Effect of a Turbojet Engine on the Dynamic Stability of an Aircraft

I t has been f requen t ly n o t e d t h a t t h e ca lcu la ted l a t e ra l d a m p i n g of a t u r b o j e t p o w e r e d a i rp l ane is n o t a lways in comple t e a g r e e m e n t wi th flight t es t s . T h i s p a p e r gives a s u m m a r y of t h r e e ma jo r effects of a t u r b o j e t engine on t h e d y n a m i c s t ab i l i ty of an a i rcraf t . These t h r e e effects a r e : (a) t h r u s t c o m p o n e n t in t h e d i rec t ion of wing lift; (b) C o r i o l i s r eac t ion of a i r a n d exhaus t gases in j e t d u c t ; a n d (c) coupl ing of l a t e ra l a n d longi t u d i n a l modes d u e t o gyroscopic ac t ion of t h e t u r b i n e a n d compressor . All these a re essent ia l ly low-speed effects.