NLR makes key contribution to European tilt rotor research

The successful conclusion of a complex test in the German-Dutch Wind Tunnels (DNW) large low-speed facility (LLF) in 2013 has brought us a lot closer to the creation of a European tilt rotor.

Tilt-rotor aircraft combine the benefits of helicopters and fixed-wing aircraft. The tilt rotor is faster than a helicopter in horizontal flight, uses less fuel and is less noisy. It can land and take off vertically, it can be used to provision oil platforms, and it can provide air transport to other less accessible locations. In 2006, NLR joined a consortium of European institutes and helicopter manufacturers cooperating on the Novel Innovative Competitive Effective Tilt Rotor Integrated Project (NICETRIP), a programme funded in part by the European Union and intended to demonstrate the feasibility of this concept.

In order to validate the concept, NLR built a scale model of the aircraft. The motorised scale model is based on the Enhanced Rotorcraft Innovative Concept Achievement (ERICA). In addition to tiltable rotors, the ERICA configuration features outer wings that can be tilted independent of the rotors, vastly increasing flight efficiency.The model is particularly complicated, since the independently rotating nacelles and outer-wings are highly instrumented. The final technical hurdle was the development of a rotor balance, a crucial component to accurately record the complex forces of the rotating propellers. The research model contains so many sensors and other electronics, that more than 2.5 km of pressure tubing and 5 km of cabling were used in its construction. It is the most complex wind-tunnel model ever built in the world in its kind – a fully functional ‘technology demonstrator’.

More than 400 different flight conditions were simulated during a testing programme in 2013, including the tilt rotor’s performance at takeoff, when rotating the nacelles, when rotating the nacelles and wing sections, and during slow forward flight. There were also tests that ‘pushed the envelope’, exploring the outer limits of operational performance. During the final preparation phase and actual testing, dedicated test teams succeeded in resolving various technical hitches.

In 2014, the physical characteristics of cruise flight will be studied at the high-speed wind tunnel of NLR’s French counterpart ONERA. If these results are favourable, the first airborne prototype is expected to take to the air in 2020, with series production projected to begin roughly five years after that. Thanks to NLR’s pioneering role in this project, series production will present excellent opportunities for Dutch industry.