Narrative:

Flying to lax on pdz 4 arrival. Cleared to descend per the arrival. Set 8000 ft for altitude and engaged managed descent. (In other words, let the computer fly the plane and make the crossing restrs.) it became obvious the restrs would be met but closer to the higher altitudes, so I selected open descent which gives an idle power descent. In this mode, the airplane descends at idle power to the selected altitude (8000 ft). I should have selected the altitude to 12000 ft for the crossing restr at tejay. I studied the chart. When I looked back up we had descended below 12000 ft and were still about 2 NM from tejay. I leveled the airplane at about 11300 ft for about 30 seconds, crossed tejay and continued uneventfully. Airspeed 310 KTS. Problems: 1) I know of no other arrs anywhere that use charted crossing restrs like lax, so it is a unique procedure in a very busy environment. Lax should issue 'descend and maintain' instructions like everybody else. 2) unless we are slowed because of traffic or WX, dscnts on the profile must be made very aggressively or we get caught too high and fast for a normal approach. The airplane often cannot respond aggressively enough for the dscnts because the computer cannot anticipate the problems. In our case, 12000 ft, 310 KTS, 44 mi from the airport is very do-able, but 13000 ft will require speed brake, early gear extension, early flap extension, etc, as we try to stay on profile. 3) automation must be managed! There are so many ways to accomplish the same things. But you must keep up with what each mode will or will not do. In our case, the one mode will not descend aggressively and the other mode ignores crossing restrs. Biggest problem: lax changes arrs frequently, close to the airport with little advance warning. It takes time to load the information in the computer and to study an arrival. I have had as many as 3 stars/approachs assigned in the last 20 mins of a flight.

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Original NASA ASRS Text

Title: A319 FLC OVERSHOOT PDZ STAR XING RESTR AT TEJAY INTXN DUE TO FMS PROGRAM AND FMS EXECUTION.

Narrative: FLYING TO LAX ON PDZ 4 ARR. CLRED TO DSND PER THE ARR. SET 8000 FT FOR ALT AND ENGAGED MANAGED DSCNT. (IN OTHER WORDS, LET THE COMPUTER FLY THE PLANE AND MAKE THE XING RESTRS.) IT BECAME OBVIOUS THE RESTRS WOULD BE MET BUT CLOSER TO THE HIGHER ALTS, SO I SELECTED OPEN DSCNT WHICH GIVES AN IDLE PWR DSCNT. IN THIS MODE, THE AIRPLANE DSNDS AT IDLE PWR TO THE SELECTED ALT (8000 FT). I SHOULD HAVE SELECTED THE ALT TO 12000 FT FOR THE XING RESTR AT TEJAY. I STUDIED THE CHART. WHEN I LOOKED BACK UP WE HAD DSNDED BELOW 12000 FT AND WERE STILL ABOUT 2 NM FROM TEJAY. I LEVELED THE AIRPLANE AT ABOUT 11300 FT FOR ABOUT 30 SECONDS, CROSSED TEJAY AND CONTINUED UNEVENTFULLY. AIRSPD 310 KTS. PROBS: 1) I KNOW OF NO OTHER ARRS ANYWHERE THAT USE CHARTED XING RESTRS LIKE LAX, SO IT IS A UNIQUE PROC IN A VERY BUSY ENVIRONMENT. LAX SHOULD ISSUE 'DSND AND MAINTAIN' INSTRUCTIONS LIKE EVERYBODY ELSE. 2) UNLESS WE ARE SLOWED BECAUSE OF TFC OR WX, DSCNTS ON THE PROFILE MUST BE MADE VERY AGGRESSIVELY OR WE GET CAUGHT TOO HIGH AND FAST FOR A NORMAL APCH. THE AIRPLANE OFTEN CANNOT RESPOND AGGRESSIVELY ENOUGH FOR THE DSCNTS BECAUSE THE COMPUTER CANNOT ANTICIPATE THE PROBS. IN OUR CASE, 12000 FT, 310 KTS, 44 MI FROM THE ARPT IS VERY DO-ABLE, BUT 13000 FT WILL REQUIRE SPD BRAKE, EARLY GEAR EXTENSION, EARLY FLAP EXTENSION, ETC, AS WE TRY TO STAY ON PROFILE. 3) AUTOMATION MUST BE MANAGED! THERE ARE SO MANY WAYS TO ACCOMPLISH THE SAME THINGS. BUT YOU MUST KEEP UP WITH WHAT EACH MODE WILL OR WILL NOT DO. IN OUR CASE, THE ONE MODE WILL NOT DSND AGGRESSIVELY AND THE OTHER MODE IGNORES XING RESTRS. BIGGEST PROB: LAX CHANGES ARRS FREQUENTLY, CLOSE TO THE ARPT WITH LITTLE ADVANCE WARNING. IT TAKES TIME TO LOAD THE INFO IN THE COMPUTER AND TO STUDY AN ARR. I HAVE HAD AS MANY AS 3 STARS/APCHS ASSIGNED IN THE LAST 20 MINS OF A FLT.

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.