CAP 722A | Second Edition
The second edition of CAP 722A released in December 2022 is intended to assist Applicants who are involved in the production of an Operational Risk Assessment (ORA) which will be used as supporting evidence for an application to the CAA for the operation of an Unmanned Aircraft System (UAS) in the Specific Category.
The intent of CAP 722A is to ensure that the required operational safety objectives and proposed target levels of safety have been met by the Applicant. This ensures regulatory compliance and that standard aviation safety practices are adopted by UAS operators before a UAS is authorised to operate in the UK.
The aim of the OSC is to present sufficient evidence that all relevant hazards and resultant Safety risks have been identified for the proposed operation and have been suitably mitigated to a tolerable and As Low As Reasonably Practicable (ALARP) level. This ensures an acceptable level of safety for the proposed operation.
This document shows how PilotAware Situational Awareness Data can be used as evidence for both the Strategic and Tactical Mitigation that will assist BVLOS operations in uncontrolled airspace to be undertaken at the As Low As Reasonably Practicable (ALARP) level.
The boundaries of LOS and BVLOS operations can be described as the Operational volume. This consists of the operating or flight geography area, and the emergency or continency area. With the operating height also taken into consideration this becomes the operating volume. A ground risk buffer is also a prudent consideration.
The risk of a mid-air collision is a generalised qualitative classification of the rate at which a UAV would encounter a manned aircraft in the specific operational Volume.
The inherent collision risks of an operational volume can be lowered through either strategic or tactical mitigation to reach the As Low As Reasonably Practicable (ALARP) risk category.
a) under the control of the Operator (mitigated by operational restriction).
b) not under the control of the Operator (mitigated by agreed or mandated common rules and structures).
Strategic Mitigations, supported by Common Flight Rules and Common Airspace Structures, are extremely important to reduce air conflicts or make conflict resolution easier.
However, it is the more dynamic Tactical Mitigation provided by the situational awareness available from the PilotAware Infrastructure that can reduce the risk of in-flight collisions. This is the subject of this document.
In an ideal world, a common, modern, universal electronic conspicuity standard, working on a single frequency and multiple technologies would be used by all aircraft to allow full interoperability. Unfortunately, due to physical, historic, operational and financial constraints, this is not possible.
Consequently, all types of cooperative electronic conspicuity devices in use today must be detected for complete situational awareness. In the UK, these different types include; Mode-S, ADSB(DF17), CAP1391(DF18), PilotAware, FLARM, OGN trackers, Fanet+ and mobile device applications.
The following diagram, taken from the EASA document Easy Access Rules for UAS, shows that Air Risk Category ARC-a is already at a level that is As Low As Reasonably Practicable (ALARP) and does not necessarily need mitigation. Also as ARC-d is in controlled airspace, the operator will be under the direct control of the responsible ATC, similar to that provided to a manned aircraft. For operational volumes with a higher risk category (TMPR) PilotAware infrastructure can provide data specific for both Strategic and Tactical Mitigation.
Tactical Mitigation of air risk includes the implementation of the ‘Detect and Avoid’ principles derived from traditional ‘See and Avoid’ techniques enhanced with Electronic Conspicuity.
The phases of Detect and Avoid are; Detect – Decide – Command – Execute – Feedback.
In a fully autonomous system, all of the above phases will be automatic and independent of the type of Electronic Conspicuity used by other air users in the Operational Area. Whilst this is a future aspiration that is currently out of financial reach, PilotAware technology is available in the UK now to enable operators to reduce MAC risks through direct operator involvement.
To undertake BVLOS operations in a defined low-risk (ARC-b) operational volume in Mainland Europe, one must be able to detect 50% of all aircraft in that volume. This increases to 90% of all aircraft in the defined medium risk (ARC-c) volume. Clearly to do this the detection of all classes of aircraft and Electronic Conspicuity is required.
Detecting the maximum number of aircraft possible.
