Born: Germany
Primarily active in: Germany

Leadership Profile from Vertiflite March/April 2023

Prof. Ilkay Yavrucuk
Chair, Institute of Helicopter Technologies and VTOL, Technical University of Munich

On the Technical University of Munich (TUM) Garching Campus — in Germany’s northern Munich metropolitan region — Dr. Ilkay Yavrucuk teaches students and advises researchers on a range of vertical takeoff and landing (VTOL) technologies. “This department used to be called the Institute for Helicopter Technologies,” he explained. “I changed the name to Helicopter Technologies and VTOL (HTVTOL), so it’s not only going to be traditional rotorcraft. It’s going to look at general VTOL vehicles.”

Prof. Yavrucuk’s Institute within the Department of Aerospace and Geodesy (ASG) is under the TUM School of Engineering and Design. “We have projects in many different directions. We are trying to increase the bio-content in helicopter structures by adding flax fibers to carbon composites. Flax fiber is essentially linen coming straight from the plant.” Coupon tests led to a helicopter door structure now undergoing environmental testing. “One property that pops out quite interestingly is that the damping is much better. Then we are looking at environmental effects like humidity, temperature and how much load it can carry. You could really replace a lot of the carbon — in some cases, such as a helicopter door, up to 85% — with flax fibers, in order to achieve up to 50% bio-content in the structure. If that comes along well, it’s a big deal in many ways.”

The HTVTOL Chair continued, “We do programs in design, aerodynamics, structures, flight simulation and handling, etc. We have programs in rotor dynamics where we use, for example, fiber optic sensors in rotors to look at their elasticity and displacement relevant to the dynamics of the rotors. Another aspect that’s interesting is to use this technology to estimate the remaining useful lifetime of parts and helicopters. Fiber-optic sensor technology allows you to see how much the rotor is loaded, and therefore how hard you are flying the vehicle. If you could really measure, during flight, how much you load the helicopter in terms of thrust and power, you could adjust the actual operational lifetime of parts.”

Student researchers this year will begin a new series of rotor tests in a TUM wind tunnel. According to Yavrucuk, “We will be looking at Mach-scaled forward-flight dynamic stall, which is very rare in the literature. What we’re doing now is looking at dynamic stall in hover, but any data for a rotor in forward flight is rare.” The Institute is also investigating hydrogen-based flight. “Our AREA drone, which weighs approximately 60 kg (132 lb), was running with electric power, but it will be converted to hydrogen-based flight.”

Prof. Yavrucuk teaches graduate-level courses in rotorcraft design, rotor dynamics, aerodynamics, systems and components, etc. “In our institute, currently graduate students are a mix of German and international students; the whole department has many foreign students.” A new undergraduate course provides an introduction to rotorcraft design. “I really enjoy teaching. I always thought that was part of my strength. I like to be with young people. I feel energized just being in a classroom, teaching something, getting feedback and seeing people learn something from me. I can’t get away from the classroom.”

One upcoming undergraduate seminar considers electric VTOL (eVTOL). “Students from the Schools of Engineering and Management come together to write a business plan for a new eVTOL project each semester. It’s a simple sizing exercise that leads to a machine that can fly and make sense, engineering- and business-wise.”

Physics Fascination
Ilkay Yavrucuk was born in Stuttgart, Germany, to a Turkish family without aerospace engineering ties. “My father is an architect, but we didn’t have anybody in aviation,” he noted. “I was always fascinated with dynamics and engineering. It wasn’t a fascination with flight. It was a fascination with physics, engineering. I wouldn’t go into computer engineering or electrical engineering. I was looking into mechanical and aerospace simply because I loved physics and dynamics. A lot of problems in dynamics are found in rotorcraft.”

The Yavrucuk family moved back to Turkey when Ilkay was 11. The gifted math student ultimately earned his bachelor’s degree in aerospace engineering at Middle East Technical University (METU) in Ankara. The TUM professor recalled, “I finished high school and university in Ankara and then went to The States. In the early 1990s, the aerospace industry in Turkey was much smaller than today. We were a very select, small group of students. We were really enthusiastic and interested in aerospace. We had one course called Introduction to Helicopter Design and Aerodynamics which, ironically, I didn’t take. My first rotorcraft course was at Georgia Tech.”

