Narrative:

I was working a moderately busy session on local control; and had been on position well more than 1 hour. I had just previously worked a very busy session that lasted nearly 2 hours; with a 17 min break in between. Another controller was receiving OJT on ground control. The supervisor was in the tower cabin attendant monitoring the operation. Another controller who had just vacated the cabin attendant coordinator (cc) position was also present. Runway 25 (6000 ft long) was active; WX was VFR with an overcast layer at 10000 ft MSL. A C172 was in the local pattern doing touch and goes. I cleared a DA20 for takeoff VFR nwbound. After it was about 1 mi northwest; I cleared an AC69 for takeoff IFR heading 290 degrees. I then cleared an SR22 for a 'no-delay' takeoff VFR nwbound. At that specific moment; the C172 was abeam the arrival numbers on downwind; previously cleared touch and go. The AC69 was cleared to 1500 ft MSL; and the DA20 was limited to the same altitude (or lower) until clearing the class B shelf overtop of the class D airspace. The AC69 quickly gained on the DA20. Neither pilot could see the other; probably due to blending into the background of a higher overcast layer. I also had difficulty seeing the aircraft; even with the aid of binoculars. I was focusing on this potential conflict northwest of the field when the former cabin attendant coordinator controller stepped up behind me and blurted out; 'go around!' I reflexively keyed my microphone and said; 'go around;' but used no identing call sign so the transmission was useless. I looked back to my final to see the C172 touching down on the runway about 1000 ft from the threshold. I looked down the runway for the preceding SR22 and located it about 3000 ft ahead and climbing through 200 ft AGL. None of the 5 persons in the tower cabin attendant witnessed the location of the SR22 and C172 simultaneously; but it is possible that I had less than the required same runway separation (3000 ft). The SR22 continued to increase the distance between itself and the C172 now on the 'go.' many factors contributed to this situation. Time on position was longer than normal to allow for a tour group and training to be conducted on ground control. The traffic volume intimidated at least one other controller to avoid local control. As one of the generally recognized better controllers and not lacking self-confidence; I felt I would 'suck it up' for the overall agency benefit; but in hindsight I was more mentally fatigued than I realized. The work environment was much noisier than normal due to OJT being conducted at ground control and a personal conversation between the supervisor and former cabin attendant coordinator controller. I should have tactfully demanded less background noise. I spent too much time focusing on our situation to the exclusion of all others. There were enough eyes and ears available to ask for help. I noticed that on the next circuit around the traffic pattern; the C172 cut the base to final turn and essentially made an unauthorized short approach. It occurred to me that on every circuit except the last two; I had extended the C172's pattern or given her some additional instruction (ie; 'follow king air on 4 mi final;' etc). If the C172 had flown a normal pattern; spacing would have been adequate. I base this opinion on nearly 10 yrs experience (both pilot and ATC) and timing via the UTC clock at the control position (a C172 takes 7 mins to complete 1 normal pattern circuit; and she was still 2 mins from the runway threshold). The SR22 did as instructed and took off without delay. I suspect the C172 made a short approach on the previous circuit as well. I had assumed the C172 would fly a normal pattern absent any other instructions; but had yet to observe her idea of 'normal' since traffic conditions had so far precluded it. The C172 was a locally based training aircraft and was known to me. I should have been more vigilant of what I assumed was a student pilot. I failed to 'trust but verify.' I trusted the SR22 and C172 pilots to do as instructed; but did not verify it because I was focusing on a situation in another direction. It only took one of them deviating from my expectations to produce a potentially serious situation. I recognized the potential conflict of the DA20 and AC69 as soon as the ground control controller passed me the AC69's IFR strip (after the DA20 had been cleared for takeoff). In hindsight I should have taken more proactive steps to prevent it so that it did not consume most of my attention the way it did.

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Original NASA ASRS Text

Title: ORL LCL CTLR DESCRIBED MINIMAL SEPARATION INCIDENT INVOLVING SR-22 DEP AND C172 ARR.

