B727 autoplt malfunction results in altitude excursion.

Attributes
ACN	477916
Time
Date	200006
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	navaid : gld.vortac
State Reference	KS
Altitude	msl bound lower : 29000 msl bound upper : 29250
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zdv.artcc
Operator	common carrier : air carrier
Make Model Name	B727-200
Operating Under FAR Part	Part 121
Navigation In Use	other vortac
Flight Phase	cruise : level
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : commercial pilot : multi engine pilot : instrument pilot : flight engineer pilot : atp
Experience	flight time last 90 days : 115 flight time total : 17000 flight time type : 6000
ASRS Report	477916
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : multi engine pilot : instrument pilot : atp pilot : flight engineer pilot : commercial
Experience	flight time last 90 days : 101 flight time total : 13000 flight time type : 8000
ASRS Report	477919
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude
Independent Detector	other flight crewa other flight crewb
Resolutory Action	flight crew : overcame equipment problem flight crew : returned to assigned altitude
Consequence	other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

A B727-200 aircraft had an autoplt write-up which had been cleared. We departed lax on jun/fri/00. We were cruising at 29000 ft everything normal. Autoplt altitude/hold appeared to oscillate as previously written up. Supplemental information from acn 477920: the captain and first officer commenced to troubleshoot the autoplt system when center called and alerted us that we may have an altitude deviation. Autoplt was then turned off and remainder of flight to day was conducted without incident.

Original NASA ASRS Text

Title: B727 AUTOPLT MALFUNCTION RESULTS IN ALT EXCURSION.

Narrative: A B727-200 ACFT HAD AN AUTOPLT WRITE-UP WHICH HAD BEEN CLRED. WE DEPARTED LAX ON JUN/FRI/00. WE WERE CRUISING AT 29000 FT EVERYTHING NORMAL. AUTOPLT ALT/HOLD APPEARED TO OSCILLATE AS PREVIOUSLY WRITTEN UP. SUPPLEMENTAL INFO FROM ACN 477920: THE CAPT AND FO COMMENCED TO TROUBLESHOOT THE AUTOPLT SYS WHEN CTR CALLED AND ALERTED US THAT WE MAY HAVE AN ALTDEV. AUTOPLT WAS THEN TURNED OFF AND REMAINDER OF FLT TO DAY WAS CONDUCTED WITHOUT INCIDENT.

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.