GM1 UAS.SPEC.050(1)(c) Responsibilities of the UAS Operator
CAA ORS9 Decision No. 16
EFFICIENT USE OF RADIO SPECTRUM
It is the responsibility of the UAS Operator to ensure that the radio spectrum used for the C2 Link and for any payload communications complies with the relevant Ofcom requirements and that any licences required for its operation have been obtained.
It is also the responsibility of the operator to 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.
Licensing of frequency allocations is the responsibility of Ofcom and hence, where required, all applications for a frequency assignment should be directed in the first instance to Ofcom. In frequency bands where the CAA is the assigning authority, the application will be passed to the CAA by Ofcom so that the CAA can conduct the technical work however, Ofcom remains the licensing authority.
Where a frequency licence is required (e.g., in protected frequency bands or where powers exceed the current regulatory limits) the CAA will not be able to issue a permission or exemption.
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) where the whereabouts of other users is usually difficult to assess.
2.4 GHz is a licence free band used for car wireless keys, household internet and a wide range of other applications. Although this is considered to be far more robust to interference than 35 MHz, operators must 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 a licenced band which requires a minimum payment and registration with Ofcom. This band is in use with other services including amateur-satellite, weather and military radars. Details can be found on the Ofcom website.
For further UAS specific guidance on whether a licence is required for your UAS, more information can be found on the Ofcom website.
Operations close to any facility that could cause interference (such as a radar station) could potentially disrupt communications with the UAS, whatever the frequency in use. GNSS jamming activities may also disrupt communications as well as C2 signals. Information on scheduled GNSS jamming exercises can be found on the Ofcom website.
The risk assessment process described in the AMC and GM to Article 11 Rules for conducting an operational risk assessment is likely to involve a radio frequency survey, in order to meet UAS.SPEC.050 Responsibilities of the UAS operator (1)(c), which should also include a physical range check.
UAS Operators are advised to carry out such a survey, when assessing the suitability of a site for a proposed UAS Operation. In doing so, the operator should:
· Explain how C2 instructions, as well as telemetry data, are relayed between the command unit and the UA.
· Describe in detail Operational C2 link management, including frequency switchovers and C2 link contingency situations.
· Provide the Link Budget Calculation, wherever possible1
The following table may assist in this survey:
| Survey element considerations when assessing the suitability of a site for a proposed UAS Operation | ||
|---|---|---|
| C2 Link |
Radio Line Of Sight (RLOS) C2 link |
|
| Beyond Radio Line Of Sight (BRLOS) C2 link (if applicable) | ||
| Transceivers / Modems |
Power Levels |
|
|
Transmission Schemes |
||
|
Operating Frequencies Used |
||
|
Third Party Link Service Provider |
||
|
Minimum and average assured data Rates |
||
|
Minimum and average assured latencies |
||
|
Means of protection against harmful interference |
||
|
Any other relevant information |
||
|
Operating Frequencies Used |
||
Providing a detailed control system architecture diagram that includes informational or data flows and subsystem performance may assist in explaining the requirements above.
C2 link could include, direct (RLOS) or relayed (BRLOS). BRLOS includes all satellite systems or relaying C2 link through UA in the air to extend the signal range.
The following examples of technical solutions may help make the C2 link secure: pairing, encryption or back up link. It is recommended to use licensed spectrum for BVLOS operations to minimise the chances of external interference and to improve latency.
The UAS Operator should identify what alerts, such as warning, caution and advisory alerts, does the system provide to the operator and RP, to advise them of C2 link disruption.
The UAS Operator should consider what design characteristics or procedures are in place to maintain the availability, continuity, and integrity of the datalink. Factors to consider:
- RF or other interference
- Flight beyond communications range
- Antenna masking (during turns and/or at high attitude angles)
- Loss of command unit functionality
- Loss of UA functionality
- Atmospheric attenuation including precipitation
- RF wireless site survey to ensure reliable connectivity, it may include:
o Survey for frequency coverage throughout the potential operating area.
o Survey for frequency capacity to ensure sufficient bandwidth to support all predicted operations.