Narrative:

Flying a routine transition for traffic, I called for the I-5 transition south over lindbergh field. I received my class B airspace clearance and proceeded into the airspace. About 2 mi into the transition, there was a call from another traffic aircraft proceeding northbound. The controller cleared the other aircraft into lindbergh's class B airspace for the northbound transition. At this time the controller told me 'aircraft X fly over the diagonal taxiway at 1000 ft.' I responded 'unable 1000 ft.' after 30 seconds or so, the controller queried me and asked 'why unable 1000 ft?' I responded 'terrain.' lindbergh field is 14 ft AGL if I came over at 1000 ft. I would be in violation of 91.119 1000 ft clearance over a congested area. The second reason I said unable was I was not comfortable with that altitude for the reason, if an inbound aircraft had to go missed for some reason, it might make the conditions real ripe for a conflict -- such as near miss or worse. It was quite hazy at the time. The controller then responded 'climb, maintain 2000 ft' which I had no trouble complying with. At 1700 ft I spotted the northbound traffic, reported this aircraft in sight and said I would maintain visual separation. At that point, the controller responded with 'maintain visual separation, cleared at 1500 ft sbound.' when I exited the class B airspace, I was told to squawk VFR frequency change approved and could I please call the tower when I land. I said sure. Upon landing, I called the tower and spoke to a controller other than I had been talking to when I was flying and explained the above. He felt I had done nothing wrong and that I was PIC. He said he would share this with the other controller, and also agreed on how I felt about the possibility of conflict with arriving aircraft. I asked if this incident was going any further and he responded no, this was it, and thanked me for the call. I just wanted to share this information because we transition that route up to 10 times a day, and I feel I have an outstanding relationship with this tower. And if ATC tells you to do something you're either uncomfortable with or unsure, it never hurts to query ATC and get some clarification.

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Original NASA ASRS Text

Title: C172 PLT WAS ISSUED CLRNC BELOW MVA AND IN VIOLATION OF FAR PART 91 PT 119, 'FLT BELOW 1000 FT IN CONGESTED AREA.

Narrative: FLYING A ROUTINE TRANSITION FOR TFC, I CALLED FOR THE I-5 TRANSITION S OVER LINDBERGH FIELD. I RECEIVED MY CLASS B AIRSPACE CLRNC AND PROCEEDED INTO THE AIRSPACE. ABOUT 2 MI INTO THE TRANSITION, THERE WAS A CALL FROM ANOTHER TFC ACFT PROCEEDING NBOUND. THE CTLR CLRED THE OTHER ACFT INTO LINDBERGH'S CLASS B AIRSPACE FOR THE NBOUND TRANSITION. AT THIS TIME THE CTLR TOLD ME 'ACFT X FLY OVER THE DIAGONAL TXWY AT 1000 FT.' I RESPONDED 'UNABLE 1000 FT.' AFTER 30 SECONDS OR SO, THE CTLR QUERIED ME AND ASKED 'WHY UNABLE 1000 FT?' I RESPONDED 'TERRAIN.' LINDBERGH FIELD IS 14 FT AGL IF I CAME OVER AT 1000 FT. I WOULD BE IN VIOLATION OF 91.119 1000 FT CLRNC OVER A CONGESTED AREA. THE SECOND REASON I SAID UNABLE WAS I WAS NOT COMFORTABLE WITH THAT ALT FOR THE REASON, IF AN INBOUND ACFT HAD TO GO MISSED FOR SOME REASON, IT MIGHT MAKE THE CONDITIONS REAL RIPE FOR A CONFLICT -- SUCH AS NEAR MISS OR WORSE. IT WAS QUITE HAZY AT THE TIME. THE CTLR THEN RESPONDED 'CLB, MAINTAIN 2000 FT' WHICH I HAD NO TROUBLE COMPLYING WITH. AT 1700 FT I SPOTTED THE NBOUND TFC, RPTED THIS ACFT IN SIGHT AND SAID I WOULD MAINTAIN VISUAL SEPARATION. AT THAT POINT, THE CTLR RESPONDED WITH 'MAINTAIN VISUAL SEPARATION, CLRED AT 1500 FT SBOUND.' WHEN I EXITED THE CLASS B AIRSPACE, I WAS TOLD TO SQUAWK VFR FREQ CHANGE APPROVED AND COULD I PLEASE CALL THE TWR WHEN I LAND. I SAID SURE. UPON LNDG, I CALLED THE TWR AND SPOKE TO A CTLR OTHER THAN I HAD BEEN TALKING TO WHEN I WAS FLYING AND EXPLAINED THE ABOVE. HE FELT I HAD DONE NOTHING WRONG AND THAT I WAS PIC. HE SAID HE WOULD SHARE THIS WITH THE OTHER CTLR, AND ALSO AGREED ON HOW I FELT ABOUT THE POSSIBILITY OF CONFLICT WITH ARRIVING ACFT. I ASKED IF THIS INCIDENT WAS GOING ANY FURTHER AND HE RESPONDED NO, THIS WAS IT, AND THANKED ME FOR THE CALL. I JUST WANTED TO SHARE THIS INFO BECAUSE WE TRANSITION THAT RTE UP TO 10 TIMES A DAY, AND I FEEL I HAVE AN OUTSTANDING RELATIONSHIP WITH THIS TWR. AND IF ATC TELLS YOU TO DO SOMETHING YOU'RE EITHER UNCOMFORTABLE WITH OR UNSURE, IT NEVER HURTS TO QUERY ATC AND GET SOME CLARIFICATION.

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.