Date: 201307
Local time of day: 0601-1200
Location: SFO.Airport, CA
Flight conditions: IMC
Light: Daylight
Aircraft: B747 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Final Approach
Airspace: Class B SFO
ATC / advisory: TRACON NCT; Tower SFO
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Confusion; Situational Awareness; Communication Breakdown
Anomaly: ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
Result: General None Reported / Taken
Contributing factors: Procedure; Human Factors
Primary problem: Human Factors

Narrative: In the overall interest of partnership with Air Traffic Control; and air safety; I would like to provide some critical comments regarding NorCal (NCT) TRACON and SFO Tower. Arriving SFO received vectors for left downwind to the LOC DME 'Y' 28R. We were completely prepared for the approach; and additionally we flew the approach in a stable and predictable fashion. Approach clearance was received; then while flying the localizer on the VNAV calculated path; we received an instruction from NCT to maintain 3;100 FT. They issued this instruction when we were at about 3;050 FT; the aircraft continued slightly below; which we reported to NCT; and they requested again that we return to 3;100 FT. I climbed back to 3;100 FT. NCT then advised to continue the approach; I flew the aircraft back to the Vertical profile; [and] then reengaged VNAV to continue descending on profile. This all happened between 3.5 miles to 2.5 miles from the FAF while in Instrument Meteorological Conditions or IMC. Never was there any compromise of our ability to maintain a stable approach; however I consider this type of handling by any Approach Control facility will cause problems with many aircrews and should be addressed. I believe in most instances; the Controller would avoid causing an undesirable approach profile by providing some advance notice of a clearance modification. Also; it would be very possible; in my opinion; for some air crews to interpret this as a cancellation of the approach clearance; and then reconfiguring for a missed approach. We then switched to SFO Tower frequency just prior to reaching the FAF. We received our landing clearance; and then Tower asked us to report where we acquired the airport visually. We responded that the bases of the clouds were at 1;300 FT and we were visual with the airport. I feel that this may be the wrong time to be making unnecessary requests from a potentially tired pilot of an overseas flight during the most critical phase of flight. They could easily ask the pilot to provide the weather conditions after the flight has landed; or have Ground Control ask us. Our company expects us to strictly adhere to sterile cockpit; and I try to enforce this policy. Doesn't seem much of a sterile cockpit when we are getting a survey on the radio by a Tower Controller at 1;000 FT AGL.




Synopsis: Air Carrier landing SFO expressed concern regarding ATC's questioning during the final phase of flight.