SIST EN 4709-004:2026
(Main)Aerospace series - Unmanned Aircraft Systems - Part 004: Lighting requirements
- Abstract
This document will provide means of compliance to cover lighting related requirements for Parts 2 to 4 of the Annex to the Commission Delegated Regulation (EU) 2019/945 on unmanned aircraft and on third country UAS operators.
The purpose is to be able to verify that an UA is equipped with lights:
— for the controllability of the UA (the effectiveness of those lights is not part of the lighting requirement but is covered by the controllability requirement; therefore, its verification is covered by the clause addressing the controllability requirement of EN 4709 001:2026);
— that ensure conspicuity of the unmanned aircraft at night (see 3.45 of ISO 21384 4:2025), 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
- Status
- Not Published
- Public Enquiry End Date
- 24-Feb-2021
- Technical Committee
- I13 - Imaginarni 13
- Current Stage
- 6060 - National Implementation/Publication (Adopted Project)
- Start Date
- 19-Oct-2026
- Due Date
- 24-Dec-2026
SIST EN 4709-004:2026 is a SIST standard in the Aerospace series for unmanned aircraft systems (UAS). It specifies lighting requirements for unmanned aircraft (UA) so that manufacturers and operators can verify lights for controllability and conspicuity, especially for night operations and compliance work linked to Delegated Regulation (EU) 2019/945.
The standard focuses on what lights are needed, how they may be installed, what colours and performance levels are used, and how those lights are tested. It is aimed at people designing, supplying, checking, or operating UA lighting systems.
What does SIST EN 4709-004:2026 specify?
SIST EN 4709-004:2026 gives means of compliance for lighting-related requirements for Parts 2 to 4 of the Annex to Delegated Regulation (EU) 2019/945. It covers UA lights for controllability, conspicuity at night, and other purposes that may be fitted on the aircraft.
The document is organized into general technical specifications, controllability lights, conspicuity lights, and lights for other purposes, followed by informative guidance and a regulatory relationship annex.
| Annex | What it covers |
|---|---|
| Annex A | Reference implementations and example light layouts for different UA types and sizes |
| Annex ZA | Relationship between the document and the essential requirements of Delegated Regulation (EU) 2019/945 |
The scope also links the lighting verification to EN 4709-001 for controllability effectiveness, so the lighting standard does not stand alone in that area.
What are the key requirements of SIST EN 4709-004:2026?
General design and installation rules
Clause 4 states that lights for controllability, conspicuity, or other purposes shall be either fixed by the UAS manufacturer or fitted by the operator as add-on lights. This matters because the standard covers both built-in and retrofit lighting arrangements.
Clause 4 also requires the lights in Clauses 5 and 6 to comply with EN IEC 62368-1 to reduce the risk of eye or skin injury from optical energy. If a manufacturer implements an automatic night switch-off for part or all of the light system, the off time of the affected controllability and conspicuity lights shall not exceed 10 seconds.
For add-on lights, Clause 4 requires either an accessible electrical power interface or independent power equipment that does not affect controllability. Add-on lights are treated as equipment under prEN 4709-001:2019, so their installation can affect maximum take-off mass (MTOM) and must be handled within the required class limits.
Colour requirements
Clause 4 limits the proposed colours for controllability and conspicuity lights to aviation green, red, and white. The document gives chromaticity coordinates for each colour family.
In practice, this means the light colours should be consistent enough to support orientation and recognition. A clear colour definition helps the remote pilot interpret the aircraft attitude and heading, and helps observers distinguish the UA from other aircraft.
Controllability lights
Clause 5 says the purpose of controllability lights is to give the remote pilot enough information about position, attitude, heading, and the control mode. If the UA is operated at night, it shall be equipped with controllability lights according to its control mode.
For manual direct piloting control mode, the UA shall indicate attitude, heading, and position. For semi-automatic control mode, it shall indicate at least heading and position while hovering or loitering. Clause 5 also states that a UA with automatic control mode should be able to switch to semi-automatic or manual control mode.
This matters because the light arrangement has to match how the aircraft is flown. A pilot needs different visual cues depending on whether the UA is fully manual, semi-automatic, or automatic.
