Altimeter system malfunction may have led to altitude deviation.

Attributes
ACN	140034
Time
Date	199003
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : acy
State Reference	NJ
Altitude	msl bound lower : 6000 msl bound upper : 6000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : acy tower : stl
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	cruise other cruise other descent : approach
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 150 flight time total : 14000 flight time type : 4500
ASRS Report	140034
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : overshoot
Independent Detector	other controllera
Resolutory Action	flight crew : returned to intended course or assigned course other
Consequence	Other
Supplementary
Primary Problem	Ambiguous
Air Traffic Incident	other

Narrative:

At our assigned altitude 6000', our electric altimeter displayed an off flag. We were advised by controller we should be at 6000'. Our barometric altimeters read 600' and my first officer responded, 'we are level at 6000'.' this intermittent flag could not be duplicated on the ground at acy. Upon termination of flight at msp the flag reappeared and maintenance observed flag and removed altimeter for repair.

Original NASA ASRS Text

Title: ALTIMETER SYSTEM MALFUNCTION MAY HAVE LED TO ALT DEVIATION.

Narrative: AT OUR ASSIGNED ALT 6000', OUR ELECTRIC ALTIMETER DISPLAYED AN OFF FLAG. WE WERE ADVISED BY CTLR WE SHOULD BE AT 6000'. OUR BAROMETRIC ALTIMETERS READ 600' AND MY F/O RESPONDED, 'WE ARE LEVEL AT 6000'.' THIS INTERMITTENT FLAG COULD NOT BE DUPLICATED ON THE GND AT ACY. UPON TERMINATION OF FLT AT MSP THE FLAG REAPPEARED AND MAINT OBSERVED FLAG AND REMOVED ALTIMETER FOR REPAIR.

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.