Air carrier conducting a visual approach to runway 10 at msy was advised by ATC that they had left r...

Narrative:

Cleared [for the] visual [approach] to [runway] 10 at msy. We had ILS tuned on both sides with localizer and glide slope working. Controller cleared us for visual about 12-15 miles out. We began descent and operated at or above glide slope all the way down. Just before handing us off to tower; controller said; 'flight number; you momentarily left class B airspace; but have re-entered. Contact tower' (or words close to that effect.) we were both surprised by the comment since we thought we were at or above glide slope and we thought if on glide slope on [runway] 10 that it would keep aircraft in class B airspace. To our knowledge there was no traffic conflict and controller did not seem upset. Looking at the class B chart 10-1; it is possible the glide slope goes below the 4;000 ft floor momentarily. In which case; I thought controller had to say; 'maintain X until Y distance and then cleared for visual.' preventative measures: if glide slope goes below class B then ATC should state so and give an altitude restriction to contain the aircraft cleared for visual. Crews should look at class B charts as backup.

Original NASA ASRS Text

Title: Air Carrier conducting a visual approach to Runway 10 at MSY was advised by ATC that they had left re-entered the Class B airspace. The reporter noted glide slope adherence should provide for Class B containment.

Narrative: Cleared [for the] visual [approach] to [Runway] 10 at MSY. We had ILS tuned on both sides with LOC and glide slope working. Controller cleared us for visual about 12-15 miles out. We began descent and operated at or above glide slope all the way down. Just before handing us off to Tower; Controller said; 'Flight number; you momentarily left class B airspace; but have re-entered. Contact Tower' (or words close to that effect.) We were both surprised by the comment since we thought we were at or above glide slope and we thought if on glide slope on [Runway] 10 that it would keep aircraft in Class B airspace. To our knowledge there was no traffic conflict and Controller did not seem upset. Looking at the Class B chart 10-1; it is possible the glide slope goes below the 4;000 FT floor momentarily. In which case; I thought Controller had to say; 'Maintain X until Y distance and then cleared for visual.' Preventative measures: If glide slope goes below Class B then ATC should state so and give an altitude restriction to contain the aircraft cleared for visual. Crews should look at Class B charts as backup.

Data retrieved from NASA's ASRS site as of April 2012 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.

Attributes
ACN	947645
Time
Date	201105
Local Time Of Day	1801-2400
Place
Locale Reference	MSY.Airport
State Reference	LA
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Flight Phase	Initial Approach
Flight Plan	IFR
Person 1
Function	Captain
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 179 Flight Crew Type 19000
Person 2
Function	First Officer
Experience	Flight Crew Last 90 Days 229 Flight Crew Type 7200
Events
Anomaly	Deviation - Procedural FAR Deviation - Procedural Published Material / Policy

Air carrier conducting a visual approach to runway 10 at msy was advised by ATC that they had left re-entered the class B airspace. The reporter noted glide slope adherence should provide for class B containment.