Narrative:

[We were] on final to 25L at klax via the seavu arrival; instructed to line up with 25R localizer at a point approximately 5 miles ahead of our position to allow traffic being vectored in from our left to land on 25L. We had been asked to level off several times during the final approach and asked to slow to 210; then 190 then 180 KTS. When asked by final controller if heavy traffic merging from the south was in sight; I instructed the first officer to report negative as I felt it was not prudent; with the acceptance of 'visual'; to assume responsibility for wake separation so close to what we understood to be a 747. The heavy rolled out in front of us at about 2 miles on our TCAS display; slightly to our left. We overheard his instructions to maintain 190 KTS. I don't remember the wording; whether we were asked or told; to follow the other aircraft and maintain 180 to the FAF-lima. I asked the first officer to let me respond and told the controller we could slow immediately to approach speed; which in my opinion might give us our separation prior to landing and was denied the option by approach and told if I wouldn't accept a 10 KT speed difference with the traffic as is he was unwilling to allow me to continue and would have to turn me out of traffic to re-sequence. Feeling this was the only safe option left for wake separation on close parallel runways; that is what we requested. On the subsequent approach; we were given a telephone number to call ATC on the ground. I did call the number after deplaning and explained my concern for safety following a 747 so close and that I would arrive in the flare just in time for his wake to spread to my runway. He mentioned that this was the only way they could support the arrival rate the airlines had imposed on ATC and it was perfectly legal if I wanted to accept the approach to 'make things work' at lax. He kept mentioning it was not his fault that the arrival rate was too high for what I might consider normal operations and they were keeping me above the 747's glide path on purpose on final to avoid his wake-totally oblivious to my oft-reiterated concern about landing right next to him in the midst of his wake. I tried to have him see the point I was trying to make in that I thought safety came first and arrival rates came second; but he mentioned that other pilots were ok with this -assuming I guess that made it safe; and I was part of the 4 or 5 out of 100 that wouldn't accept. Having been flipped into 70 degrees of bank well behind an A300 on approach to lax and 60 degrees of bank on a close-interval takeoff in T-38s; though I rarely have to ask for regulated wake turbulence separation; I have a healthy respect for it. Having now been able to calculate spacing offered on this approach and the 5 mph lateral spread of a wake vortex on the ground; my landing on the parallel runway would have indeed been perfectly timed for his vortex to arrive. Why is it prudent for me in 'see-and-avoid' VFR conditions to abandon the minimal safe IFR allowance of 5 miles behind a heavy to avoid invisible; IFR or VFR; wake turbulence? Do 747 vortices not; under normal and crosswind conditions; travel 600-800 ft before dissipating? If they don't; can you pass this along to us to alleviate concerns? If no data exists; I don't believe it is appropriate for a plane full of passengers to be the fact-finder on this.

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Original NASA ASRS Text

Title: B757 landing Runway 25R at LAX elected to be re-sequenced rather than land side by with a B747 landing on Runway 25L; questioning ATC's operational techniques that could produce a wake encounter.

Narrative: [We were] on final to 25L at KLAX via the SEAVU arrival; instructed to line up with 25R LOC at a point approximately 5 miles ahead of our position to allow traffic being vectored in from our left to land on 25L. We had been asked to level off several times during the final approach and asked to slow to 210; then 190 then 180 KTS. When asked by Final Controller if heavy traffic merging from the south was in sight; I instructed the First Officer to report negative as I felt it was not prudent; with the acceptance of 'visual'; to assume responsibility for wake separation so close to what we understood to be a 747. The heavy rolled out in front of us at about 2 miles on our TCAS display; slightly to our left. We overheard his instructions to maintain 190 KTS. I don't remember the wording; whether we were asked or told; to follow the other aircraft and maintain 180 to the FAF-Lima. I asked the First Officer to let me respond and told the Controller we could slow immediately to approach speed; which in my opinion might give us our separation prior to landing and was denied the option by Approach and told if I wouldn't accept a 10 KT speed difference with the traffic as is he was unwilling to allow me to continue and would have to turn me out of traffic to re-sequence. Feeling this was the only safe option left for wake separation on close parallel runways; that is what we requested. On the subsequent approach; we were given a telephone number to call ATC on the ground. I did call the number after deplaning and explained my concern for safety following a 747 so close and that I would arrive in the flare just in time for his wake to spread to my runway. He mentioned that this was the only way they could support the arrival rate the airlines had imposed on ATC and it was perfectly legal if I wanted to accept the approach to 'make things work' at LAX. He kept mentioning it was not his fault that the arrival rate was too high for what I might consider normal operations and they were keeping me above the 747's glide path on purpose on final to avoid his wake-totally oblivious to my oft-reiterated concern about landing right next to him in the midst of his wake. I tried to have him see the point I was trying to make in that I thought safety came first and arrival rates came second; but he mentioned that other pilots were OK with this -assuming I guess that made it safe; and I was part of the 4 or 5 out of 100 that wouldn't accept. Having been flipped into 70 degrees of bank well behind an A300 on approach to LAX and 60 degrees of bank on a close-interval takeoff in T-38s; though I rarely have to ask for regulated wake turbulence separation; I have a healthy respect for it. Having now been able to calculate spacing offered on this approach and the 5 MPH lateral spread of a wake vortex on the ground; my landing on the parallel runway would have indeed been perfectly timed for his vortex to arrive. Why is it prudent for me in 'see-and-avoid' VFR conditions to abandon the minimal safe IFR allowance of 5 miles behind a heavy to avoid invisible; IFR or VFR; wake turbulence? Do 747 vortices not; under normal and crosswind conditions; travel 600-800 FT before dissipating? If they don't; can you pass this along to us to alleviate concerns? If no data exists; I don't believe it is appropriate for a plane full of passengers to be the fact-finder on this.

Data retrieved from NASA's ASRS site as of April 2012 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.