MRO & Manufacturing
DLR Tests Rotor Technology to Reduce Helicopter Noise and Vibration
DLR’s STAR project uses piezoceramic actuators to reduce helicopter noise by 7 dB and vibrations by 50% in wind tunnel tests.
This article is based on an official press release from the German Aerospace Center (DLR).
Researchers at the German Aerospace Center (DLR), in collaboration with a consortium of international aerospace agencies, have successfully demonstrated a new rotor technology capable of significantly reducing helicopter noise and vibration. The breakthrough, achieved under the Smart Twisting Active Rotor (STAR) project, utilizes “artificial muscles” to actively twist rotor blades during flight without the need for heavy mechanical components.
According to the DLR, wind tunnel tests conducted in late 2025 confirmed that the system reduces noise during the critical landing phase by up to 7 decibels (dB) and cuts hub vibrations by more than 50 percent. These results mark a significant step forward for rotorcraft engineering, particularly for the emerging Urban Air Mobility (UAM) sector where noise pollution is a primary barrier to adoption.
Traditional helicopter rotors rely on complex mechanical linkages, swashplates, and hydraulic systems to change blade pitch. While effective for basic flight control, these systems are often too slow or heavy to counteract the rapid, complex aerodynamic interactions that generate the characteristic “whop-whop” sound of a helicopter, known as Blade-Vortex Interaction (BVI).
The STAR project takes a fundamentally different approach. Instead of mechanical flaps, the rotor blades are equipped with piezoceramic actuators integrated directly into the blade skin. When an electrical voltage is applied, these actuators expand or contract, functioning like artificial muscles to twist the blade.
The DLR reports that this system allows for both static and dynamic twisting. Static twisting adjusts the blade for general flight regimes, such as hovering or cruising. However, the system’s true innovation lies in its dynamic capabilities. The actuators can twist the blades hundreds of times per second, allowing the rotor to adapt instantaneously to changing airflow and neutralize the aerodynamic shocks that cause noise and vibration.
“The special thing about this approach is that the active twisting of a rotor blade requires no mechanical components and is only minimally affected by the centrifugal forces acting on the rotor blades.”
, Berend Gerdes van der Wall, Project Manager at DLR Institute of Flight Systems
The technology was validated during a three-week campaign at the Large Low-Speed Facility (LLF) of the German-Dutch Wind Tunnels (DNW) in the Netherlands. The team utilized a four-meter diameter model rotor, a 40 percent scale model of a BO 105 helicopter rotor, to gather acoustic and aerodynamic data. Data collected during the tests revealed a noise reduction of up to 7 dB during descent. In acoustic terms, a reduction of this magnitude corresponds to cutting the perceived noise intensity by more than half for observers on the ground. This reduction is critical for operations over populated areas, where landing noise is often the most disruptive phase of flight.
In addition to acoustic benefits, the system demonstrated a massive improvement in ride quality. Vibrations acting on the rotor hub were reduced by over 50 percent. According to the project data, this reduction not only improves passenger comfort but also decreases mechanical stress on the aircraft, potentially extending the lifespan of critical components.
“The results show that efficiency increased while noise and vibration were significantly reduced. During the measurement campaign, we were able to successfully test our concept in a realistic environment.”
, Berend Gerdes van der Wall, DLR
While led by DLR, the STAR project represents a major global effort in aerospace research. The technology was developed and tested with contributions from several leading organizations, ensuring the data is validated across different engineering standards.
The consortium includes:
The success of the STAR project has implications far beyond traditional helicopters. As the aviation industry pivots toward eVTOL vehicles for air taxis, noise remains the single largest hurdle to regulations approval and public acceptance. A 7 dB reduction is not merely an incremental improvement; it could be the difference between a vertiport being approved in a city center or being pushed to the outskirts.
Furthermore, the elimination of mechanical parts in favor of solid-state piezoceramic actuators aligns with the industry’s push for lower maintenance costs. If this technology scales effectively from the 40 percent model to full-size aircraft, we expect to see “active twisting” blades become a standard feature in next-generation military and civilian rotorcraft.
What is the primary benefit of the STAR rotor system? How does the blade twist without mechanics? Who was involved in the testing?
DLR Successfully Tests “Artificial Muscles” to Slash Helicopters Noise and Vibration
The STAR Project: How Active Twisting Works
Static and Dynamic Control
Wind Tunnel Results: Efficiency and Comfort
Significant Noise Reduction
Vibration Dampening
International Collaboration
AirPro News Analysis
Frequently Asked Questions
The system reduces helicopter noise by up to 7 dB and vibrations by over 50 percent without using heavy mechanical parts.
It uses piezoceramic actuators embedded in the blade skin. These “artificial muscles” deform when voltage is applied, twisting the blade structure.
The project was led by DLR (Germany) with partners including NASA, the U.S. Army, ONERA, JAXA, KARI, Konkuk University, and DNW.
Sources
Photo Credit: DLR