A321 flight crew reported inadvertently flying below the floor of the den class B airspace sector du...

Attributes
ACN	1699814
Time
Date	201911
Local Time Of Day	1201-1800
Place
Locale Reference	DEN.Airport
State Reference	CO
Environment
Flight Conditions	VMC
Aircraft 1
Make Model Name	A321
Operating Under FAR Part	Part 121
Flight Phase	Initial Approach
Route In Use	Visual Approach
Flight Plan	IFR
Person 1
Function	First Officer Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP) Flight Crew Multiengine Flight Crew Instrument
Experience	Flight Crew Total 9000
Person 2
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP) Flight Crew Multiengine Flight Crew Instrument
Events
Anomaly	Airspace Violation All Types Deviation - Procedural Published Material / Policy

Narrative:

Inbound to den runway 35R; we were cleared direct to fronz (fap on the ILS) for the visual approach about 30 miles or so ssw of the field. Captain set 7;000 feet for the altitude at fronz. We both pulled up our class B reference charts for denver to make sure we would remain in the class B for the approach. We were descending through about 11;000 feet at the time and it looked like the only altitude that would be a concern on the way to 7;000 feet was the 9;000 feet floor at 20 DME. We made that crossing and headed down to 7;000 feet. Both of us thought that the next shelf had a base of 6;500 feet. We got down to 7;000 feet and we looked pretty low for how far out we were. I looked at the class B reference chart again and saw we were in a sector with only an 8;000 feet base. The 6;500 feet base was for a tiny sector closer to the airport.the marking on the jeppeson chart is very misleading. It's showing the altitudes for another sector that the actual text is not in. It has a tiny line drawn up to the small sector which is easy to miss with all of the other lines going every which way on the chart. The actual altitude for the sector we were in is not centered and not easily readable.redesign the class B reference page with an easier to read altitude for the small sector south of the airport. Perhaps even a numbered ball note would help.

Original NASA ASRS Text

Title: A321 flight crew reported inadvertently flying below the floor of the DEN Class B airspace sector due to unclear charting.

Narrative: Inbound to DEN Runway 35R; we were cleared direct to FRONZ (FAP on the ILS) for the visual approach about 30 miles or so SSW of the field. Captain set 7;000 feet for the altitude at FRONZ. We both pulled up our Class B reference charts for Denver to make sure we would remain in the Class B for the approach. We were descending through about 11;000 feet at the time and it looked like the only altitude that would be a concern on the way to 7;000 feet was the 9;000 feet floor at 20 DME. We made that crossing and headed down to 7;000 feet. Both of us thought that the next shelf had a base of 6;500 feet. We got down to 7;000 feet and we looked pretty low for how far out we were. I looked at the Class B reference chart again and saw we were in a sector with only an 8;000 feet base. The 6;500 feet base was for a tiny sector closer to the airport.The marking on the Jeppeson chart is very misleading. It's showing the altitudes for another sector that the actual text is not in. It has a tiny line drawn up to the small sector which is easy to miss with all of the other lines going every which way on the chart. The actual altitude for the sector we were in is not centered and not easily readable.Redesign the Class B reference page with an easier to read altitude for the small sector south of the airport. Perhaps even a numbered ball note would help.

Data retrieved from NASA's ASRS site 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.

A321 flight crew reported inadvertently flying below the floor of the den class B airspace sector due to unclear charting.