PA34 on visual approach had less than standard separation from departing GS. System error.

Attributes
ACN	300650
Time
Date	199503
Day	Fri
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : apf
State Reference	FL
Altitude	msl bound lower : 2000 msl bound upper : 2000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : rsw tower : apf tower : cys
Operator	general aviation : personal
Make Model Name	PA-34-200T Turbo Seneca II
Operating Under FAR Part	Part 91
Flight Phase	descent : approach
Flight Plan	IFR
Aircraft 2
Operator	general aviation : corporate
Make Model Name	Gulfstream II
Operating Under FAR Part	Part 91
Navigation In Use	Other
Flight Phase	climbout : takeoff climbout : initial
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Experience	controller radar : 11
ASRS Report	300650
Person 2
Affiliation	government : faa
Function	controller : local
Qualification	controller : non radar
Events
Anomaly	conflict : airborne less severe non adherence : published procedure non adherence : required legal separation
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance other
Consequence	Other
Miss Distance	horizontal : 6000 vertical : 0
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error Inter Facility Coordination Failure

Narrative:

I cleared PA34 for visual approach to runway 22 at apf. I switched frequencys and terminated radar with him. Released G2 off of runway 13 reference the PA34. LOA with apf tower allows them to use visual separation for arrs/departures (they have no radar/BRITE). I observed the PA34 northeast of apf and he appeared to be high (2000 ft). I called apf tower and inquired of PA34's intentions, they said they did not know and the G2 was rolling. I canceled PA34's approach clearance and issued heading 130 degrees and climb to 2000 ft. Apparently apf tower released G2 without establishing visual separation with PA34. It appeared to me they may be a possible midair conflict, so I broke out the PA34. He reported climbing to 2000 ft and was observed at 2900 ft. The G2 departed and I believe the PA34 may have had invalid mode C because he appeared to continue climb up to 3700 ft. He reported climbing to 2000 ft. I believe this situation occurred because visual separation was not applied reference our LOA with apf (per 7110.65) and due to (possible) erroneous mode C readout on the PA34. I took corrective action to avoid what I thought may be a possible collision.

Original NASA ASRS Text

Title: PA34 ON VISUAL APCH HAD LTSS FROM DEPARTING GS. SYS ERROR.

Narrative: I CLRED PA34 FOR VISUAL APCH TO RWY 22 AT APF. I SWITCHED FREQS AND TERMINATED RADAR WITH HIM. RELEASED G2 OFF OF RWY 13 REF THE PA34. LOA WITH APF TWR ALLOWS THEM TO USE VISUAL SEPARATION FOR ARRS/DEPS (THEY HAVE NO RADAR/BRITE). I OBSERVED THE PA34 NE OF APF AND HE APPEARED TO BE HIGH (2000 FT). I CALLED APF TWR AND INQUIRED OF PA34'S INTENTIONS, THEY SAID THEY DID NOT KNOW AND THE G2 WAS ROLLING. I CANCELED PA34'S APCH CLRNC AND ISSUED HDG 130 DEGS AND CLB TO 2000 FT. APPARENTLY APF TWR RELEASED G2 WITHOUT ESTABLISHING VISUAL SEPARATION WITH PA34. IT APPEARED TO ME THEY MAY BE A POSSIBLE MIDAIR CONFLICT, SO I BROKE OUT THE PA34. HE RPTED CLBING TO 2000 FT AND WAS OBSERVED AT 2900 FT. THE G2 DEPARTED AND I BELIEVE THE PA34 MAY HAVE HAD INVALID MODE C BECAUSE HE APPEARED TO CONTINUE CLB UP TO 3700 FT. HE RPTED CLBING TO 2000 FT. I BELIEVE THIS SIT OCCURRED BECAUSE VISUAL SEPARATION WAS NOT APPLIED REF OUR LOA WITH APF (PER 7110.65) AND DUE TO (POSSIBLE) ERRONEOUS MODE C READOUT ON THE PA34. I TOOK CORRECTIVE ACTION TO AVOID WHAT I THOUGHT MAY BE A POSSIBLE COLLISION.

Data retrieved from NASA's ASRS site as of July 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.