Narrative:

We were arriving in san diego on the BARET4 arrival for a localizer approach to runway 27. The captain was the pilot monitoring; the first officer was the PF. The arrival and approach had been inserted into the FMS and briefed. The approach was in the database and had been briefed to fly using 'localizer only' and a profile descent. WX was VFR but as we arrived it was very hazy and we were looking into the sun. Early in the arrival; approach gave us a vector to intercept the localizer and a series of stepdown dscnts. Because of the distance; we manually tuned the localizer and armed 'localizer only.' at one point; the roll mode dropped out of 'localizer armed.' the first officer caught it; and we re-armed 'localizer only.' as we intercepted the localizer; approach instructed us to maintain 4000 ft until vydda; cleared us for the approach; and switched us to tower. As we crossed over vydda; we reviewed that all of the parameters had been met to dial our altitude down to minimums. The first officer did that and I confirmed the correct altitude. At that time; the vertical descent indicator showed that we were slightly high on the profile. I noted that; and that as soon as minimums had been dialed in; the aircraft began to descend. I monitored the descent until the vertical descent indicator indicated that we were back on the profile. At that time I contacted tower; received landing clearance; dialed in ground frequency and looked out visually for traffic. We also completed configuring the aircraft for landing and completed the 'before landing checklist.' when I looked back outside; I still could not see the runway and I also sensed a high rate of descent. I looked back inside and noted that the descent rate was over 1000 FPM; and that we were low on the profile. At the same time; tower called and reported us low on the approach. I immediately instructed the first officer to disconnect the autoplt and climb back up to our next crossing restr altitude of 2000 ft. He did this expeditiously; and then continued hand flying for an uneventful landing. After shutdown; we conducted an extensive debrief. Although we were unable to determine exactly why the aircraft failed to follow the profile descent; both the PF and pilot monitoring failed to correctly monitor the vertical descent of the aircraft. Through a very thorough debrief; both crew members learned valuable lessons that we will take with us for the rest of our aviation careers.

Google
 

Original NASA ASRS Text

Title: AN MD10 ON LOC APCH TO SAN DEVIATED BELOW THE CHARTED ALTITUDE.

Narrative: WE WERE ARRIVING IN SAN DIEGO ON THE BARET4 ARR FOR A LOC APCH TO RWY 27. THE CAPT WAS THE PLT MONITORING; THE FO WAS THE PF. THE ARR AND APCH HAD BEEN INSERTED INTO THE FMS AND BRIEFED. THE APCH WAS IN THE DATABASE AND HAD BEEN BRIEFED TO FLY USING 'LOC ONLY' AND A PROFILE DSCNT. WX WAS VFR BUT AS WE ARRIVED IT WAS VERY HAZY AND WE WERE LOOKING INTO THE SUN. EARLY IN THE ARR; APCH GAVE US A VECTOR TO INTERCEPT THE LOC AND A SERIES OF STEPDOWN DSCNTS. BECAUSE OF THE DISTANCE; WE MANUALLY TUNED THE LOC AND ARMED 'LOC ONLY.' AT ONE POINT; THE ROLL MODE DROPPED OUT OF 'LOC ARMED.' THE FO CAUGHT IT; AND WE RE-ARMED 'LOC ONLY.' AS WE INTERCEPTED THE LOC; APCH INSTRUCTED US TO MAINTAIN 4000 FT UNTIL VYDDA; CLRED US FOR THE APCH; AND SWITCHED US TO TWR. AS WE CROSSED OVER VYDDA; WE REVIEWED THAT ALL OF THE PARAMETERS HAD BEEN MET TO DIAL OUR ALT DOWN TO MINIMUMS. THE FO DID THAT AND I CONFIRMED THE CORRECT ALT. AT THAT TIME; THE VERT DSCNT INDICATOR SHOWED THAT WE WERE SLIGHTLY HIGH ON THE PROFILE. I NOTED THAT; AND THAT AS SOON AS MINIMUMS HAD BEEN DIALED IN; THE ACFT BEGAN TO DSND. I MONITORED THE DSCNT UNTIL THE VERT DSCNT INDICATOR INDICATED THAT WE WERE BACK ON THE PROFILE. AT THAT TIME I CONTACTED TWR; RECEIVED LNDG CLRNC; DIALED IN GND FREQ AND LOOKED OUT VISUALLY FOR TFC. WE ALSO COMPLETED CONFIGURING THE ACFT FOR LNDG AND COMPLETED THE 'BEFORE LNDG CHKLIST.' WHEN I LOOKED BACK OUTSIDE; I STILL COULD NOT SEE THE RWY AND I ALSO SENSED A HIGH RATE OF DSCNT. I LOOKED BACK INSIDE AND NOTED THAT THE DSCNT RATE WAS OVER 1000 FPM; AND THAT WE WERE LOW ON THE PROFILE. AT THE SAME TIME; TWR CALLED AND RPTED US LOW ON THE APCH. I IMMEDIATELY INSTRUCTED THE FO TO DISCONNECT THE AUTOPLT AND CLB BACK UP TO OUR NEXT XING RESTR ALT OF 2000 FT. HE DID THIS EXPEDITIOUSLY; AND THEN CONTINUED HAND FLYING FOR AN UNEVENTFUL LNDG. AFTER SHUTDOWN; WE CONDUCTED AN EXTENSIVE DEBRIEF. ALTHOUGH WE WERE UNABLE TO DETERMINE EXACTLY WHY THE ACFT FAILED TO FOLLOW THE PROFILE DSCNT; BOTH THE PF AND PLT MONITORING FAILED TO CORRECTLY MONITOR THE VERT DSCNT OF THE ACFT. THROUGH A VERY THOROUGH DEBRIEF; BOTH CREW MEMBERS LEARNED VALUABLE LESSONS THAT WE WILL TAKE WITH US FOR THE REST OF OUR AVIATION CAREERS.

Data retrieved from NASA's ASRS site as of May 2009 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.