DLR and Airbus conduct new test to reduce helicopter noise


German Aerospace Centre (DLR) and Airbus Helicopters Deutschland have carried out a test that aims to reduce noise and vibration produced by helicopters.

A part of the Scalability and Risk Minimisation of Technology (SKAT) research project, the test saw the DLR and Airbus trial active rotor control on a modern, five-blade rotor in a wind tunnel.

Through the test, DLR researchers were able to reduce vibration and noise emissions during landing approaches with the five-blade rotor.

By individually controlling the blades, researchers were also able to lower the rotor noise on the ground during the approach by up to three decibels, which is equivalent to a 30% reduction.

“The challenge with a five-blade rotor is that the rotor blades are asymmetrically divided between the two swashplates, which complicates the dynamic control of the entire system.”

The amount of power required for the main rotor was also reduced by more than 5% during high-speed flight at more than 270km/h.

Researchers were further able to minimise the vibrations created by the rotor during flight by more than 80% with the new adaptive control system.

During the latest test at the large low-speed facility (LLF) of German-Dutch Wind Tunnels (DNW), researchers used the META multiple swashplate system developed and patented by DLR.

The system was used to adjust the rotor blades’ angle of attack multiple times during each revolution, actively influencing the noise and vibration generation of the helicopter.

SKAT project manager Philip Küfmann said: “META is comprised of two combined swashplates, which allows us to individually control the rotor blades.

“The challenge with a five-blade rotor is that the rotor blades are asymmetrically divided between the two swashplates, which complicates the dynamic control of the entire system.”

Improved measurement technology was also used to calculate the main rotor's power requirement, as well as vibrations on the rotor head and noise emissions during the test, which received funds from the German Federal Ministry for Economic Affairs and Energy’s aviation research programme.


Image: Active rotor control technologies in a wind tunnel test. Photo: courtesy of German Aerospace Center (DLR).