Narrative:

Descent to lax on the paradise 2 arrival. Encountered moderate turbulence. Unable to use autoplt and autothrottle due to turbulence. We were unfamiliar with this arrival. At approximately rifft intersection, we were assigned 12000 ft, then told by approach that we were being switched to the mudde 4 arrival. We were given no reason for this and quickly tried to retrieve this new and again unfamiliar arrival from our books. I got the arrival out but due to hand flying the aircraft in moderate turbulence and navigating a demanding STAR, I left it to the first officer to study the new STAR and figure out that it was a change of runway with no transition from our current routing. Soon after crossing paradise VOR, and established on the pdz 277 degree radial, we were told by approach that runway 25L was open again and now cleared to cross arnes intersection at 10000 ft. Believing this to be a 'descend now' clearance, the first officer set 10000 ft on the altitude alert and said 'cleared to 10000 ft.' I began descent from 12000 ft to 10000 ft. At approximately 11700 ft, socal approach said 'via the paradise 2 arrival.' I then realized that on this STAR, we were not good down below 12000 ft until 'tejay' 4 DME from pdz. I added power, the aircraft bottomed out at 11500 ft. I climbed back to 12000 ft. By this time we were past tejay and we continued the arrival. There was no conflict that I was aware of. 1) unfamiliar with lax arrs. 2) heavy turbulence. Hand flying, relying on first officer for interpretation of plates. 3) last min somewhat confusing instructions from approach control.

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Original NASA ASRS Text

Title: B747 FLC DEVIATES FROM CLRED ALT AFTER RECEIVING CONFUSING CLRNC IN LAX AIRSPACE.

Narrative: DSCNT TO LAX ON THE PARADISE 2 ARR. ENCOUNTERED MODERATE TURB. UNABLE TO USE AUTOPLT AND AUTOTHROTTLE DUE TO TURB. WE WERE UNFAMILIAR WITH THIS ARR. AT APPROX RIFFT INTXN, WE WERE ASSIGNED 12000 FT, THEN TOLD BY APCH THAT WE WERE BEING SWITCHED TO THE MUDDE 4 ARR. WE WERE GIVEN NO REASON FOR THIS AND QUICKLY TRIED TO RETRIEVE THIS NEW AND AGAIN UNFAMILIAR ARR FROM OUR BOOKS. I GOT THE ARR OUT BUT DUE TO HAND FLYING THE ACFT IN MODERATE TURB AND NAVING A DEMANDING STAR, I LEFT IT TO THE FO TO STUDY THE NEW STAR AND FIGURE OUT THAT IT WAS A CHANGE OF RWY WITH NO TRANSITION FROM OUR CURRENT ROUTING. SOON AFTER XING PARADISE VOR, AND ESTABLISHED ON THE PDZ 277 DEG RADIAL, WE WERE TOLD BY APCH THAT RWY 25L WAS OPEN AGAIN AND NOW CLRED TO CROSS ARNES INTXN AT 10000 FT. BELIEVING THIS TO BE A 'DSND NOW' CLRNC, THE FO SET 10000 FT ON THE ALT ALERT AND SAID 'CLRED TO 10000 FT.' I BEGAN DSCNT FROM 12000 FT TO 10000 FT. AT APPROX 11700 FT, SOCAL APCH SAID 'VIA THE PARADISE 2 ARR.' I THEN REALIZED THAT ON THIS STAR, WE WERE NOT GOOD DOWN BELOW 12000 FT UNTIL 'TEJAY' 4 DME FROM PDZ. I ADDED PWR, THE ACFT BOTTOMED OUT AT 11500 FT. I CLBED BACK TO 12000 FT. BY THIS TIME WE WERE PAST TEJAY AND WE CONTINUED THE ARR. THERE WAS NO CONFLICT THAT I WAS AWARE OF. 1) UNFAMILIAR WITH LAX ARRS. 2) HVY TURB. HAND FLYING, RELYING ON FO FOR INTERP OF PLATES. 3) LAST MIN SOMEWHAT CONFUSING INSTRUCTIONS FROM APCH CTL.

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.