Narrative:

I was the airbus A320 first officer, PNF on a flight from phx to san. We were descending into the san diego area via the baret 4 arrival. We had been on radar vectors, then received a direct clearance to pillo intersection. Previous to the altitude deviation, we were cleared and leveled off at FL190. We asked for lower to meet the expected crossing constraint at pillo at 10000 ft MSL. We were held high for lower traffic then cleared late to meet 10000 ft at pillo. As first officer, I was busy finishing the descent/approach checklist with the captain. Upon looking at how close pillo was coming up and we were very high on the profile, I advised the captain. He then deployed full speed brakes with the autoplt off (most A320's will not deploy full boards with autoplt engaged). I then tried to advise ZLA that we would be high at pillo but due to the radio traffic, did not get through until passing 13000 ft MSL. We were relieved of the constraint and to contact socal approach. At this time, the captain tried to start a leveloff. Our airspeed was selected at 345 KIAS. The captain then moved the speed brakes back to half and tried to reengage the autoplt. At this time, we hit some light turbulence that caused a momentary overspd condition with appropriate aural/ECAM warnings. This would not allow the autoplt to reengage and our descent continued unchked approaching 11500 ft. I continued to advise the captain that the autoplt was off, made the 11000 ft to 10000 ft call and at 10500 ft advised I was adding back pressure to the sidestick controller. At this point the captain said he had the aircraft and continued to add back pressure inputs to the sidestick controller. We eventually leveled off at 9150 ft MSL, slowed enough to reengage the autoplt and started to climb back to 10000 ft. I advised socal approach of our deviation and our correction. There were no traffic conflicts due to the altitude deviation. My perspective on the chain of events: as PNF, my duties at the time were to get the current ATIS, make the descent announcement to the cabin, then run the descent/approach checklist. This, I feel, kept me out of the loop longer than I intended. Thus, I was behind in helping the captain in assessing our descent profile in a timely manner. Once back to the descent task at hand, I immediately tried to contact ZLA. However, due to the intense radio traffic during this time of day, I was not able to get through. Other factors involved are the mountainous terrain that one descends over from the east into san. For as many times that I've flown into san I rarely feel that a normal descent profile is being flown. Compound this with a late descent clearance due to lower traffic exacerbated our problems. I also feel I could have been more aggressive in my advice to the captain and could have taken more immediate action once realizing we would not leveloff at the appropriate altitude. The captain did a very good job in trying to comply with ATC instructions for the crossing constraint, but he too was late in acknowledging the leveloff problem and trying to reengage the autoplt. The unfortunate circumstance was the light turbulence that led to the momentary overspd, which then precluded the reengagement of the autoplt to start the leveloff when the captain wanted it to. Had the autoplt reengaged, I feel we would have still overshot the altitude but would have stayed in the 3000 ft ATC standard. This was our second of 3 legs (jfk-phx-san-phx) finishing our 4TH day. The previous leg (mine as PF) we had considerable WX deviations to contend with. This may have led to a slight mental letdown in my oversight of this descent and thus my not helping the captain in managing this flight regime.

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Original NASA ASRS Text

Title: A320 FLC, ENCOUNTERING TURB AND TFC RESTRS, OVERSHOOT ASSIGNED ALT DSNDING FOR APCH TO SAN.

