YAK50 PLT ON TKOF HAS SEATBELT UNLATCH AND PREVENT RIGHT STICK MOVEMENT ON TAKEOFF. PLT ROLLS THE ACFT INVERTED TO CONTINUE HIS LEFT 'WING WAG' TO FRIENDS AND THE SEATBELT COMES FREE.

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MY SEATBELT/HARNESS IS A 7 POINT SYS. THE LAP BELT HAS 4 STRAPS (2 EITHER SIDE) THAT CONNECT TO THE ACFT WITH 2 LATCHES. THERE ARE ALSO 2 SHOULDER BELTS AND 1 BELT BTWN THE LEGS TO CTR THE LAP BELT. NORMALLY; I SLIDE THE 2 SHOULDER BELT FITTINGS AND THE CTR (THROUGH THE LEGS) FITTING TO THE TOP LATCH OF THE LAP BELT. ON THIS DAY; I ATTACHED THE SHOULDER HARNESS FITTINGS TO THE TOP LATCH AND THE CTR BTWN THE LEG STRAP TO THE LOWER LAP BELT LATCH. NO PARTICULAR REASON. ON TKOF; I PLANNED TO LET THE ACFT ACCELERATE IN A SLOW CLB AND THEN TRANSITION TO A STEEP CLB AND HOLD ABOUT A 35 DEG CLB ANGLE TO CRUISE HT DURING A L TURNOUT. AS I CAME ABREAST OF SOME FRIENDS ON THE GND; I WAGGLED MY WINGS TO SAY GOODBYE. THE STICK FELT NORMAL WHILE WAGGING THE WINGS. AS I PULLED UP AND ROLLED L; THE STICK DID NOT WANT TO RETURN TO THE R. IT WAS NOT A HARD BIND; BUT FELT MUSHY. I RELEASED BACK PRESSURE; AND MOVED THE STICK TO THE L AND IT WENT EASILY; AND WHEN I LET OFF; IT ONCE AGAIN STAYED WHERE IT WAS AND FELT MUSHY BUT FIRM RESISTANCE TO BEING MOVED TO THE R. AT THIS POINT I WAS SLIGHTLY NOSE HIGH WITH ABOUT 70 DEGS L WING DOWN AND ABOUT 300-400 FT; WITH AIRSPD ABOUT 140 KTS. AT THIS POINT IT JUST FELT NATURAL TO KEEP ON ROLLING; SO I PUSHED HARD L AILERON AND CONTINUED THE ROLL TO INVERTED. AT THE INVERTED POINT; I PUSHED A FULL NEGATIVE G OR MORE; TO KEEP THE NOSE WELL ABOVE THE HORIZON. WHEN I DID THIS; SOMETHING CAME OUT OF THE FLOORBOARDS AND SMACKED ME RIGHT BTWN THE LEGS; WITH SOME SLIGHT PAIN. I GLANCED DOWN AND SAW THE METAL ADJUSTMENT/CONNECTION POINT FOR THE CTR PART OF THE HARNESS; THE PART THAT GOES BTWN THE LEGS WAS FLOATING AND HANGING IN MY VISION. AS I CONTINUED THE ROLL TO UPRIGHT; THE CTLS THEN WERE TOTALLY FREE WITH NO BINDING IN ANY MANNER WHATSOEVER. WHAT HAD CLEARLY HAPPENED; BUT UNKNOWN BY ME AT THE TIME; WAS WHEN I DID THE 'WAGGLE THE WINGS' MOVE ON TKOF; THE LOWER LATCH TO MY LAP BELT CAME UNSNAPPED AND THAT CTR STRAP FELL TO THE FLOORBOARD; WHERE IT THEN FELL RIGHT INTO THE PUSHROD TUBING AREA WHERE THE STICK CONNECTS TO THE AILERON PUSH TUBES. WHEN I THEN ROLLED L; THE BELT FELL MORE INTO THE AREA JUST DESCRIBED AND PREVENTED THE STICK FROM MOVING BACK TO THE R AFTER A L STICK WAS INPUT. THE 'MUSHY' FEEL I DESCRIBED WAS THE BELT COMPRESSING AS I PUSHED AGAINST IT. WHEN I DECIDED TO PUT IN FULL L AILERON; IT COULD HAVE GOTTEN EVEN WORSE; BUT WHEN INVERTED; THE HARD PUSH NEGATIVE FORCED THE STRAP TO FALL RIGHT OUT OF THE HOLE AND EXTEND STRAIGHT OUT; STRIKING ME IN THE PROCESS AND BRINGING MY ATTN TO IT. AFTER THE FLT; I REMOVED THE SEAT AND TRIED DROPPING THE CTR STRAP A FEW TIMES; AND MANAGED TO ACTUALLY DUPLICATE WHAT HAPPENED; MORE OR LESS. CONCLUSION: MANY ACFT HAVE EXPOSED FLT CTL CABLES; PULLEYS; PUSHRODS; ETC. THE DANGER OF THINGS FALLING INTO THOSE CTL AREAS IS SOMETHING I AM WELL AWARE OF; AND IS A KNOWN HAZARD ON YAK ACFT; ESPECIALLY IN THE TAIL BELL CRANK AREA. I HAD NEVER BEFORE ATTACHED THIS MIDDLE BELT FITTING TO THE LOWER BELT LEVER SNAP. THIS SIMPLE CHANGE IN NORMAL PROC ALLOWED THIS STRAP TO COME LOOSE WITHOUT MY KNOWLEDGE AND CAUSE A MINOR BINDING IN FLT CTLS. I THINK HAD I REALLY PUT SERIOUS FORCE ON THE STICK; I COULD HAVE REGAINED R ROLL CAPABILITY; AND HINDSIGHT HAS ME DOING THINGS A LITTLE DIFFERENTLY THAN I DID; AS I SIT HERE WRITING THIS. IN THE 'FOR WHAT IT IS WORTH' CATEGORY; I HAVE A SECOND YAK-50 THAT I USE FOR PARTS. THE PREVIOUS OWNER OF THAT YAK-50 INSTALLED COMPLETE FLOORBOARDS TO COVER THESE CTL AREAS. MY PLAN NOW IS TO PULL THESE FLOORBOARDS OUT OF THE 'PARTS' ACFT AND INSTALL THEM IN THE YAK-50 THAT I FLY.