Research Programs

Boeing/DARPA/NASA/Army/Air Force
SMART helicopter Rotor Wind Tunnel Test

SMART Rotor test team group picture

The benefits of high frequency, helicopter blade pitch control have been pursued under the DOD and NASA rotary wing technology programs for decades. Yet mechanical implementation of higher harmonic control is limited in blade pitch frequencies and requires substantial hydraulic power to dynamically alter the blade pitch around the azimuth.

The next generation of controllable helicopter rotor, the first using smart-material actuators – the Boeing SMART rotor, was successfully tested in the 40- by 80-Foot Wind Tunnel of the National Full-Scale Aerodynamics Complex from February through April, 2008. The test program was jointly conducted by the Boeing Company, DARPA, NASA, the Army, and the Air Force.

The Boeing Smart Materials Actuated Rotor Technology (SMART) rotor development was a decade-long technology development effort that included critical contributions from a number of people and organizations including Boeing, DARPA, NASA, the Army, MIT, UCLA, and the University of Maryland.

The SMART rotor is a civilian, full-scale MD 900 Explorer helicopter rotor with on-blade piezoelectric actuators driving trailing edge flaps. The 0.30-chord flaps extend from 0.75 radius to 0.92 radius. It is the only flight-worthy, full-scale, smart material actuated rotor ever designed and built in the United States. The SMART rotor had been successfully whirl tower tested in 2003 prior to this most recent test campaign.

The DARPA Helicopter Quieting Phase 1B effort funded the test preparation, the majority of the wind tunnel test occupancy time, and data reduction and analysis. The data was used to validate the next generation of helicopter aeroacoustic analysis codes developed by Georgia Tech, Stanford University, the University of Maryland, and Penn State University under the HQP Program.

The NASA Subsonic Rotary Wing Project of the Fundamental Aeronautics Program, together with its partner the U.S. Army Aeroflightdynamics Directorate (AMRDEC) and Boeing Helicopters also conducted the first closed-loop control study of a full-scale helicopter rotor with active flaps under carefully controlled wind tunnel test conditions. Benefits to rotor aeromechanics were explored and quantified, including dramatic noise and vibration reduction benefits. This effort included support from MIT, UCLA, and the University of Maryland.

The SMART rotor was tested up to 155 knots with open- and closed-loop excitation to the flaps.

The SMART rotor development and tests represent outstanding improvements in helicopter technology, in the disciplines of aerodynamics, acoustics, dynamics, structures, smart material actuators, electronics, and controls. Advances in the state-of-the-art in each area as well as testing and system integration were synergized to overcome the limitations of previous high frequency, helicopter blade pitch control implementations. The SMART rotor team successfully demonstrated the feasibility, robustness, authority, and aeromechanical benefits of on-blade, smart material actuation.

The significance of the contribution and its importance in basic science and technology is further evidenced by five technical papers to be presented at the 2009 AHS Annual Forum. These papers address the SMART rotor development effort and wind tunnel test program (Test & Evaluation session), the reduced in-plane, low frequency noise (Acoustics), the blade-vortex induced noise reduction (Acoustics), the rotor dynamics, active flap control, and vibration reduction (Dynamics), and correlation of rotor loads and dynamics with wind tunnel test data (Dynamics).

Point of Contact

Sesi Kottapalli
NASA Ames Research Center
Moffett Field CA 94035-1000

Related Publications

Kottapalli, S., "Low Speed and High Speed Correlation of SMART Active Flap Rotor Loads" , Presented at American Helicopter Soc. Specialists' Conference on Aeromechanics. Jan 2010 Download

Straub, F., Anand, V., Birchette, T., Lau, B., "SMART Rotor Development and Wind-Tunnel Test", 35th European Rotorcraft Forum will take place in Hamburg, Germany from 22nd to 25th September 2009. Download

Potsdam, M., Fulton, M. V., and Dimanlig, A., 2010, “Multidisciplinary CFD/CSD Analysis of the SMART Active Flap Rotor,” Proceedings of the 66th Annual Forum of the American Helicopter Society, Phoenix, Arizona, May 11–13. Download

Kottapalli, S. "Enhanced Correlation of SMART Active Flap Rotor Loads" 52nd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference, Denver, Colorado, April 4-7, 2011 Download

Lau, B., Obriecht, N., Gasow, T., Hagerty, B., Cheng, K., Sim, B., "Boeing-SMART Test Report for DARPA Helicopter Quieting Program" NASA TM 2010-216404 Download and DATA CD