The challenges to detecting the maximum number of aircraft in any operating volume is to accurately and cost-effectively;
i. Detect all classes of aircraft transmitting any EC genre chosen by UK pilots.
ii. Overcome signal obscuration due to hills, high buildings, moisture and temperature.
iii. Overcome airframe blocking the UHF signals transmitted by all EC devices.
iv. Provide sufficient redundancy to overcome single-point failures in detection.
v. Detect other UAVs using any EC down to ground level.
vi. Reduce the latency and refresh rates to a minimum across all data paths
vii. Provide RT and NRT information in both directions through interoperability.
In the UK and Europe, PilotAware infrastructure uses multiple types of Access Node to collect data from low-flying aircraft transmitting one, or more, of the major cooperative Electronic Conspicuity signals linked to a common aircraft ICAO address. These are ADSB (DF17) from a transponder, ADSB (DF18) from a CAP1391 transceiver (UK only), Mode-S, Fanet+, OGN trackers, FLARM, PilotAware and mobile applications. The diagram below shows one element of the PilotAware infrastructure – the ATOM ground station.
PilotAware has been developing Electronic Conspicuity and Situational Awareness systems since 2016. During this time it has become apparent that simple single point-to-point solutions do not provide sufficient integrity and redundancy to be able to consistently and continuously track all classes of aircraft and EC types, particularly at low levels. This is due to the nature of the UHF signals transmitted which are affected by attenuation and blocking due to airframe and topographical obscuration.
PilotAware has developed and refined technology to overcome this using multiple paths from multiple technologies. The combined network detects aircraft transmissions using airborne and ground-based assets that; detect, broadcast and relay information to other users and to the PilotAware servers.
The positions of aircraft detected locally can be accessed from an individual ground-based Access Node or the data can be joined together to provide a combined regional, national or continental view available to users from the PilotAware central servers.
All airborne PilotAware Rosetta EC devices will directly detect the location of other PilotAware users, ADSB and CAP1391 devices and Mode-C/S transmissions as a bearingless target. This is done instantly with an uninterrupted line of sight range of 30-50 km. This covers an amazing area when looking down from 4000ft. The single-board computer built into PilotAware in-flight devices also records all aircraft detected on all flights on a continuous basis for onward transmission or to be archived as required.
To enhance this basic air-to-air detection, a network of over 290 ground stations has been installed in the UK and a further 60 sites in mainland Europe. All PilotAware-equipped aircraft connect to one or more in range ATOM ground stations to mutually share situational awareness of the local area.
In addition, the ATOM stations detect all aircraft transmitting FLARM, FANET+, ADSB, CAP1391, PilotAware and Mode-S signals (using multilateration) and rebroadcast their locations to the airborne PilotAware-equipped aircraft if required. All data collected at the individual ATOM ground station is also transmitted to the PilotAware servers using a low-latency encrypted software-defined GRID network.
In the UK, in addition to the 290+ ATOM ground stations, a further 1,300 ground stations from 360 RADAR Ltd are used to provide data on the position of low-flying Mode-S equipped aircraft using multilateration.
All ATOM ground stations are interconnected through the software-defined PilotAware GRID to provide greater integrity, redundancy and multi-path detection.
Individual aircraft signals received by multiple ground stations and airborne assets are used to compensate for the airframe obscuration that affects simple point-to-point solutions. This continually keeps the target aircraft in view for ATC situational awareness and UAV applications.
As discussed earlier, EC radio signals from low-flying aircraft and UAVs are susceptible to obscuration (blocking or attenuation) from topographical obstacles such as hills forests and urban high-rise buildings. To overcome this Sky GRIDTM technology, installed in all PilotAware-equipped aircraft, detects and relays the location of low-flying PilotAware-equipped aircraft and UAVs.
These relays are received by ground stations and other aircraft to ensure that the data containing the location of the low-flying aircraft is available to other users and also sent to the PilotAware servers. In this way, the location of the low-flying aircraft or UAV is not lost to a user of the PilotAware infrastructure whether acting as a pilot in the air or a UAV operator on the ground.
In addition, information on the locations of all aircraft within a required operational area is relayed to the low-flying aircraft or UAV. Having this enhanced situational awareness view is especially useful in mountainous regions and for low-flying operations across the water. This data, provided to a PilotAware-equipped UAV has been successfully used to drive Artificial Intelligence software to demonstrate the autonomous sense and avoidance of local aircraft independent of what EC they transmit.
