A JETSTREAM 4100 IN CRUISE AT 16000 FT DECLARED AN EMER AND DIVERTED DUE TO BEING UNABLE TO TRIM THE ACFT WITH AUTOPLT; MAIN ELECTRIC OR MANUAL SYS CAUSED BY A SOCKET TOOL OBSTRUCTING THE TRIM MECHANISM.

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AT CRUISE (16000 FT) WITH AUTOPLT SELECTED ON TRIM; WARNING LIGHTS ILLUMINATED. THE PF (FO) SELECTED THE AUTOPLT OFF AND ACFT HAD A LOT OF NOSE UP PRESSURE. FO ATTEMPTED TO TRIM ACFT VIA ELECTRICAL TRIM BUT WAS UNABLE TO OPERATE (MOVE TRIM). AUTOPLT TRIM MASTER SWITCH WAS SELECTED OFF (PIC ACTION) AND MANUAL TRIM CHANGE WAS ATTEMPTED WITH NO RESULTS (NO TRIM). THE TRIM/TRIM WAS STUCK IN AUTOELECTRICAL/MANUAL MODES. I (PIC CAPT) ASSUMED CTL OF ACFT. EMER WAS DECLARED AND FLT XYZ STARTED A 180 DEG TURN TOWARD MSN; WI. TO RELEASE SOME CTL PRESSURE; I (CAPT PIC) SLOWED THE ACFT SPD. AT ABOUT 170 KIAS AND WITH SOME APPLICATION OF PRESSURE ON CTL TRIM WHEEL; TRIM BECAME FREE AND ALL OTHER OPS OF FLT CTLS BECAME NORMAL (NO UP/DOWN PRESSURES). LANDED AT MSN WITH NO FURTHER PROBS. ZZZ (COMPANY ACR) FLT CTL AND ZZZ MAINT OPS WERE NOTIFIED BY THE CREW AND BY MSN STATION OPS. I WAS INSTRUCTED BY ZZZ FLT CTL AND ZZZ MAINT CTL TO OPEN THE COCKPIT VOICE RECORDER AND FLT DATA RECORDER CIRCUIT BREAKERS UPON NTSB REQUEST. ACR ACFT MAINT FLT LOG DISCREPANCY #2. ZZZ MAINT CTL WAS IN CONTACT WITH THE NTSB AND ZZZ MAINT CTL CONTRACTED AN A&P TO INSPECT ACFT (A&P NOT FROM ACR COMPANY BUT FROM MSN FBO). AFTER WORKING WITH THE A&P (I WAS INSTRUCTED BY THE A&P TO SIT IN THE FLT DECK AND MOVE THE ELECTRIC/MANUAL TRIM) THE PROB DID NOT DUPLICATE ON THE GND. THE A&P THEN PROCEEDED TO REMOVE A TAIL SECTION OF THE ACFT TO BETTER INSPECT THE TRIM COMPONENTS. AFTER HIS INSPECTION; HE RPTED TO ME (PIC) AND VIA PHONE TO ZZZ MAINT CTL (MXMX) THAT HE HAD FOUND A 'SOCKET' (WORK TOOL) IN THE AREA OF HIS INSPECTION. THE A&P THEN SPOKE TO ZZZ MAINT CTL. THE A&P THEN (INSTRUCTED BY ZZZ MAINT CTL) MEL'ED THE AUTOPLT FUNCTIONS. I (PIC) THEN SPOKE TO ZZZ MAINT CTL AND WAS TOLD BY ZZZ MAINT MXMX TO BRING BACK THE 'SOCKET' TO OUR HOME BASE IN ZZZ. I WAS TOLD TO GIVE IT TO BZXX IN ARPT ZZZ MAINT OFFICE/OPS. I DID JUST SO.