Narrative:

I was acting as a safety pilot for mr X to help him prepare for his instrument check ride. We departed grand prairie airport (gpm) at about XA45, with a target altitude of 2500 ft MSL. Our destination was alliance forth worth (afw). We stayed north of arlington airport (gky) because of heavy traffic. We switched frequencys to regional approach to request vectors for the ILS approach at alliance. We were given a squawk code and were advised of radar contact. We were then instructed to fly a heading of 330 degrees and we were not instructed to remain clear of class B airspace. A few mins later, we were given another vector of 350 degrees. Approximately XB00, the controller advised us that we had penetrated class B airspace without a clearance, directly followed by a clearance through class B airspace. After the incident, we were given vectors for 2 ILS approachs into alliance. The rest of the flight went without any problems. A contributing factor to the incident was a mode C transponder indicating 300 ft below the altimeter, which could have caused the controller to give us a vector that took our route of flight under the shelf of class B that starts at 2000 ft MSL. Another was a high pilot workload because of heavy traffic and a request from approach that we listen to the ATIS. To prevent a recurrence, ATC should issue a 'remain clear of class B airspace' or a 'cleared through class B airspace' instruction. There have been many flts by many pilots who have been cleared through class B airspace without the controller actually saying 'cleared through class B.' so even under very workloads, I believe the controllers must not forget to say those magic words so that pilots don't get complacent in assuming that they are cleared through class B. If the controller does not want the pilot to be cleared through class B, then I believe they should issue a 'maintain clear of class B airspace' alert. When nothing is said, the pilot will assume he is cleared and the controller may assume otherwise. Because of this, I believe that even if our vectored heading took us through class B airspace, it would be ok, because ATC told us to do so. From now on when I go flying, I will demand ATC to give me a clearance so other pilots on the frequency could learn from me to not assume that ATC has cleared you through.

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Original NASA ASRS Text

Title: C172 PLT ENTERED DFW CLASS B WITHOUT CLRNC.

Narrative: I WAS ACTING AS A SAFETY PLT FOR MR X TO HELP HIM PREPARE FOR HIS INST CHK RIDE. WE DEPARTED GRAND PRAIRIE ARPT (GPM) AT ABOUT XA45, WITH A TARGET ALT OF 2500 FT MSL. OUR DEST WAS ALLIANCE FORTH WORTH (AFW). WE STAYED N OF ARLINGTON ARPT (GKY) BECAUSE OF HVY TFC. WE SWITCHED FREQS TO REGIONAL APCH TO REQUEST VECTORS FOR THE ILS APCH AT ALLIANCE. WE WERE GIVEN A SQUAWK CODE AND WERE ADVISED OF RADAR CONTACT. WE WERE THEN INSTRUCTED TO FLY A HDG OF 330 DEGS AND WE WERE NOT INSTRUCTED TO REMAIN CLR OF CLASS B AIRSPACE. A FEW MINS LATER, WE WERE GIVEN ANOTHER VECTOR OF 350 DEGS. APPROX XB00, THE CTLR ADVISED US THAT WE HAD PENETRATED CLASS B AIRSPACE WITHOUT A CLRNC, DIRECTLY FOLLOWED BY A CLRNC THROUGH CLASS B AIRSPACE. AFTER THE INCIDENT, WE WERE GIVEN VECTORS FOR 2 ILS APCHS INTO ALLIANCE. THE REST OF THE FLT WENT WITHOUT ANY PROBS. A CONTRIBUTING FACTOR TO THE INCIDENT WAS A MODE C XPONDER INDICATING 300 FT BELOW THE ALTIMETER, WHICH COULD HAVE CAUSED THE CTLR TO GIVE US A VECTOR THAT TOOK OUR RTE OF FLT UNDER THE SHELF OF CLASS B THAT STARTS AT 2000 FT MSL. ANOTHER WAS A HIGH PLT WORKLOAD BECAUSE OF HVY TFC AND A REQUEST FROM APCH THAT WE LISTEN TO THE ATIS. TO PREVENT A RECURRENCE, ATC SHOULD ISSUE A 'REMAIN CLR OF CLASS B AIRSPACE' OR A 'CLRED THROUGH CLASS B AIRSPACE' INSTRUCTION. THERE HAVE BEEN MANY FLTS BY MANY PLTS WHO HAVE BEEN CLRED THROUGH CLASS B AIRSPACE WITHOUT THE CTLR ACTUALLY SAYING 'CLRED THROUGH CLASS B.' SO EVEN UNDER VERY WORKLOADS, I BELIEVE THE CTLRS MUST NOT FORGET TO SAY THOSE MAGIC WORDS SO THAT PLTS DON'T GET COMPLACENT IN ASSUMING THAT THEY ARE CLRED THROUGH CLASS B. IF THE CTLR DOES NOT WANT THE PLT TO BE CLRED THROUGH CLASS B, THEN I BELIEVE THEY SHOULD ISSUE A 'MAINTAIN CLR OF CLASS B AIRSPACE' ALERT. WHEN NOTHING IS SAID, THE PLT WILL ASSUME HE IS CLRED AND THE CTLR MAY ASSUME OTHERWISE. BECAUSE OF THIS, I BELIEVE THAT EVEN IF OUR VECTORED HDG TOOK US THROUGH CLASS B AIRSPACE, IT WOULD BE OK, BECAUSE ATC TOLD US TO DO SO. FROM NOW ON WHEN I GO FLYING, I WILL DEMAND ATC TO GIVE ME A CLRNC SO OTHER PLTS ON THE FREQ COULD LEARN FROM ME TO NOT ASSUME THAT ATC HAS CLRED YOU THROUGH.

Data retrieved from NASA's ASRS site as of July 2007 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.