Looking at the drone industry today, there is an obvious trend towards multi-rotors being used...
A year ago, SmartPlanes started discussing what unmanned aerial vehicle (UAV) beyond visual line-of-sight (BVLOS) flights really meant, and what impacts it would have on the industry. Sometime after that we started considering what our own strategy would be regarding this game changer of a possibility. It was clearly going to be market driven, the question was more from who and in what market segment we would see the first traction. It was also going to be technology driven as well as require significant regulatory changes.
Today we have a much stronger understanding of what is needed, even if many questions remain unanswered. The fact that some other questions have been answered through both advances in technology, an understanding of market needs and early regulatory discussions ongoing, means that we are getting closer to solving the puzzle.
Defining the concept of autonomous flights
For safety, and regulatory, reasons we are not ever letting drones be fully autonomous. They are today, always in view, we have a feed of information with regards to the position, behaviour and outside interference, and we have different override options. The question is, – what happens in a truly autonomous situation, flying BVLOS and perhaps even beyond telemetry range? And what kind of requirements does this put on the UAV, and on the operator? What level of reliability?
Challenges associated with flying drones BVLOS
The SmartPlanes fixed wing drone Freya has an endurance of 102 minutes and has an average cruise speed of 13m/s, 29mph or 47km/h, giving it a range of almost 80km, or 50 miles. The fact that we can no longer see the UAV is only part of the problem though. With such range, we can no longer see the terrain and how it changes, we cannot see other incoming aerial vehicles, are unable to determine local weather conditions and we might also find ourselves beyond the reach of our telemetry, which can under very good conditions reach as far as 20km, or 12.5 miles. We are in fact flying truly autonomous. So, we are faced with a number of challenges.
- Solving the telemetry issue
First and foremost, – how can we solve the telemetry issue? Well, today there are several cellular modems on the market that can extend the range even far beyond the current flight endurance. We are sadly then dependent on the cellular network coverage, a fact that might be an issue in, for example a search-and-rescue situation where a hiker has gone missing in the middle of nowhere. There are other examples, from border control to infrastructure inspection, but you get the idea. Another possibility is to use lower frequencies and directional antennas, with other challenges, such as bandwidth degradation, spectrum availability and power consumption, emerging as a result.
- Ensuring altitude awareness
Also, a fully autonomous flight requires altitude awareness. This is something one could simply add a sensor to achieve, but with the side effect that the planning tool has no way to calculate the flight path. A better way is to implement a terrain following feature in the planning SW. However, such a solution comes with its own challenges such as where do you find accurate enough terrain data and how well can you trust the onboard positioning system? Sure, there are real-time kinematic (RTK) GNSS positioning solutions available, but most RTK solutions need to stay within 10km, or six miles, from a baseline in order to receive good enough corrections, which is not in parity with the range we are discussing here.
- Corridor flying
While it might seem obvious to some, corridor flight planning capabilities is a must. Flying long distances by the way of waypoints is not detailed enough positioned to ensure that one avoids flying over people, control zones and avoids steep altitude changes. It also gives us a possibility to plan geofences that are based on a corridor flight plan.
- Poor infrastructure
Currently, there is no established infrastructure to enable and safely manage the use of BVLOS UAVs. A UAS Traffic Management (UTM) system for low-altitude airspace may be needed. According to Nasa, a UTM system would enable safe and efficient low-altitude airspace operations by providing services such as airspace design, corridors, dynamic geofencing, severe weather and wind avoidance, congestion management, terrain avoidance, route planning and re-routing, separation management, sequencing and spacing, and contingency management. I would suggest that in the future we might have to extend this to high-altitude as well. Such UTM systems would also require the UAVs to be equipped with ADS-B transponders, providing GPS altitude, airspeed and location information.
- Lack of regulations
With an industry that is evolving super-fast, and with nearly no global standards established, the drone industry risks being treated as too immature to be allowed flying BVLOS. It is not an easy task solving all the challenges, showing the decision makers that there is a plan on how to enable BVLOS flights, but thanks to the market crying out for solutions it’s bound to happen, remains to be seen who the players will be.
- View on collision avoidance
A bit of a side topic, but related: Some view collision avoidance as a must, I disagree. In my view this is more of a gimmick that perhaps has its use during the landing sequence but hardly during flight. There is no way a drone travelling at speeds in and around 13m/s could ever detect and avoid a manned aerial vehicle travelling at 65m/s in time, it is simply not fast enough. More likely the pilot of the manned aircraft can get a warning from the UAV transponder through a UTM system, or if flying by night from the UAVs positioning lights, the latter which I do see as a necessity when flying BVLOS and by night. Separation of airspace would be yet another feasible idea.
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