Flying safely without pilot

Detect-and-avoid radar helps to avoid collisions

The future is bright for unmanned aviation and the opportunities that this technology will bring for both civil and military operators. However, there are still a number of challenges that need to be tackled in order to realise its full potential.

October 16, 2020

Radar, Unmanned Flying, Automation, Detect and Avoid

Challenges of unmanned flying

These challenges range from regulatory to technical aspects that have to be considered for true airspace integration of unmanned systems, which will facilitate the effective and safe operation of unmanned aircraft alongside manned aviation.

Regulations need to allow for unmanned aerial systems (UAS) to fly in different types of airspace. Therefore, they will have to demonstrate the same technical abilities as manned aircraft. This includes an ability to communicate with air traffic control, as well as being able to manoeuvre in airspace as if a human pilot was onboard. Sensor specialist HENSOLDT is working on several of these technical requirements, in particular on the development of a sensor which generates the data necessary for safe avoidance procedures.

However, one of the most mission-critical requirements for the full integration of unmanned aircraft into the airspace to support both military and civil applications is the ability to avoid collisions with other aircraft in any given airspace.


The whole area of integration of unmanned aircraft into controlled airspace, whether for military or civilian applications, is truly the topic of the future.

Dietmar Klarer
Technical Lead for detect-and-avoid at HENSOLDT

Standardisation of regulations and collision avoidance

Standardisation of regulations and collision avoidance are mutually dependent: the former has to formulate the requirements for a detect-and-avoid system, whereas the technology has to be reliable enough for regulatory bodies to consider it equivalent to manned capabilities in detecting oncoming aircraft.

“To this end, many standardisation efforts are underway to develop the technology necessary to turn flying in controlled airspace into reality. But of course, it is not only a matter of performance and technical issues. There has to be a European standardisation that allows an unmanned aircraft to enter into controlled airspace,” Klarer added.

The US has developed certification documents for this requirement. In addition, the European Organisation for Civil Aviation Equipment (EUROCAE) is working on standardisation in a number of working groups. However, there is still some work to be done to set out final regulations for this.

Studies for sense and avoid systems

In anticipation of these regulations – but also as a contribution to their development – studies have been carried out to explore the technological requirements of sense and avoid systems. HENSOLDT has been pivotal with its involvement in both German and pan-European efforts.

The European Defence Agency’s (EDA’s) Mid-air Collision Avoidance System (MIDCAS) programme, for example, is the largest European study to date, which had begun in 2009 and has developed into a Standardisation Support Phase (SSP) that was carried out from 2017 to 2019.

Although a standardisation of regulations (the aim of the SSP project) was not developed by the end of the efforts – mainly due to the lack of test flights – this was a clear step in the right direction. In the meantime, corresponding drafts have been developed. 

Germany’s Project ‘Sense and Avoid – national’ (ProSA-n), meanwhile, began in 2015 and resulted in a radar sensor system demonstrator being developed by HENSOLDT to support all performance requirements for a sense and avoid radar.

Project ‘Sense and Avoid – national’ (ProSA-n)

This project comprised a number of flight tests which were carried out in cooperation with Diehl and the German Aerospace Center (DLR). The tests started in 2018 and were successfully completed in 2019. The results of the flight tests confirmed the HENSOLDT detect-and-avoid Concept. In a next step, the first flight test with the system actually controlling the flight management system will be carried out as part of an aviation research programme supported by the German Ministry of Economics and Energy.

The two initial test flights were conducted as part of the Ministry of Defence’s funding of the ProSA-n programme. While there is still an urgent need for a sense and avoid system for defence applications, Germany’s Ministry of Economics and Energy is now overseeing the project, which it has transferred into a civil aviation research programme. 

“At the beginning of our research programme it was already clear that there would be both military and civil applications,” Klarer affirmed. Civil efforts identified for sense and avoid technologies include air taxis, cargo UAVs, and single-pilot civil aircraft configurations in which such a sensor system can assist  carrying out situational awareness work that would normally be performed by a co-pilot.


For the first time it is not the pilot who will perform the collision avoidance manoeuvre, but rather the HENSOLDT sense and avoid system that performs the whole collision avoidance manoeuvre in flight, in controlled airspace in Germany, without the interaction of the pilot

Dietmar Klarer
Technical Lead for detect-and-avoid at HENSOLDT

HENSOLDT’s test system includes a radar system in the nose of the aircraft as well as  a large test rig in the cabin. The flights include collision risks from so-called intruder aircraft that are flying in circles to test the radar.

This helps building a comprehensive database of collision scenarios, checking the system and the system performance while also collecting data to use in simulations since it is not possible to cover all scenarios in flight tests. HENSOLDT gathers the data on how the system is performing and then uses this data to cover all possible encounters.


European medium-altitude, long-endurance: MALE

Developing the required technology for collision avoidance will ultimately be applied to a range of applications. In addition, one of the most exciting projects for Europe and HENSOLDT in unmanned aviation is the ongoing pan-continent European medium-altitude, long-endurance (MALE) programme.

Initially involving Germany, Italy, France and Spain, the programme will result in the development of a MALE UAV indigenous to Europe, and will require a detect-and-avoid capability.

Although HENSOLDT is one of many companies involved in the European MALE programme and could contribute to this element, and there has been much discussion in the last few years about the detect-and-avoid technology for the project, it is worth mentioning that Germany is a pioneer in the area of detect-and-avoid systems for unmanned aircraft.


This part of European MALE is mainly driven by the German Ministry of Defence, and I think we are also the only programme which has built a radar demonstrator with the performance required for a detect-and-avoid system of class HALE/MALE UAVs in Europe

Dietmar Klarer
Technical Lead for detect-and-avoid at HENSOLDT

HENSOLDT has developed a mature detect-and-avoid system for large UAVS, based on its years of research, and anticipates that a system for this purpose would include two antenna arrays covering a large arched horizontal field of view.

It will use active electronically scanned array technology that can be packaged into the nose of the UAV, which can also double up as a weather radar.

Since this technology is scalable, HENSOLDT anticipates systems of different sizes for different applications, including a large variant for the European MALE, single-pilot airliner cockpits and cargo unmanned aircraft, as well as smaller arrays for air taxis, helicopters and smaller UAVs.

Following an award of the contract for the European MALE aircraft, follow-up contracts for systems including the collision avoidance are expected. Until an award decision has been made, HENSOLDT will continue to develop its detect-and-avoid offerings.

“HENSOLDT is committed to this development also with own funding, because this is an essential element of future unmanned flight,” Klarer added. “HENSOLDT is well positioned to take a leading role in the development of this specific mission-critical segment, and we are excited about helping facilitate the further opening up of the skies to the potential that unmanned aviation can bring to both the military and civil markets.”

HENSOLDT Detect and Avoid Radar

The Detect and Avoid Radar for remotely piloted aircraft systems (RPAS) facilitates a safe integration of unmanned systems into the non-segregated airspace. It replaces the pilot’s perception by a technical system which outclasses the human eye regarding range, probability of detection and accuracy in order to avoid collision of aircraft (cooperative and non-cooperative).