Altitude deviation excursion from assigned.

Attributes
ACN	294208
Time
Date	199501
Day	Sun
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : dfw
State Reference	TX
Altitude	msl bound lower : 4740 msl bound upper : 5000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : dfw artcc : zlc
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	descent other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 180 flight time total : 5000 flight time type : 180
ASRS Report	294208
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : instrument pilot : flight engineer pilot : cfi pilot : atp pilot : commercial
Experience	flight time last 90 days : 190 flight time total : 14667 flight time type : 3750
ASRS Report	294413
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance
Independent Detector	other controllera other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

While descending to 5000 ft on descent into dfw, autoplt on, we were instructed to slow to 210 KIAS. I asked the captain to extent the slats. I dialed in 210 KTS in the speed window. I then selected 210 KIAS in the vertical speed/IAS window. At the same time, the aircraft leveled at 5000 ft. The captain reports that he saw 'altitude hold' in the FMA. Somehow, possibly while I was changing the speeds, IAS was selected in the FMA and the power was still back at idle. The aircraft left 5000 ft in a descent. The captain, noticing IAS in the FMA, said 'where are you going?' realizing that the aircraft was descending, I immediately pushed 'althold.' I then rolled the vertical speed wheel to start a climb. The vertical speed window showed '1000 ft' and I continued to roll the wheel nose up. At that time, the aircraft was 200 ft low. The aircraft was still descending when the captain took control, disconnected the autoplt and climbed back up to 5000 ft. Not realizing that he had relinquished control back to me, the aircraft sank again to 200 ft below our assigned altitude. I reengaged the autoplt, commanded a climb, and leveled off at 5000 ft. During the first altitude deviation, the approach controller reminded us to stay at 5000 ft. We responded that we were then level at 5000 ft. Maximum deviation was 260 ft.

Original NASA ASRS Text

Title: ALTDEV EXCURSION FROM ASSIGNED.

Narrative: WHILE DSNDING TO 5000 FT ON DSCNT INTO DFW, AUTOPLT ON, WE WERE INSTRUCTED TO SLOW TO 210 KIAS. I ASKED THE CAPT TO EXTENT THE SLATS. I DIALED IN 210 KTS IN THE SPD WINDOW. I THEN SELECTED 210 KIAS IN THE VERT SPD/IAS WINDOW. AT THE SAME TIME, THE ACFT LEVELED AT 5000 FT. THE CAPT RPTS THAT HE SAW 'ALT HOLD' IN THE FMA. SOMEHOW, POSSIBLY WHILE I WAS CHANGING THE SPDS, IAS WAS SELECTED IN THE FMA AND THE PWR WAS STILL BACK AT IDLE. THE ACFT LEFT 5000 FT IN A DSCNT. THE CAPT, NOTICING IAS IN THE FMA, SAID 'WHERE ARE YOU GOING?' REALIZING THAT THE ACFT WAS DSNDING, I IMMEDIATELY PUSHED 'ALTHOLD.' I THEN ROLLED THE VERT SPD WHEEL TO START A CLB. THE VERT SPD WINDOW SHOWED '1000 FT' AND I CONTINUED TO ROLL THE WHEEL NOSE UP. AT THAT TIME, THE ACFT WAS 200 FT LOW. THE ACFT WAS STILL DSNDING WHEN THE CAPT TOOK CTL, DISCONNECTED THE AUTOPLT AND CLBED BACK UP TO 5000 FT. NOT REALIZING THAT HE HAD RELINQUISHED CTL BACK TO ME, THE ACFT SANK AGAIN TO 200 FT BELOW OUR ASSIGNED ALT. I REENGAGED THE AUTOPLT, COMMANDED A CLB, AND LEVELED OFF AT 5000 FT. DURING THE FIRST ALTDEV, THE APCH CTLR REMINDED US TO STAY AT 5000 FT. WE RESPONDED THAT WE WERE THEN LEVEL AT 5000 FT. MAX DEV WAS 260 FT.

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.