibility. A wide range of flight control modes are semi-automatic, from low level attitude/rate control,
autopilot heading/speed/altitude control, velocity control; position control may be considered semi-automatic if
pilot input is transformed into position commands continuously (or an automatic mode if pilot inputs only modify
waypoint coordinates in on-board autopilot)
manual direct piloting control operational mode
control operational mode where the remote pilot directly commands UA controls (e.g. aerodynamic
surfaces through servo-actuators and engine through electronic speed control)
Note 1 to entry This control mode does not benefit (as a general rule) of autopilot aiding action (e.g.
stability/control augmentation systems SAS/CAS, flight envelope protection FEP) and the pilot is also directly
responsible for vehicle stability (no hand-off control is allowed). Link performance and latency is critical (e.g.
<< 1 s).
Note 2 to entry derived from STANAG 4703 UL47.1 definition.
effective frequency
frequency at which the UA complete light for conspicuity system is observed from a distance and applies
to each sector of light including any overlaps that exist when the system consists of more than one light

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4 Technical specifications
4.1 General
Used Lights for controllability, conspicuity or other purposes shall be either fixed by the UAS
manufacturer or attached by the UA operator as add-on lights.
All lights described in the following Clause 5 and Clause 6 shall comply with requirements of EN
IEC 62368-1 to reduce the likelihood of painful effects and injury due to optical energy to eyes or skin.
If the UAS manufacturer implements a solution to automatically switch off the UA light system partly or
completely at night, the off time of the affected lights for controllability and conspicuity shall not exceed
10 seconds.
4.2 Add-on lights
Add-on lights shall be equipped on the UA with either
a) a connection to an accessible interface for electrical power or
b) without affecting the controllability of the UA (prEN 4709-001:2019) using independent power
Add-on lights are considered as equipment in accordance to definition prEN 4709-001:2019. Therefore,
equipping an UA with Add-on lights should lead to not exceed the allowed maximum take-off mass
(MTOM) for the required class in accordance to prEN 4709-001:2019.
If Add-on lights are used, the manufacturer of the Add-on lights shall place instructions on how to install
and operate the Add-on light.
4.3 Colours
Every light colour proposed for lights for controllability and for conspicuity should follow the aviation
colour system for orientation indication in the colours aviation green, red and white [CS-
23 Amendment 4 - CS 23.1397 Colour specifications].
Each light colour should have the applicable International Commission on Illumination chromaticity
coordinates as follows:
a) Aviation Red:
´y´ is not greater than 0.335; and
´z´ is not greater than 0.002.
b) Aviation Green:
´x´ is not greater than 0.440 – 0.320 y;
´x´ is not greater than y – 0.170; and
´y´ is not less than 0.390 – 0.170 x.
c) Aviation White:
´x´ is not less than 0,300 and not greater than 0,540;
´y´ is not less than “x – 0,040” or “y – 0,010,” whichever is the smaller; and

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´y´ is not greater than “x + 0,020” nor “0,636 – 0,400x”;
where ´y ´ is the y coordinate of the Planckian radiator for the value of ´x´ considered.

Figure 1 — Colour representation of aviation colours in CIE1931 format
5 Lights for controllability
5.1 General
The purpose of lights for controllability is to provide the remote pilot with sufficient information about
the position, attitude and heading of the UA and regarding the control mode [see 3.1].
Annex A provides additional guidance of acceptable light positions according to types and size of UA.
5.2 Performance Specification
5.2.1 General
If the UA is operated during night , the UA shall be equipped with lights for controllability according to
their control mode [3.1].

2) Night means the hours between the end of evening civil twilight and the beginning of morning civil twilight as defined in

Implementing Regulation (EU) N 923/2012.


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NOTE If the UA manufacturer decides to equip and operate the UA with lights for controllability for daytime
operations as well, the same specifications in Clause 5 apply.
The UA shall be equipped with one or more lights for controllability using one of the following colour
• red, green, and white permanent light.
• red or white alternating light alternating with green light for conspicuity.
Every UA with

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