Date: 201902
Location: DEN.Airport, CO
Flight conditions: VMC
Light: Daylight
Aircraft: B737 Next Generation Undifferentiated
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Descent
Airspace: Class B DEN
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Human factors: Situational Awareness; Confusion; Distraction
Second reporter function: First Officer; Pilot Flying
Anomaly: ATC Issue All Types; Airspace Violation All Types; Deviation - Speed All Types; Deviation / Discrepancy - Procedural FAR
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert
Contributing factors: Human Factors; Company Policy; Airspace Structure; Procedure
Primary problem: Ambiguous

Narrative: We were told to descend with at least 2;000 FPM at roughly the same time a heading to the southwest was issued as initial vectors for the runway. To comply; we kept the speed high (320 Knots or so). After leveling at 10;000 feet; Approach gave us a descent to 9000 feet and then switched us to another Approach Control frequency. The First Officer slowed to 250 knots and began the descent while I tuned the radio and switched frequencies. Upon check in; the new Controller asked; 'Did anyone tell you that you exited the Class Bravo?' I replied that I was not aware of that. Immediately; I asked the First Officer to slow to 200 knots in case we were in fact below the Class B airspace. I looked at the 10-1B chart; entered our destination in the fix page; and noted that we were on the 140 radial and 21NM; just 1 mile outside the Class B section where our speed would have been appropriate. Admittedly; this felt to me very much like a setup by the controllers. In no way did we intend to exceed the Class B boundaries. But their requests for expedited descents and their vectors to final placed us just slightly outside the Class B boundaries. With few other airplanes in our area (based on TCAS display); it would have been easy for the controllers to have at least prompted us prior to exiting the Bravo or to have vectored us just slightly farther west in order to stay inside the appropriate Class B boundaries.


Second narrative: While flying at FL 280 and direct to Denver Airport; we were requested to 'hurry down' to 10;000 feet. Once level at 10;000 feet and a speed of 300 kts; a controller gave us a Vector for the approach ILS 35R at Denver and cleared us to 9;000 feet. I proceeded to slow down and once I had 250 kts; pressed Flight Level Change on the assigned Vector by the controller. To our surprise; we then heard the voice of another controller inquiring if we were aware that we were out of Class B airspace. We proceeded to check the radio and I had radio 148-21 miles from DEN VOR. I believe that the controllers are more familiar with the area and restrictions than the pilots and felt that the last instructions put us closer to the limits of being out of Class B airspace. We were given a lot of shortcuts into DEN. We presumed this criteria (short cut/short approach) was the ATC's intentions.


Synopsis: B737NG Captain reported exceeding 200 kts below DEN Class B airspace while being vectored by ATC.