B747-400
Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Flight Crew Last 90 Days 175.9; Flight Crew Total 9182.2; Flight Crew Type 938.4
Conflict Airborne Conflict; Deviation - Track / Heading All Types; Inflight Event / Encounter Wake Vortex Encounter
General None Reported / Taken
Environment - Non Weather Related; Human Factors; Procedure
I was the pilot not flying on a flight [to] LAX [and] as we got closer to LAX we were cleared via the SADDE 6 arrival AVE transition. Clearance then followed direct SMO; depart on a 070 heading; maintain 7;000 FT. Just prior to SMO; we were given a vector to a heading to cross over the airport and to expect vectors for the ILS 25L. At this time we had numerous altitude changes and speed reductions. As pilot not flying I was busy re-programming the FMC for a runway change to 25L for the pilot flying and taking multiple radio calls. Once we were established on downwind and well past the abeam final approach fix; we were given a base turn heading of 340. There was a high level of activity and the Controller seemed extremely busy. The Controller seemed concerned about the spacing of the B747 just ahead of us. A sense of urgency came to the Controller's voice. As we were almost on the localizer course; we were issued a heading change of about 260 or 280 to join the localizer and cleared for the ILS Runway 25L approach. The Controller also called out [B737] traffic at 1 o'clock and helicopter traffic in addition to the B747 ahead of us. I reported the [B737] traffic in sight on approach to the north complex. At that time; the left wing dropped abruptly to a 30 degree left bank as the aircraft aggressively attempted to capture the localizer course. Shortly thereafter; the aircraft rolled right while still on automation due to a wake turbulence encounter from the B747 ahead. We perceived a minor deviation through the localizer; given these circumstances; which the Captain instantly corrected by disconnecting the autopilot. At the same time; the Controller urgently instructed '[Call sign]; turn left to 230; descend and maintain 2;000 FT; intercept the localizer; 25L' and reissued a traffic advisory for [the B737]. I repeated the clearance and reported that we encountered wake turbulence. We recaptured the localizer; descended and intercepted the glide slope; completed the landing check; and made an uneventful landing.At no time during this approach did we receive any aircraft TCAS warnings for traffic. [The B737] was in sight visually and we appeared to maintain a safe distance from that aircraft. [The B737] never verbally responded to any complications they may have encountered. After shutting down; due to the sense of urgency in the Controller's voice; we discussed the need for a report and all agreed that at no time was the flight safety in jeopardy. There were no aircraft warnings; no comments from any controllers concerning any possible deviations; and no abnormal maneuvers by other aircraft in response to our own aircraft. It seemed that our flight was squeezed into the arrival corridor with very little margin of spacing.Aircraft data later presented to us showed the localizer being captured in the turn to final at approximately 304 degrees of heading; nearly 60 degrees from the runway course; causing some degree of deviation through the localizer course. The winds aloft were unknown at the time. We were also made aware of a controller change during our flight in the traffic pattern. It seemed from this data that the turn to final was issued later than normal. We were told that the aircraft intercepted the course at a heading still 54 degrees from the localizer course; which placed the aircraft in a position where it was impossible to capture the LOC without a small deviation through the course. Also; the wake turbulence encounter was a factor.
While precision parallel approaches are in progress; it may be wise to increase the space available for vectoring. 90 degree vectors close in while these types of approaches are in progress should be open for discussion. The ATC Controller had a shift change between our 340 heading and 260 heading/cleared for the approach. This may have contributed to the late intercept 260 heading. We were told that the aircraft intercepted the course at 54 degrees which would place the aircraft in a position unable to capture LOC.
B747 First Officer reported a wake vortex encounter on approach to LAX that was a factor in a slight track deviation.