B727-200 crew had an autoplt not level the aircraft at the selected altitude.

Attributes
ACN	506670
Time
Date	200103
Day	Thu
Place
Locale Reference	airport : atl.airport
State Reference	GA
Altitude	msl bound lower : 28000 msl bound upper : 28300
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	B727-200
Flight Phase	cruise : enroute altitude change
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Experience	flight time last 90 days : 160 flight time total : 9000 flight time type : 1100
ASRS Report	506670
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : overshoot non adherence : clearance other anomaly other
Resolutory Action	flight crew : returned to assigned altitude
Consequence	faa : reviewed incident with flight crew
Supplementary
Problem Areas	Flight Crew Human Performance Aircraft
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation

Narrative:

During climb to 28000 ft, as the aircraft reached 28000 ft, it became apparent that the autoplt was malfunctioning and would not level at the selected cruise altitude. I was flying and immediately intervened pushing the aircraft 'over' to return in a expeditious and safe manner back to 28000 ft. Mode C altitude reporting is connected to the left altimeter. The left altimeter indicated as high as 28300 ft. The right altimeter was reading slightly higher. At no time did ATC contact us and advise us of any altitude deviation. At no time was there any conflict with other traffic. There was an FAA examiner in the jump seat who said we handled the malfunction in an appropriate manner. The whole episode lasted only 1 or 2 seconds.

Original NASA ASRS Text

Title: B727-200 CREW HAD AN AUTOPLT NOT LEVEL THE ACFT AT THE SELECTED ALT.

Narrative: DURING CLB TO 28000 FT, AS THE ACFT REACHED 28000 FT, IT BECAME APPARENT THAT THE AUTOPLT WAS MALFUNCTIONING AND WOULD NOT LEVEL AT THE SELECTED CRUISE ALT. I WAS FLYING AND IMMEDIATELY INTERVENED PUSHING THE ACFT 'OVER' TO RETURN IN A EXPEDITIOUS AND SAFE MANNER BACK TO 28000 FT. MODE C ALT RPTING IS CONNECTED TO THE L ALTIMETER. THE L ALTIMETER INDICATED AS HIGH AS 28300 FT. THE R ALTIMETER WAS READING SLIGHTLY HIGHER. AT NO TIME DID ATC CONTACT US AND ADVISE US OF ANY ALTDEV. AT NO TIME WAS THERE ANY CONFLICT WITH OTHER TFC. THERE WAS AN FAA EXAMINER IN THE JUMP SEAT WHO SAID WE HANDLED THE MALFUNCTION IN AN APPROPRIATE MANNER. THE WHOLE EPISODE LASTED ONLY 1 OR 2 SECONDS.

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.