An air carrier medium large transport descended through its assigned altitude.

Attributes
ACN	261441
Time
Date	199401
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : cvg
State Reference	OH
Altitude	msl bound lower : 11500 msl bound upper : 12000
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	descent other
Route In Use	arrival other arrival star : star enroute airway : zid
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : instrument pilot : flight engineer pilot : atp pilot : commercial
Experience	flight time last 90 days : 170 flight time total : 10000 flight time type : 700
ASRS Report	261441
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : overshoot non adherence : clearance other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified
Resolutory Action	flight crew : overcame equipment problem
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation

Narrative:

Cleared to cross blunt intersection at and maintain 12000 ft. Autoplt engaged. Aircraft in VNAV. 2000 ft prior to level off, flight management annunciator (FMA) indicated VNAV capture (meaning the autoplt had captured 12000 ft altitude and would level the aircraft at 12000 ft) autoplt continued through 12000 with no attempt whatsoever to level. This is not a common occurrence, but this situation and others similar (failure to capture and level at proper altitude) occur not infrequently with this FMS/autoplt system. It is poorly designed, not reliable and should never have gotten FAA certification.

Original NASA ASRS Text

Title: AN ACR MLG DSNDED THROUGH ITS ASSIGNED ALT.

Narrative: CLEARED TO CROSS BLUNT INTXN AT AND MAINTAIN 12000 FT. AUTOPLT ENGAGED. ACFT IN VNAV. 2000 FT PRIOR TO LEVEL OFF, FLT MGMNT ANNUNCIATOR (FMA) INDICATED VNAV CAPTURE (MEANING THE AUTOPLT HAD CAPTURED 12000 FT ALT AND WOULD LEVEL THE ACFT AT 12000 FT) AUTOPLT CONTINUED THROUGH 12000 WITH NO ATTEMPT WHATSOEVER TO LEVEL. THIS IS NOT A COMMON OCCURRENCE, BUT THIS SIT AND OTHERS SIMILAR (FAILURE TO CAPTURE AND LEVEL AT PROPER ALT) OCCUR NOT INFREQUENTLY WITH THIS FMS/AUTOPLT SYS. IT IS POORLY DESIGNED, NOT RELIABLE AND SHOULD NEVER HAVE GOTTEN FAA CERTIFICATION.

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.