ISO 24355:2023

INTERNATIONAL ISO
STANDARD 24355
First edition
2023-05
Flight control system for civil small
and light multicopter unmanned
aircraft system (UAS) — General
requirements
Système de contrôle de vol pour les multicoptères civils télépilotés
petits et légers — Exigences générales
Reference number
© ISO 2023
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ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviated terms . 1
5 Systems and functions .2
5.1 System composition . 2
5.2 Flight control unit . 2
5.2.1 Angular velocity control . 2
5.2.2 Attitude control . 3
5.2.3 Velocity control . 3
5.2.4 Position control . 3
5.3 Navigation unit . 3
5.3.1 General . 3
5.3.2 General requirements . 3
5.3.3 Optional function . 3
5.3.4 Flight management . 4
5.4 Flight recorder . 5
5.5 Safety and emergency management. 5
5.6 Interface . 6
5.7 Communication with RPS . 6
6 Performance requirements . .7
6.1 Performance requirements for FCS manufacturer . 7
6.1.1 System accuracy requirements . 7
6.1.2 Flight quality requirements . 7
6.2 Performance requirements of the navigation system . 7
7 Requirements and recommendations of support and maintenance .7
7.1 Firmware upgrade and version management . 7
7.2 User configuration and tuning support . 8
7.3 User manual . 8
8 Identification, packaging, transportation and storage . 8
8.1 General . 8
8.2 Identification . 8
8.3 Packaging . 9
8.4 Transportation and storage . 9
Bibliography .10
iii
Foreword
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iv
INTERNATIONAL STANDARD ISO 24355:2023(E)
Flight control system for civil small and light multicopter
unmanned aircraft system (UAS) — General requirements
1 Scope
This document specifies the composition, functional and performance requirements of flight controls
for civil multicopter unmanned aircrafts (UAs) with the maximum take-off mass (MTOM) less than or
equal to 25 kg corresponding to unmanned aircraft systems (UAS) at levels I, II, III and IV as graded in
ISO 21895 which does not include fully autonomous flights.
The flight control system in this document consists of flight control unit, navigation unit, fault diagnosis
and management unit, flight planning, flight recorder, etc. This document is applicable to the design
and manufacture of other UA flight control systems or subsystems.
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.
ISO 21384-4, Unmanned aircraft systems — Part 4: Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 21384-4 and the following
apply.
ISO and IEC maintain terminology 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
attitude control mode
flight control system mode that controls the attitude of the aircraft, but not the position of the aircraft
3.2
hover state
function or mode of keeping the position and height of an aircraft relatively unchanged in position mode
without receiving any external control instructions
4 Abbreviated terms
AGL above ground level
C2 command and control
FCS flight control system
GNSS global navigation satellite system
ICAO International Civil Aviation Organisation
IMU inertial measurement unit
MTOM maximum take-off mass
RNP required navigation performance
RTK real time kinematic
RPS remote pilot station
UA unmanned aircraft
UAS unmanned aircraft system
5 Systems and functions
5.1 System composition
The FCS of multicopter UAS usually includes aircraft motion control unit, navigation unit, fault diagnosis
and management unit, power management unit and flight recorder. The typical information flow of the
FCS is described in Figure 1.
Figure 1 — Typical information flow of the FCS
5.2 Flight control unit
5.2.1 Angular velocity control
The FCS shall have the following angular velocity control functions:
a) respond to angular velocity commands in pitch, roll and yaw directions based on navigation
information;
b) control the UA angular velocity to reach the target angular velocity within the allowable time;
c) when the angular velocity control command is zero, the system should maintain current attitude
angle unchanged.
NOTE Angular velocity control is also called rate control in many cases.
5.2.2 Attitude control
The FCS shall have the following attitude control functions:
a) adjust the aircraft attitude to the target value in a certain time according to the attitude angle
command;
b) withstand the unexpected change of aircraft attitude angle caused by external forces during the
flight.
5.2.3 Velocity control
When equipped with navigation sensors for velocity measurements/estimation, the FCS shall have the
following velocity control functions:
a) adjust the aircraft velocity to the target value in a certain time according to the velocity command;
b) withstand the unexpected change of aircraft speed caused by external forces during the flight.
5.2.4 Position control
When equipped with navigation sensors for position measurements/estimation, position control should
have the following functions:
a) control the aircraft to the target position;
b) keep the position of the aircraft when the position control command remains unchanged.
5.3 Navigation unit
5.3.1 General
This subclause applies to the FCS with navigation capability.
5.3.2 General requirements
The navigation unit shall have the following functions:
a) calculate all or some of other values such as the longitude and
...