LANDING-GEAR BEHAVIOR DURING TOUCHDOWN AND RUNOUT FOR 17 LANDINGS OF THE X-15 RESEARCH AIRPLANE

Data a r e presented f o r t h e pretouchdown condition, t h e impact period, and t h e runout phase of 17 landings made with t h e X-15 a i r p l a n e .V e r t i c a l v e l o c i t i e s up t o 9.5 f e e t per second and t r u e ground speeds between 145 knots and 238 knots were recorded during t h e landings.The r e s u l t s of t h e i n v e s t i g a t i o n i n d i c a t e t h a t t h e highest maingear shock-strut force, drag reaction, a i r p l a n e upper-mass response, and h o r i z o n t a l -t a i l load occurred during t h e nose-gear touchdown f o r a l l of t h e landings.The mean value of t h e c o e f f i c i e n t of f r i c t i o n of t h e main-gear skids c a l c u l a t e d f o r one landing w a s 0.33.high skid drag and low rolling f r i c t i o n of t h e nosewheel t i r e s provided more than adequate d i r e c t i o n a l s t a b i l i t y during t h e runout.A s a consequence, pilot-induced inputs r e s u l t e d i n only small changes t o t h e a i r p l a n e d i r e c t i o n of motion during t h e runout.The combined e f f e c t of t h e No nosewheel shimmy was observed i n any of t h e landings, d e s p i t e t h e absence of a shimmy damper.