A conceptual design program for educational purposes

A descr ipt ion is g i v e n of a h e l i c o p t e r c o n c e p t u a l d e s i g n c o u r s e . The d e s i g n is p r i m a r i l y c o n c e r n e d w i t h t h e p e r f o r m a n c e o f t h e h e l i c o p t e r , and d o e s n o t c o n s i d e r s t a b i l i t y e f f e c t s . The d e s i g n process is e n h a n c e d t h r o u g h t h e e x t e n s i v e u s e o f c o m p u t e r programs. I n t c o d u c t i o n The h e l i c o p t e r d e s i g n p r o c e s s c a n b e d i v i d e d i n t o f i v e b a s i c p h a s e s . The f i r s t p h a 5 e is a background s t u d y of t h e h i s t o r i c a l d a t a and t h e c u r r e n t t r e n d s i n h e l i c o p t e r d e s i g n . Second, a conc e p t u a l s t u d y is c o n d u c t e d u s i n g " r u l e s o f thumb" and e x p e r i e n c e t o d e v e l o p s imple l a y o u t s . T h i r d , p r e l i m i n a r y d e s i g n s are drawn which i n c l u d e v o l u metric s i z i n g , a i r f r a m e l i n e s , mechani s m s and s t r u c t u r a l c o n c e p t s . F o u r t h , t h e d e s i g n e n t e r s a " p r o p o s a l s t a t u s " i n which s u b s y s t e i o s are d e v e l o p e d , s t r u c t 'd u r a l s i z i n g is r e f i n e d and mockups are c o n s t r u c t e d . F i f t h , t h e f i n a l d e t a i l s are c o m p l e t e d . In a l l o f t h e s e p h a s e s , much u s e is made o f "corporate knowledge". I t is n o t by a c c i d e n t t h a t o n e c a n e a s i l y r e c o g n i z e t h e m a n u f a c t u r e r of !nost h e l i c o p ters, f o r r e g a r d l e s s o f any a d v a n c i n g of t h e s ta te o f t h e a r t , much o f any new d e s i g n is p r e d i c a t e d on p r e v i o u s work. T r a d i t i o n a l l y , i n t h e a c a d e m i c e n v i r o n m e n t , d e s i g n c o u r s e s a re p r e s e n t e d i n o r d e r to e q u i p t h e s t u d e n t w i t h t h e s k i l l s needed t o meet t h e c h a l l e n g e s i n t h e real w o r l d of e n g i n e e r i n g . e n g i n e e r i n g d e s i g n C O U K S ~ S are u s u a l l y "caps t o n e " c o u r s e s , w i t h t h e i n t e n t o f P u l l i n g t o g e t h e r material d e v e l o p e d i n o t h e r c o u r s e s i n t o a " u s e r ' s " c o u r s e . S e v e r a l p r o b l e m s are i n h e r e n t i n d e s i g n c o u r s e s . B e c a u s e of t i m e l i m i t a t i o n s , v e r y l i t t l e , i f a n y , n e w material can b e i n t r o d u c e d and t h e scope of t h e d e s i g n s must b e s e v e r e l y l i m i t e d . T h i s u s u a l l v d i c t a t e s t h a t o n l y t h e p h a s e may b e c o n s i d e r e d . c o n c e p t u a l d e s i g n A s e c o n d p r o b l e m e x i s t s i n t h a t t h e s t u d e n t does not have t h e b e n e f i t of " c o r p o r a t e knowledge" . However, w i t h o u t some b a c k g r o u n d i n f o r m a t i o n , t h e d e s i g n P r o c e s s e s c o u l d e v e n t a k e t h e e n t i r e (I P r o f e s s o r and A c t i n g Chai rman, Dept . .