Loss of #1 navigation gyro results in deviation from altitude.

Attributes
ACN	170972
Time
Date	199102
Day	Wed
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : ric
State Reference	VA
Altitude	msl bound lower : 23000 msl bound upper : 23000
Environment
Flight Conditions	IMC
Light	Dusk
Aircraft 1
Controlling Facilities	artcc : zdc
Operator	general aviation : corporate
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time total : 11500 flight time type : 6000
ASRS Report	170972
Person 2
Affiliation	Other
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : excursion from assigned altitude non adherence : clearance
Independent Detector	other flight crewa
Resolutory Action	flight crew : overcame equipment problem flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

Were on vectors by ZDC and had been turned to rtc VOR to intercept the ott-1 arrival to baltimore. On intercept autoplt was on. At the point of intercept the autoplt turned the aircraft to the left and ADI rolled to the left, nose level, but started to lose altitude. At that point checking copilot INS it was quickly noted that they were different. Attitude indicator not level. Aircraft was removed off of autoplt and recovered, and discovered that the #1 navigation-gyro had intermittent failure.

Original NASA ASRS Text

Title: LOSS OF #1 NAVIGATION GYRO RESULTS IN DEVIATION FROM ALT.

Narrative: WERE ON VECTORS BY ZDC AND HAD BEEN TURNED TO RTC VOR TO INTERCEPT THE OTT-1 ARR TO BALTIMORE. ON INTERCEPT AUTOPLT WAS ON. AT THE POINT OF INTERCEPT THE AUTOPLT TURNED THE ACFT TO THE LEFT AND ADI ROLLED TO THE LEFT, NOSE LEVEL, BUT STARTED TO LOSE ALT. AT THAT POINT CHKING COPLT INS IT WAS QUICKLY NOTED THAT THEY WERE DIFFERENT. ATTITUDE INDICATOR NOT LEVEL. ACFT WAS REMOVED OFF OF AUTOPLT AND RECOVERED, AND DISCOVERED THAT THE #1 NAV-GYRO HAD INTERMITTENT FAILURE.

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.