Sikorsky Aircraft signed a contract in 1992 to build Black Hawk helicopters for the Turkish Armed Forces. Yavrucuk recalled, “Sikorsky and Georgia Tech, together with the Turkish government, had an offset program. I was one of five students who went to Georgia Tech for a year, followed by six months at Sikorsky in Connecticut. When the program ended, I went back to Turkey. Four months later, I sent an email to Dr. J.V.R. Prasad and Dr. Daniel Schrage to say, ‘I want to do a PhD now. Can I come back?’”

The Georgia Institute of Technology varied research opportunities. It remains today one of three US Army-sponsored Vertical Lift Research Centers of Excellence (VLRCOE) that links academia with industry.

“They had a software-enabled control project for DARPA [Defense Advanced Research Projects Agency]. It was basically building the software for unmanned helicopters. We had R-MAX helicopters — the GTMax we called it back then. I was one of the PhD students who started working on that project. After that, I continued working with Boeing in Philadelphia on active sidestick controllers for pilots. We tried to estimate control limits for aircraft and cue the pilots through active inceptors to allow care-free maneuvering and tell them when the vehicle would reach its envelope limits. My PhD thesis was on the estimation of control limits for envelope protection.”

Dr. Yavrucuk continued a post-doctoral fellowship at Georgia Tech until he rejoined METU in Ankara. “I started teaching that undergraduate elective course I had passed up, but then I started my own courses. I started a whole graduate helicopter dynamics and stability control course. There I was teaching rotor dynamics, helicopter handling and stability issues.”

In 2007, Yavrucuk founded Aerotim Engineering, Ltd. in Ankara. The rotorcraft modeling, simulation and control company continues to develop flight dynamic models for EASA-certified Level D flight simulators (see “Independent Training Alternative,” Vertiflite, Jan/Feb 2020). Turkish Aerospace provided more industry exposure. “Turkey started an indigenous helicopter program, now called the Gökbey,” explained Yavrucuk. “I took a sabbatical from the university and went to Turkish Aerospace. As program manager, I helped put together a capable team and after one-and-a-half years went back to the University.”

Eurocopter, now Airbus Helicopters, first sponsored the Helicopter Chair at TUM in 2010. “The professor who started it, Prof. Manfred Hayek, retired last year,” explained Yavrucuk. “I got a call saying I was the first candidate, so I decided to come here.” The HTVTOL chair continued, “There are research programs in every direction. We do programs in design, aerodynamics, structures, flight simulation and handling, etc.”

Electric Field
Yavrucuk plans more multidisciplinary studies. “One thing that I would find very interesting would be if somebody could put together a tool chain for the design of these electric VTOL vehicles. That’s what I’m trying to build these days. In all these disciplines, we have a lot of software and know-how. If you can put this all together and go from requirements to vehicles, that would be very interesting.”

The teacher-researcher observed, “A lot of these electric vehicle companies, as I see it, rather come up with a concept and try to see where the concept can be used. This is quite backwards from what we learned in school. We usually have a set of requirements and try to find the best vehicle. Now we’re in a position where we have a vehicle and try to find what can be done with it. I want to take the requirements and design a whole tool chain where you look at the aerodynamics, the aeroelasticity, the safety, and all together come up with the best configuration that would fit those requirements.”

Yavrucuk added, “eVTOL is attractive because it changed the whole landscape, the ecosystem we live in. When I left Georgia Tech in 2005 after my post-doc, I had essentially five big companies where I could work. Now, there are many, many more. That changed our whole mindset. A VTOL aircraft for us was a single-main-rotor aircraft with a swashplate and flapping hinges. We looked in that direction for so long that we couldn’t think of anything else. The alternatives we could come up with were a tiltrotor, or a helicopter rotor with a pusher, or maybe quadrotors. This new electric VTOL world of young people and young companies takes a fresh look to the VTOL problem that’s been around for a long time.

“I love that fresh look,” Yavrucuk acknowledged. “Just having a free mind starting with a blank white paper and looking at the VTOL problem from scratch, that idea alone I find super exciting. I’m supporting that whole waterfall of VTOL ideas. Whether it becomes a success, time will show. After all this investment, something is going to come out of it. They have changed our VTOL landscape already, and that’s good enough.”

Ilkay Yavrucuk joined the American Helicopter Society, today’s Vertical Flight Society, in 1998 when he presented a paper at the 55th Annual Forum in Washington, DC. He noted, “Ever since, it’s still my favorite forum. We are really a small community, a small family, if you like. We know each other quite well. The VFS has really glued us together.”