A321
Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Flight Crew Total 12800
Situational Awareness; Communication Breakdown; Confusion
ATC Issue All Types; Airspace Violation All Types; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural FAR
Air Traffic Control Provided Assistance; Flight Crew Exited Penetrated Airspace; Flight Crew Returned To Clearance
Airspace Structure; Human Factors; Procedure
We were approaching runway 12R in MSP and we were cleared to 4000 feet and 190 knots. Then we were given a base turn and subsequently cleared to a heading to join ILS 12R and 3000 feet until established. I selected vertical speed of -500 FPM to join the ILS. ATC then told us we had exited Class B airspace by 200 feet but then had reentered Class B airspace. Our speed at this point was 170 knots. Not sure if a deviation has occurred as we were following ATC clearance. We understood the clearance of '3000 feet until established; cleared for the approach' as a clearance to descend to 3000 feet. Also we relied on ATC to keep us in Class B airspace as it was IMC conditions A more thorough study of the Class B airspace would have been useful.
[Report narrative contained no additional information.]
A321 flight crew reported exiting and reentering Class B Airspace while complying with an ATC clearance.