The latest PilotAware iGRID technology links airborne PilotAware devices to the PilotAware servers via the mobile network to ensure greater redundancy and reach, and also record the position of all aircraft detected by every airborne device.
All transmissions are time-stamped so that only the latest data is used ensuring the lowest latency. Data can be transferred from the PilotAware servers directly to individual or multiple aircraft or UAVs, to ATC or the UAV operator to show all detected aircraft in a required operational volume.
The diagram below shows the combined detection and reporting paths of the PilotAware infrastructure. This interlocking mesh infrastructure is highly intelligent and ensures high integrity and redundancy through multi-node and multi-technology integration.
This ensures that single points of failure in the network are reduced wherever possible. All flight data is retained on the servers for onward transmission and analysis. We are not aware that any other company can provide such detailed data as PilotAware.
Using the PilotAware infrastructure described above, GA pilots using PilotAware devices receive quality information on more aircraft types than any other system. As shown the combined data from the ATOM GRID, Sky GRIDTM and iGRID ensure that the greatest possible continuous detection of aircraft, transmitting any form of EC, is achieved.
Transmissions from aircraft detected directly will be received at the speed of light with very little latency. Similarly, the rebroadcast of FLARM and Fanet+ data is detected at the speed of light with a few 10mS of rebroadcast computing delay being typical.
Mode-S-equipped aircraft are detected using the multilateration of their response to an SSR or TCAS interrogation. This 1030MHz interrogation can come from multiple terrestrial or airborne sources. The refresh rate of the MLAT position is primarily caused by the 1030MHz interrogation rate. When the interrogation is from a single interrogator, the refresh rate is between 4-9 seconds. Sub-second latency is incurred for the multilateration calculation process. This is commensurate with the latency and refresh rates inherent in traditional Primary and SSR detection of Mode-S targets used by the ANSP’s.
Latency within the mobile network is more variable and depends on many factors including the region of operation, the aircraft's height, traffic density and range.
The PilotAware encrypted software defined GRID induces a low latency, with a few 100mS of delay being typical.
Using the multiple technologies described above provides a high level of availability and redundancy. The fidelity of the system will depend on the number and quality of the data-collecting assets available within the Operational Volume. The PilotAware technology that does this is available now for installation in your operational area.
We believe that we have demonstrated that PilotAware technology detects and presents the broadest amount of data from the widest possible range of aircraft. How can this be best used, now and in the future?
There are many operational use cases and no one solution fits all. That which is suitable for continuous line monitoring will differ from UAV operations that need more flexibility in operation. However, a full situational awareness of all aircraft in the Operational Volume is required for tactical safety mitigation.
Whilst fully autonomous flight, controlled by AI is the ultimate goal, we have the technology today to provide the necessary data to provide situational awareness in the Operational Volume and beyond.
The Direct Detection, ATOM GRID and SkyGRID technology described above is available now for UAVs that are using an installed PilotAware Rosetta.
Rosetta weighs 230 grams and is powered by an external 5.2v 2.5V power supply. iGRID technology is also available if there is an accessible mobile connection on the UAV.
When using Rosetta a UAV Operator with internet access will have an enhanced situational awareness of the Operational Volume just as if he/she was sitting in the UAV under their control. In other words, local aircraft would appear with the UAV in the centre.
In addition, the UAV will be shown on remote USP screens as a unique UAV detected directly by the ATOM Ground Network or relayed through Sky GRID and iGRID by in range PilotAware equipped aircraft
In normal operations, the UAV would be flying much lower than the manned aircraft. In the screenshot below the UAV is shown flying at the allocated 125M (400ft) maximum height and taking advantage of the onboard Direct, ATOM GRID and Sky GRID technologies to have a full situational awareness of the other technologies.
The RADAR screen below is one of many visualisations that can be used by UAV operators. This one shows the UAV in the centre and the various aircraft in the operational volume relative to its position. The compass rose is oriented as direction up. Vertical and Horizontal scales can be zoomed in or out as required.