Narrative: I WAS THE AIRBUS A320 FO, PNF ON A FLT FROM PHX TO SAN. WE WERE DSNDING INTO THE SAN DIEGO AREA VIA THE BARET 4 ARR. WE HAD BEEN ON RADAR VECTORS, THEN RECEIVED A DIRECT CLRNC TO PILLO INTXN. PREVIOUS TO THE ALTDEV, WE WERE CLRED AND LEVELED OFF AT FL190. WE ASKED FOR LOWER TO MEET THE EXPECTED XING CONSTRAINT AT PILLO AT 10000 FT MSL. WE WERE HELD HIGH FOR LOWER TFC THEN CLRED LATE TO MEET 10000 FT AT PILLO. AS FO, I WAS BUSY FINISHING THE DSCNT/APCH CHKLIST WITH THE CAPT. UPON LOOKING AT HOW CLOSE PILLO WAS COMING UP AND WE WERE VERY HIGH ON THE PROFILE, I ADVISED THE CAPT. HE THEN DEPLOYED FULL SPD BRAKES WITH THE AUTOPLT OFF (MOST A320'S WILL NOT DEPLOY FULL BOARDS WITH AUTOPLT ENGAGED). I THEN TRIED TO ADVISE ZLA THAT WE WOULD BE HIGH AT PILLO BUT DUE TO THE RADIO TFC, DID NOT GET THROUGH UNTIL PASSING 13000 FT MSL. WE WERE RELIEVED OF THE CONSTRAINT AND TO CONTACT SOCAL APCH. AT THIS TIME, THE CAPT TRIED TO START A LEVELOFF. OUR AIRSPD WAS SELECTED AT 345 KIAS. THE CAPT THEN MOVED THE SPD BRAKES BACK TO HALF AND TRIED TO REENGAGE THE AUTOPLT. AT THIS TIME, WE HIT SOME LIGHT TURB THAT CAUSED A MOMENTARY OVERSPD CONDITION WITH APPROPRIATE AURAL/ECAM WARNINGS. THIS WOULD NOT ALLOW THE AUTOPLT TO REENGAGE AND OUR DSCNT CONTINUED UNCHKED APCHING 11500 FT. I CONTINUED TO ADVISE THE CAPT THAT THE AUTOPLT WAS OFF, MADE THE 11000 FT TO 10000 FT CALL AND AT 10500 FT ADVISED I WAS ADDING BACK PRESSURE TO THE SIDESTICK CTLR. AT THIS POINT THE CAPT SAID HE HAD THE ACFT AND CONTINUED TO ADD BACK PRESSURE INPUTS TO THE SIDESTICK CTLR. WE EVENTUALLY LEVELED OFF AT 9150 FT MSL, SLOWED ENOUGH TO REENGAGE THE AUTOPLT AND STARTED TO CLB BACK TO 10000 FT. I ADVISED SOCAL APCH OF OUR DEV AND OUR CORRECTION. THERE WERE NO TFC CONFLICTS DUE TO THE ALTDEV. MY PERSPECTIVE ON THE CHAIN OF EVENTS: AS PNF, MY DUTIES AT THE TIME WERE TO GET THE CURRENT ATIS, MAKE THE DSCNT ANNOUNCEMENT TO THE CABIN, THEN RUN THE DSCNT/APCH CHKLIST. THIS, I FEEL, KEPT ME OUT OF THE LOOP LONGER THAN I INTENDED. THUS, I WAS BEHIND IN HELPING THE CAPT IN ASSESSING OUR DSCNT PROFILE IN A TIMELY MANNER. ONCE BACK TO THE DSCNT TASK AT HAND, I IMMEDIATELY TRIED TO CONTACT ZLA. HOWEVER, DUE TO THE INTENSE RADIO TFC DURING THIS TIME OF DAY, I WAS NOT ABLE TO GET THROUGH. OTHER FACTORS INVOLVED ARE THE MOUNTAINOUS TERRAIN THAT ONE DSNDS OVER FROM THE E INTO SAN. FOR AS MANY TIMES THAT I'VE FLOWN INTO SAN I RARELY FEEL THAT A NORMAL DSCNT PROFILE IS BEING FLOWN. COMPOUND THIS WITH A LATE DSCNT CLRNC DUE TO LOWER TFC EXACERBATED OUR PROBS. I ALSO FEEL I COULD HAVE BEEN MORE AGGRESSIVE IN MY ADVICE TO THE CAPT AND COULD HAVE TAKEN MORE IMMEDIATE ACTION ONCE REALIZING WE WOULD NOT LEVELOFF AT THE APPROPRIATE ALT. THE CAPT DID A VERY GOOD JOB IN TRYING TO COMPLY WITH ATC INSTRUCTIONS FOR THE XING CONSTRAINT, BUT HE TOO WAS LATE IN ACKNOWLEDGING THE LEVELOFF PROB AND TRYING TO REENGAGE THE AUTOPLT. THE UNFORTUNATE CIRCUMSTANCE WAS THE LIGHT TURB THAT LED TO THE MOMENTARY OVERSPD, WHICH THEN PRECLUDED THE REENGAGEMENT OF THE AUTOPLT TO START THE LEVELOFF WHEN THE CAPT WANTED IT TO. HAD THE AUTOPLT REENGAGED, I FEEL WE WOULD HAVE STILL OVERSHOT THE ALT BUT WOULD HAVE STAYED IN THE 3000 FT ATC STANDARD. THIS WAS OUR SECOND OF 3 LEGS (JFK-PHX-SAN-PHX) FINISHING OUR 4TH DAY. THE PREVIOUS LEG (MINE AS PF) WE HAD CONSIDERABLE WX DEVS TO CONTEND WITH. THIS MAY HAVE LED TO A SLIGHT MENTAL LETDOWN IN MY OVERSIGHT OF THIS DSCNT AND THUS MY NOT HELPING THE CAPT IN MANAGING THIS FLT REGIME.

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.