Narrative:

I was providing OJT on the local control position at sarasota-bradenton ATC tower. The controller receiving OJT cleared small aircraft for takeoff on an IFR flight plan en route to lakeland, fl. When the small aircraft was 5 mi southeast of sarasota airport, large transport was cleared for takeoff. Tpa approach was on a high/low split with small aircraft on frequency 119.65 and large transport on frequency 124.95. The controller receiving OJT instructions was late switching large transport due to local traffic. At the time large transport was switched to 124.95 the small aircraft was 7 mi southeast of sarasota airport appearing to be turned southbound. Tpa approach had been talking to small aircraft for 1:32 mins before large transport was cleared for takeoff. One of the problems is that on the tpa high/low split turbo jets and propellers are both assigned the same heading and initial altitude (runway heading and 3000'), but the propellers are assigned 119.65 and turbojets 124.95. This provides for frequency sep, but not airspace sep. As an almost standard operating procedure, as a controller at srq ATC tower I have used the 5 mi sep factor between departures when the leading aircraft is faster of if slower turning. It appeared that small aircraft was turning southbound, away from large transport. Tpa turned the small aircraft northeast and on srq's radar it appeared that large transport passed 2 mi from NAA4P. An additional problem is no way for the controllers to communicate readily between positions due to land line problems, ie, no direct line from local control to tpa when the split is in effect. Also, was the factor of providing OJT and allowing the controller receiving instruction as much leeway as possible west/O loss of sep or compromise of safety. Clearing large transport for takeoff with small aircraft 4 mi southeast did not compromise safety or sep.

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Original NASA ASRS Text

Title: LOSS OF SEPARATION OCCURRED WHEN LCL CTLR RELEASED IFR LGT TOO CLOSE BEHIND IFR SMA.

Narrative: I WAS PROVIDING OJT ON THE LCL CTL POS AT SARASOTA-BRADENTON ATC TWR. THE CTLR RECEIVING OJT CLRED SMA FOR TKOF ON AN IFR FLT PLAN ENRTE TO LAKELAND, FL. WHEN THE SMA WAS 5 MI SE OF SARASOTA ARPT, LGT WAS CLRED FOR TKOF. TPA APCH WAS ON A HIGH/LOW SPLIT WITH SMA ON FREQ 119.65 AND LGT ON FREQ 124.95. THE CTLR RECEIVING OJT INSTRUCTIONS WAS LATE SWITCHING LGT DUE TO LCL TFC. AT THE TIME LGT WAS SWITCHED TO 124.95 THE SMA WAS 7 MI SE OF SARASOTA ARPT APPEARING TO BE TURNED SBND. TPA APCH HAD BEEN TALKING TO SMA FOR 1:32 MINS BEFORE LGT WAS CLRED FOR TKOF. ONE OF THE PROBS IS THAT ON THE TPA HIGH/LOW SPLIT TURBO JETS AND PROPS ARE BOTH ASSIGNED THE SAME HDG AND INITIAL ALT (RWY HDG AND 3000'), BUT THE PROPS ARE ASSIGNED 119.65 AND TURBOJETS 124.95. THIS PROVIDES FOR FREQ SEP, BUT NOT AIRSPACE SEP. AS AN ALMOST STANDARD OPERATING PROC, AS A CTLR AT SRQ ATC TWR I HAVE USED THE 5 MI SEP FACTOR BTWN DEPS WHEN THE LEADING ACFT IS FASTER OF IF SLOWER TURNING. IT APPEARED THAT SMA WAS TURNING SBND, AWAY FROM LGT. TPA TURNED THE SMA NE AND ON SRQ'S RADAR IT APPEARED THAT LGT PASSED 2 MI FROM NAA4P. AN ADDITIONAL PROB IS NO WAY FOR THE CTLRS TO COMMUNICATE READILY BTWN POSITIONS DUE TO LAND LINE PROBS, IE, NO DIRECT LINE FROM LCL CTL TO TPA WHEN THE SPLIT IS IN EFFECT. ALSO, WAS THE FACTOR OF PROVIDING OJT AND ALLOWING THE CTLR RECEIVING INSTRUCTION AS MUCH LEEWAY AS POSSIBLE W/O LOSS OF SEP OR COMPROMISE OF SAFETY. CLRING LGT FOR TKOF WITH SMA 4 MI SE DID NOT COMPROMISE SAFETY OR SEP.

Data retrieved from NASA's ASRS site as of August 2007 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.