Conspicuity lights
Clause 6 states that conspicuity lights are intended to make the aircraft visible at night and allow a person on the ground to distinguish a UA from a manned aircraft. The standard allows green blinking or flashing lights, or green alternating with red or white lights used for controllability.
Clause 6 requires conspicuity lights to be recognizable from up to 120 m when the UA is flying. It also sets a field of coverage requirement extending at least 5° below the horizontal plane, with total obstructed visibility not exceeding 0.05 steradians.
For blinking and flashing modes, Clause 6 sets limits on cycle frequency and on-time. For alternating modes, it sets limits on the off interval and on-time as well.
In practice, this means the lighting has to be visible far enough away and from enough angles to support night recognition, not just straight ahead or directly below.
Other lights on the UA
Clause 7 covers lights used for other purposes, such as anti-collision, warning, caution and advisory, landing, and auxiliary lights. These lights shall not impair the remote pilot’s vision or distract from conspicuity lights.
Installed lights for other purposes should also reduce the likelihood of optical injury in line with EN IEC 62368-1, or they should be used only at a safe distance from people on the ground, or be placed above the horizontal plane of the UA. Add-on lights in this category must also comply with the payload installation and MTOM requirements from prEN 4709-001:2019.
Clause 7 also says these extra lights must be included in the test setups used for conspicuity, so their presence does not hide the required conspicuity signals.
What terms does SIST EN 4709-004:2026 define?
- Unmanned aircraft (UA) - The aircraft covered by the lighting requirements, including its lighting setup for controllability and conspicuity.
- Unmanned aircraft system (UAS) - The aircraft together with the supporting system, used here in connection with manufacturer-installed or operator-installed lights.
- Control operational modes - The safety control categories for operation: automatic, semi-automatic, and manual direct piloting.
- Automatic control operational mode - A mode where the flight control system fully controls attitude, speed, and flight path, with no pilot input needed for steering except to load or adjust the flight plan.
- Semi-automatic control operational mode - A mode where the remote pilot commands outer-loop parameters such as altitude, heading, and speed, while the flight control system carries out the control action.
- Manual direct piloting control operational mode - A mode where the remote pilot directly commands the UA controls and is directly responsible for vehicle stability.
- Effective frequency - The frequency at which the complete conspicuity light system is observed from a distance, including each sector and any overlaps.
Who uses SIST EN 4709-004:2026?
SIST EN 4709-004:2026 is used by UAS manufacturers, add-on light manufacturers, operators, and verification teams working on night-capable UA lighting. It is also relevant to engineering, quality, and conformity assessment staff who need to design, install, test, or review lighting systems against regulatory requirements.
It is particularly useful in aerospace and UAS development where the aircraft must support controllability cues for the remote pilot and conspicuity for people on the ground. Test engineers and compliance specialists use it to plan lighting checks and interpret the required test methods.
Which standards are used with SIST EN 4709-004:2026?
- prEN 4709-001:2019, Aerospace series - Unmanned Aircraft Systems - Part 001: Product requirements and verification - Provides the product requirements and verification basis for controllability, add-on equipment, payload installation, and MTOM-related considerations.
- EN IEC 62368-1:2020, Audio/video, information and communication technology equipment - Part 1: Safety requirements - Provides the optical energy safety requirements referenced for reducing the likelihood of painful effects and injury to eyes or skin.
What does the SIST EN 4709-004:2026 document contain?
The document contains clause-based technical requirements, defined terms, and test methods for UA lighting. It includes a colour section with aviation colour guidance and a figure showing colour representation in CIE1931 format.
It also contains test setups for conspicuity distance verification, field of coverage checking, and cycle-rate measurement. These include both outdoor video-based methods and an indoor direct test arrangement with specified viewing positions and measurement steps.
Annex A adds reference implementations with example light layouts for multicopters and fixed-wing UA. The examples show how controllability and conspicuity functions can be combined in a practical design, but they are guidance rather than verification by themselves.