Real-time data can be readily imported directly into local applications to enhance existing 3rd party including maps of fixed objects and topology or to animate moving maps.
Customised screens can be constructed for individual use cases with data for an operational volume with a radius of 30Kms being common. Local ATOM stations installed for a specific UAV operation will be augment with data fro all ATOM stations and airborne assets within an agreed dat collection volume.
Data is archived for post-mission analysis showing all detected aircraft that came close and how the UAV and the other aircraft responded.
Heatmaps of Operational Volumes, and beyond can be readily produced to also provide evidence for Strategic Mitigation or to help reduce an area to a lower risk category than originally defined.
This can be done in 4 dimensions across all EC and at predetermined low levels. For example, the following screenshot shows the past 3 months' view of all aircraft detected below 500ft altitude in the Solent region of the UK.
The GA airfields at Sandown, Bembridge and Lee on Solent and areas of lower density can be clearly seen. This is a combination of all EC transmitted including hang gliders and paragliders.
GA aircraft don’t generally file flight plans in uncontrolled airspace however, having anecdotal data of where the majority of flights coalesce in time and space will assist your route planning. Alternatively, areas of low flight density can be easily seen as evidence for Strategic Mitigation at various heights and times of the day.
PilotAware technology is extremely innovative and uses all technology genres to meet the aim of providing the best Operational Situational awareness possible.
We have developed and are testing a smaller integrated version of Rosetta (DX) that weighs only 90 grams and has all the functionality of the GA Rosetta device described earlier. Rosetta DX will be commercially available in 2023.
Within the Rosetta (DX) roadmap is the inclusion of a Mobile Tx/RX module to allow iGrid functionality for two-way situational awareness for those UAVs that are not already mobile-equipped. All PilotAware technology is backwards compatible.
During 2022 PilotAware supported EASA in the development of the standard message set defined in
Technical Specification for ADS-L transmissions using SRD860 frequency band(ADS-L 4 SRD860) ACCEPTABLE METHODS, TECHNIQUES AND PRACTICES FOR CARRYING OUT ADS-L TRANSMISSIONS ON SRD860 FREQUENCY BAND AS PERMITTED PURSUANT TO AMC1 SERA.6005(c) POINT (a)(3)(i)
This is the proposed standard message set for
SERA.6005 Requirements for communications, SSR transponder and electronic conspicuity in U-space airspace whereby, Manned aircraft operating in airspace designated by the competent authority as a U-space airspace, and not provided with an air traffic control service by the ANSP, shall continuously make themselves electronically conspicuous to the U-space service providers.
Its objective is for manned aircraft to provide continuous position information to USSPs so that UAS operators can use it to eliminate collision hazards between manned aircraft and UAS operating jointly within U-space airspace.
EASA has subsequently through NPA 2021-14 published the draft Acceptable Means of Compliance (AMC) and Guidance Material (GM) to U-space regulations. One of the proposed technical means to comply with the new SERA requirement is transmissions of aircraft position from devices/systems using the SRD-860 frequency band. The draft specification AMC1 SERA.6005(c) describes further technical details of these transmissions to allow U-space Service Providers (USSPs) to receive transmitted information and process it in accordance with U-space regulations.
An additional objective of the draft technical specification is to improve the air-to-air interoperability of existing traffic awareness systems transmitting on the SRD-860 frequency band. PilotAware transmits on the SRD-860 band (869.525)
PilotAware ltd fully supports this approach by EASA and will be working to help them with full compliance.
In September 2021 PilotAware and the University of Central Lancashire (UCLan) demonstrated autonomous UAV flight including the sense and avoidance of drones flying autonomously using the locations of nearby traffic supplied by the PilotAware Network. In this demonstration, it was shown that it is not necessary for the UAV to receive all genres of EC if their position. The integration was done centrally by PilotAware with demonstrable low latency. Since this demonstration, PilotAware has increased the amount and integrity of traffic detected through the multiple nodes available with the introduction of Sky GRID and iGRID in 2022.
PilotAware and UCLAN are seeking partnerships to develop this concept further to bring this autonomous technology to market.