Medium large transport on autoflt control failed to level at altitude set in automatic control.

Attributes
ACN	112714
Time
Date	198905
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : grr
State Reference	MI
Altitude	msl bound lower : 1400 msl bound upper : 2700
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : grr
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other
Flight Phase	descent : approach descent other
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 200 flight time total : 5000 flight time type : 500
ASRS Report	112714
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : less severe 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:

Aircraft is an medium large transport. I get to fill out one of these reports about every 4-5 months. Cleared to 1700. Autoplt was armed at 2700 but failed to capture at 1700. We caught it at 1400, was looking for traffic. The autoplt system on this plane is always doing strange things for no reason at all. Common knowledge at the company. Even our instructors tell us to be alert for the above problem plus uncommanded turns (which I have had) and other abnormalities which magically appear and disappear. How did this system get certified by our great FAA?

Original NASA ASRS Text

Title: MLG ON AUTOFLT CONTROL FAILED TO LEVEL AT ALT SET IN AUTO CONTROL.

Narrative: ACFT IS AN MLG. I GET TO FILL OUT ONE OF THESE REPORTS ABOUT EVERY 4-5 MONTHS. CLRED TO 1700. AUTOPLT WAS ARMED AT 2700 BUT FAILED TO CAPTURE AT 1700. WE CAUGHT IT AT 1400, WAS LOOKING FOR TFC. THE AUTOPLT SYSTEM ON THIS PLANE IS ALWAYS DOING STRANGE THINGS FOR NO REASON AT ALL. COMMON KNOWLEDGE AT THE COMPANY. EVEN OUR INSTRUCTORS TELL US TO BE ALERT FOR THE ABOVE PROBLEM PLUS UNCOMMANDED TURNS (WHICH I HAVE HAD) AND OTHER ABNORMALITIES WHICH MAGICALLY APPEAR AND DISAPPEAR. HOW DID THIS SYSTEM GET CERTIFIED BY OUR GREAT FAA?

Data retrieved from NASA's ASRS site as of August 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.