Annex ZA links the document to the essential requirements of Delegated Regulation (EU) 2019/945. This makes the standard usable as a technical route for demonstrating conformity within its stated scope.
Relations
- Effective Date
- 21-Oct-2026
- Effective Date
- 21-Oct-2026
- Effective Date
- 28-Jan-2026
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Frequently Asked Questions
SIST EN 4709-004:2026 is a draft published by the Slovenian Institute for Standardization (SIST). Its full title is "Aerospace series - Unmanned Aircraft Systems - Part 004: Lighting requirements". This standard covers: This document will provide means of compliance to cover lighting related requirements for Parts 2 to 4 of the Annex to the Commission Delegated Regulation (EU) 2019/945 on unmanned aircraft and on third country UAS operators. The purpose is to be able to verify that an UA is equipped with lights: — for the controllability of the UA (the effectiveness of those lights is not part of the lighting requirement but is covered by the controllability requirement; therefore, its verification is covered by the clause addressing the controllability requirement of EN 4709 001:2026); — that ensure conspicuity of the unmanned aircraft at night (see 3.45 of ISO 21384 4:2025), 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
This document will provide means of compliance to cover lighting related requirements for Parts 2 to 4 of the Annex to the Commission Delegated Regulation (EU) 2019/945 on unmanned aircraft and on third country UAS operators. The purpose is to be able to verify that an UA is equipped with lights: — for the controllability of the UA (the effectiveness of those lights is not part of the lighting requirement but is covered by the controllability requirement; therefore, its verification is covered by the clause addressing the controllability requirement of EN 4709 001:2026); — that ensure conspicuity of the unmanned aircraft at night (see 3.45 of ISO 21384 4:2025), 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
SIST EN 4709-004:2026 is classified under the following ICS (International Classification for Standards) categories: 49.020 - Aircraft and space vehicles in general. The ICS classification helps identify the subject area and facilitates finding related standards.
SIST EN 4709-004:2026 has the following relationships with other standards: It is inter standard links to SIST EN 4709-001:2026, SIST EN 17206-3:2026, SIST EN ISO 5270:2022. Understanding these relationships helps ensure you are using the most current and applicable version of the standard.
SIST EN 4709-004:2026 is associated with the following European legislation: EU Directives/Regulations: 2019/945; Standardization Mandates: M/567. When a standard is cited in the Official Journal of the European Union, products manufactured in conformity with it benefit from a presumption of conformity with the essential requirements of the corresponding EU directive or regulation.
SIST EN 4709-004:2026 is available in PDF format for immediate download after purchase. The document can be added to your cart and obtained through the secure checkout process. Digital delivery ensures instant access to the complete standard document.
Standards Content (Sample)
SLOVENSKI STANDARD
oSIST prEN 4709-004:2021
01-februar-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
lumineux
Ta slovenski standard je istoveten z: prEN 4709-004
ICS:
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.
oSIST prEN 4709-004:2021
oSIST prEN 4709-004:2021
DRAFT
EUROPEAN STANDARD
prEN 4709-004
NORME EUROPÉENNE
EUROPÄISCHE NORM
December 2020
ICS
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-
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, 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.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
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.
oSIST prEN 4709-004:2021
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
oSIST prEN 4709-004:2021
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
Enquiry.
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
document.
oSIST prEN 4709-004:2021
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
operators.
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.
1)
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 http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
control operational modes
safety control categories for which the UA can be operated: automatic, semi-automatic, manual direct
piloting
Note 1 to entry Several flight control modes can be used for each category.
1)
At draft stage.
oSIST prEN 4709-004:2021
prEN 4709-004:2020 (E)
3.2
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
3.3
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)
3.4
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.
3.5
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
source
oSIST prEN 4709-004:2021
prEN 4709-004:2020 (E)
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
equipment.
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
oSIST prEN 4709-004:2021
prEN 4709-004:2020 (E)
´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
2)
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
o
Implementing Regulation (EU) N 923/2012.
oSIST prEN 4709-004:2021
prEN 4709-004:2020 (E)
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
schemes:
• red, green, and white permanent light.
• red or white alternating light alternating with green light for conspicuity.
Every UA with
...