Narrative: I WAS WORKING A MODERATELY BUSY SESSION ON LCL CTL; AND HAD BEEN ON POS WELL MORE THAN 1 HR. I HAD JUST PREVIOUSLY WORKED A VERY BUSY SESSION THAT LASTED NEARLY 2 HRS; WITH A 17 MIN BREAK IN BTWN. ANOTHER CTLR WAS RECEIVING OJT ON GND CTL. THE SUPVR WAS IN THE TWR CAB MONITORING THE OP. ANOTHER CTLR WHO HAD JUST VACATED THE CAB COORDINATOR (CC) POS WAS ALSO PRESENT. RWY 25 (6000 FT LONG) WAS ACTIVE; WX WAS VFR WITH AN OVCST LAYER AT 10000 FT MSL. A C172 WAS IN THE LCL PATTERN DOING TOUCH AND GOES. I CLRED A DA20 FOR TKOF VFR NWBOUND. AFTER IT WAS ABOUT 1 MI NW; I CLRED AN AC69 FOR TKOF IFR HDG 290 DEGS. I THEN CLRED AN SR22 FOR A 'NO-DELAY' TKOF VFR NWBOUND. AT THAT SPECIFIC MOMENT; THE C172 WAS ABEAM THE ARR NUMBERS ON DOWNWIND; PREVIOUSLY CLRED TOUCH AND GO. THE AC69 WAS CLRED TO 1500 FT MSL; AND THE DA20 WAS LIMITED TO THE SAME ALT (OR LOWER) UNTIL CLRING THE CLASS B SHELF OVERTOP OF THE CLASS D AIRSPACE. THE AC69 QUICKLY GAINED ON THE DA20. NEITHER PLT COULD SEE THE OTHER; PROBABLY DUE TO BLENDING INTO THE BACKGROUND OF A HIGHER OVCST LAYER. I ALSO HAD DIFFICULTY SEEING THE ACFT; EVEN WITH THE AID OF BINOCULARS. I WAS FOCUSING ON THIS POTENTIAL CONFLICT NW OF THE FIELD WHEN THE FORMER CAB COORDINATOR CTLR STEPPED UP BEHIND ME AND BLURTED OUT; 'GAR!' I REFLEXIVELY KEYED MY MIKE AND SAID; 'GAR;' BUT USED NO IDENTING CALL SIGN SO THE XMISSION WAS USELESS. I LOOKED BACK TO MY FINAL TO SEE THE C172 TOUCHING DOWN ON THE RWY ABOUT 1000 FT FROM THE THRESHOLD. I LOOKED DOWN THE RWY FOR THE PRECEDING SR22 AND LOCATED IT ABOUT 3000 FT AHEAD AND CLBING THROUGH 200 FT AGL. NONE OF THE 5 PERSONS IN THE TWR CAB WITNESSED THE LOCATION OF THE SR22 AND C172 SIMULTANEOUSLY; BUT IT IS POSSIBLE THAT I HAD LESS THAN THE REQUIRED SAME RWY SEPARATION (3000 FT). THE SR22 CONTINUED TO INCREASE THE DISTANCE BTWN ITSELF AND THE C172 NOW ON THE 'GO.' MANY FACTORS CONTRIBUTED TO THIS SITUATION. TIME ON POS WAS LONGER THAN NORMAL TO ALLOW FOR A TOUR GROUP AND TRAINING TO BE CONDUCTED ON GND CTL. THE TFC VOLUME INTIMIDATED AT LEAST ONE OTHER CTLR TO AVOID LCL CTL. AS ONE OF THE GENERALLY RECOGNIZED BETTER CTLRS AND NOT LACKING SELF-CONFIDENCE; I FELT I WOULD 'SUCK IT UP' FOR THE OVERALL AGENCY BENEFIT; BUT IN HINDSIGHT I WAS MORE MENTALLY FATIGUED THAN I REALIZED. THE WORK ENVIRONMENT WAS MUCH NOISIER THAN NORMAL DUE TO OJT BEING CONDUCTED AT GND CTL AND A PERSONAL CONVERSATION BTWN THE SUPVR AND FORMER CAB COORDINATOR CTLR. I SHOULD HAVE TACTFULLY DEMANDED LESS BACKGROUND NOISE. I SPENT TOO MUCH TIME FOCUSING ON OUR SITUATION TO THE EXCLUSION OF ALL OTHERS. THERE WERE ENOUGH EYES AND EARS AVAILABLE TO ASK FOR HELP. I NOTICED THAT ON THE NEXT CIRCUIT AROUND THE TFC PATTERN; THE C172 CUT THE BASE TO FINAL TURN AND ESSENTIALLY MADE AN UNAUTH SHORT APCH. IT OCCURRED TO ME THAT ON EVERY CIRCUIT EXCEPT THE LAST TWO; I HAD EXTENDED THE C172'S PATTERN OR GIVEN HER SOME ADDITIONAL INSTRUCTION (IE; 'FOLLOW KING AIR ON 4 MI FINAL;' ETC). IF THE C172 HAD FLOWN A NORMAL PATTERN; SPACING WOULD HAVE BEEN ADEQUATE. I BASE THIS OPINION ON NEARLY 10 YRS EXPERIENCE (BOTH PLT AND ATC) AND TIMING VIA THE UTC CLOCK AT THE CTL POS (A C172 TAKES 7 MINS TO COMPLETE 1 NORMAL PATTERN CIRCUIT; AND SHE WAS STILL 2 MINS FROM THE RWY THRESHOLD). THE SR22 DID AS INSTRUCTED AND TOOK OFF WITHOUT DELAY. I SUSPECT THE C172 MADE A SHORT APCH ON THE PREVIOUS CIRCUIT AS WELL. I HAD ASSUMED THE C172 WOULD FLY A NORMAL PATTERN ABSENT ANY OTHER INSTRUCTIONS; BUT HAD YET TO OBSERVE HER IDEA OF 'NORMAL' SINCE TFC CONDITIONS HAD SO FAR PRECLUDED IT. THE C172 WAS A LOCALLY BASED TRAINING ACFT AND WAS KNOWN TO ME. I SHOULD HAVE BEEN MORE VIGILANT OF WHAT I ASSUMED WAS A STUDENT PLT. I FAILED TO 'TRUST BUT VERIFY.' I TRUSTED THE SR22 AND C172 PLTS TO DO AS INSTRUCTED; BUT DID NOT VERIFY IT BECAUSE I WAS FOCUSING ON A SITUATION IN ANOTHER DIRECTION. IT ONLY TOOK ONE OF THEM DEVIATING FROM MY EXPECTATIONS TO PRODUCE A POTENTIALLY SERIOUS SITUATION. I RECOGNIZED THE POTENTIAL CONFLICT OF THE DA20 AND AC69 AS SOON AS THE GND CTL CTLR PASSED ME THE AC69'S IFR STRIP (AFTER THE DA20 HAD BEEN CLRED FOR TKOF). IN HINDSIGHT I SHOULD HAVE TAKEN MORE PROACTIVE STEPS TO PREVENT IT SO THAT IT DID NOT CONSUME MOST OF MY ATTN THE WAY IT DID.

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.