In the coming years, remotely piloted aircraft systems (RPAS) will become ever-present in our skies serving as vehicles for cargo delivery and many other important services, says Federico Corraro, CIRA. He is the coordinator of the SESAR JU URClearED project, which is investigating a critical technology to ensure that these air vehicles can go about their business safely and securely.

What is the rationale for your project?

There is a general consensus among experts in the field of air transport that we will see a growth in the use of certified remotely piloted aircraft systems (RPAS) for civil and commercial purposes, from monitoring and surveillance to autonomous cargo delivery servicing remote and isolated regions.

Safety of these operations will be critical. That is why the URClearED project addresses the ‘remain-well-clear‘ (RWC) function, one of the key technological issues that will allow certified RPAS to safely share airspace with other (manned and unmanned) aircraft at intermediate altitudes. Here we are referring to altitudes below 18,000 feet, well below typical cruise altitudes of commercial airliners which fly at around 40,000 feet. Down there the air traffic is typically made up of by small and medium-sized aircraft, like helicopters, general aviation and even smaller vehicles.

What is remain-well-clear (RWC) functionality? How is it achieved in manned aviation?

In aviation, ‘well clear‘ refers to a state in which a pilot considers the situation of the aircraft to be safe in relation to the surrounding air traffic. It is a prognostic function in the sense that its aim is to identify well in advance situations in which two aircraft would fly too close to each other. Therefore, remaining well-clear is a critical function for keeping a safe distance from other aircraft, avoiding that such situations could become a hazardous mid-air collision.

In manned aviation, air traffic controllers ensure separation using specific ground-based surveillance systems (primary and secondary radars). However, depending on the airspace class in which the aircraft flies and type of mission (instrument or visual flight rules – IFR or VFR ), you may have situations in which controllers have no responsibility in providing separation services to aircraft, such as general aviation flying in class G airspace. In these cases, the pilots currently rely on their ‘out-of-window’ view or on-board surveillance sensors (when available) to keep safe distances from other traffic.

What is the challenge you are trying to address?

URClearED aims to define the requirements and capabilities for the RWC function, to be integrated in RPAS vehicles flying IFR into specific parts of the sky that are referred to as airspace classes D-G. These air segments are indeed the most challenging portions of the airspace for the design of such a function for two main reasons:

• In most parts of airspace (D to G), air traffic controllers provide separation, which means the RWC is considered only as a backup function (for example, in class D with IFR traffic). However, in the case of class G, separation is not provided by the controllers, so the remote pilot must rely on the capabilities of the RPAS, hence the inbuilt RWC function.
• D to G airspace refers to low altitude portions of the sky, below 18,000 feet, in which small and medium-sized aircraft typically fly. Since these aircraft are possibly not equipped with transponders of any kind, they are only visible to the RPAS through active traffic sensors like radar, which in turn are limited in their range and field of view.

How are the authorities, ANSPs, and end users involved in the project?

Several stakeholders, like pilot and air traffic controller associations, research centres and unmanned industries, are taking part in the project advisory board supporting the team both to identify scenario and to define the RWC requirements. They will also support the analysis of the results of the validation campaigns that will be performed end of this year and during the next one These validations will be carried out by means of both fast and real-time simulations and will involve experienced air traffic controllers and remote pilots at both CIRA and DLR experimental laboratories, with the purpose to collect valuable information about the impact of the designed RWC function on human performance.

What benefits do you hope your project will bring?

By providing evidence of the effectiveness and safety of our implementation of the RWC function, we hope to facilitate the introduction and integration of certified RPAS in classes D to G allowing this part of the sky to be safe for day-to-day civil use.

This project has received funding from the SESAR Joint Undertaking under the European Union’s Horizon 2020 research and innovation programme under grant agreement No 892440