NLR People – Arun Karwal

In the series ‘NLR People’, we show you who the experts at the Royal Netherlands Aerospace Centre are, what drives them, and what they are working on behind the scenes. In this episode: Arun Karwal, Research Test Pilot at NLR.

Understanding what the engineers are developing and want to test

Performing braking tests on a very slippery runway. Flying an electric plane. Or testing an innovative concept for a landing system by creating a go-around situation 32 times (a go-around means steering away and starting a new round just before the aircraft makes contact with the ground).

For Arun Karwal, it is the most normal thing in the world. He has been working passionately as a Research Test Pilot at the Royal Netherlands Aerospace Centre (NLR) for over thirty years. “My colleagues and I (NLR has three test pilots) test innovations for aircraft and the aviation sector in a safe and controlled way. This is how we contribute to the aviation sector to innovate and become safer and more sustainable at the same time.”

Bridging the gap between research and the real world in the cockpit

Arun’s fascination with space travel as a child developed into a general interest in science and technology. So it was no surprise when Arun decided to study at the Faculty of Aerospace Engineering at TU Delft. There he graduated in 1991 in the subject of Flight Testing and then went on to obtain his commercial pilot’s licence in Eelde.

When he started as a junior pilot and researcher at NLR in 1993, he had logged very few flying hours at that point. But he did have an academic education and a pilot’s licence.  “As a test pilot, you need to understand what the engineers are developing and want to test. You also have to be able to translate this to the operational environment of a cockpit. To successfully carry out this dual function, it’s a great advantage that I also fly commercial scheduled flights. Because that means I know exactly what’s happening in the cockpit of passenger aircraft. The variety makes my job fun: one day I’m working on a complicated safety analysis for NLR, and the next day I’m piloting a flight to Las Vegas.”

What I like most about my job? When I see innovations I tested years ago now being used on scheduled flights

From calibration to zero-G test flights

Arun has more than sixteen thousand flying hours to his name. Besides working for the research institute, he also works as a pilot for an international airline. In fact, he is wearing his pilot’s uniform when he arrives for our interview. Earlier that morning, he had flown a calibration test for a landing system with the Cessna Citation at a Ministry of Defence air base. This plane is jointly owned by TU Delft and NLR and is the only operational research aircraft in the Netherlands.

It was a routine job, as NLR performs these tests for all the commercial and military airports in the Netherlands. “In order to land properly even in bad weather, beacons that emit signals are set up along the runway. These beacons must be validated twice a year. We do this by flying in a kind of cross pattern, from top to bottom and from left to right. A Flight Inspection System on board measures the radio signals emitted by the beacons and compares them with a precisely determined reference path. If a signal deviates too much, the beacon must be adjusted. These are intensive runs (test flights, Ed.) that are important for flight safety.”


NLR performs the test flights for a wide range of clients. “For manufacturers, for example, we test products that are already highly developed. But we also work for scientists who want to conduct tests for fundamental research. As well as everything in between.”

Arun’s favourite flights are the parabolic flights he performs for ace2space together with TU Delft. During these zero-G test flights, the aircraft is in a weightless state for several seconds. So it can simulate the weightless conditions in space. “For example, a client wants to know how a satellite antenna unfolds or how a liquid medicine reacts in space. This often relates to products or devices that will be launched to a space station. To create a parabola situation, you have to fly steeply upwards at an angle of approximately 45 degrees. As soon as the flight path becomes less steep, you reach a weightless state. Parabolic flights are very dynamic by nature; it’s totally different to flying from A to B in a straight line. That makes them very special.”

Nothing left to chance

It sounds exciting, but in reality it isn’t like that. Nothing is left to chance when the flight tests are being prepared. As soon as a customer comes with a question, a safety analysis is drawn up. Every possible doomsday scenario is covered: a flat tyre, a strong gust of wind or the loss of brake pressure. “Then we look at how we can do something about it. Sometimes we decide not to do a run because it’s too dangerous. Or we decide to plan extra safety measures on board, factor in more space around the runway or arrange for extra firefighters to be on standby. On top of that, we can train in the simulator. Every flight is prepared to the maximum, and all the possible risks are taken into account.”

WiFi on board Arun’s test flights

What Arun likes most about his job? When he sees an innovation that NLR tested years ago being used on one of his scheduled flights. For example, almost every airline now has WiFi, but just ten years ago Arun was flying the first tests with equipment for radio and satellite communication in his ‘crate’.

An internet connection can be set up in an aircraft in two ways: using a ground system (radio communications) or using a satellite (satellite communications: SATCOM). When an aircraft flies over the sea or the ocean, a ground connection isn’t possible. To solve this problem, many aircraft today are equipped with both radio and SATCOM antennas.

The question is, what is the best way to install the technology on board? “In this particular case it was really a process of trial and error because it was very difficult to adjust the technology,” says Arun. The two greatest challenges involved designing and testing a suitable aircraft antenna and developing and testing a router that switches between ground stations. “You can compare the radio connection with a mobile phone. So when you’re in your car, the phone ‘roams’ from GSM mast to GSM mast. But that’s not possible when you’re flying 800 kilometres per hour at an altitude of ten kilometres. These are pretty extreme conditions.”

Added to that, aircraft need satellite communication to facilitate an internet connection when they are flying over the ocean and are outside the range of ground antennas (or mobile phone masts). Arun: “We eventually settled on a certain type of antenna for radio communications underneath and on top of the aircraft, and there are now aircraft that use both satellite and radio communications.”

Electric flying, smarter landing and hydrogen propulsion

In recent years, the transition to sustainable aviation has become an increasingly important part of Arun’s work. Among other things, he was part of the European DREAMS project. For this project, he tested alternative ways of landing. This included taking steeper approach paths and shifting the threshold at which the aircraft first touches the runway. This way of landing can be less a burden to the environment, cause less noise pollution and make it possible for more aircraft to land at an airport.

Arun has been flying a smaller electric aircraft – the Pipistrel Velis Electro PH-NLX – since 2021. NLR uses the aircraft for research and experience with electric flying. “The first time I flew electric was pretty crazy. The actual flying doesn’t change much, as the joystick works in the same way. The big difference is that you have much less endurance on board. The battery runs out pretty quickly, so it requires more planning. If you suddenly find yourself wit a strong headwind, the range comes down quickly.”

NLR is working on a showcase of the Pipistrel Velis Electro that flies on hydrogen. This modification should be ready by 2026. “We will build in a fuel cell that can generate energy from hydrogen. NLR is conducting a lot of research for this and is using the test facilities for hydrogen in Marknesse. That puts NLR right in the European vanguard. If there’s one flight I’d really like to make in my career as a test pilot, that’s flying in a plane fuelled by hydrogen. We expect a lot from this technology as part of the transition to a more sustainable aviation sector. I think it’s wonderful that I’m able to play my own small part in these types of innovations.”

More inspiring NLR People stories: NLR People