PRC CTLR EXPERIENCED OPERROR WHEN RESPONSE TO GAR CLRNC TO ACFT ON SHORT FINAL WAS UNCLEAR AND ACFT COMPLETED TOUCH AND GO.

Narrative

ACFT #1 WAS ON THE RWY AND UNABLE TO EXIT AT THE FIRST 4 TXWYS AND WAS TOLD TO EXPEDITE TO THE END OF THE RWY AND EXIT TO THE R. ACFT #2 WAS TOLD TO GO AROUND WHEN THEY WERE ON A 1/4 MI FINAL. READBACK OF THE GAR INSTRUCTION WAS GARBLED AND UNREADABLE BUT ACFT #2 APPEARED TO BE PWRING UP FOR THE GAR. I TURNED MY ATTN TO SEVERAL OTHER ACFT IN MY PATTERN AND ENTERING CLASS D AIRSPACE. ACFT #2 EXECUTED A TOUCH-AND-GO AND SEPARATION WAS LOST. ACFT #2 STATES THAT THEY NEVER HEARD THE GAR INSTRUCTION. THE INSTRUCTION IS CLR ON POS RECORDINGS. THE CTLR-IN-CHARGE AND MY LCL ASSIST CTLR ALL SAW WHAT APPEARED TO BE A PWR-UP CONFIGN ON ACFT #2. I BELIEVE THE ON-GOING PROB WITH THE COM 'BLIND SPOT' AT THE APCH ENDS OF RWYS 21R AND 21L CONTRIBUTED TO THIS INCIDENT. ADDITIONALLY; THE COMMON PRACTICE FOR FLT SCHOOLS TO WAIT 1-3 MINS BLOCKING A RWY EXIT BEFORE CALLING GND CTL HAD A DIRECT IMPACT ON THIS INCIDENT. FIRST TIME STUDENTS AND LOW TIME INSTRUCTOR PLTS MAY HAVE ALSO BEEN CONTRIBUTING FACTORS. SUPPLEMENTAL INFO FROM ACN 766015: AS WE APCHED SHORT FINAL I LOOKED DOWN THE RWY AND NOTICED A CESSNA ON TXWY A2. I KNEW WE WERE FOLLOWING A CESSNA SO I THOUGHT THAT WAS OUR TFC; AND THEY WERE CLR OF THE RWY. AFTER WE TOUCHED DOWN AND ADVANCED THE THROTTLES TO COMPLETE THE TOUCH AND GO; I NOTICED ANOTHER ACFT ON TXWY A1. WE ROTATED AND CLBED OUT LIKE NORMAL. I DID NOT KNOW THAT THERE WAS A PROB UNTIL AFTER WE MADE A FULL STOP LNDG AND TWR ASKED US TO CALL THEM. NEITHER MY STUDENT NOR I HEARD ANY RADIO CALLS ON SHORT FINAL TELLING US TO GO AROUND OR THAT OUR LNDG CLRNC HAD BEEN CANCELED.