Dr. Peter Konstanzer, Head of Department Dynamics & Vibrations, Eurocopter Research & Development, explains the Bluecopter technologies.
Eurocopter’s full resources are being applied to its bluecopter® technology programme, which is a continuous improvement effort for the company’s entire product range and focuses on five areas: emissions, noise, hazardous materials, recyclability and renewable resources.
One of the programmes early achievements is the futuristic-looking Blue Edge™ main rotor blade, which is the result of noise reduction technology that has been validated in Eurocopter flight trails since 2007. With its revolutionary double-swept shape, the Blue Edge™ design changes the blade-vortex interaction (BVI) that occurs at the tip of any helicopter blade – significantly reducing noise levels and attenuating the pulsating phenomenon commonly associated with helicopter flight.
As a passive, “plug and play” solution, Blue Edge™ is highly effective in treating the noise created during a typical descent profile. This was demonstrated in flight with an EC155 helicopter testbed, effectively halving the noise profile during descent. The Blue Edge™ shape can be optimised according to the weight, flight characteristics and number of blades on Eurocopter’s rotary-wing aircraft product line.
Did you know…?
The unit commonly used to measure sound pressure levels is decibel (dB). The suffix (A) takes into account the varying frequency sensitivity of the human ear. People with normal hearing have an auditory threshold of 0 dB (A); rotor-blade noise emitted by today’s helicopters is around 89 dB, while levels above 120 dB (A), the pain barrier, can cause loss of hearing.
Radical noise reduction
Another element of Eurocopter’s bluecopter® programme is an active noise reduction system that has shown its ability to significantly reduce a helicopter’s acoustic profile and dramatically decrease in-flight vibration. Flight tests with this piezo-active main rotor blade control system – Blue Pulse™ – have demonstrated reductions of peak noise by up to 7 dB. Another benefit is the lowering of vibrations to near jet-smooth levels.
Blue Pulse™ treats the interference of rotor blade tip vortices from one rotor blade with the following blades. Its control system uses multiple flap modules on the trailing edge of each rotor blade, which are actuated 15 to 40 times per second by piezoelectric actuators located inside the blades themselves. Tests have provided very good results, both in terms of noise reduction and in the decrease of vibration, which creates a smoother ride for passengers and should extend the lifetime of sensitive onboard components such as electronics. Eurocopter is now fully exploring all of the cost and maintainability aspects for the Blue Pulse™ active system.
When the colour matters
The image below shows a comparison of noise measurements made during test flights with the Blue Pulse™ active noise (and vibration) reduction system. When the system is turned on (right-hand image), the results show that high noise levels (red) are reduced to lower noise levels (yellow and green).
The active Blue Pulse™ rotor control system uses flap modules located at the trailing edge of each rotor blade. The flaps are driven by piezoelectric actuators developed by EADS Innovation Works.