Narrative:

I was the captain of a scheduled air carrier flight that departed dfw at XA55 on jun/xx/97 operating a B727. The flight was full, with a pilot from another carrier occupying the jump seat. We were filed on the marcs 3 STAR to sat. After being handed off by ZHU to sat approach, we were given descent clearance to cross the marcs intersection at and maintain 12000 ft MSL. The copilot was flying the aircraft and is very new in this position. Passing FL180, the descent checklist was accomplished, and the flight was normal to this point. Passing approximately 17000 ft MSL, the jump seat occupant and I were discussing the new austin airport and the construction of the new runway which was visible out the left side of the airplane. Passing 13000 ft MSL I announced 13000 ft for 12000 ft, and mandatory callout for the PNF. The copilot acknowledged the callout and continued to descend to 12000 ft MSL. We received the proper aural and visual warnings from the altitude reminder that we were approaching the altitude selected in the reminder window. I continued to talk with the jump seat rider and did not focus on the fact that the copilot was leveling off properly at the assigned altitude. He passed through 12000 ft and continued down to 11500 ft before I realized he had descended too far. I immediately asked him if we had been reclred down to 11000 ft by approach control, and he said no. 12000 ft still was in view in the altitude reminder window. We do not have an autoplt which will capture the altitude selected in the reminder window, it must be captured by using a pitch knob on the autoplt, then altitude hold must be manually selected. I initiated a radio call to sat approach to verify the altitude to which we had been cleared. They asked me to stand by, and 5 seconds later cleared us to a heading of 250 degrees and to descend to 5000 ft. I asked him for a telephone number which I could call to discuss our situation with him after we landed, and after landing at sat, I initiated a call to him. He was on station at the time, however, I talked with the TRACON supervisor who was aware of and had watched our altitude excursion. I asked him if we had prompted any warnings or alerts that would require further action either on my part or theirs. He said no. He assured me that there would be nothing more initiated by them. I advised him of the specifics of what happened, and the reason I felt the excursion took place and that I appreciated their cooperation in not filing a violation. In all, we deviated from the assigned altitude by a total of 600 ft, and upon noticing the deviation, initiated corrective action back to the assigned altitude of 12000 ft MSL. However, we were issued a further descent clearance before we had climbed back to 12000 ft. In addition, we did not notice any conflict on our TCASII that was anywhere near us. The nearest target that was indicated on the TCASII was more than 10 mi away, and below our altitude. I believe it is for this reason that nothing more will become of this issue, ie, no warnings in the TRACON facility. The following is a list of contributing factors that lent themselves to causing this altitude excursion: 1) lack of entire crew diligence in monitoring the situation to preclude further descent beyond the assigned altitude. 2) my allowing for a non essential conversation to take place, at a critical stage in the flight, that distraction my attention long enough to allow for the altitude excursion to take place. Sterile cockpit procedures below 10000 ft were in use, however, this happened above 10000 ft MSL. 3) autoplt did not have arming for capture capability of the altitude selected in the altitude reminder window. A good lesson was learned by all of my crew. It is my hope that this situation will not happen again. I have been a commercial airline pilot for 21 yrs, and this is the first and hopefully the last NASA report that I have to file. Thank you for providing airmen the opportunity to file these reports.

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Original NASA ASRS Text

Title: B727 ACFT ON STAR DSNDED THROUGH ASSIGNED ALT BY 600 FT. CTLR ISSUED NEW CLRNC. NO CONFLICTS. CAPT RPTR DISTR BY JUMP SEAT RIDER.

