Date: 201411
Local time of day: 1801-2400
Location: SJC.Airport, CA
Flight conditions: VMC
Weather elements / visibility: 10
Light: Night
Aircraft: Helicopter
Operator: Air Taxi
Operating under: Part 135
Flight plan: None
Mission: Passenger
Flight phase: Cruise
Airspace: Class C SJC
ATC / advisory: TRACON NCT
Reporter organization: Air Taxi
Reporter function: Single Pilot; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Human factors: Communication Breakdown; Confusion
Anomaly: ATC Issue All Types; Airspace Violation All Types
Detector: Person Air Traffic Control
When detected: In-flight
Contributing factors: Airspace Structure; Human Factors; Procedure
Primary problem: Procedure

Narrative: Contacted NorCal Approach while VFR between Santa Cruz and San Jose; about 15nm south of SJC; and told the controller our destination was ZZZ; east of San Jose International.  I asked whether it would be easier if I went above San Jose International (on our flight to Santa Cruz we flew over San Jose International at 3500 ft); or made a low-level transition.  The controller informed me that whatever I requested; he would accommodate us.  He gave me an IFF code; and I replied that as soon as I cleared the hills; I would descend to around 1000 feet for my transition to ZZZ. After clearing the hills; we descended to between 1500 and 1000 feet and proceeded to ZZZ; generally following the 680 freeway.  As we approached San Jose Class C; I expected a frequency change; since none was given; I assumed approach had coordinated clearance through the San Jose Class C area; and I proceeded to ZZZ; no other traffic appeared to be in the vicinity (on TCAS).  NorCal Approach was handling two or three other aircraft on our frequency during our transition to ZZZ.  Following the freeway; we turned final for ZZZ; and I contacted approach and stated we were on final;landing assured.  NorCal approach replied 'Roger'; then a few seconds later stated; 'Frequency change approved; squawk VFR.'  After dropping the passenger; started the aircraft and contacted San Jose Tower for departure.  After receiving clearance for departure; the controller asked me to contact them by phone and gave me a number for the tower supervisor.  He stated they wanted to discuss a pilot deviation.  Contacted the supervisor after we returned to base.  He informed me that they had an unidentified aircraft that transited their airspace; crossing the final approach for Rwy 30; then going in to Reid-Hillview airspace before descending and going back into San Jose's Class C and landing at ZZZ.  I told him that was me; and explained that I had contacted NorCal approach for the transition; had been given a squawk code; and had never been instructed to change frequencies until landing.  I also told the supervisor that I thought it was a little odd that I wasn't switched to San Jose tower; but assumed they had coordinated the transition through tower's area.  The supervisor said that there was one other aircraft in the Class C at the time; but it was much higher than our aircraft; so there were no traffic conflicts during our transit.  The tower supervisor suggested that if it seems odd not to be talking to the tower; it's probably best to ask about a frequency change.  However; I told him that during my previous experience flying in the Bay Area; when we were vectored through airport class C areas and asked about frequency changes; the controllers generally stated that our transitions through the class C were coordinated; so there was no need to talk to each tower.  Since we were a Medevac flight last night; I assumed the same coordination took place between NorCal Approach and San Jose tower to get us to our destination; as I was not directed to change frequencies.  The supervisor agreed and said approach probably could have handled it better; but they were proceeding with a required investigation.  The supervisor asked for my name; FAA license number; and contact information; which I provided.




Synopsis: Pilot reports of being questioned about violating Class C airspace; while being under flight following from the overlying TRACON.