C310 pilot clips the edge of sea class B airspace and is advised by boeing field tower.

Attributes
ACN	472740
Time
Date	200005
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	navaid : sea.vortac
State Reference	WA
Altitude	msl bound lower : 1500 msl bound upper : 2000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : bfi.tower
Operator	general aviation : personal
Make Model Name	Cessna 310/T310C
Operating Under FAR Part	Part 91
Navigation In Use	other
Flight Phase	climbout : intermediate altitude
Route In Use	departure : vfr
Flight Plan	None
Person 1
Affiliation	other
Function	flight crew : single pilot
Qualification	pilot : private pilot : multi engine
ASRS Report	472740
Person 2
Affiliation	government : faa
Function	controller : local
Qualification	controller : radar
Events
Anomaly	airspace violation : entry non adherence : far non adherence : published procedure
Independent Detector	other controllerb
Resolutory Action	controller : issued advisory flight crew : exited penetrated airspace
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Bfi requested my altitude on a northbound departure. When I was crossing the south shoreline by west point (sea) I was looking for seaplanes departing from lake union (VFR). Bfi tower requested my altitude. I responded '2000 ft,' thinking I was clear of the class B airspace (1800 ft at 12 NM sea VOR). They (bfi tower) responded I was 'in class B airspace by 1.5 mi.' my visual clue of the shoreline should have been sufficient to identify my position. I did not respond to the tower other than to repeat my n-number. I do not think I violated the class B airspace. I descended to 1500 ft as soon as possible, even though I was clear of the class B. Note: a lot of thermal activity at the time, my vsi was showing a descent at the time of this call (-500 ft).

Original NASA ASRS Text

Title: C310 PLT CLIPS THE EDGE OF SEA CLASS B AIRSPACE AND IS ADVISED BY BOEING FIELD TWR.

Narrative: BFI REQUESTED MY ALT ON A NBOUND DEP. WHEN I WAS XING THE S SHORELINE BY WEST POINT (SEA) I WAS LOOKING FOR SEAPLANES DEPARTING FROM LAKE UNION (VFR). BFI TWR REQUESTED MY ALT. I RESPONDED '2000 FT,' THINKING I WAS CLR OF THE CLASS B AIRSPACE (1800 FT AT 12 NM SEA VOR). THEY (BFI TWR) RESPONDED I WAS 'IN CLASS B AIRSPACE BY 1.5 MI.' MY VISUAL CLUE OF THE SHORELINE SHOULD HAVE BEEN SUFFICIENT TO IDENT MY POS. I DID NOT RESPOND TO THE TWR OTHER THAN TO REPEAT MY N-NUMBER. I DO NOT THINK I VIOLATED THE CLASS B AIRSPACE. I DSNDED TO 1500 FT ASAP, EVEN THOUGH I WAS CLR OF THE CLASS B. NOTE: A LOT OF THERMAL ACTIVITY AT THE TIME, MY VSI WAS SHOWING A DSCNT AT THE TIME OF THIS CALL (-500 FT).

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.