Narrative:

On approach to lax when the WX was 2200 ft RVR, we briefed a CAT IIIA approach. When slowed on approach, we selected flaps 5 degrees and initially had a leading edge flaps transit light that later cleared itself. On approximately 12 mi final, we were given a 360 degree turn and finally cleared lower once we were outbound in this turn because of a spacing problem that was developing with a lifeguard flight that they were squeezing in ahead of us. Once cleared for the approach, a normal CAT IIIA HUD company procedures approach was flown with the WX now reported as indefinite. Ceiling 200 ft, overcast 6000 ft, RVR. Upon clearing the runway we realized that the #1 communication had inadvertently been flipped off tower frequency back to socal approach frequency and that we may have been off tower frequency for a short period of time on final. Immediately on arrival at the gate, I contacted the current lax tower supervisor. He voiced no concern in reference to this situation but wanted to ensure we knew that we were to stay on the tower frequency between the runway 24L&right runways. He also said he had no reason or intent to pursue any action since nothing had really occurred (no infringement). I think that the following factors contributed to this situation: 1) workload dealing with a leading edge transit light. 2) added workload of the hgs approach. 3) added workload of the 360 degree turn on 12 mi, 10 mi final in IMC. 4) being kept high on approach due to a lifeguard flight slowing more than socal approach had anticipated. 5) the desire to conserve fuel for the possibility of a divert (a divert that may have included performance considerations of a leading edge device problem). 6) location of the bright/dim button on the hgs control panel, right above the communication 1 xfer toggle for swapping frequencys (first officer remembers brightening the hgs control head display to verify a CAT IIIA mode).

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Original NASA ASRS Text

Title: A B737-300 FLC HAS A LOSS OF COM FREQ ON SHORT FINAL DURING A CAT IIIA HUD ILS APCH TO RWY 24L AT LAX, CA.

Narrative: ON APCH TO LAX WHEN THE WX WAS 2200 FT RVR, WE BRIEFED A CAT IIIA APCH. WHEN SLOWED ON APCH, WE SELECTED FLAPS 5 DEGS AND INITIALLY HAD A LEADING EDGE FLAPS TRANSIT LIGHT THAT LATER CLRED ITSELF. ON APPROX 12 MI FINAL, WE WERE GIVEN A 360 DEG TURN AND FINALLY CLRED LOWER ONCE WE WERE OUTBOUND IN THIS TURN BECAUSE OF A SPACING PROB THAT WAS DEVELOPING WITH A LIFEGUARD FLT THAT THEY WERE SQUEEZING IN AHEAD OF US. ONCE CLRED FOR THE APCH, A NORMAL CAT IIIA HUD COMPANY PROCS APCH WAS FLOWN WITH THE WX NOW RPTED AS INDEFINITE. CEILING 200 FT, OVCST 6000 FT, RVR. UPON CLRING THE RWY WE REALIZED THAT THE #1 COM HAD INADVERTENTLY BEEN FLIPPED OFF TWR FREQ BACK TO SOCAL APCH FREQ AND THAT WE MAY HAVE BEEN OFF TWR FREQ FOR A SHORT PERIOD OF TIME ON FINAL. IMMEDIATELY ON ARR AT THE GATE, I CONTACTED THE CURRENT LAX TWR SUPVR. HE VOICED NO CONCERN IN REF TO THIS SIT BUT WANTED TO ENSURE WE KNEW THAT WE WERE TO STAY ON THE TWR FREQ BTWN THE RWY 24L&R RWYS. HE ALSO SAID HE HAD NO REASON OR INTENT TO PURSUE ANY ACTION SINCE NOTHING HAD REALLY OCCURRED (NO INFRINGEMENT). I THINK THAT THE FOLLOWING FACTORS CONTRIBUTED TO THIS SIT: 1) WORKLOAD DEALING WITH A LEADING EDGE TRANSIT LIGHT. 2) ADDED WORKLOAD OF THE HGS APCH. 3) ADDED WORKLOAD OF THE 360 DEG TURN ON 12 MI, 10 MI FINAL IN IMC. 4) BEING KEPT HIGH ON APCH DUE TO A LIFEGUARD FLT SLOWING MORE THAN SOCAL APCH HAD ANTICIPATED. 5) THE DESIRE TO CONSERVE FUEL FOR THE POSSIBILITY OF A DIVERT (A DIVERT THAT MAY HAVE INCLUDED PERFORMANCE CONSIDERATIONS OF A LEADING EDGE DEVICE PROB). 6) LOCATION OF THE BRIGHT/DIM BUTTON ON THE HGS CTL PANEL, RIGHT ABOVE THE COM 1 XFER TOGGLE FOR SWAPPING FREQS (FO REMEMBERS BRIGHTENING THE HGS CTL HEAD DISPLAY TO VERIFY A CAT IIIA MODE).

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.