A YAK-52 PLT EXPERIENCES A JAMMED ELEVATOR DURING AEROBATIC MANEUVERS CAUSED BY A FOREIGN OBJECT IN THE ELEVATOR CTL ASSEMBLY. SUCCESSFUL RECOVERY WAS MADE BELOW 500 FT AGL FOLLOWED BY A DIFFICULT LNDG AT A DIVERSION ARPT.

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I WAS PERFORMING AEROBATICS IN A YAK-52 EXPERIMENTAL/EXHIBITION CATEGORY ACFT. AFTER PERFORMING SEVERAL MANEUVERS WITHOUT INCIDENT I ENTERED A CUBAN-8 AT AN ALT OF 2000 FT AGL; FLOATED OVER THE TOP AT 2700 FT AGL; AND ROLLED-OUT IN A 45 DEG DIVE. I PAUSED IN THE DIVE AND BEGAN A PULL ON THE STICK. THE ACFT DID NOT RESPOND. I PULLED HARDER; MUCH HARDER THAN NORMAL. IT STILL DIDN'T RESPOND. I PULLED THE PWR TO IDLE AND PULLED HARDER. THE NOSE BEGAN TO SLOWLY WORK ITS WAY UP. I BOTTOMED-OUT AT APPROX 300-400 FT AGL. I MANAGED A SLOW CLB AND PERFORMED A CONTROLLABILITY CHK. HVY AFT STICK PRESSURE WAS REQUIRED BY BOTH ME AND THE PAX IN THE REAR COCKPIT; WHO WAS NOT A PLT; TO MAINTAIN LEVEL FLT WITH THE PWR OFF. I THOUGHT ABOUT PUMPING THE STICK FORWARD TO ATTEMPT TO DISLODGE OR DROP WHATEVER WAS BINDING THE ELEVATOR BUT DECIDED THAT IF THE BIND FOLLOWED THE STICK FORWARD WE WOULD NOT HAVE THE ALT TO BAIL OUT. I DETERMINED THAT A LNDG WAS MARGINAL. WITH FUEL DOWN TO 25 LITERS (15-20 MINS) I HAD NO MORE TIME TO EXPERIMENT. I DECIDED NOT TO LAND AT THE HOME FIELD WHICH WAS A 2500 FT GRASS STRIP. I FLEW TOWARD HUNTSVILLE INTL WHICH HAD A 10000 FT RWY AND A WILD AREA TO THE S WHERE WE COULD BAIL OUT IF NECESSARY. I CONTACTED APCH CTL AND DECLARED AN EMER. ENRTE; I TOLD THE PAX TO LOCK HIS HANDS AROUND THE STICK AND USE HIS ARMS TO METER BACK PRESSURE ACCORDING TO MY INSTRUCTIONS. 'MORE' WAS TO MEAN MORE STEADY BACK PRESSURE. 'EASE OFF' WOULD MEAN GRADUALLY RELEASE THE PRESSURE. I WAS CONCERNED THAT TOO MUCH PRESSURE MIGHT BREAK A CABLE. I PUT THE GEAR DOWN AND FLEW A LONG FLAT NO FLAP AT A HIGH AIRSPD. THE PAX DID A FINE JOB. I REDUCED PWR FOR A FLARE AND THE NOSE DROPPED ALARMINGLY. I YELLED 'MORE MORE MORE!' AND HE TRIED TO COMPLY BUT THE PLANE STRUCK THE RWY HARD IN A SLIGHTLY NOSE LOW ATTITUDE. THE AIRPLANE ROLLED OUT AND I TAXIED TO PARKING. THERE WAS NO DAMAGE. UPON SHUT-DOWN I WENT BACK TO THE TAIL AND SAW THAT THE ELEVATOR WAS JAMMED IN THE NEUTRAL POS. HARD BACK STICK PRESSURE BY BOTH OF US APPARENTLY GAVE IT ANOTHER DEGREE OR TWO UP; WHICH MUST HAVE BEEN OUR SAFETY MARGIN. I PUSHED THE ELEVATOR DOWN AND IT WENT WITHOUT RESISTANCE AND I HEARD A METALLIC PLUNK IN THE TAIL. I TOOK OFF AN INSPECTION PANEL AND REACHED INSIDE AND RETRIEVED A 7 IN VICEGRIP TOOL. IT HAD FALLEN FROM A JAMMED POS IN THE ELEVATOR CTL HORN ASSEMBLY. IT HAD APPARENTLY WORKED ITS WAY TAIL WARD FROM THE COCKPIT AREA WHERE IT HAD BEEN LEFT UNNOTICED. IN SUM; THE RECOVERY FROM THE DIVE WAS PURELY MECHANICAL. I JUST DID WHAT CAME NATURAL -- PULLED HARD. HAD WE BEEN PERFORMING AEROBATIC FLT NEAR OR BELOW THE FAA MINIMUM ALT (1500 FT AGL) IT WOULD HAVE BEEN FATAL. BUT THE NEXT 15 MINS TURNED AN ACCIDENT-IN-THE-MAKING INTO A SCARY STORY. THE PAX IN BACK KEPT HIS COOL. I LEVELED WITH HIM AND TOLD HIM THAT WE WERE IN A VERY SERIOUS SIT. HAD HE PANICKED AND NOT BEEN COOPERATIVE I THINK WE WOULD HAVE HAD TO ABANDON THE ACFT. THIS WAS A CLR CASE WHERE CRM; EVEN WITH A NON-PLT PAX; WORKED. THE ONLY THING I WOULD DO DIFFERENT IS I WOULD NOT HAVE PULLED THE PWR OFF WHEN LNDG; BUT WOULD HAVE SIMPLY DRIVEN IT ONTO THE RWY. THAT WOULD HAVE PREVENTED THE DANGEROUS NOSE DROP. THERE WAS PLENTY OF RWY LENGTH TO STOP. IT DOESN'T MATTER TO ME WHO LEFT THE TOOL THERE. IT MAY HAVE BEEN ME. SEVERAL PEOPLE HAD WORKED ON THE PLANE SINCE ITS CONDITIONAL INSPECTION 5 MONTHS EARLIER AND SINCE IT HAD BEEN PAINTED 2 MONTHS AFTER THAT. THE IMPORTANT THING IS TO ADOPT PROCS TO SEE THAT IT DOES NOT HAPPEN AGAIN AND TO FOLLOW THEM RELIGIOUSLY. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR SAID THAT THE 2 OWNERS DO A LOT OF THE MAINT ON THE ACFT ASSISTED BY SEVERAL OTHER A&P MECHS. THEY HAVE SINCE REVIEWED THEIR TOOL CTL PROCS. THERE WAS; AFTER A THOROUGH INSPECTION; FOUND TO BE NO DAMAGE TO THE ACFT. WITH THE PROSPECT OF HAVING TO BAIL OUT OF THE ACFT THE OWNERS ARE NOW CONSIDERING THE USE OF HELMETS AND COMMITTING TO A DETAILED BRIEFING OF PAX ON BAIL OUT PROCS.