Small Transport; Low Wing; 2 Turboprop Eng
Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Instructor; Flight Crew Instrument
Flight Crew Last 90 Days 125; Flight Crew Total 13000; Flight Crew Type 4000
Communication Breakdown; Distraction; Situational Awareness; Workload
Airspace Violation All Types; Conflict NMAC
Flight Crew Took Evasive Action
Human Factors; Environment - Non Weather Related; Airspace Structure
When about to initiate descent to at SQL (1;200 FT); a TCAS target appeared directly below and just in front of my nose at 300 FT below. I stopped my descent until I could see the other aircraft; but while doing so might have slipped the 1;500 FT shelf of the SFO Class B that overlies SQL at 1;500 FT.
A light twin pilot took evasive action from another aircraft while on approach to SQL and; after stopping his descent; entered SFO Class B at 1;500 FT.