A cga came in close proximity to an small aircraft just after departure.

Attributes
ACN	113759
Time
Date	198906
Day	Mon
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : bfi
State Reference	WA
Altitude	msl bound lower : 1500 msl bound upper : 1500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : bfi
Operator	general aviation : personal
Make Model Name	Small Aircraft
Flight Phase	cruise other
Flight Plan	None
Aircraft 2
Operator	general aviation : corporate
Make Model Name	Light Transport, Low Wing, 2 Turbojet Eng
Flight Phase	climbout : intermediate altitude
Route In Use	departure other
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : local
Qualification	controller : non radar
Experience	controller non radar : 4
ASRS Report	113759
Person 2
Affiliation	government : faa
Function	controller : local
Qualification	controller : non radar
Events
Anomaly	conflict : airborne less severe non adherence : required legal separation non adherence : published procedure
Independent Detector	other controllera other flight crewa
Resolutory Action	none taken : detected after the fact
Consequence	Other
Miss Distance	horizontal : 1500 vertical : 300
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

I was working local ii at bfi. Small aircraft X called local-I, off rtn, and would like to take some pictures. Local-I then sent small aircraft X to my frequency. During this time I had cleared cga Y for takeoff on runway 13R. Cga Y was IFR departing straight out sebnd (heading 130 and climbing to 10,000). Small aircraft X first call to me was, with you on 120.6. I asked small aircraft X his position. He answered with, were at the south end of 31L, at 1500'. After hearing his position I looked out the window to the southeast and observed small aircraft X passing the extended centerlines approximately 2 southeast in front of cga Y. I stepped on the rest of his transmission to issue traffic. After I unkeyed the microphone cga Y had stopped transmitting so I issued the traffic to him again and told him to contact departure. Cga Y was already turning east and descending to avoid small aircraft X, whether from my first traffic advisory or the fact he had already seen the floatplane. Cga Y said he had the floatplane and was going to departure. I believe the floatplane and small aircraft X missed by approximately 300' vertically and 1500' horizontally.

Original NASA ASRS Text

Title: A CGA CAME IN CLOSE PROX TO AN SMA JUST AFTER DEP.

Narrative: I WAS WORKING LOCAL II AT BFI. SMA X CALLED LCL-I, OFF RTN, AND WOULD LIKE TO TAKE SOME PICTURES. LCL-I THEN SENT SMA X TO MY FREQ. DURING THIS TIME I HAD CLRED CGA Y FOR TKOF ON RWY 13R. CGA Y WAS IFR DEPARTING STRAIGHT OUT SEBND (HDG 130 AND CLIMBING TO 10,000). SMA X FIRST CALL TO ME WAS, WITH YOU ON 120.6. I ASKED SMA X HIS POSITION. HE ANSWERED WITH, WERE AT THE SOUTH END OF 31L, AT 1500'. AFTER HEARING HIS POSITION I LOOKED OUT THE WINDOW TO THE SE AND OBSERVED SMA X PASSING THE EXTENDED CENTERLINES APPROX 2 SE IN FRONT OF CGA Y. I STEPPED ON THE REST OF HIS XMISSION TO ISSUE TFC. AFTER I UNKEYED THE MIKE CGA Y HAD STOPPED XMITTING SO I ISSUED THE TFC TO HIM AGAIN AND TOLD HIM TO CONTACT DEP. CGA Y WAS ALREADY TURNING EAST AND DESCENDING TO AVOID SMA X, WHETHER FROM MY FIRST TFC ADVISORY OR THE FACT HE HAD ALREADY SEEN THE FLOATPLANE. CGA Y SAID HE HAD THE FLOATPLANE AND WAS GOING TO DEP. I BELIEVE THE FLOATPLANE AND SMA X MISSED BY APPROX 300' VERTICALLY AND 1500' HORIZONTALLY.

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.