Drucella Andersen
Headquarters, Washington, D.C.                                                 
August 13, 1993
(Phone:  202/358-4727)

Linda Ellis
Lewis Research Center, Cleveland
(Phone:  216/433-2900)


RELEASE:  93-147

NASA TESTS HELICOPTER MODEL IN ICING CONDITIONS

     Icing studies, that may result in major improvements in 
predicting helicopter rotor performance in icing conditions, were 
recently completed in the Icing Research Tunnel at NASA's Lewis 
Research Center, Cleveland.

     A one-sixth scale Sikorsky Black Hawk helicopter model was 
tested for 10 weeks over a wide range of icing conditions and 
critical forward flight conditions.

     The tests by NASA, the U.S. Army and Sikorsky Aircraft, 
Stratford, Conn., were focused to expand the experimental database 
as well as develop reliable methods to reduce the cost and time 
required to certify civil helicopters for flight into forecasted 
icing.

     "The new experimental database resulting from these tests 
will be used to further refine and validate a computer code that 
Sikorsky and NASA developed in earlier testing," according to 
Thomas H. Bond, Project Manager at Lewis.

     The code predicts helicopter rotor performance loss occurring 
when ice accumulates on the rotors during an icing encounter.  

   "We expect this computer code can be used to predict full-scale 
helicopter performance in icing after the code is further 
validated with full-scale flight test data," Bond said.

     Engineers also undertook a pioneering effort to define and 
develop the methodology for testing simulated icing shapes on 
rotors.

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     "We constructed molds of the ice buildup on the blades, then 
produced castings or artificial ice shapes," Bond explained.  
Engineers now will attach these shapes to the leading edges of the 
scale model rotors for testing in a conventional (dry air) wind 
tunnel.

     "We'll compare these dry air wind tunnel results for 
artificial ice shapes with the Icing Research Tunnel test 
results," said Bond.

     This is the first time artificial ice shapes have been 
seriously suggested as part of the icing certification process for 
rotary-wing aircraft.  Results of the testing will be made 
available to the U.S. helicopter industry for further 
recommendations.

     "We hope that the code predictions and artificial ice shapes 
ultimately can be accepted as an alternative to some of the icing 
flight testing now required by the Federal Aviation Administration 
to certify a helicopter for flight into forecasted icing," said 
Bond.

EDITORS NOTE:  A photograph is available to media representatives 
to illustrate this release by calling the Lewis Media Relations 
Office at 216/433-2901.  

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