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5 Answers

Marking “T/15” on sectional

Asked by: 1592 views Airspace, Commercial Pilot

Just passed commercial written. Among others missed questions i'd like to ask this one.

The picture for the question we can see on KSFO TAC where KSFO Bravo overlying  KOAK Charlie. Here exists sector where Charlie altitudes marked as "T/15" and Bravo   - "100/30"

The question is if we're flying at 3000 MSL in what airspace we are?

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5 Answers



  1. KDS on Nov 01, 2019

    The reference is the Aeronautical User’s Guide.

    The T over the 15 means the Class C airspace goes from 1,500′ MSL up to but not including the overlying terminal airspace.

    If you are in the section that says 100 over 30 and you are at EXACTLY 3,000′ MSL, then you are in Class B airspace. If you are at EXACTLY 2,999′ MSL, then you are in Class C airspace.

    However, ATC considers 3,000′ MSL to be their Class B airspace and they will drop aircraft down to the bottom of their airspace. The altimeter reading for an aircraft is not taken at the bottom of the landing gear. It’s somewhere higher than that, plus there is always an error factor. So, flying close to the bottom of overlying airspace is about as dangerous as flying in the airspace. Not to mention that a pilot would have a pretty weak argument should an enforcement action come up saying that the aircraft was being flown at 3,000′ MSL in the Class B airspace.

    Congratulations on passing your commercial written test.

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  2. Rkon on Nov 02, 2019

    Thanks, KDS. But I didn’t found statement for “… but not including the overlying terminal airspace”. Where is it?

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  3. Craig on Nov 02, 2019

    https://www.faa.gov/air_traffic/flight_info/aeronav/digital_products/aero_guide/media/editions/cug-complete.pdf

    See p. 17. The figure depicts T/SFC…………”The figure at left identifies a sector that extends from the surface to the base of the Class B”

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  4. Gary S. on Nov 02, 2019

    KDS, just for funzies, I just read today (I think in AIM) where altimeters are calibrated at 10 ft. above sea level to account for the location of altimeters inside many cockpits. I guess each jumbo model would have it’s own adjustment. A 747 would be about twice that. Thanks for your input!

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  5. Gary S. on Nov 02, 2019

    KRON, you can find the verbiage “ceiling is to but not including floor of class B” next to where it says (in large print) “San Francisco Class B.” Just about 4’Oclock. See it?.

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