OSO 6 – C3 link characteristics
AMC1 Article 11 Annex E. Operational Safety Objective 6
CAA ORS9 Decision No. 46
OSO 6 – C3 link characteristics (e.g. performance spectrum use) are appropriate
Level of integrity
| Criterion | Low (SAIL 2, 3) | Medium (SAIL 4) | High (SAIL 5, 6) |
|---|---|---|---|
| Technical issue with the UAS | OSO6.L.I |
OSO6.L.I |
OSO6.L.I OSO6.H.I |
Level of assurance
| Criterion | Low (SAIL 3) | Medium (SAIL 4) | High (SAIL 5, 6) |
|---|---|---|---|
| Technical issue with the UAS | OSO6.L.A |
OSO6.M.A |
OSO6.M.A OSO6.H.A |
Low level of robustness (SAIL 2 and 3)
OSO6.L.I
(a) The performance, RF spectrum usage and environmental conditions for C3 links must be adequate to safely conduct the intended operation.
(b) The remote pilot must have the means to continuously monitor the C3 performance and to ensure that the performance continues to meet the operational requirements.
OSO6.L.A
The Applicant must declare and provide evidence of compliance with the Integrity requirements. The detailed evidence of compliance may be assessed by the CAA. AMC.OSO6.L.I
(a) The use of unlicensed frequency bands may be acceptable under certain conditions, such as:
(1) The Applicant demonstrates compliance with other applicable RF spectrum usage requirements. Further information on spectrum allocation can be found in Ofcom guidance. And,
(2) The Applicant provides evidence of the use of mechanisms to protect against interference (e.g. FHSS frequency deconfliction by procedure).
(b) This may be demonstrated by monitoring the C2 link signal strength and receiving an alert from the UAS HMI if the signal becomes too low (SAIL 2 and 3 only).
Medium level of robustness (SAIL 4)
Lower robustness level requirements to be complied with:
• OSO6.L.I
Additional requirements to be compiled with:
OSO6.M.I
No additional requirements.
OSO6.M.A
(a) The C3 link performance must be demonstrated per a standard or means of compliance acceptable to the CAA.
(b) The Applicant must provide evidence of compliance with the Integrity requirements, which will be assessed by the CAA.
AMC.OSO6.M.A
Annex E – AMC 1 Integrity and assurance levels for the Operational Safety Objectives (OSO) paragraph 1.5 provides further information about proposing a standard as an AMC.
High level of robustness (SAIL 5 and 6)
Lower robustness level requirements to be complied with:
• OSO6.L.I
• OSO6.M.A
Additional requirements to be compiled with:
OSO6.H.I
Licensed frequency bands must be used for the C2 link.
OSO6.H.A
The Applicant must provide evidence of compliance with the Integrity requirements, which will be assessed by the CAA. The CAA will validate continuing compliance through oversight.
AMC.OSO6.H.I
Depending on the operation:
The use of non-aeronautical bands (e.g. licensed bands for cellular network) may be acceptable.
The use of bands allocated to the aeronautical mobile service for the use of C2 Link (e.g. 5030 – 5091 MHz) may be required. The use of FSS satellite links may be acceptable. The use of MSS satellite links and particularly AMS(R)S capacity may be required.
GM1 Article 11 Annex E. Operational Safety Objective 6
CAA ORS9 Decision No. 46
GM.OSO6
(a) In this OSO, the term “C3 link” encompasses:
(1) The Command and Control (C2) link, and
(2) Any communication link required for the safety of the flight.
(b) To correctly assess the integrity of this OSO, the applicant should identify:
(1) The C3 links performance requirements necessary for the intended operation.
(2) All C3 links, together with their actual performance and Radio Frequency (RF) spectrum usage.
The specification of performance and RF spectrum for a C2 Link is typically documented by the UAS designer in the UAS manual.
Main parameters associated with Required C2 Link Performance (RLP) and the performance parameters for other communication links (e.g. Required Communication Performance (RCP) for communication with ATC) include, but are not limited to the following:
(i) Transaction expiry time
(ii) Availability
(iii) Continuity
(iv) Integrity
The Applicant should refer to ICAO references for definitions, and to JARUS RPAS “Required C2 Link Performance” (RLP) concept.
(3) The RF spectrum usage requirements for the intended operation (including the need for authorization if required).
The UAS operator should ensure that the radio spectrum used for the C3 Link and for any payload communications complies with the relevant Ofcom requirements and that any licenses required for its operation have been obtained. The operator should ensure that the appropriate aircraft radio licence has been obtained for any transmitting radio equipment that is installed or carried on the aircraft, or that is used in connection with the conduct of the flight and that operates in an aeronautical band. There are no specific frequencies allocated for use by UAS in the UK, however the most used frequencies are 35 MHz, 2.4 GHz and 5.8 GHz.
35 MHz is a frequency designated for model aircraft use only, with the assumption that clubs and individuals will be operating in a known environment to strict channel allocation rules. It is therefore not considered to be a suitable frequency for more general UAS operations (i.e., not in a club environment).
2.4 GHz is an unlicenced band; although this is considered to be more robust to interference than 35 MHz, operators should act with appropriate caution in areas where it is expected that there will be a high degree of 2.4 GHz activity.
5.8 GHz is another unlicensed band. All operations of radio on a UAS including cellular and satellite communications requires registration with Ofcom.
(4) Environmental conditions that might affect the C3 links performance.
GM.OSO6.L.I
(b) The remote pilot should have continuous and timely access to the relevant C3 information that could affect the safety of flight.
GM.OSO6.M.I
Depending on the intended operation:
(a) The use of licensed frequency bands may be required by the CAA.
(b) The use of non-aeronautical bands (e.g. licensed bands for cellular network) may be acceptable.
GM.OSO6.H.I
The use of licensed frequency bands ensures a minimum level of performance and is not limited to aeronautical licensed frequency bands (e.g. licensed bands for cellular network). Nevertheless, some operations may require the use of bands allocated to the aeronautical mobile service for the use of C2 Link (e.g. 5030-5091 MHz) or MSS satellite link.
In any case, the use of licensed frequency bands requires authorisation.