+d o f A e r o n a u t i c s . Assoc ia te F e l l o w A I A A ~ .. * CPT U. S. Army; Former g r a d u a t e s t u d e n t , Naval P o s t g r a d u a t e S c h o o l c o l l e g i a t e time s p a n , and as a r e s u l t , some t y p e of t h i s i n f o r m a t i o n must be f u r n i s h e d t o t h e s t u d e n t . F u r n i s h i n g background i n f o r m a t i o n i s a syndrome of a t h i r d b a s i c p r o b l e m i n e d u c a t i o n a l d e s i g n p r o g r a m s . Inasmuch as t h e s t u d e n t h a s n e v e r g o n e t h i s way b e f o r e , he must be g u i d e d a l o n g a prod u c t i v e p a t h . T h i s o f f e r s a n e x t r e m e c h a l l e n g e €OK t h e i n s t r u c t o r b e c a u s e t h e r e is a v e r y t h i n l i n e be tween p r o v i d i n g a g e n e r a l p r o c e d u r a l o u t l i n e and f u r n i s h i n g a " f i l l i n t h e b l a n k s " c o u r s e . A f i n a l p r o b l e m e x i s t s i n t h a t i n a d d i t i o n t o showing t h e s t u d e n t how a d e s i g n p r o c e s s operates, a p u r p o s e of t h e c o u r s e is t o r e q u i r a t h e s t u d e n t t o u s e h i s t h o u g h t p r o c e s s e s , p a r t i c u l a r l y i n making d e c i s i o n s . T h i s d i c t a t e s t h a t t h e s t u d e n t must h a v e o p p o r t u n i t i e s t o make s e l e c t i o n s , d e c i s i o n s a n d / o r op t imi z a t i o n s . The S p e c i f i c a t i o n I n o r d e r t o c h a n n e l t h e e E f o r t s of a l l of t h e s t u d e n t s i n a somewhat s i m i l a r d i r e c t i o n , it is a d v a n t a g e o u s t o p r e s e n t a s p e c i f i c a t i o n s h e e t as a g o a l . A l t h o u g h m u l t i r o t o r h e l i c o p t e r s are c o v e r e d i n t h e p r e r e q u i s i t e P e r f o r m a n c e c o u r s e , a t t h e Naval P o s t g r a d u a t e S c h o o l t h e d e s i g n s are l imi t ed t o s i n g l e main rotor s y s t e m s , p r i m a r i l y d u e t o t i m e r e s t r a i n t s . T h r e e b a s i c d e s i g n g r o u p s h a v e been e s t a b l i s h e d w i t h e a c h s p e c i f i c a t i o n r e p r e s e n t i n g a d i f f e r e n t w e i g h t c lass of h e l i c o p t e r . Inasmuch as o u r s t u d e n t s are m i l i t a r y o f f i c e r s , t h e s e t h r e e classes r e p r e s e n t u t i l i t y (cum U H 1 1 , o b s e r v a t i o n (H-60A/B) and c a r g o (H-53) t y p e s o f v e h i c l e s . The d e s i g n process is performed b y teams of from two to f o u r s t u d e n t s e a c h . I n o r d e r to p e r m i t some d e g r e e of i n d e p e n d e n t t h o u g h t , e a c h member o f a team i s e n c o u r a g e d t o p u r s u e some v a r i a t i o n s on t h e basic d e s i g n t h a t h i s team h a s p r o d u c e d . R a t h e r t h a n b e i n g a f u l l s c a l e d e v i a t i o n , t h i s work g e n e r a l l y is f o c u s e d on o n e or t w o f a c t o r s . The S p e c i f i c a t i o n is v e r y a b b r e v i a t e d , as shown i n T a b l e I. A l t h o u g h t h e d e t a i l s of t h e S p e c i f i c a t i o n are f i r m d e s i g n g o a l s , f a i l u r e to meet t h e S p e c s s h o u l d n o t n e c e s s a r i l y reflect n e g a t i v e l y on t h e s t u d e n t s i f t h e y c a n p r o p e r l y j u s t i f y t h e r e a s o n s €OK t h e d e v i a t i o n s . Thisp.p~rindce1srrdnvorkoflh~U.S. Covrmmenl m d Ihrrcfm 1s In lhe public domsin.