kSIST FprEN 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
- 5020 - Formal vote (FV) (Adopted Project)
- Start Date
- 13-Apr-2026
- Due Date
- 01-Jun-2026
- Completion Date
- 14-Apr-2026
kSIST FprEN 4709-004:2026 is a CEN aerospace standard for unmanned aircraft systems (UAS) lighting requirements. It specifies how to verify that an unmanned aircraft (UA) has lights for controllability, conspicuity at night, and other light functions, for manufacturers, integrators, operators, and test teams working to EU unmanned-aircraft rules.
What does kSIST FprEN 4709-004:2026 specify?
kSIST FprEN 4709-004:2026 specifies lighting-related means of compliance for Parts 2 to 4 of the Annex to Delegated Regulation (EU) 2019/945. It focuses on the UA being equipped with the right lights, the right colours, and the right test methods so that the lights can be checked in practice.
The document links controllability lighting to the control mode of the UA, and conspicuity lighting to night-time visibility. It also covers add-on lights, other purpose lights, and how to verify performance by test.
Document structure
- Clause 1 Scope
- Clause 2 Normative references
- Clause 3 Terms and definitions
- Clause 4 Technical specifications
- Clause 5 Lights for controllability
- Clause 6 Lights for conspicuity
- Clause 7 Lights for other purposes
- Annex A - Reference implementations
- Annex ZA - Relationship with Delegated Regulation (EU) 2019/945
| Annex | What it covers |
|---|---|
| Annex A | Example light layouts and design guidance for different UA types and sizes |
| Annex ZA | Relationship between the document and the essential requirements of Delegated Regulation (EU) 2019/945 |
What are the key requirements of kSIST FprEN 4709-004:2026?
kSIST FprEN 4709-004:2026 sets out the main lighting choices, the colour rules, and the tests used to show that the UA lighting behaves as required. In practice, this is the part of the document that tells a manufacturer or test lab what must be present on the aircraft and how to check it.
General technical rules
Clause 4.1 says lights for controllability, conspicuity, or other purposes may be fixed by the UAS manufacturer or added by the operator as add-on lights. The same clause requires the lights covered by Clauses 5 and 6 to comply with EN IEC 62368-1 to reduce the risk of eye or skin injury from optical energy. If the manufacturer uses an automatic night switch-off, the affected controllability and conspicuity lights may be off for no more than 10 seconds.
Clause 4.2 requires add-on lights to have access to electrical power or their own independent power source, without harming controllability. It also treats add-on lights as equipment, so their mass has to be considered against the allowed MTOM for the UA class. This matters because the lights can affect both flight performance and class compliance.
Colours and visible identification
Clause 4.3 limits the colour choices to the aviation orientation colours green, red, and white, with chromaticity coordinates tied to the aviation colour system. In practical terms, this keeps the light signals recognizable and consistent, rather than leaving colour interpretation open.
Controllability lights
Clause 5 says that if the UA is operated at night, it shall have controllability lights matched to the control mode. For manual direct piloting, the lights shall indicate attitude, heading, and position. For semi-automatic control, the lights shall indicate at least heading and position while hovering or loitering.
Clause 5 also says an automatic control mode should be able to switch to semi-automatic or manual control mode, and if an emergency or abnormal function forces manual mode, the manual lighting requirements apply. This matters because the pilot must still read the aircraft state when control is changed during flight.
Clause 5.3 sends the verification of safe controllability at night to the test methods in EN 4709-001. That means the lighting checks are not isolated from the wider aircraft controllability assessment.
Conspicuity lights
Clause 6 requires lights that make the UA visible and distinguishable from a manned aircraft at night. The light system uses either green blinking/flashing lights or green alternating with red or white controllability lights, and it must be recognizable from up to 120 m when the UA is flying.
The field of coverage has to extend at least 5° below the horizontal plane, except for limited obstructed areas totaling no more than 0.05 steradians. This matters because the aircraft has to remain visible from realistic viewing angles, not only from one ideal direction.
