Drucella Andersen
Headquarters, Washington, D.C.                                            
February 26, 1992
(Phone:  202/453-8613)

Donald G. James
Ames Research Center, Mountain View, Calif.
(Phone:  415/604-3935)

Ken Jensen
McDonnell Douglas Helicopter Co., Mesa, Ariz.
(Phone:  602/891-2301)


RELEASE:  92-27

NASA, MCDONNELL DOUGLAS TEST BEARINGLESS ROTOR SYSTEM


     NASA is conducting wind tunnel tests of a new bearingless 
rotor system that promises to be a significant advance in 
helicopter technology.  The rotor system, developed by 
McDonnell Douglas Helicopter Company, Mesa, Ariz., eliminates 
the hinges and bearings that usually connect the blades to the 
rotor shaft.  

     The rotor blades and their link to the rotor shaft are the 
keys to the innovative system.  The blades have advanced 
airfoils and are made of high strength composites.  

     The technology is expected to have many benefits, 
including better maintenance and lower fuel use.  "The new 
rotor system would allow for faster, more agile, more cost 
effective and safer helicopters," said Steve Jacklin, Project 
Manager for the wind tunnel tests at NASA's Ames Research 
Center, Mountain View, Calif.

     The tests in Ames' 40-by-80-foot wind tunnel will evaluate 
the rotor concept and will gather data to help develop computer 
programs needed to design a new generation of bearingless 
rotors.

     Standard helicopter blades have hinges and bearings that 
let the rotors flap up and down, move back and forth and twist.  
A helicopter needs these motions to fly, but the hinges and 
bearings are complex and difficult to maintain and cause 
aerodynamic drag that increases fuel use.

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     The new rotor system being tested mimics the hinges with 
an elastic flexible attachment that needs no bearings and can 
be made aerodynamically smooth.  The system has far fewer 
moving parts, yet it allows the necessary blade motions.

     "Bearingless rotor systems promise to reduce maintenance 
rates, improve safety, and improve helicopter cost efficiency 
by having fewer moving parts and using stronger, lighter 
materials," Jacklin explained.

     Under an agreement between NASA and McDonnell Douglas, the 
rotor system will be evaluated for an initial 10-week run.  A 
second series of tunnel tests is planned for early 1993.

     "This is a landmark case -- a major step for us to enter 
with NASA and Ames Research Center to test our new advanced 
technology," said Dean Borgman, President of McDonnell Douglas 
Helicopter Company.

     Test data will remain proprietary to McDonnell Douglas for 
1 year after the wind tunnel tests according to terms of the 
agreement, but NASA researchers will have access to the data 
for advanced rotorcraft research -- one of NASA's national 
aeronautics goals.

     The rotor blade system will be installed on a test stand 
made by McDonnell Douglas.  Ames will provide a 1500-horsepower 
motor to turn the rotor and will supply the test personnel and 
the instruments and computers that collect and analyze the 
data.

     The 40-by-80-foot wind tunnel can test full-scale aircraft 
and models at wind speeds up to 345 mph.  NASA has tested more 
than 550 aircraft and helicopters in the tunnel during its 
50-year history.  It has the second largest test section in the 
world; the biggest is the 80-by-120-foot wind tunnel that is 
part of the same facility.

     McDonnell Douglas Helicopter Company is developing the 
bearingless rotor system for its new MDX helicopter.  "The 
aircraft itself will have many advanced technologies: 
composites, onboard health monitoring, the new rotor system, 
new engine technology and the NOTAR_  (no tail rotor) 
anti-torque system technology," Borgman said.

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