Narrative:

Aircraft #1 was on the runway and unable to exit at the first 4 txwys and was told to expedite to the end of the runway and exit to the right. Aircraft #2 was told to go around when they were on a 1/4 mi final. Readback of the go around instruction was garbled and unreadable but aircraft #2 appeared to be pwring up for the go around. I turned my attention to several other aircraft in my pattern and entering class D airspace. Aircraft #2 executed a touch-and-go and separation was lost. Aircraft #2 states that they never heard the go around instruction. The instruction is clear on position recordings. The controller-in-charge and my local assist controller all saw what appeared to be a power-up confign on aircraft #2. I believe the on-going problem with the communication 'blind spot' at the approach ends of runways 21R and 21L contributed to this incident. Additionally; the common practice for flight schools to wait 1-3 mins blocking a runway exit before calling ground control had a direct impact on this incident. First time students and low time instructor pilots may have also been contributing factors. Supplemental information from acn 766015: as we approached short final I looked down the runway and noticed a cessna on taxiway A2. I knew we were following a cessna so I thought that was our traffic; and they were clear of the runway. After we touched down and advanced the throttles to complete the touch and go; I noticed another aircraft on taxiway A1. We rotated and climbed out like normal. I did not know that there was a problem until after we made a full stop landing and tower 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 landing clearance had been canceled.

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Original NASA ASRS Text

Title: 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.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.