Air carrier widebody transport altitude deviation because aircraft altimeters were out of tolerance.

Attributes
ACN	137560
Time
Date	199002
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : fmg
State Reference	NV
Altitude	msl bound lower : 36600 msl bound upper : 37725
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zoa artcc : zoa
Operator	common carrier : air carrier
Make Model Name	Widebody, Low Wing, 2 Turbojet Eng
Navigation In Use	Other
Flight Phase	cruise other
Route In Use	enroute airway : zoa
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : instrument pilot : flight engineer pilot : atp
Experience	flight time last 90 days : 150 flight time total : 12000 flight time type : 1150
ASRS Report	137560
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 85 flight time total : 4500
ASRS Report	138307
Events
Anomaly	aircraft equipment problem : critical altitude deviation : excursion from assigned altitude non adherence : clearance
Independent Detector	other controllera other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course other
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation

Narrative:

Aircraft altimeters had maintenance history of being out of tolerance. At FL370 captain's altimeter read 370, center altimeter 37725', first officer's 37350'. At same time ATC reported us to be at 36800'. We switched to alternate static source and ATC reported us at 36600' or 400' low and reported conflicting opposite direction traffic at FL350. We switched back to normal static source and climbed 200'.

Original NASA ASRS Text

Title: ACR WDB ALT DEVIATION BECAUSE ACFT ALTIMETERS WERE OUT OF TOLERANCE.

Narrative: ACFT ALTIMETERS HAD MAINT HISTORY OF BEING OUT OF TOLERANCE. AT FL370 CAPT'S ALTIMETER READ 370, CENTER ALTIMETER 37725', F/O'S 37350'. AT SAME TIME ATC RPTED US TO BE AT 36800'. WE SWITCHED TO ALTERNATE STATIC SOURCE AND ATC RPTED US AT 36600' OR 400' LOW AND RPTED CONFLICTING OPPOSITE DIRECTION TFC AT FL350. WE SWITCHED BACK TO NORMAL STATIC SOURCE AND CLBED 200'.

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.