Captain of an medium large transport canceled the VNAV mode for the FMS causing the aircraft to overshoot the descent assigned altitude.

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Attributes
ACN	351680
Time
Date	199601
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : atl
State Reference	GA
Altitude	msl bound lower : 11000 msl bound upper : 13000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
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
Route In Use	arrival other arrival star : star enroute airway : atl
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : cfi
Experience	flight time last 90 days : 200 flight time total : 10200 flight time type : 3632
ASRS Report	351680
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : crossing restriction not met altitude deviation : overshoot non adherence : clearance
Independent Detector	other flight crewa
Resolutory Action	none taken : detected after the fact
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

We were inbound to atl on the rome 8 arrival. Our clearance was to cross erlin intersection at 13000 ft then descend to 9000 ft. The aircraft was in VNAV descent and FMS was set to cross erlin at 250 KTS and 13000 ft. The captain selected 9000 ft in altitude select window. The aircraft was set to cross erlin at 13000 ft and we would have complied with the ATC clearance. Somewhere prior to 13000 ft the captain canceled VNAV and selected IAS on the autoplt. I didn't see this happen as I was getting gate information off the ACARS printer. Now the altitude restr at erlin was canceled and the aircraft would go direct to 9000 ft. As a result we crossed erlin at approximately 11000 ft. As it turned out the captain said he didn't realize we needed to cross erlin at 13000 ft and thought we were cleared directly to 9000 ft. I think fatigue had something to do with this incident because we had an XA00 am report at the airport and we were both tired that morning. This led to the breakdown in crew coordination because we were not aggressive in making sure we both understood the clearance.

Original NASA ASRS Text

Title: CAPT OF AN MLG CANCELED THE VNAV MODE FOR THE FMS CAUSING THE ACFT TO OVERSHOOT THE DSCNT ASSIGNED ALT.

Narrative: WE WERE INBOUND TO ATL ON THE ROME 8 ARR. OUR CLRNC WAS TO CROSS ERLIN INTXN AT 13000 FT THEN DSND TO 9000 FT. THE ACFT WAS IN VNAV DSCNT AND FMS WAS SET TO CROSS ERLIN AT 250 KTS AND 13000 FT. THE CAPT SELECTED 9000 FT IN ALT SELECT WINDOW. THE ACFT WAS SET TO CROSS ERLIN AT 13000 FT AND WE WOULD HAVE COMPLIED WITH THE ATC CLRNC. SOMEWHERE PRIOR TO 13000 FT THE CAPT CANCELED VNAV AND SELECTED IAS ON THE AUTOPLT. I DIDN'T SEE THIS HAPPEN AS I WAS GETTING GATE INFO OFF THE ACARS PRINTER. NOW THE ALT RESTR AT ERLIN WAS CANCELED AND THE ACFT WOULD GO DIRECT TO 9000 FT. AS A RESULT WE CROSSED ERLIN AT APPROX 11000 FT. AS IT TURNED OUT THE CAPT SAID HE DIDN'T REALIZE WE NEEDED TO CROSS ERLIN AT 13000 FT AND THOUGHT WE WERE CLRED DIRECTLY TO 9000 FT. I THINK FATIGUE HAD SOMETHING TO DO WITH THIS INCIDENT BECAUSE WE HAD AN XA00 AM RPT AT THE ARPT AND WE WERE BOTH TIRED THAT MORNING. THIS LED TO THE BREAKDOWN IN CREW COORD BECAUSE WE WERE NOT AGGRESSIVE IN MAKING SURE WE BOTH UNDERSTOOD THE CLRNC.

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.