From test flights with a scale design of an Airbus A320 to the integration of unmanned and manned air traffic: at Koninklijke NLR there are various jobs that contribute to the future of air travel in the Netherlands. Dr. Barbara Ohlenforst, department manager Vertical Flight & & Aeroacoustics, and Joost Vreeken, NLR’s Unmanned & & Autonomous programme director, together with Dronewatch, look back on 2021 and are already expecting next year.

Scaled Aircraft

How do you evaluate a groundbreaking new airplane style without having to construct a very expensive prototype? And how can you take measurements of brand-new airplane propulsion systems based upon battery innovation or hydrogen? Computer system simulations are just part of the answer. Since there are numerous elements that there will constantly be deviations between computer design and reality. Even wind tunnel tests with scale models have their constraints.

NLR is therefore working on a test approach for flying scale designs under the name SCALAIR– quickly prior to Scaled Aircraft. In 2020, a very first post discussing SCALAIR appeared on Dronewatch; in 2021, it was actually checked. The idea is that a scale model can function as a bridge in between the research world and practice: computer models can be made more accurate by performing dry runs with geometrically scaled designs.

Taxi initially, then fly

Last year, the first tests for the SCALAIR project happened, with a 1:8,5 scale model of an Airbus A320 airplane developed by Orange Aircraft, likewise called Scaled Flight Demonstrator (SFD). This project belongs to the European Clean Sky 2 research study program which includes Airbus, ONERA, CIRA and TU Delft. Eventually, the objective is to be able to figure out the difference in behavior between the scale model and the real aircraft, in order to discover the scaling guidelines. Before the design really goes into the air in 2022, the essential very first had actually to be tested and trained.

“During the very first series of tests with the scale design, we taxied cab at high speed on the runway of Deelen airport,” says Barbara Ohlenforst, who handles sustainable aviation from NLR, among the core styles within the company. “During these tests, various aspects were discussed, such as the information connection between aircraft and pilot, safety and, obviously, training aspects. Next year, initially in Deelen and later on in Italy, we will in fact fly. By the way, we trained the remote pilot (an NLR drone test pilot) ourselves, so it’s not about an A320 pilot.”

Significant interests

The SCALAIR scale model is managed from what Ohlenforst calls a “state-of-the-art trailer”. “You need to imagine a ground control station in the type of a cockpit environment, and that in a trailer. Given high flight speed and restricted flight envelope, the flight location required for the operation of this aircraft becomes large. This makes it no longer possible to fly VLOS with a transmitter at the track however it is required to fly BVLOS from a pilot seat. A video camera on the tail was chosen in mix with a head-up display screen to make the pilot’s perspective as excellent as possible. Due to the lack of a safety pilot on the track, it is therefore needed to have a premium video and telemetry connection to the device. This sets the needed requirements for the connection, as we have likewise come across throughout other BVLOS tests. 4G is not quickly sufficient to pass on video footage without too much delay.”

The tests need a great deal of those included. In this regard, the Ohlenforst department plays a crucial role in the SCALAIR task: “The interests are large and the device is very pricey. With this job, we are truly in entirely brand-new ground, operating at the crossway of unmanned and manned aviation. There are lots of elements involved and there is a great deal of pressure on the group.”

Airspace integration

Of an entirely different order are the projects in the field of discover&& avoid and airspace combination in which NLR is involved. Joost Vreeken, responsible for the program Unmanned & & Autonomous, explains about this. “At NLR, we have actually been doing a lot in the field of drones for years. It was typically about loose and sometimes successive jobs. In the coming years, we will focus more on programmatic work. The 3 core styles are sustainable aviation, competitive aerospace, and safe society. Unmanned & & Autonomous provides even more analysis as a multidisciplinary program.”

As an example, Vreeken discusses a job in the field of airspace integration. “For this, it is important to know the positions of all drones in a certain piece of airspace. E-conspicuity (electronic visibility) plays a big role. Think of miniaturization of transponder systems, however likewise the development of systems to discover so-called non-cooperative gadgets, such as microphones, radar or visual sensors.”

Preparing for U-space

Another problem worries the combination of drones that fly according to instrument rules (IFR) into routine airspace, within the framework of U-space. “For this, we require to incorporate UTM (unmanned traffic management) and ATC (air traffic control) systems. In addition, you should not only consider small package-delivery drones, however also of unmanned freight planes and potentially even from another location managed passenger aircraft in the future.”

There will also need to be checked here, explains Vreeken. “We are now preparing ourselves together with, to name a few, the Ministry of Infrastructure and Water Management, Air Traffic Control Netherlands and KNMI for different testing grounds to evaluate U-space concepts, specifically aimed at the Dutch situation. Because you always encounter variances nationally. Think about abolishing the PH numbers for drones and the transponder codes. We have to come up with something else for that.”


Of an entirely various order is the scheduled commissioning of DigiCity, a test location for drones and air taxis in the urban environment. As you might read earlier in this short article, DigiCity belongs to the Smart Mobility and Infrastructure Knowledge and Test Center (MITC), which takes shape in the province of Flevoland. DigiCity will be operational for the first time in 2022. This facility is recognized through a grant from Opportunities for West in the context of REACT EU.

DigiCity is made up of a few lots reconfigurable containers, which are set up with the necessary wind sensors and other determining instruments. In this method, numerous forms of structures can be simulated quickly. Vreeken: “At this place, we are going to deal with embedding Urban Air Mobility in cities. Several parties can begin evaluating there. As a releasing consumer of DigiCity, Avy will develop a VTOL hydrogen transportation drone in collaboration with NLR.”


In the area of hydrogen as a fuel for drones and aircraft, the necessary will likewise occur next year. The beginning point is that hydrogen will fill the gap between small battery-powered drones and large aircraft that fly on standard fuel. Completion goal is emission-free air travel. What started in 2019 with a drone that flew on hydrogen (the HYDRA), has now turned into an NLR-wide research theme.

“Hydrogen runs as a common thread through various programs at NLR, particularly sustainable air travel and Unmanned & & Autonomous. However the downside of hydrogen is that strong tanks are required to transfer it. These are still too heavy for many aviation applications now. That’s why we’re going to check with light-weight tanks next year, and with procedures around filling them,” says Vreeken.


From testing with scale models to airspace integration and hydrogen: the reality that numerous advancements are going on at the same time is also the greatest obstacle.

Vreeken: “We try to watch on all advancements. To this end, we are in close contact with the program group of the Ministry of IenW. Consider themes such as unmanned cargo, unmanned satellite launchers, making larger aviation remotely controllable. We constantly ask ourselves whether it is relevant for the Netherlands, and whether it fits NLR’s goals and tasks. We also support business neighborhood in essential research study, and attempt to bridge the space between research study and market intro. Constantly with an eye for social approval.”