Narrative:

Arriving from the north, approach control advised us to expect an ILS runway 24R. On downwind, heading 070 degrees, following a 747, we were told to change plans for an ILS runway 25L and maintain 3500 ft. At that time, I advised our controller that we had positive visual contact with the 747 ahead. Vectors to the southeast, then south, then southwest took us over the approach path of the 747, which would be landing on runway 24R. Controller advised us to maintain 3500 ft to hunda. I do not recall if we had been cleared for the approach yet. A 220 degree heading vector put us through the runway 25L localizer to the south. We were then given a 270 degree heading to intercept the runway 25L localizer. At a point approximately abeam hunda, my first officer began a normal approach descent following GS guidance. A moment later a different approach control voice asked us our altitude. I replied 3000 ft. Controller then said, 'maintain 3500 ft until on the runway 25L localizer.' we eased back up to 3500 ft, momentarily thereafter intercepted the localizer from the south side, now inside hunda and 2 dots high on the GS. I informed the controller we were on the localizer and asked if we were cleared for the approach. Controller confirmed that we were cleared and switched us to tower. There was never any conflict with the 747 on runway 24R and I don't think approach got our visual call on the 747 earlier in the downwind. We maintained visual with the 747 until approximately 2400 ft 2500 ft on the approach. A follow-up telephone call was made by me to socal approach at their request. Hopefully, the misunderstanding was mutually resolved by that call. I feel that it was. Socal approach is one of the very best approach facilities that my airline works with. I probably should have asked for clarification of altitude and approach clearance before leaving 3500 ft.

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Original NASA ASRS Text

Title: ALTDEV DURING APCH.

Narrative: ARRIVING FROM THE N, APCH CTL ADVISED US TO EXPECT AN ILS RWY 24R. ON DOWNWIND, HDG 070 DEGS, FOLLOWING A 747, WE WERE TOLD TO CHANGE PLANS FOR AN ILS RWY 25L AND MAINTAIN 3500 FT. AT THAT TIME, I ADVISED OUR CTLR THAT WE HAD POSITIVE VISUAL CONTACT WITH THE 747 AHEAD. VECTORS TO THE SE, THEN S, THEN SW TOOK US OVER THE APCH PATH OF THE 747, WHICH WOULD BE LNDG ON RWY 24R. CTLR ADVISED US TO MAINTAIN 3500 FT TO HUNDA. I DO NOT RECALL IF WE HAD BEEN CLRED FOR THE APCH YET. A 220 DEG HDG VECTOR PUT US THROUGH THE RWY 25L LOC TO THE S. WE WERE THEN GIVEN A 270 DEG HDG TO INTERCEPT THE RWY 25L LOC. AT A POINT APPROX ABEAM HUNDA, MY FO BEGAN A NORMAL APCH DSCNT FOLLOWING GS GUIDANCE. A MOMENT LATER A DIFFERENT APCH CTL VOICE ASKED US OUR ALT. I REPLIED 3000 FT. CTLR THEN SAID, 'MAINTAIN 3500 FT UNTIL ON THE RWY 25L LOC.' WE EASED BACK UP TO 3500 FT, MOMENTARILY THEREAFTER INTERCEPTED THE LOC FROM THE S SIDE, NOW INSIDE HUNDA AND 2 DOTS HIGH ON THE GS. I INFORMED THE CTLR WE WERE ON THE LOC AND ASKED IF WE WERE CLRED FOR THE APCH. CTLR CONFIRMED THAT WE WERE CLRED AND SWITCHED US TO TWR. THERE WAS NEVER ANY CONFLICT WITH THE 747 ON RWY 24R AND I DON'T THINK APCH GOT OUR VISUAL CALL ON THE 747 EARLIER IN THE DOWNWIND. WE MAINTAINED VISUAL WITH THE 747 UNTIL APPROX 2400 FT 2500 FT ON THE APCH. A FOLLOW-UP TELEPHONE CALL WAS MADE BY ME TO SOCAL APCH AT THEIR REQUEST. HOPEFULLY, THE MISUNDERSTANDING WAS MUTUALLY RESOLVED BY THAT CALL. I FEEL THAT IT WAS. SOCAL APCH IS ONE OF THE VERY BEST APCH FACILITIES THAT MY AIRLINE WORKS WITH. I PROBABLY SHOULD HAVE ASKED FOR CLARIFICATION OF ALT AND APCH CLRNC BEFORE LEAVING 3500 FT.

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.