Eurocopter tests EC145 helicopter equipted with fenestron. Although based on EC145 it will became EC146. The aicraft was photographed by AP member Marc Ulm in Donauwörth - Eurocopter Heliport, Germany, during test flight.
A Fenestron is a shrouded tail rotor of a helicopter that is essentially a ducted fan. The housing is integral with the tail skin, and, like the conventional tail rotor it replaces, is intended to counteract the torque of the main rotor.
While conventional tail rotors typically have two or four blades, Fenestrons have between eight and 18 blades. The main benefit of fenestron tail is that the noise it produces is distributed over different frequencies and thus sounds quieter.
See the photos of conventinal tail rotor and fenestron.