Altitude deviation. Altitude crossing restriction not met.

Attributes
ACN	142308
Time
Date	199004
Day	Fri
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : eno
State Reference	DE
Altitude	msl bound lower : 24000 msl bound upper : 26500
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zdc
Operator	common carrier : air carrier
Make Model Name	Widebody, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	descent other
Route In Use	arrival other arrival star : star
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 90 flight time total : 25000
ASRS Report	142308
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : flight engineer pilot : commercial pilot : atp pilot : instrument
Experience	flight time last 90 days : 260 flight time total : 4800 flight time type : 1100
ASRS Report	142557
Events
Anomaly	altitude deviation : crossing restriction not met altitude deviation : undershoot non adherence : clearance
Independent Detector	other flight crewa
Resolutory Action	flight crew : overcame equipment problem flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Air carrier flight xx was cleared by ZDC to cross 20 NM south of eno at FL240. First officer was flying aircraft in autoplt #2 command mode. The descent was programmed into the FMS, and with autoplt in profile mode, the aircraft began descending on schedule. All parameters appeared normal. As the aircraft descended through approximately FL265, the first officer was monitoring and involved with traffic watch. I (captain) was involved with obtaining the ewr ATIS and obtaining the air carrier company changeover #'south (altimeter settings, gate, etc). At about FL255, the aircraft started a gradual level-off, at first imperceptible to me (head in cockpit writing down #'south). Our attention was immediately drawn when the autoplt began an uncommanded (by pilots) climb to FL260. As the thrust levers advanced, and the aircraft climbed, the first officer disengaged the autoplt, and in order to perform a non-violent recovery, we missed the 20 NM crossing restriction by approximately 2 NM. At FL240 the autoplt was reengaged. Profile mode again selected, further dscnts and altitude restrictions were complied with, all with no problem. We were unable to explain or duplicate the problem.

Original NASA ASRS Text

Title: ALT DEVIATION. ALT CROSSING RESTRICTION NOT MET.

Narrative: ACR FLT XX WAS CLRED BY ZDC TO CROSS 20 NM S OF ENO AT FL240. F/O WAS FLYING ACFT IN AUTOPLT #2 COMMAND MODE. THE DSNT WAS PROGRAMMED INTO THE FMS, AND WITH AUTOPLT IN PROFILE MODE, THE ACFT BEGAN DSNDING ON SCHEDULE. ALL PARAMETERS APPEARED NORMAL. AS THE ACFT DSNDED THROUGH APPROX FL265, THE F/O WAS MONITORING AND INVOLVED WITH TFC WATCH. I (CAPT) WAS INVOLVED WITH OBTAINING THE EWR ATIS AND OBTAINING THE ACR COMPANY CHANGEOVER #'S (ALTIMETER SETTINGS, GATE, ETC). AT ABOUT FL255, THE ACFT STARTED A GRADUAL LEVEL-OFF, AT FIRST IMPERCEPTIBLE TO ME (HEAD IN COCKPIT WRITING DOWN #'S). OUR ATTN WAS IMMEDIATELY DRAWN WHEN THE AUTOPLT BEGAN AN UNCOMMANDED (BY PLTS) CLB TO FL260. AS THE THRUST LEVERS ADVANCED, AND THE ACFT CLBED, THE F/O DISENGAGED THE AUTOPLT, AND IN ORDER TO PERFORM A NON-VIOLENT RECOVERY, WE MISSED THE 20 NM XING RESTRICTION BY APPROX 2 NM. AT FL240 THE AUTOPLT WAS REENGAGED. PROFILE MODE AGAIN SELECTED, FURTHER DSCNTS AND ALT RESTRICTIONS WERE COMPLIED WITH, ALL WITH NO PROB. WE WERE UNABLE TO EXPLAIN OR DUPLICATE THE PROB.

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.