PLT OF SMT CLRED ONTO RWY TO HOLD WAS LATER INSTRUCTED TO CLR THE RWY FOR LNDG ACFT.

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GND CTL CLRED ME TO TAXI MY TURBOPROP TO RWY 19. AFTER TAXIING OUT AND ARRIVING AT THE APCH END OF RWY 19; I WAS SECOND IN SEQUENCE FOR RELEASE. I CALLED TWR AND ANNOUNCED I WAS READY FOR RELEASE IN SEQUENCE. TWR ADVISED ME TO HOLD PRESENT POS; I WAS SECOND IN LINE FOR RELEASE. AFTER THE PLANE IN FRONT OF ME WAS CLRED ONTO 19 AND RELEASED; TWR CALLED AND CLRED ME TO TAXI AND HOLD IN POS ON RWY 19 AND BE READY FOR IMMEDIATE TKOF. I READ BACK THE INSTRUCTIONS TO THE TWR; THEN TAXIED INTO POS AND HELD. AFTER SITTING IN POS FOR APPROX 30 SECONDS I WONDERED WHAT THE 'BE READY FOR IMMEDIATE TKOF' HAD BEEN FOR AND WHEN WAS THE TWR GOING TO RELEASE ME. THEN THE TWR CLRED A HVY JET TO TKOF ON RWY 27. RWY 27 CROSSES THE DEP END OF 19. I THEN REASONED THAT THE TWR MUST HAVE DECIDED TO RELEASE THE FASTER TFC ON 27 BEFORE RELEASING ME. SECONDS AFTER THE HVY DEP FROM 27 CROSSED MY RWY; THE TWR CLRED ANOTHER HVY JET TO LAND ON 19; TWR THEN ASKED WHAT MY POS WAS. WHICH I ANNOUNCED. TWR THEN ORDERED ME TO VACATE RWY 19 IMMEDIATELY; THAT I HAD NOT BEEN CLRED ONTO 19. I IMMEDIATELY WENT TO FULL PWR ON THE STARBOARD ENG TO TURN ME TO THE CLOSEST TAXI EXIT. ON MY TURN AROUND; I WAS SHOCKED TO SEE THE HVY JET SO CLOSE ON SHORT FINAL WITH ME ON THE RWY. AS I EXITED THE RWY AND CROSSED THE DEP HOLD LINE; THE HVY JET LANDED BEHIND ME. I WAS THEN ORDERED TO HOLD CLR OF 19. 5 MINS LATER I WAS CLRED FOR TKOF AND RELEASED. MY DIRECT INQUIRY ON THIS INCIDENT TO THE TWR RESULTED IN THIS STATEMENT FROM THEM: 'WE DID NOT HEAR YOU REPEAT OUR INSTRUCTIONS BACK TO US; SOMEONE XMITTED ON TOP OF YOU.' AFTER REVIEWING THE FACTS AS THEY HAPPENED; I WILL NEVER AGAIN HOLD ON A RWY WITHOUT A SECOND CONFIRMATION; INFORMING THE TWR THAT 'I AM IN POS ON THE RWY AND HOLDING!' YES; I BELIEVE; I FOLLOWED THE INSTRUCTIONS AS INSTRUCTED. BUT I'M AMAZED THAT THE TWR DID NOT ASK ME TO REPEAT THEIR INSTRUCTIONS BACK TO THEM; WHEN SOMEONE ELSE XMITTED OVER MY READBACK TO THEM. OR DID THE TWR JUST FORGET WHERE HE HAD ME POSITIONED; UNTIL IT WAS ALMOST TOO LATE?