The flight crew deviated from assigned course 10 mi and assigned altitude 600 ft.

Attributes
ACN	320996
Time
Date	199511
Day	Tue
Local Time Of Day	0001 To 0600
Place
Locale Reference	atc facility : czeb
State Reference	AB
Altitude	msl bound lower : 33000 msl bound upper : 33000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : czeb
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	320996
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	aircraft equipment problem : critical altitude deviation : excursion from assigned altitude other anomaly other other spatial deviation other spatial deviation
Independent Detector	other controllera other flight crewa
Resolutory Action	controller : issued new clearance other
Consequence	faa : reviewed incident with flight crew
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

Approximately 5 mi east of ysm aircraft began an abrupt right climbing turn. (I) first officer was flying using B autoplt and pms. HSI switch was in INS. A gyroscope flag and computer flag were in view in #2 ADI and also heading flags on HSI and RMI. By time aircraft was recovered, we had climbed 600 ft and turned right off course. Edmonton called us approximately 1 min later to say we were headed north approximately 10 mi off course. We explained our problem to them at that time. We shut down #2 INS using our cockpit operating manual procedures. When #2 INS failed, we also got #1 and #3 red comparator lights on front panel because of error of 3 plus 3T on #3 INS.

Original NASA ASRS Text

Title: THE FLC DEVIATED FROM ASSIGNED COURSE 10 MI AND ASSIGNED ALT 600 FT.

Narrative: APPROX 5 MI E OF YSM ACFT BEGAN AN ABRUPT R CLBING TURN. (I) FO WAS FLYING USING B AUTOPLT AND PMS. HSI SWITCH WAS IN INS. A GYROSCOPE FLAG AND COMPUTER FLAG WERE IN VIEW IN #2 ADI AND ALSO HEADING FLAGS ON HSI AND RMI. BY TIME ACFT WAS RECOVERED, WE HAD CLBED 600 FT AND TURNED R OFF COURSE. EDMONTON CALLED US APPROX 1 MIN LATER TO SAY WE WERE HEADED N APPROX 10 MI OFF COURSE. WE EXPLAINED OUR PROB TO THEM AT THAT TIME. WE SHUT DOWN #2 INS USING OUR COCKPIT OPERATING MANUAL PROCS. WHEN #2 INS FAILED, WE ALSO GOT #1 AND #3 RED COMPARATOR LIGHTS ON FRONT PANEL BECAUSE OF ERROR OF 3 PLUS 3T ON #3 INS.

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.