Narrative:

Our flight was inbound to seattle, wa, from wenatchee, wa, on the ephrata 4 arrival. We were given a descent clearance to 10000 ft, restr by a crossing altitude at flaak intersection of 11000 ft. Approximately 10 mi outside of flaak I left the first officer, who was the PF, responsible for both flying and ATC communications as I contacted our company maintenance control with news of an inoperative deice boot indicator. Company frequency was congested so it took me a few mins to establish contact, then to adequately explain what the exact problem appeared to be. While conversing with the maintenance controller and explaining the way in which I had written up the faulty indicator in the maintenance logbook, I felt the aircraft attitude change from a descent pitch attitude to an immediate climb pitch attitude. I glanced at our altitude and saw a climb through 9400 ft. I then heard ATC inquire about our altitude. I immediately wrapped up my discussion with our maintenance controller and asked the first officer what had happened. Apparently he had failed to select 'altitude select' on the flight director, which then didn't give him a leveloff command at 10000 ft. He also failed to notice he was descending through 10000 ft until we reached 9300 ft whereupon he immediately initiated a climb back to our assigned altitude. With the TCASII set to 20 NM, there appeared to be no immediate conflict with other transponder equipped aircraft. Factors contributing to this incident: 1) although highly experienced with over 10000 hours, the first officer was fairly new to the company, and probably not quite comfortable yet with the aircraft and company procedures regarding the use of the flight director. 2) a previous flight crew had written up the same maintenance problem but the mechanics had been unable to duplicate it on the ground, so the write-up was cleared without further action. When the same problem occurred on our flight, we were already running over an hour late. Given that, I was motivated to talk directly to our maintenance controller regarding the details of the failure, in order to expedite a resolution once we reached seattle. In addition, company procedure also dictated a call to the maintenance controller so that delays on the ground were minimized in terms of coordination within the maintenance structure. 3) I failed to adequately supervise the first officer while I was talking with maintenance control. I was lulled into complacency by the first officer's level of experience and his previous 2 days of outstanding performance. In retrospect, I should not have 'left the aircraft' as I did to call our maintenance folks at that point in the flight. Given the first officer's relative inexperience in the airplane and with the company, I should have kept an extremely wide eye and ear open inside the aircraft as I was making the call to company maintenance personnel, or I should have delayed the call altogether until we landed. We were extremely fortunate in this instance that there were no conflicts, but it sure got my heart racing nonetheless.

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Original NASA ASRS Text

Title: A FLC OF A DSNDING DHC8 OVERSHOOTS THEIR ASSIGNED ALT ON THE STAR PROC NE OF SEA, WA.

Narrative: OUR FLT WAS INBOUND TO SEATTLE, WA, FROM WENATCHEE, WA, ON THE EPHRATA 4 ARR. WE WERE GIVEN A DSCNT CLRNC TO 10000 FT, RESTR BY A XING ALT AT FLAAK INTXN OF 11000 FT. APPROX 10 MI OUTSIDE OF FLAAK I LEFT THE FO, WHO WAS THE PF, RESPONSIBLE FOR BOTH FLYING AND ATC COMS AS I CONTACTED OUR COMPANY MAINT CTL WITH NEWS OF AN INOP DEICE BOOT INDICATOR. COMPANY FREQ WAS CONGESTED SO IT TOOK ME A FEW MINS TO ESTABLISH CONTACT, THEN TO ADEQUATELY EXPLAIN WHAT THE EXACT PROB APPEARED TO BE. WHILE CONVERSING WITH THE MAINT CTLR AND EXPLAINING THE WAY IN WHICH I HAD WRITTEN UP THE FAULTY INDICATOR IN THE MAINT LOGBOOK, I FELT THE ACFT ATTITUDE CHANGE FROM A DSCNT PITCH ATTITUDE TO AN IMMEDIATE CLB PITCH ATTITUDE. I GLANCED AT OUR ALT AND SAW A CLB THROUGH 9400 FT. I THEN HEARD ATC INQUIRE ABOUT OUR ALT. I IMMEDIATELY WRAPPED UP MY DISCUSSION WITH OUR MAINT CTLR AND ASKED THE FO WHAT HAD HAPPENED. APPARENTLY HE HAD FAILED TO SELECT 'ALT SELECT' ON THE FLT DIRECTOR, WHICH THEN DIDN'T GIVE HIM A LEVELOFF COMMAND AT 10000 FT. HE ALSO FAILED TO NOTICE HE WAS DSNDING THROUGH 10000 FT UNTIL WE REACHED 9300 FT WHEREUPON HE IMMEDIATELY INITIATED A CLB BACK TO OUR ASSIGNED ALT. WITH THE TCASII SET TO 20 NM, THERE APPEARED TO BE NO IMMEDIATE CONFLICT WITH OTHER XPONDER EQUIPPED ACFT. FACTORS CONTRIBUTING TO THIS INCIDENT: 1) ALTHOUGH HIGHLY EXPERIENCED WITH OVER 10000 HRS, THE FO WAS FAIRLY NEW TO THE COMPANY, AND PROBABLY NOT QUITE COMFORTABLE YET WITH THE ACFT AND COMPANY PROCS REGARDING THE USE OF THE FLT DIRECTOR. 2) A PREVIOUS FLC HAD WRITTEN UP THE SAME MAINT PROB BUT THE MECHS HAD BEEN UNABLE TO DUPLICATE IT ON THE GND, SO THE WRITE-UP WAS CLRED WITHOUT FURTHER ACTION. WHEN THE SAME PROB OCCURRED ON OUR FLT, WE WERE ALREADY RUNNING OVER AN HR LATE. GIVEN THAT, I WAS MOTIVATED TO TALK DIRECTLY TO OUR MAINT CTLR REGARDING THE DETAILS OF THE FAILURE, IN ORDER TO EXPEDITE A RESOLUTION ONCE WE REACHED SEATTLE. IN ADDITION, COMPANY PROC ALSO DICTATED A CALL TO THE MAINT CTLR SO THAT DELAYS ON THE GND WERE MINIMIZED IN TERMS OF COORD WITHIN THE MAINT STRUCTURE. 3) I FAILED TO ADEQUATELY SUPERVISE THE FO WHILE I WAS TALKING WITH MAINT CTL. I WAS LULLED INTO COMPLACENCY BY THE FO'S LEVEL OF EXPERIENCE AND HIS PREVIOUS 2 DAYS OF OUTSTANDING PERFORMANCE. IN RETROSPECT, I SHOULD NOT HAVE 'LEFT THE ACFT' AS I DID TO CALL OUR MAINT FOLKS AT THAT POINT IN THE FLT. GIVEN THE FO'S RELATIVE INEXPERIENCE IN THE AIRPLANE AND WITH THE COMPANY, I SHOULD HAVE KEPT AN EXTREMELY WIDE EYE AND EAR OPEN INSIDE THE ACFT AS I WAS MAKING THE CALL TO COMPANY MAINT PERSONNEL, OR I SHOULD HAVE DELAYED THE CALL ALTOGETHER UNTIL WE LANDED. WE WERE EXTREMELY FORTUNATE IN THIS INSTANCE THAT THERE WERE NO CONFLICTS, BUT IT SURE GOT MY HEART RACING NONETHELESS.

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.