Clause 6.2.2 sets timing rules for blinking and flashing green lights, including the allowed effective frequency, on-time, and duty range. Clause 6.2.3 does the same for alternating-light arrangements, with its own frequency and on-time limits. These timing rules make the visual signal predictable enough to be recognized at distance.
Verification methods
Clause 6.3 provides three ways to test conspicuity performance: an outdoor distance video test, an indoor field-of-coverage test, and a cycle-rate test. The tests use night conditions, defined camera positions, light meters, and repeated runs so the result can be documented and compared to the performance limits.
Other purpose lights
Clause 7 covers lights such as anti-collision, warning, caution and advisory, landing, and auxiliary lights. These lights must not distract the remote pilot or interfere with conspicuity lights, and add-on versions must respect the payload installation and MTOM rules from the companion UAS requirements document. For verification, they are included in the lighting test setups so the conspicuity lights remain visible at all times.
What terms does kSIST FprEN 4709-004:2026 define?
kSIST FprEN 4709-004:2026 defines the operating modes and signal terms used to decide which lights are needed. These definitions matter because the lighting requirement changes with the way the UA is flown.
- Control operational modes - The safety control categories for operating a UA: automatic, semi-automatic, and manual direct piloting.
- Automatic control operational mode - The flight control system fully controls attitude, speed, and flight path, with no pilot input needed for direct steering.
- Semi-automatic control operational mode - The remote pilot commands outer-loop values such as altitude, heading, or speed, while the flight control system carries out the control action.
- Manual direct piloting control operational mode - The remote pilot directly commands the UA controls, and the pilot remains responsible for stability.
- Effective frequency - The observed frequency of the full conspicuity-light cycle, including any overlap between multiple light sources.
- Conspicuity - The night-time visibility condition that allows a person on the ground to distinguish a UA from a manned aircraft.
Who uses kSIST FprEN 4709-004:2026?
kSIST FprEN 4709-004:2026 is used by UA and UAS manufacturers, especially teams designing flight lights and choosing light positions for different UA categories and sizes. It is also used by add-on light manufacturers because the document sets installation, power, and instruction needs for those products.
Test laboratories and conformity assessment teams use it to run the distance, field-of-coverage, and cycle-rate tests. Operators and buyers use it to check whether a UA lighting setup matches the intended control mode and night-operation use.
Which standards are used with kSIST FprEN 4709-004:2026?
kSIST FprEN 4709-004:2026 uses a small set of companion documents to define related requirements and verification.
- EN 4709-001 - Provides product requirements and verification for the broader UA system, and its test methods are used for controllability verification.
- EN IEC 62368-1:2020 - Provides safety requirements for audio/video, information and communication technology equipment, used here to reduce optical-energy injury risk.
- ISO 21384-4:2025 - Is cited in the scope for the meaning of conspicuity at night.
- CS-23 Amendment 4 - CS 23.1397 Colour specifications - Is cited for the aviation colour system used for red, green, and white light colours.
What does the kSIST FprEN 4709-004:2026 document contain?
kSIST FprEN 4709-004:2026 contains technical specifications, colour guidance, and test methods rather than design formulas or worked product examples. Clause 4 sets the general light rules, including add-on lights and colour coordinates.
Clauses 5 and 6 provide the performance requirements for controllability and conspicuity, along with the test methods used to check them. Those tests include the outdoor video setup, the indoor field-of-coverage setup, and the cycle-rate check.
Annex A gives reference implementations and example light layouts for multicopter and fixed-wing UA, using pictograms and patterns to show how the clauses can be applied in design. Annex ZA links the document to the essential requirements of Delegated Regulation (EU) 2019/945 so users can see which parts of the standard support each class requirement.
Relations
- Effective Date
- 28-Jan-2026
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Frequently Asked Questions
kSIST FprEN 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
kSIST FprEN 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.
kSIST FprEN 4709-004:2026 has the following relationships with other standards: It is inter standard links to SIST EN ISO 5270:2022. Understanding these relationships helps ensure you are using the most current and applicable version of the standard.
kSIST FprEN 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.
kSIST FprEN 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
...