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R i c h a r d P. Woodward, I r v i n J . L o e f f l e r , and James H. D i t t m a r N a t i o n a l A e r o n a u t i c s and Space A d m i n i s t r a t i o n Lewis Research Center C l e v e l a n d , O h i o 44135 SUMMARYModern high-speed p r o p e l l e r (advanced t u r b o p r o p ) a i r c r a f t a r e expected t o o p e r a t e on 50 t o 60 p e r c e n t l e s s f u e l t h a n t h e 1980 v i n t a g e t u r b o f a n f l e e t w h i l e a t t h e same t i m e matching t h e f l i g h t speed and performance o f t h o s e a i rc r a f t . C o u n t e r r o t a t i o n t u r b o p r o p engines o f f e r a d d i t i o n a l f u e l s a v i n g sb y means o f upstream p r o p e l l e r s w i r l r e c o v e r y . T h i s paper p r e s e n t s a c o u s t i c s i d el i n e r e s u l t s f o r a f u l l -s c a l e c o u n t e r r o t a t i o n t u r b o p r o p e n g i n e a t c r u i s e c o n d it i o n s . The engine was i n s t a l l e d on a Boeing 727 a i r c r a f t i n p l a c e o f t h e r i g h t -s i d e t u r b o f a n engine. A c o u s t i c d a t a were t a k e n from an i n s t r u m e n t e d2 L e a r j e t chase p l a n e . S i d e l i n e a c o u s t i c r e s u l t s a r e p r e s e n t e d f o r 0.50 and i n a wind t u n n e l a t 0.72 Mach c r u i s e c o n d i t i o n s . The model d a t a were a d j u s t e d t o f l i g h t a c q u i s i t i o n c o n d i t i o n s and were i n g e n e r a l agreement w i t h t h e f l i g h t r e s u l t s .

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