Narrative:

Flight X inbound to seal beach cross at 6000 ft with so-cal approach. After seal beach vectored 350 degrees, received lower altitude. Then vectored 280 degrees for localizer intercept. Intercept approximately 12 mi out, still above GS. Traffic for runway 25R (air carrier Y) given and sighted. We were for runway 25L. Told to 'follow air carrier Y' stay behind him, 'keep the speed up' 180 KTS or better' to lima (FAF) cleared approach runway 25L. Initial spacing approximately 1 mi. Still slightly high on GS. Speed 180 KTS, flaps 20 and gear extended by marker. GS intercept just inside marker with slight closure in air carrier Y. Began final speed reduction, idle thrust, landing flaps, still slight closure rate, got TCASII 'RA' -- turned off TCASII to silence warning. Speed stable at 157 KTS, on localizer and GS approximately 2 mi inside marker, separation appeared constant (approach 1/2-3/4 mi) through '1000 ft' and just prior to '500 ft' warning air carrier Y appeared to rapidly decelerate. We initiated further speed reduction to 150 KTS (minimum approach) unable to stay behind air carrier Y and passed just below 500 ft. I know we were ahead of and slightly below. The runway was assured and I received a safe landing was possible for both aircraft and made decision to continue for an uneventful landing. Problem?: technically, once we passed air carrier Y and lost visual contact, we could no longer 'maintain visual separation' and I believe we were illegal to continue. However, at that point, a 'GA' would have also left air carrier Y behind us and out of sight (only below, instead of slightly above our aircraft) and that did not seem prudent. How could this have been avoided?: 1) crossing seal beach at 6000 ft already puts us very high on the initial approach segment for a massive aircraft like the 747-400 (I understand this is being debated with the FAA) and being instructed to keep 'our speed up' further compounds the problem (we call it the 'slam dunk'). I think we could have been more adamant about getting lower and reduced to final speed sooner. 2) ATC is very unrealistic at times with crossing altitude, speed and separation regarding 'hvys' and other aircraft. This needs to be addressed. Our AGL speed and air carrier Y approach speed would obviously be very different (ours being much higher). 3) finally, the air carrier Y did appear to make a large and final speed adjustment when inside the marker, perhaps not good planning on their part either. It caught us totally by surprise.

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Original NASA ASRS Text

Title: ACR CLRED FOR VISUAL NOT TO PASS ADJACENT ACR BUT UNABLE TO STAY BEHIND WHEN ADJACENT ACR SLOWED.

Narrative: FLT X INBOUND TO SEAL BEACH CROSS AT 6000 FT WITH SO-CAL APCH. AFTER SEAL BEACH VECTORED 350 DEGS, RECEIVED LOWER ALT. THEN VECTORED 280 DEGS FOR LOC INTERCEPT. INTERCEPT APPROX 12 MI OUT, STILL ABOVE GS. TFC FOR RWY 25R (ACR Y) GIVEN AND SIGHTED. WE WERE FOR RWY 25L. TOLD TO 'FOLLOW ACR Y' STAY BEHIND HIM, 'KEEP THE SPD UP' 180 KTS OR BETTER' TO LIMA (FAF) CLRED APCH RWY 25L. INITIAL SPACING APPROX 1 MI. STILL SLIGHTLY HIGH ON GS. SPD 180 KTS, FLAPS 20 AND GEAR EXTENDED BY MARKER. GS INTERCEPT JUST INSIDE MARKER WITH SLIGHT CLOSURE IN ACR Y. BEGAN FINAL SPD REDUCTION, IDLE THRUST, LNDG FLAPS, STILL SLIGHT CLOSURE RATE, GOT TCASII 'RA' -- TURNED OFF TCASII TO SILENCE WARNING. SPD STABLE AT 157 KTS, ON LOC AND GS APPROX 2 MI INSIDE MARKER, SEPARATION APPEARED CONSTANT (APCH 1/2-3/4 MI) THROUGH '1000 FT' AND JUST PRIOR TO '500 FT' WARNING ACR Y APPEARED TO RAPIDLY DECELERATE. WE INITIATED FURTHER SPD REDUCTION TO 150 KTS (MINIMUM APCH) UNABLE TO STAY BEHIND ACR Y AND PASSED JUST BELOW 500 FT. I KNOW WE WERE AHEAD OF AND SLIGHTLY BELOW. THE RWY WAS ASSURED AND I RECEIVED A SAFE LNDG WAS POSSIBLE FOR BOTH ACFT AND MADE DECISION TO CONTINUE FOR AN UNEVENTFUL LNDG. PROBLEM?: TECHNICALLY, ONCE WE PASSED ACR Y AND LOST VISUAL CONTACT, WE COULD NO LONGER 'MAINTAIN VISUAL SEPARATION' AND I BELIEVE WE WERE ILLEGAL TO CONTINUE. HOWEVER, AT THAT POINT, A 'GA' WOULD HAVE ALSO LEFT ACR Y BEHIND US AND OUT OF SIGHT (ONLY BELOW, INSTEAD OF SLIGHTLY ABOVE OUR ACFT) AND THAT DID NOT SEEM PRUDENT. HOW COULD THIS HAVE BEEN AVOIDED?: 1) XING SEAL BEACH AT 6000 FT ALREADY PUTS US VERY HIGH ON THE INITIAL APCH SEGMENT FOR A MASSIVE ACFT LIKE THE 747-400 (I UNDERSTAND THIS IS BEING DEBATED WITH THE FAA) AND BEING INSTRUCTED TO KEEP 'OUR SPD UP' FURTHER COMPOUNDS THE PROB (WE CALL IT THE 'SLAM DUNK'). I THINK WE COULD HAVE BEEN MORE ADAMANT ABOUT GETTING LOWER AND REDUCED TO FINAL SPD SOONER. 2) ATC IS VERY UNREALISTIC AT TIMES WITH XING ALT, SPD AND SEPARATION REGARDING 'HVYS' AND OTHER ACFT. THIS NEEDS TO BE ADDRESSED. OUR AGL SPD AND ACR Y APCH SPD WOULD OBVIOUSLY BE VERY DIFFERENT (OURS BEING MUCH HIGHER). 3) FINALLY, THE ACR Y DID APPEAR TO MAKE A LARGE AND FINAL SPD ADJUSTMENT WHEN INSIDE THE MARKER, PERHAPS NOT GOOD PLANNING ON THEIR PART EITHER. IT CAUGHT US TOTALLY BY SURPRISE.

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.