A B727's autoplt failed to maintain engaged altitude.

Attributes
ACN	427929
Time
Date	199902
Day	Sat
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : zjx
State Reference	FL
Altitude	msl bound lower : 35000 msl bound upper : 35000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : dca.tower
Operator	common carrier : air carrier
Make Model Name	B727 Undifferentiated or Other Model
Flight Phase	cruise other
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Experience	flight time last 90 days : 210 flight time total : 13000 flight time type : 1000
ASRS Report	427929
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument pilot : flight engineer
Experience	flight time last 90 days : 210 flight time total : 8000 flight time type : 900
ASRS Report	427801
Events
Anomaly	altitude deviation : excursion from assigned altitude other anomaly other
Independent Detector	other flight crewa
Resolutory Action	other
Consequence	Other
Supplementary
Air Traffic Incident	Pilot Deviation

Narrative:

Tampa to atlanta. FL350 autoplt in use straight and level. Autoplt malfunction. Aircraft climbed very slowly from FL350 to FL355 (500 ft high). No aural warning and no indication in cockpit that autoplt malfunctioned except for altimeter. ATC did not remark on this situation. We went back down to FL350, put autoplt back on. Autoplt deviated again. We wrote it up and hand flew to atlanta.

Original NASA ASRS Text

Title: A B727'S AUTOPLT FAILED TO MAINTAIN ENGAGED ALT.

Narrative: TAMPA TO ATLANTA. FL350 AUTOPLT IN USE STRAIGHT AND LEVEL. AUTOPLT MALFUNCTION. ACFT CLBED VERY SLOWLY FROM FL350 TO FL355 (500 FT HIGH). NO AURAL WARNING AND NO INDICATION IN COCKPIT THAT AUTOPLT MALFUNCTIONED EXCEPT FOR ALTIMETER. ATC DID NOT REMARK ON THIS SIT. WE WENT BACK DOWN TO FL350, PUT AUTOPLT BACK ON. AUTOPLT DEVIATED AGAIN. WE WROTE IT UP AND HAND FLEW TO ATLANTA.

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.