Narrative: I WAS THE CAPT OF A SCHEDULED ACR FLT THAT DEPARTED DFW AT XA55 ON JUN/XX/97 OPERATING A B727. THE FLT WAS FULL, WITH A PLT FROM ANOTHER CARRIER OCCUPYING THE JUMP SEAT. WE WERE FILED ON THE MARCS 3 STAR TO SAT. AFTER BEING HANDED OFF BY ZHU TO SAT APCH, WE WERE GIVEN DSCNT CLRNC TO CROSS THE MARCS INTXN AT AND MAINTAIN 12000 FT MSL. THE COPLT WAS FLYING THE ACFT AND IS VERY NEW IN THIS POS. PASSING FL180, THE DSCNT CHKLIST WAS ACCOMPLISHED, AND THE FLT WAS NORMAL TO THIS POINT. PASSING APPROX 17000 FT MSL, THE JUMP SEAT OCCUPANT AND I WERE DISCUSSING THE NEW AUSTIN ARPT AND THE CONSTRUCTION OF THE NEW RWY WHICH WAS VISIBLE OUT THE L SIDE OF THE AIRPLANE. PASSING 13000 FT MSL I ANNOUNCED 13000 FT FOR 12000 FT, AND MANDATORY CALLOUT FOR THE PNF. THE COPLT ACKNOWLEDGED THE CALLOUT AND CONTINUED TO DSND TO 12000 FT MSL. WE RECEIVED THE PROPER AURAL AND VISUAL WARNINGS FROM THE ALT REMINDER THAT WE WERE APCHING THE ALT SELECTED IN THE REMINDER WINDOW. I CONTINUED TO TALK WITH THE JUMP SEAT RIDER AND DID NOT FOCUS ON THE FACT THAT THE COPLT WAS LEVELING OFF PROPERLY AT THE ASSIGNED ALT. HE PASSED THROUGH 12000 FT AND CONTINUED DOWN TO 11500 FT BEFORE I REALIZED HE HAD DSNDED TOO FAR. I IMMEDIATELY ASKED HIM IF WE HAD BEEN RECLRED DOWN TO 11000 FT BY APCH CTL, AND HE SAID NO. 12000 FT STILL WAS IN VIEW IN THE ALT REMINDER WINDOW. WE DO NOT HAVE AN AUTOPLT WHICH WILL CAPTURE THE ALT SELECTED IN THE REMINDER WINDOW, IT MUST BE CAPTURED BY USING A PITCH KNOB ON THE AUTOPLT, THEN ALT HOLD MUST BE MANUALLY SELECTED. I INITIATED A RADIO CALL TO SAT APCH TO VERIFY THE ALT TO WHICH WE HAD BEEN CLRED. THEY ASKED ME TO STAND BY, AND 5 SECONDS LATER CLRED US TO A HDG OF 250 DEGS AND TO DSND TO 5000 FT. I ASKED HIM FOR A TELEPHONE NUMBER WHICH I COULD CALL TO DISCUSS OUR SIT WITH HIM AFTER WE LANDED, AND AFTER LNDG AT SAT, I INITIATED A CALL TO HIM. HE WAS ON STATION AT THE TIME, HOWEVER, I TALKED WITH THE TRACON SUPVR WHO WAS AWARE OF AND HAD WATCHED OUR ALT EXCURSION. I ASKED HIM IF WE HAD PROMPTED ANY WARNINGS OR ALERTS THAT WOULD REQUIRE FURTHER ACTION EITHER ON MY PART OR THEIRS. HE SAID NO. HE ASSURED ME THAT THERE WOULD BE NOTHING MORE INITIATED BY THEM. I ADVISED HIM OF THE SPECIFICS OF WHAT HAPPENED, AND THE REASON I FELT THE EXCURSION TOOK PLACE AND THAT I APPRECIATED THEIR COOPERATION IN NOT FILING A VIOLATION. IN ALL, WE DEVIATED FROM THE ASSIGNED ALT BY A TOTAL OF 600 FT, AND UPON NOTICING THE DEV, INITIATED CORRECTIVE ACTION BACK TO THE ASSIGNED ALT OF 12000 FT MSL. HOWEVER, WE WERE ISSUED A FURTHER DSCNT CLRNC BEFORE WE HAD CLBED BACK TO 12000 FT. IN ADDITION, WE DID NOT NOTICE ANY CONFLICT ON OUR TCASII THAT WAS ANYWHERE NEAR US. THE NEAREST TARGET THAT WAS INDICATED ON THE TCASII WAS MORE THAN 10 MI AWAY, AND BELOW OUR ALT. I BELIEVE IT IS FOR THIS REASON THAT NOTHING MORE WILL BECOME OF THIS ISSUE, IE, NO WARNINGS IN THE TRACON FACILITY. THE FOLLOWING IS A LIST OF CONTRIBUTING FACTORS THAT LENT THEMSELVES TO CAUSING THIS ALT EXCURSION: 1) LACK OF ENTIRE CREW DILIGENCE IN MONITORING THE SIT TO PRECLUDE FURTHER DSCNT BEYOND THE ASSIGNED ALT. 2) MY ALLOWING FOR A NON ESSENTIAL CONVERSATION TO TAKE PLACE, AT A CRITICAL STAGE IN THE FLT, THAT DISTR MY ATTN LONG ENOUGH TO ALLOW FOR THE ALT EXCURSION TO TAKE PLACE. STERILE COCKPIT PROCS BELOW 10000 FT WERE IN USE, HOWEVER, THIS HAPPENED ABOVE 10000 FT MSL. 3) AUTOPLT DID NOT HAVE ARMING FOR CAPTURE CAPABILITY OF THE ALT SELECTED IN THE ALT REMINDER WINDOW. A GOOD LESSON WAS LEARNED BY ALL OF MY CREW. IT IS MY HOPE THAT THIS SIT WILL NOT HAPPEN AGAIN. I HAVE BEEN A COMMERCIAL AIRLINE PLT FOR 21 YRS, AND THIS IS THE FIRST AND HOPEFULLY THE LAST NASA RPT THAT I HAVE TO FILE. THANK YOU FOR PROVIDING AIRMEN THE OPPORTUNITY TO FILE THESE RPTS.

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.